Department of Biology St. Francis Xavier University Antigonish, Nova Scotia Canada B2G 2W5
dgarbary@gmail.com
Born: Dublin, Ireland Citizenship: Canadian BSc (1973) - Acadia University, Wolfville, Nova Scotia - Biology MSc (1975) - Acadia University, Wolfville, Nova Scotia - Biology PhD (1978) - Liverpool, England - Botany Research Associate (1978-1980): University of British Columbia - Herbarium Botanist NSERC University Research Fellow (1980-1984) - University of British Columbia - Department of Botany St. Francis Xavier University - Antigonish, Nova Scotia (1984-present) -Professor of Biology Visiting Professor, University of Washington (1984, 1985, 1997) Research interests: Marine ecology, algae, marine symbioses, plant evolution, sea level rise
Abstract: The ribbed mussel, Geukensia demissa, is highly dependent on the cordgrass Spartina alterniflora for amelioration from environmental stress and substrate sta- bilization. Spartina alterniflora is a foundation species in marshes, and G. demissa is typically associated with cordgrass beds. Marshes in the southern Gulf of St. Law- rence are experiencing erosion and degradation, presum- ably as a result of increases in sea level, which increases salinity exposure and negatively impacts S. alterniflora. The population structure of the ribbed mussel, Geukensia demissa, was studied at nine sites in six estuaries in the southern Gulf of St. Lawrence in Nova Scotia, Canada, where marsh degradation is occurring. Mussel length was used as a proxy for age of G. demissa in three salt marsh zones characterized by density and elevation of Spartina alterniflora: (1) a lower zone in which the S. alterniflora was dead, but where the basal mat was coherent, (2) a zone of living, but low density S. alterniflora at the margin of the living marsh, and (3) a zone of dense S. alterniflora one to three meters back from the edge. Mussel length was sig- nificantly different across the three zones in seven of the nine sites. Mean length decreased as elevation increased, and small mussels (i.e., 1â3 cm) were absent at seven sites. The smallest mussels occurred in the dense S. alterniflora zone, higher in the marsh. Mussel length in the two western sites did not differ between zones, and small mussels (i.e., 1â3 cm) were present, but rare. The absence of small mussels in seven of the nine sites, and the size frequency distribution at remaining sites, suggests a lack of recent recruitment and a long-term threat to the survival of G. demissa. Salt marsh degradation and the death of S. alterniflora have negatively impacted G. demissa recruit- ment, and population decline is evident.
Abstract: Phenotypic plasticity was examined in the economically and ecologically important brown alga Ascophyllum nodosum in southwestern Nova Scotia, considering specifically how nutrient loading affected its vegetative and reproductive features. To determine this, we examined morphometric changes in A. nodosum from two sites receiving direct effluent impacts from a land-based finfish aquaculture facility and from two control sites, approximately 2 km away from the aquaculture facility in opposite directions. Fronds from test sites were significantly younger than from control sites (5 y vs. 8 y); however, fronds from farm sites were significantly larger (219 g vs. 90 g) because of their higher growth rates. Thalli from farm sites had greater reproductive potential, as shown by numbers of receptacle initials (797 initials vs. 281 initials). These results suggest limited nutrient inflows from land-based aquaculture may positively affect adjacent Ascophyllum populations by inducing higher growth rates. We conclude that the coordination of effluent management from land-based aquaculture with natural resource harvesting of A. nodosum may be beneficial. Further study is necessary to determine the limits of nutrient loading for this potentially beneficial outcome.
Abstract: hirty populations of Chondrus crispus Stackhouse from Nova Scotia were collected during the years 1993 to 2011. Taken from estuaries, wave exposed open coasts, high intertidal rock pools and shallow subtidal habitats, the populations were evaluated for relative abundance of tetrasporophytic and gametophytic life history phases. Over 2,800 thalli were characterized using the resorcinol-acetal test to distinguish the kappa- and lambda-carrageenan containing fronds of gametophytes and tetrasporophytes, respectively. These populations had 77 ± 5% gametophytes (mean ± 95% confidence interval), with most populations having gametophyte : sporophyte ratios ranging from 2 : 1 to 9 : 1. No population had a dominance of tetrasporophytes, although two populations had 1 : 1 ratios. A meta-analysis of our data along with previously published accounts showed no significant changes in ametophyte dominance with respect to hypothesized gradients of wave exposure, salinity, or water depth. Significant changes occurred in ratios at five sites where replicate sampling occurred in different years. We conclude that C. crispus in Maritime Canada has a natural ratio of 3 : 1 or greater in stable conditions, and that lower ratios represent recovery from disturbance in which bare substratum is created that is subsequently colonized by carpospores from remaining gametophytic thalli.
Abstract: The chironomid Halocladius variabilis (Staeger) is reported from rocky intertidal shores from both the east and west coasts of Scotland. Larvae of H. variabilis occurred on both sheltered and exposed shores in fully marine to estuarine conditions. The insects were found primarily with the brown seaweed Elachista fucicola on Fucus vesiculosis although other primary and secondary hosts occurred. Older records are reviewed to provide a general distribution of H. variabilis in the United Kingdom and the Republic of Ireland.
Abstract: The underlying physiology of algal antioxidant compounds is reviewed in the context of seaweed biology and utilization. The application of seaweed antioxidants in foods, food supplements, nutraceuticals and medicine is considered from the perspective of benefits to human health. We advocate that direct consumption of seaweed products for their antioxidant composition alone provides a useful alternative to non-natural substances, while simultaneously providing worthwhile nutritional benefits. Economic utilization of seaweeds for their antioxidant properties remains in its infancy. This review provides examples ranging from laboratory studies through to clinical trials where antioxidants derived from seaweeds may provide major health benefits that warrant subsequent investigative studies and possible utilization.
Abstract: Evaluating and understanding biodiversity in marine ecosystems are both necessary and challenging for conservation. This paper compiles and summarizes current knowledge of the diversity of marine taxa in Canada's three oceans while recognizing that this compilation is incomplete and will change in the future. That Canada has the longest coastline in the world and incorporates distinctly different biogeographic provinces and ecoregions (e.g., temperate through ice-covered areas) constrains this analysis. The taxonomic groups presented here include microbes, phytoplankton, macroalgae, zooplankton, benthic infauna, fishes, and marine mammals. The minimum number of species or taxa compiled here is 15,988 for the three Canadian oceans. However, this number clearly underestimates in several ways the total number of taxa present. First, there are significant gaps in the published literature. Second, the diversity of many habitats has not been compiled for all taxonomic groups (e.g., intertidal rocky shores, deep sea), and data compilations are based on short-term, directed research programs or longer-term monitoring activities with limited spatial resolution. Third, the biodiversity of large organisms is well known, but this is not true of smaller organisms. Finally, the greatest constraint on this summary is the willingness and capacity of those who collected the data to make it available to those interested in biodiversity meta-analyses. Confirmation of identities and intercomparison of studies are also constrained by the disturbing rate of decline in the number of taxonomists and systematists specializing on marine taxa in Canada. This decline is mostly the result of retirements of current specialists and to a lack of training and employment opportunities for new ones. Considering the difficulties encountered in compiling an overview of biogeographic data and the diversity of species or taxa in Canada's three oceans, this synthesis is intended to serve as a biodiversity baseline for a new program on marine biodiversity, the Canadian Healthy Ocean Network. A major effort needs to be undertaken to establish a complete baseline of Canadian marine biodiversity of all taxonomic groups, especially if we are to understand and conserve this part of Canada's natural heritage.
Abstract: Understanding epiphyte distribution in coastal communities is important because these organisms affect many others directly or indirectly. Yet, their distribution has been considerably less studied than that of their hosts and other primary-space holders. Identifying major sources of variation in epiphyte abundance is thus still a need. Environmental gradients help predict species distribution and are pervasive on marine shores. In this study, we test the notion that environmental gradients across intertidal elevation, throughout host canopies, and along host fronds explain a large variation in the abundance of sympatric epiphytes. Our model system was the assemblage of Ascophyllum nodosum (L.) Le Jol. and its epiphytes Vertebrata lanosa (L.) T. A. Chr. [= Polysiphonia lanosa (L.) Tandy], Elachista fucicola (Velley) Aresch., and Pylaiella littoralis (L.) Kjellm. On the coast of Nova Scotia (Canada), we found evidence of a spatial segregation among these species at almost all scales. While the red epiphyte V. lanosa was more common at high- and midintertidal elevations (peaking at midelevations) and on middle segments of host fronds, the brown epiphytes E. fucicola and P. littoralis were more common at low elevations and restricted to distal segments of host fronds. Canopy habitat affected abundance only for V. lanosa, which was more common within the host canopy than on its periphery at midelevations. Since the studied gradients are related to predictable changes in abiotic factors, the identification of likely causes behind the observed patterns was facilitated. Our study ends by proposing abiotic and biotic factors that deserve priority in the experimental testing of the forces structuring this assemblage.
Abstract: Five moss species were found in the high intertidal zone of salt marshes in Nova Scotia, eastern Canada. This is the first report of bryophytes from salt marshes from North America. In each of the salt marshes where mosses occurred, one to three moss species occurred in monospecific or mixed species assemblages. Campylium stellatum and Bryum capillare were the most common species, followed by Didymodon rigidulus, Mnium hornum and Amblystegium serpens in decreasing abundance. All mosses were present below the litter line and occurred in association with Juncus arcticus and J. gerardii, although some collections were also made in association with Spartina pectinata and S. patens. The mosses were exposed in situ to seawater of > 20 ppt. In a laboratory experiment, mats of C. stellatum were exposed to a range of salinities (0, 8, 16, 32 ppt); plants survived 24 h of immersion in seawater of 32 ppt followed by four days in which mats were fully saturated with seawater. There was a slight reduction in effective quantum yield of photosystem II (WPSII) in the 32 ppt treatment relative to 0 and 8 ppt. Following four subsequent days of desiccation, the full-seawater- and 16-ppt-treated plants had significant reduction in quantum yield. This experiment is consistent with field observations and shows considerable physiological tolerance to salinity in salt marsh mosses.
Abstract: The symbiosis of a brown alga, Ascophyllum nodosum (L.) Le Jolis and its obligate fungal symbiont, Mycophycias ascophylli (Cotton) Kohlmeyer and Volkmann-Kohlmeyer, was studied using transmission electron microscopy. A high quality of cell preservation was achieved after propane-freezing and freeze substitution; this allowed us to observe the interaction of the symbiosis without extensive artifacts. The fungus was found in the middle portion of cortical-cell walls, and at the edge of medullary cells and air-bladder filaments, but never close to host cell protoplasm. Host cell-wall modification was limited to a short distance around the hyphae. A sheath with electron-dense materials around the fungus was found in the older hyphae, but not in the hyphal tips. A range of hyphal ultrastructure was observed from cells with dense cytoplasm, absent to slight vacuolation and with well-defined organelles, to highly vacuolated cells with little cytoplasm and poorly defined organelles, to senescent cells that were often collapsed with no recognizable organelles. No sign of typical cytological resistance responses was observed in host cells, thus confirming the nonantagonistic nature of the two symbionts.
Abstract: Codium fragile ssp. tomentosoides from Caribou Harbour, an estuarine site in the southern Gulf of St. Lawrence, was extremely tolerant to stresses from desiccation and reduced salinity. Photosynthetic responses of both rhizomatous and erect growth forms were measured using pulse amplitude modulation (PAM) fluorometry of chlorophyll a fluorescence to determine effective quantum yield (Phi(PSII)) and relative electron transport rate (rETR). After 5 h of desiccation, thalli lost 20% of their mass, but still showed high levels of Phi(PSII). Thalli survived for at least 6 h in freshwater, and showed virtually complete recovery of photosynthetic capacity within a few hours of return to full seawater. Immersion in 8 psu showed virtually complete recovery until the 24 h treatment period. Combining desiccation and salinity stresses produced a synergistic effect, but plants still showed strong recovery even after 86% dehydration and reimmersion in 16 psu. These results suggest that the photosynthetic physiology of Codium fragile is highly adapted to growth in estuarine conditions.
Abstract: Nineteen Blandingâs turtles (Emydoidea blandingii), eight snapping turtles (Chelydra serpentina) and fourteen painted (Chrysemys picta) turtles trapped in Nova Scotia in 2005 were examined for epizoic algae. Algae were macroscopically apparent on 14 Blandingâs and seven snapping turtles; microscopic examination of material scraped from various surfaces of these turtles revealed the predominance of two algal taxa. cladophoroid green alga Basicladia chelonum was common on the shell of both Blandingâs and snapping turtles and also present on the head and tail of the latter. R chelonum is reported for the first time in Canada east of Ontario. A filamentous cyanobacterium, Konivophoron sp., formed extensive colonies solely in the leg bases of Blandingâs turtles, where B. chelonum was absent. Although the nature of the interaction is unknown, this is the first potential symbiosis between a cyanobacterium and a turtle. Examination of a historical (2001-05) photographic database for Blandingâs turtle in Nova Scotia revealed a colonization rate of 10% for B. chelonum and 46% for Komvophoron sp. It also revealed population and age-specific differences in frequency of the two algal taxa on Blandingâs turtles.
Abstract: Pulse amplitude modulation (PAM) fluorometry was used in 2004 and 2005 to measure chlorophyll a fluorescence associated with photosystem II in eggs and embryos of Ascophyllum nodosum (Linnaeus) Le Jolis from the Atlantic coast of Nova Scotia. Fucoid eggs and embryos were maintained in the laboratory for 8 days over which fluorescence measurements were taken. Newly released eggs saturated at about 20 mu mol photons m(-2) s(-1) with maximum electron transport rate (rETR(max)) declining to < 3 after 3 days. Embryos Saturated at about 50 mu mol photons, m(-2) s(-1) and rETR(max) increased to > 11 by day 3. Although some egg senescence was apparent by day 3, some eggs continued to generate a strong photosynthetic signal throughout the 8-day experimental period, even though rETR(max) was reduced. Differences in photosynthetic responses associated with fertilisation were apparent in F-v/F-m, within 24 h. and in rETR(max) after 2 days. Eggs showed relatively stable or declining responses, whereas embryos showed stable or increasing responses. By day 8, quantum yield of embryos was similar to values reported elsewhere for mature fucoids.
Abstract: Using optical and scanning electron microscopy the structure and development of the air bladders of Fucus vesiculosus and Ascophyllum nodosum are described in an ecological context from Nova Scotia. The air bladders consist of a bladder wall that surrounds an air space traversed by a complex network of white fibers. Microscopically, the fibers consist of branched, uniseriate filaments in which cells are uninucleate with a thin cytoplasmic region and thick cell walls. The filaments are formed from irregular sheets of cells consisting of a cluster of filaments surrounded by mucilaginous material. These become detached from the surrounding material as the bladder inflates. In very large bladders the filamentous network can be broken and leave a felt-like mat on the bladder wall. Bladders of F. vesiculosus have thinner walls than A. nodosum (300 pm vs 500 mu m, respectively). In addition, successively older bladders in the former species become damaged and lose their structural integrity, whereas this does not occur in the latter species. After 10 years of age, almost 90% of bladders in A. nodosum are still intact with no change between year 1 and year 10. In the shorter-lived F. vesiculosus, more than 50% of the visible bladders have been damaged, and only one or two bladders remain intact near the apices of branches. We conclude that the bladders of A. nodosum are able to undergo repair when the bladder wall is punctured, whereas those of F. vesiculosus do not.
Abstract: Diurnal and age-related changes in air pressure were measured in air bladders of Ascophyllum nodosumfrom the
Atlantic coast of Nova Scotia. Exterior and interior bladder volumes vary significantly with 4 and 6 y bladders being
about 40% larger than 2 y bladders (p < 0.01). Freshly collected bladders yielded a mean pressure of 40.8 ±6.5 cm
H2O. Overnight (20 h) dark treatment at 15°C generated pressure reductions by 80% in 2 y bladders but only by
about 30% in 4 and 6 y bladders. Furthermore, in 2 y bladders 8 out of 11 bladders were reduced to atmospheric
pressure. Pressure losses were inversely related to pressure recovery after 2.5 h in natural daylight, but after 5 h in
daylight there was no significant difference in pressure within the age groups. Even under 25% of full illumination,
bladders inflated to full pressure after 5 h. The results show that differences in bladder age and bladder wall
thickness have roles in diurnal patterns of bladder inflation and deflation. These results confirm that bladder
inflation is based on photosynthetic O2production and not on partial pressures of O2in the surrounding medium as
was suggested for Sargassum. Chemical analyses of fluid recovered after the interior of bladders were washed with
saline showed no evidence for the occurrence of surfactant that might be responsible for maintaining the air-liquid
interface.
Abstract: A winter collection of the intertidal, red algal crust, Hildenbrandia rubra (Sommerfelt) Meneghini, was examined for tolerance of photosynthesis to extremes of temperature, salinity and desiccation. Pulse amplitude modulation fluorometry of chlorophyll a fluorescence was used to determine various photosynthetic parameters including effective quantum yield (Phi(PSII)) and relative electron transport rate (rETR). Thalli from the same collection were successively exposed to freezing, desiccation, hyposalinity and high temperature. Thus thalli over 13 days experienced temperature fluctuations from -17 to 27 degrees C, from fully hydrated to extremely desiccated, from full seawater to 4 psu and back, all without any apparent long-term effects to the photosynthetic apparatus. There was no significant difference in Phi(PSII) between thalli at the beginning and end of the experiments. Algae showed a significant acclimation to low light in that immediately after collection thalli had optimum light intensity, I-k, in terms of rETR at 50 mu mol photons m(-2) s(-1), whereas 24 h later maximal rETR was at about 20 mu mol photons m(-2) s(-1). Hildenbrandia rubra is the most physiologically tolerant of any tested seaweed, and this helps explain its wide geographic and ecological range.
Abstract: Benthic sediment samples ranging from poorly aggregated sand to complex, stratified mats were collected from
six hypersaline ponds from March and July 1995 in the British Virgin Islands. Assemblages were analyzed with
respect to species composition and abundance within visibly distinct layers in each mat sample. In individual ponds
there was no apparent association between changing depth and the development of the benthic mats. Some species
were present in all samples (e.g. Oscillatoriasp.) while others were restricted to single sites (e.g. Johannesbaptistia
pellucida). Primary species included Microcoleus chthonoplastes, Phormidiumspp., Coccochloris stagnina, and purple
sulfur bacteria. Quantitative analysis of community structure included cluster and principal component analysis.
Samples from individual ponds were often clustered; however, this was subject to seasonal variation. Mats collected
in March were generally thicker and contained more layers than those in July. Variation among sites was not
explained by the measured variation in environmental factors such as average pond salinity, depth, and oxygen
concentration (mg/L). This study provides a detailed analysis of mat communities in hypersaline ponds and
compares them with similar mat communities from other areas.
Abstract: Mitochondrial distribution and abundance were assessed during the growth of apical and subapical cells in the
red algae Colaconema caespitosum(J. Agardh) Jackelman, Stegenga and Bolton and Antithamnion cruciatum(C.
Agardh) Nägeli after staining with 3,3â-dihexyloxacarbocyanine iodide [DiOC6(3)] and 2,4â-dimethylaminostyryl-N-
ethylpyridinium iodide (DASPEI). In fully elongate apical cells of C. caespitosumthere were 100-120 mitochondria.
During apical cell enlargement and division there is a doubling and then halving of the mitochondrial numbers.
Apical cells prior to cytokinesis in young filaments are smaller than in mature filaments (ca. 50 and 100 μm long,
respectively) and have fewer mitochondria (ca. 100 and 120 mitochondria per cell, respectively). In older vegetative
cells mitochondria tend to aggregate at opposite ends of the cells with some mitochondria associated with the cen-
tral nucleus or at points of apparent branch initiation. There is a greater density of mitochondria in apical cells of
smaller versus larger plants (one mitochondrion per 6.3 μm3and 9.8 μm3, respectively), suggesting that apical cells
of younger plants may be more metabolically active. Male and female gametophytic thalli of Antithamnion cruciatum
had similar numbers of mitochondria in apical cells of indeterminate axes, as did gametophytic and sporophytic
thalli. There were about 40-50 mitochondria in fully elongated apical cells with about half this number in newly
divided apical and subapical cells. Apical cells of determinate branches had more mitochondria (60-77) than indeter-
minate branches (60-70 vs. 40-50). In both species and in all cell types mitochondrial numbers were highly correlated
with cell size.
Abstract: Sporocladopsis jackii is a new species of green seaweed from eastern Canada and Maine. The species is abundant in late summer and is a conspicuous part of the epizoic flora on living shells of the mud snail, Ilyanassa obsoleta. The alga comprises a densely packed, branched filamentous base from which arise numerous unbranched to sparsely branched erect free axes. Multicellular attenuate hairs are rare to common and terminal on erect axes. Sporangia are clavate, terminal or lateral, usually borne singly, and produced abundantly in summer. Prior floristic accounts from eastern North America may have included S. jackii under the name Pilinia rimosa, now known to refer to a phaeophyte. Pulse amplitude modulation fluorometry of chlorophyll fluorescence (Phyto-PAM) for pigment analysis confirm microscopic observations of the communities living on snails as consisting of primarily Cyanobacteria and Chlorophyta.
Abstract: Larvae of the marine insect Halocladius variabilis (Diptera, Chironomidae) are symbiotic with the filamentous and syntagmatic brown alga, Elachista fucicola (Chordariales, Elachistaceae), which, in turn, is epiphytic on the intertidal brown alga Ascophyllum nodosum (Fucales, Fucaccae). On the Atlantic coast of Nova Scotia, H. variabilis was found only on thalli of E. fucicola with 1-7 larvae commonly present per host thallus. From June to November over 80% of host thalli were colonized. The symbiosis between E. fucicola and H. variabilis is at least commensal and possibly mutualistic. Evidence for mutualism is circumstantial and based on the host specificity of H. variabilis in Nova Scotia, the larger size of hosting versus non-hosting thalli of E. fucicola (10 mg vs. 5 mg dry weight, significant at p < 0.05), and a significant, positive correlation (r=0.44) between larval number and host dry weight. E. fucicola may benefit from grazing by the larvae on the epiphytic diatoms on its assimilatory filaments, and through fecal nitrogen enrichment. This is the first account of a potential mutualistic symbiosis between a marine insect and a marine alga.
Abstract: Green tides, i.e. blooms of Ulva species, occur on rocky intertidal shores over a wide geographic area in Korea. For the first time we report seasonal fluctuations in biomass, photosynthetic performance and chemical composition of the green-tide forming Ulva pertusa on the southern coast of Korea. Water temperature, salinity, inorganic nutrients and precipitation influencing Ulva mat dynamics were also monitored. There was a pronounced seasonality, not only in the biomass of U. pertusa, but also in photosynthetic performance and in variation in tissue pigments and nutrients. In addition to a primary seasonal response, significant variation in biomass was correlated in parts of the year with nutrient inputs from the surrounding watershed, heavy rain events and summer desiccation. There was a unimodal seasonal pattern in which biomass peaked in May (2.2 kg fw m(-2)) and dropped significantly from June to September. Recovery of Ova mats, as indicated by recruitment of new plants, began during autumn. Photosynthetic rates, maximum photosynthesis (P-max) and photosynthetic efficiency (a) were highest during the growth period and were lowest when biomass peaked or declined in May and July. Tissue pigments had a less clear seasonal pattern. Relative amounts of nitrogen and phosphorus bound in U. pertusa also displayed an obscure seasonal trend. Complex interactions among biological and environmental variables precluded strong correlations with any particular environmental factor. Stochastic events also played a major role in seasonality and can override normal physiological adaptations.
Abstract: Kelp gametophytes were previously observed in nature living endophytically in red algal cell walls. Here we examine the interactions of two kelp species and six red algae in culture. Gametophytes of Nereocystis luetkeana (Mertens) Postels et Ruprecht became endophytic in the cell walls of Griffithsia pacifica Kylin and Antithamnion defectum Kylin, and grew epiphytically in high abundance on G. japonica Okamura and Aglaothamnion oosumiense Itono. Alaria esculenta (Linnaeus) Greville from the Atlantic coast of Nova Scotia became endophytic in Aglaothamnion oosumiense, Antithamnion defectum, Callithamnion sp., G. japonica, G. pacifica, and Pleonosporium abysicola Gardner, all from the Pacific Ocean. Some cultures were treated with phloroglucinol before infection to thicken the cell walls. The endophytic gametophytes were smaller and grew more slowly than gametophytes epiphytic on the same host. N. luetkeana failed to become endophytic in some of the potential hosts, and this may reflect host specificity, or culture artifacts. This work improves our understanding of the process of infection of red algae by kelp gametophytes, and broadens our knowledge of host specificity in endophytic symbioses.
Abstract: Large numbers of the introduced ladybird beetle, Coccinella septempunctata L., were present at Wood Islands and Green Point, Prince Edward Island, in wrack consisting primarily of Zostera marina L. (Eelgrass). The wrack occurred in a 0.5 to 1.0 m band parallel to the shore, and was from five to 25 cm thick. The other ladybirds, Propylea quatuordecimpunctata (L.), an introduced coccinellid also found in high numbers, and an individual of the native Hippodamia tredecimpunctata (Say) were found only at Wood Islands. At both sites the ladybird beetles occurred in the mid-intertidal zone along at least 100 m of shoreline, and were absent to rare on the terrestrial vegetation above the high tide mark. At four of the other eight sites surveyed, occasional individuals were present in the wrack, but they were no more abundant than could be observed on landward vegetation. Mean densities of C. septempunctata at the two primary sites were 52 m(-2) (Green Point) and 410 m(-2) (Wood Islands).
Abstract: A rhizomatous growth form of Codium fragile is described for the first time. Plants were collected in the Gulf of St. Lawrence in estuaries dominated by Zostera marina. Rhizomatous plants developed from propagules of whole plants that settled horizontally. Horizontal axes of C. fragile were up to 1 m long in plants collected in situ. Plants developed several to dozens of erect axes at right angle to the base. Horizontal growth of up to 0.2 m was found in field experiments where fragments were tied to plastic mesh and left in situ for 4 months. The unconsolidated filaments at the base of C. fragile often wrapped around the rhizomes of Z. marina and up to five separate attachment sites to eelgrass were found in single plants of C. fragile. In four estuaries, 57-100% of Codium plants with identifiable substratum were attached to shoots and rhizomes of Z. marina. The rhizomatous growth form was found in plants identified as C. fragile ssp. tomentosoides (Nova Scotia and Prince Edward Island) and C. fragile ssp. atlanticum (Prince Edward Island), suggesting that this is a phenotypic response to growth in soft bottom environments.
Abstract: Continuous exposure for 7-10 days to 60% of ambient levels (sea level at mid-day in December) of UV-A and UV-B radiation caused cytological damage to regenerating fragments of Griffithsia pacifica under laboratory conditions. There was high mortality of individual cells and entire fragments in UV treated filaments. Rhizoid initiation was slower and rhizoids grew more slowly following UV treatment. After 7 days, UV radiated thalli showed chloroplast and nuclear degeneration. In addition, filaments tended to disarticulate so that single or groups of apparently healthy cells were common in the medium. These data suggest that the subtidal habitat of G. pacifica is based in part on lack of tolerance to UV radiation, and that UV protection mechanisms are not inducible or insufficient to prevent the accumulation of damage in this species.
Abstract: Weekly determination of cell number and cell volume of phytoplankton (excluding picoplankton) was carried out over a 13 month period (August 1996 to August 1997) in Pomquet Harbour. Nova Scotia, Canada, in the southern Gulf of St Lawrence. Eighty-eight species were identified, of which 72 species contributed 0.1% or more to the cell volume from all sampling. Ten to 35 species were present at individual sampling times. and there was it 4-67% turnover in species composition from week to week. This turnover may be a function of low species diversity (Hâ = 0.06-2.59), low phytoplankton abundances (mean of 76 cells ml(-1)) and high flushing rates in Pomquet Harbour. A Summer nutrient increase was correlated with a summer phytoplankton bloom in August of two successive years, in which at least 80% of cell volume was contributed by Ceratium fusus (1996) or Gonyaulox spinifera (1997). A fall bloom of Skeletonema costatum contributed 52% of cell counts. but only 3.2% of cell volume. Nutrients and phytoplankton populations were lower than comparable lagoon systems of Cape Cod. but similar to another site from the Gulf of St Lawrence. multivariate analyses (cluster and principal component analyses) showed four distinct phytoplankton seasons: summer (July, August), fall (September to mid-December). winter (mid-December to April) and spring (May, June).
Abstract: Over 90 species of herbaceous dicotyledonous plants, representing 62 genera and 19 families, were recorded in blossom from northern Nova Scotia, Canada, during November and December 2001. Most observations were made during 10-20 November, but 29 species were in flower after 10 December. The number of species flowering declined steadily with time, rather than declining precipitously after the first frost. Only 6 of these 92 species are specifically reported in the floras of Nova Scotia as flowering in November. Examination of plant collections in the primary Nova Scotia herbaria showed that our collections represent the latest flowering records for all but one of these species in Nova Scotia. Accordingly, our collection extends the known flowering times for these species by an average of 45 days. For most species the late flowering is interpreted as an extension of normal phenology in response to unusually warm autumn weather, but for some species (e.g., Viola cucullata, Ranunculus acris, Fragaria virginiana) it appears to represent a second flowering period. Our collections establish a base line of late flowering times that could be used as an indicator of regional climate change.
Abstract: Agalinis kingsii (Scrophulariaccae) is a rare Grand Cayman species that is poorly known taxonomically and ecologically. Sampling in 1999 suggested that approximately 43,000 individuals occurred within a single 500,000 m(2) sedge wetland habitat in the Salina Reserve and that approximately 500 plants occurred in a 9 m(2) location in the Central Mangrove Wetland. For every tenth individual located during the population count in the Salina Reserve, vegetation community associations, environmental parameters, and individual morphology were noted. Based on the findings, we suggest that rarity is a consequence of habitat availability. Since both populations were found within a narrow geographic and ecological range, we conclude that this species may be sensitive to extinction via a stochastic event.
Abstract: Intraplant variation in nuclear DNA content was quantified in DAPI-stained cells of Laminaria saccharina and Alaria esculenta. In both species, meristoderm. cortical and medullary cells were examined from vegetative fronds. In addition, DNA was quantified during sporogenesis, in free-swimming zoospores and gametophytes of A. esculenta. Zoospores and gametophytes had 1C (= N) levels of nuclear DNA in all cells, but vegetative bells of sporophytes varied from 2C to 16C. In A. esculenta nuclear DNA was significantly, correlated with cell length, total cell volume and nuclear volume,whereas in Laminaria saccharina these correlations were not apparent. During sporogenesis of Alaria esculenta, maximal nuclear DNA levels of 8C were present in post-meiotic nuclei. During four subsequent mitotic divisions (to form 64 zoospores per sporangium at the 1C level) only one cycle of DNA synthesis occurred. These results show that mitosis can be independent of DNA synthesis in Laminariales, and that endopolyploidy is a generalized feature of multicellular plants.
Abstract: Within twelve years of its discovery in 1989 on the south shore of Nova Scotia, Codium fragile (Suringar) Hariot is now dispersed in eastern Canada at sites along over 1200 km of shoreline in Nova Scotia, New Brunswick and Prince Edward Island. Collections of plants from eight sites in the summer of 1999 showed considerable morphological variation. Plants were described using 12 macroscopic features of whole thalli and nine microscopic features associated with utricles. Statistical analyses showed two groups of populations: one group with smaller, regularly dichotomous thalli (morphotype A), and the other group with larger, more irregularly branched thalli (morphotype B). The smaller thalli had flat-topped utricles with small mucrons, whereas the larger plants had utricles with more lanceolate tips and larger mucrons. Cluster analysis and principle component analysis largely distinguished these forms. The larger plants are typical of C fragile ssp. tomentosoides (Van Goor) Silva whereas the smaller plants have features more characteristic of C fragile ssp. atlanticum (Cotton) Silva. Whether these different morphologies represent independent introductions, or patterns of phenotypic plasticity adaptating to local environments remains to be established.
Abstract: Mean numbers of migrant Canada geese (Branta canadensis) in Antigonish Harbour in the southern Gulf of St. Lawrence (Canada) during October to December were similar (approx. 450-500 birds) for the period 1998-2000. Similarly, during this period, geese used two foraging sites. However, in 200 1, the average number of birds decreased by half and the primary foraging sites were used only rarely. This coincided with a decline of about 95% in the biomass of roots and rhizomes of eelgrass (Zostera marina) that occurred between October 2000 and 2001. Eelgrass is the principal food of geese in this estuary. In addition, there was a reduction of around 50% in the numbers of common goldeneye (Bucephala clangula), which feed on invertebrates associated with eelgrass. Lower than usual weekly abundances of geese and goldeneye are probably the result of an unusually short residence time in the estuary, rather than a decline in the total number of visiting migrants. We attribute these changes in the distribution and abundance of geese and goldeneyes to the dramatic decline in eelgrass.
Abstract: Apoptosis is demonstrated for the first time in red algae, in the trichoblasts of Polysiphonia harveyi. Trichoblasts. which form at the apex of each vegetative axis, undergo a series of rapid cell divisions to form colourless. branched filaments of 10-15 uninucleate cells that are c. 50 mum long upon completion of mitoses. The 4â-6-diamidino-2-phenolindole (DAPI) staining of nuclei shows that cells in trichoblasts that have just finished dividing have more DNA than apical cells of indeterminate axes. The trichoblasts do not then divide further, but undergo considerable cell elongation until they are 500-1000 mum long. They are then shed. leaving a characteristic sear cell along the branch axes. During cell elongation, nuclear DNA content in trichoblast cells decreases to c. 25% of maximal levels. with a greater than 50% decrease in nuclear volume. Many large trichoblast cells have no DAPI-stainable nuclei. Staining of trichoblast nuclei using a terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end in situ labelling (TUNEL)-protocol indicates that during DNA decrease there is a major increase in 3â ends of DNA. The loss of DAPI fluorescence and the increase in 3â ends demonstrate that these cells are apoptotic.
Abstract: Spermatogenesis is a morphogenetic system in plants that is unparalled in its potential to yield diverse and informative structural and developmental data. The unquestionable homology of terrestrial plant spermatozoids to each other and to gametes of related lineages allows an examination of cellular evolution and provides sound data for phylogenetic analyses. In this review we examine the architecture and ontogeny of motile male gametes among major groups of land plants. We begin with a historical perspective that emphasizes the utility of spermatogenesis in understanding cellular evolution and in determining phylogenetic relationships. A cladistic analysis of data based solely on spermatogenesis and a conceptual phylogeny based on combined morphological and molecular data serve as the basis for the comprehensive discussion of architectural and developmental features of plant spermatozoids. Spermatozoids of green plants have two fundamental architectural designs: biflagellated or multiflagellated. Biflagellated gametes vary among basal archegoniates and charophytes in degree of coiling, position, and substructure of the basal bodies and number of organelles. Hornwort spermatozoids are simple, bilaterally symmetrical, and uniquely exhibit a right-handed coil. An autapomorphy among setaphytes (a clade containing mosses and liverworts) is the production of coiled biflagellated sperm cells with dimorphic staggered basal bodies. Like bryophytes, gametes of most lycophytes are biflagellated; two exceptions are Isoetes and Phylloglossum, taxa that independently evolved multiflagellated sperm cells with approximately 20 flagella. Developmental information, especially related to the origin and development of the locomotory apparatus, are essential to determine structural homology among these taxa. Evaluation of the more complicated multiflagellated gametes of other vascular plants reveals similarities that support a monophyletic fern, Equisetum and Psilotum assemblage. Autapomorphies of this clade include the arrangement of the microtubular cytoskeleton, origin of the locomotory apparatus, and structural details of the basal bodies and multilayered structure. Sperm cell development in archegoniates involves the complete transformation of virtually every cellular component. Crucial to this process are proteinaceous elements of the cytoskeleton. Complex microtubule arrays unique to these cells include the spline, basal bodies, and flagella. The discrete microtubule-organizing centers (MTOCs) that generate these cytoskeletal arrays are equally complex and enable the examination of molecular constituents and ontogenetic modifications. The protein centrin is found in a variety of structures, including the diverse MTOCs and the locomotory apparatus. Actin plays a role in organellar shaping and positioning as well as in cytoplasmic deletion and the maintenance of spatial integrity in the mature cell. We conclude with an overview of the current and potential utility of male gametogenesis as an informative system in approaching fundamental questions relating to cellular differentiation and motility. Characterization of motility mutants will elucidate genetic control of structure-function relationships among cellular components, while biochemical and molecular investigations provide crucial data on the mechanism of development. The examination of spermatogenesis in additional taxa is essential to characterize further developmental variations. Moreover, such studies provide a more comprehensive understanding of plant biodiversity at the cellular level and lead to even greater phylogenetic resolution from this elegant morphogenetic system.
Abstract: Partial sequences of the genes coding for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) and the nuclear ribosomal small subunit (18S rRNA) were used to determine the phylogenetic position of the order Prasiolales among other members of the Chlorophyta. Sequences were obtained for seven representatives of the Prasiolales (Prasiola fluviatilis, P. furfuracea, P. linearis, two collections of P. mexicana, P. meridionalis and Rosenvingiella sp.) together with two Ulvophyceae, for which sequences were not previously available. Sequences of the representative Prasiolales were aligned with those of 17 green algal representatives for the rbcL gene and 20 for the 18S rRNA gene. Parsimony and distance analyses of the rbcL and 18S rRNA sequences indicate that the Prasiolales is a well-defined order. Parsimony and distance analyses of the rbcL gene give moderate support to an alliance with the Ulvophyceae, but support for the remaining nodes of the trees is very low to negligible. Both parsimony and distance analysis of the 18S rRNA gene provide moderate support for a relationship with the Trebouxiophyceae, which has been postulated in past studies based on cellular and ultrastructural characters. Although a large polytomy was determined by parsimony analysis containing many of the lineages within the Chlorophyta, the analyses of the 18S rRNA gene are more resolved than the rbcL gene analyses. Sequence divergence values within the Prasiolales for the rbcL gene are low (0-6.1%) compared to values among the other green algal sequences used in our analyses, confirming the cohesive nature of the order. Divergence values among the Prasiolales for the 18S rRNA gene are also low (0.4-3.8%).
Abstract: As the oldest extant lineages of land plants, bryophytes provide a living laboratory in which to evaluate morphological adaptations associated with early land existence. In this paper we examine reproductive and structural innovations in the gametophyte and sporophyte generations of hornworts, liverworts, mosses and basal pteridophytes. Reproductive features relating to spermatogenesis and the architecture of motile male gametes are overviewed and evaluated from an evolutionary perspective. Phylogenetic analyses of a data set derived from spermatogenesis and one derived from comprehensive morphogenetic data are compared with a molecular analysis of nuclear and mitochondrial small subunit rDNA sequences. Although relatively small because of a reliance on water for sexual reproduction, gametophytes of bryophytes are the most elaborate of those produced by any land plant. Phenotypic variability in gametophytic habit ranges from leafy to thalloid forms with the greatest diversity exhibited by hepatics. Appendages, including leaves, slime papillae and hairs, predominate in liverworts and mosses, while hornwort gametophytes are strictly thalloid with no organized external structures. Internalization of reproductive and vegetative structures within mucilage-filled spaces is an adaptive strategy exhibited by hornworts. The formative stages of gametangial development are similar in the three bryophyte groups, with the exception that in mosses apical growth is intercalated into early organogenesis, a feature echoed in moss sporophyte ontogeny. A monosporangiate, unbranched sporophyte typifies bryophytes, but developmental and structural innovations suggest the three bryophyte groups diverged prior to elaboration of this generation. Sporophyte morphogenesis in hornworts involves non-synchronized sporogenesis and the continued elongation of the single sporangium, features unique among archegoniates. In hepatics, elongation of the sporophyte seta and archegoniophore is rapid and requires instantaneous wall expandability and hydrostatic support. Unicellular, spiralled elaters and capsule dehiscence through the formation of four regular valves are autapomorphies of liverworts. Sporophytic sophistications in the moss clade include conducting tissue, stomata, an assimilative layer and an elaborate peristome for extended spore dispersal. Characters such as stomata and conducting cells that are shared among sporophytes of mosses, hornworts and pteridophytes are interpreted as parallelisms and not homologies. Our phylogenetic analysis of three different data sets is the most comprehensive to date and points to a single phylogenetic solution for the evolution of basal embryophytes. Hornworts are supported as the earliest divergent embryophyte clade with a moss/liverwort clade sister to tracheophytes. Among pteridophytes, lycophytes are monophyletic and an assemblage containing ferns, Equisetum and psilophytes is sister to seed plants. Congruence between morphological and molecular hypotheses indicates that these data sets are tracking the same phylogenetic signal and reinforces our phylogenetic conclusions. It appears that total evidence approaches are valuable in resolving ancient radiations such as those characterizing the evolution of early embryophytes. More information on land plant phylogeny can be found at: http://www.science.siu.edu/landplants/index.html.
Abstract: To evaluate structural homology among streamlined, biflagellated male gametes of Selaginella and bryophytes, we undertook a thorough ultrastructural study of spermatogenesis in Selaginella kraussiana (Kunze) A. Br. As in Lycopodium and bryophytes, centrioles originate as bicentrioles in the spermatid mother cell. In the nascent spermatid, a fibrous connective band is involved in the separation and rotation of the two centriolar constituents of the bicentriole. The locomotory apparatus consists of two staggered monomorphic basal bodies that originate from the centrioles and an underlying multilayered structure (MLS), including a spline of parallel microtubules and subtending elongated lamellar strip. Beneath the MLS lies the anterior mitochondrion, which elongates during development to a length of over 1.5 cellular revolutions by progressive fusion of mitochondria. Spline microtubules (MTs) increase posteriorly from one at the anterior tip to a maximum of 19 at the cell posterior. The angle between lamellar strip plates and spline MTs changes front to back from 85 degrees to 40 degrees. In the late midstage spermatid, the rounded nucleus compacts and elongates in register with spline growth. Individualization of cellular coils begins at the cell anterior and progresses posteriorly leaving a cytoplasmic mass in the region between coils. In the final stages of development, the lamellar strip regresses and the cylindrical nucleus shortens. Concomitantly, the posterior mitochondrion and plastid, containing two starch grains, are positioned alongside the spline at the posterior of the cell. In development, the spermatozoid of Selaginella more closely resembles those of pteridophytes than bryophytes. Common developmental and structural features of the locomotory apparatus among Selaginella and members of the Lycopodiaceae are consistent with a monophyletic lycopsid assemblage.
Abstract: The development of kelp gametophytes is described from field collections from the San Juan Islands, Washington from November, 1997 to March 1998. All gametophytes were endophytic in the cell walls of red algae, especially species with filamentous or polysiphonous construction. Gametophyte density ranged from a few to many hundreds of distinct individuals per host plant. Gametophytes formed extensive vegetative growths of irregularly branching filaments, mostly parallel to the host surface, consisting of up to 50 or more cells. Antheridia were formed at/or just above the surface of the host thallus. The stalked egg apparatus was perpendicular to the host surface. Following presumed fertilization, the zygotes developed with typical kelp embryology to form small epiphytic blades. The specific identity of the gametophytes is unknown, although the host plants were collected from three sites where the dominant kelp species were: a) Agarum fimbriatum, b) Nereocystis luetkeana and c) Alaria marginata, Costaria costata and Laminaria groenlandica.
Abstract: We observed kelp gametophytes endophytic in the cell walls of 17 species of red algae from the San Juan Islands, Washington, USA. Host algae were collected primarily from three sites dominated by different kelp assemblages, including (1) a subtidal site dominated by Agarum fimbriatum Harvey, (2) a second subtidal site dominated by Nereocystis luetkeana (Mertens) Postels et Ruprecht, and (3) a floating dock on which the dominant kelp species were Alaria marginata Postels et Ruprecht, Laminaria groenlandica Rosenvinge, and Costaria costata (C. Agardh) Saunders. Most hosts were filamentous [e.g. Pleonosporium vancouverianum (J. Agardh) J. Agardh, Callithamnion acutum Kylin], or polysiphonous [e.g. Polysiphonia paniculata Montagne, Pterosiphonia dendroidea (Montagne) Falkenberg]; however, similar endophytes were also observed in membranous or bladed red algae [e.g. Membranoptera platyphylla (Setchell et Gardner) Kylin, Polyneura latissima (Harvey) Kylin]. Dozens to hundreds of separate kelp gametophytes were associated with single host thalli. In many cases, the gametophytes developed conspicuous oogonia raised above the thallus surface on characteristic stalks. Presumed zygotes developed through typical embryonic stages into juvenile sporophytes. We argue that the endophytic habit plays an important role in the biology of kelp gametophytes.
Abstract: A phylogenetic analysis of 29 species from the Laurencia complex was carried out based on 36 morphological and developmental characters. Taxa included nine species of subgenus Laurencia, 12 species of subgenus Chondrophycus and eight species of Osmundea. Chondria was the outgroup. Characters were associated with ecology(1 character), vegetative features (17 characters), male reproduction (8 characters), female reproduction and carposporophytes (3 characters) and tetrasporangia (7 characters). Twelve most parsimonious trees were produced with treelength of 148. Three large clades were resolved that corresponded to Osmundea, Laurencia subgenus Laurencia and Laurencia subgenus Chondrophycus. Subgenus Chondrophycus was resolved as the sister group of Osmundea. The position of L. translucida Fujii & Cordeiro-Marino is problematic, but it is probably allied to Chondrophycus. Chondrophycus is raised to generic rank and 12 new combinations in Chondrophycus are proposed.
Abstract: Seasonal and spatial variations of subtidal algae are described from Daedo Island in southern Korea based on quantitative and qualitative estimates of species occurrence in three habitats: shelf, crest and drop off Maximum species diversity occurred during the winter. Perennial algae, including Gracilaria textorii, Ecklonia cava cmd Undaria pinnatifida became particularly abundant in spring. There was a dramatic increase in crustose red algae and Cyanobacteria in the summer. As autumn approached the cover of large perennial species decreased. In general, the number of species decreased with increasing depth. The subtidal shelf habitat showed an assemblage of bushy or thin-bladed forms such as Ulva pertusa, Sargassum thunbergii and Corallina officinalis. Sargassum horneri, S. confusum, Undaria pinnatifida and Mayagropsis myagroides had high cover in the crest habitat. Gracilaria textorii and Ecklonia cava occurred only on the crest and drop off habitats. Sampling at this site in the autumn of 1995 relative to the autumn of 1994 showed about a 50% decline in number of species, with a further decline by the autumn of 1996. These changes are attributed to increased sediment load and scouring resulting from heavy construction in the area (coal-fired power plant). Despite these perturbations, the basic pattern of seasonal cycling, as modeled with principal component analysis, was maintained during the 1995-1996 sampling period.
Abstract: Reciprocal crosses between male and female gametes of Ascophyllum nodosum (L.) LeJolis and Fucus vesiculosus L. were made from plants collected at Tor Bay, Nova Scotia. Crosses within each species were viable and resulted in normal zygote development. Hybrids occurred in low frequency in the cultures (ca. 1-5%) and developed either an initial rhizoid or underwent one or two internal divisions. Hybrid zygotes did not develop further. More developing embryos were observed in crosses when F. vesiculosus provided the eggs, and these zygotes developed longer rhizoids. Maximum development was to three or four cells, which occurred in ca. 10 days. By 5 weeks, all zygotes had disintegrated. Nuclear diameter was the same in both species (6 mu m) although almost twice as much nuclear DNA was present in A. nodosum than in F. vesiculosus. Nuclei in hybrids were larger than in the parental species.
Abstract: At maturity, spermatozoids of the green alga Chara vulgaris are biflagellated, anterior of the cell contains an ovoid headpiece anchoring two slightly staggered basal bodies that are positioned above and directly in front of approximately 30 linearly arranged mitochondria. An elongated stellate pattern occupies the transition zone between the BBs and axonemes. Flagella emerge from the cell just in front of the nucleus and encircle the full length of the spermatozoid. The spline comprises a maximum of 38 microtubules surrounding the anterior mitochondria and gradually decreases posteriorly to a minimum of 11. The dense nucleus is narrow, cylindrical, and occupies the central revolution of the cell. Six starch-laden plastids and associated mitochondria are linearly arranged at the cell posterior. Phylogenetic analyses of charalean taxa and archegoniates based on spermatogenesis strongly support the order Charales, with Nitella as the sister group to Chara. Diagnostic features of Chara spermatozoids include absence of a lamellar strip and axonemes embedded in the cell for almost the entire length of the anterior mitochondria. Potential relationships among Charales, Coleochaetales and archegoniates are evaluated in regards to the probable course of evolution of streamlined biflagellated gametes.
Abstract: The subtidal marine algal flora of northern Senegal has been characterized based on a literature review and collections made during December and February, 1993-94. At present, 242 species are listed from northern Senegal of which 80 species were found in this study (16 Chlorophyta, 12 Phaeophyta and 52 Rhodophyta). This includes 29 species not previously recorded for Senegal and 8 species previously unknown from West Africa. The biogeographic affinities of Senegal are primarily with the more temperate floras to the north, and there is a sharp transition in species composition between northern Senegal and regions to the south. The relative absence of tropical species is explained by southward directed ocean currents and the occurrence of major areas of brackish water and mangrove communities to the south.
Abstract: The spermatozoid of Lycopodiella lateralis (R. Br.) B. Ollgaard is ovoid and biflagellated and contains little cytoplasm. A large, rounded, condensed nucleus occupies the central region of the cell. At the rear of the cell is a cluster of starch-containing plastids associated with numerous elongated mitochondria and small pockets of remnant cytoplasm. The multilayered structure coils laterally around the cell anterior for just over one revolution. An anterior mitochondrion underlies the multilayered structure over its entire length and several smaller mitochondria line the inner anterior coil. Some 150 spline microtubules extend from the multilayered structure and coil posteriorly at approximately a 45 degrees angle to the longitudinal axis of the cell. Microtubules progressively increase in length from the margins of the multilayered structure to the center and thus only a central core of approximately 30 microtubules encircles the organelles at the base of the cell. The two basal bodies are parallel and staggered in their position over the multilayered structure and are separated by about 80 degrees around the circumference of the cell anterior. The flagella emerge in parallel and coil for nearly two revolutions. Comparisons among Lycopodiella, Palhinhnea, and Lycopodium provide the basis for evolutionary inferences associated with modifications in spermatozoid structure such as changes in cell size, whole cell coiling, and distance between basal bodies. Phylogenetic analysis of male gametogenesis suggests that Lycopodiella is part of a monophyletic lycopsid assemblage near the base of the vascular plants. Within this clade, Lycopodiella is most closely related to Palhinhaea, with Lycopodium, Phylloglossum, and Selaginella forming a sister clade.
Abstract: Codium fragile (Suhr) Harlot ssp. tomentosoides (van Goer) Silva is reported for the first time from the Gulf of St Lawrence in Nova Scotia based on collections made in August 1996. Three drift thalli were collected initially from the southeast corner of Doctor Island, Caribou Harbour. Later an extensive subtidal population extending over 0.5 km(2) was located in the adjacent subtidal zone (1 m) associated with a former oyster lease. The habitat was a soft bottom embayment dominated by Zostera marina, and the Codium fragile was found as scattered individuals in scours in the Z. marina bed. The potential ecological impact of C. fragile on community structure and human activities in the southern Gulf of St Lawrence is discussed.
Abstract: The dinoflagellate Haidndinium ichthyophilum gen.nov. et sp.nov. is associated with the threespine stickleback, Gasterosteus aculeatus L., in freshwater. This new genus differs from all previously described dinoflagellates in the morphology and ultrastructure of its complex life history stages and in the ecology of its interaction with G. aculeatus. Distinguishing characters included (i) the absence of thecal plates and the occurrence of chloroplastes in the short-lived swarmer (=dinospore) stage; (ii) the development of four distinct amoeboid stages including a spheroidal, rolling amoeba unknown in any other species; and (iii) the fact that this dinoflagellate causes epithelial hyperplasia in the stickleback and does not result in massive fish kills. Haidadinium ichthyophilum is known only from two acidic lakes in the Queen Charlotte Islands, British Columbia, Canada. Haidadinium is tentatively assigned to the family Phytodiniaceae of the order Phytodiniales.
Abstract: Using rhodamine-phalloidin to detect F-actin/microfilaments and indirect immunofluorescence to detect tubulin/microtubules, we studied the cytoskeleton in axial cells of Ceramium strictum Harv., especially microfilaments and microtubules associated with cytoplasmic strands (trabeculae) that extend longitudinally through the central vacuole. As axial cells attained mature size, trabeculae became progressively thinner, branched, and then broke down. An extensive microfilament array was present in peripheral parts of axial cells as well as in trabeculae. Microfilament array were highly disrupted by cytochalasin-B; this resulted in small irregular actin structures in axial cell peripheries and occasional dense aggregations at the base of cells. No actin-fluorescence was detected in intact trabeculae after cytochalasin-B treatment. Microtubules formed a primary structural component in trabeculae, which were disrupted by griseofulvin (5 to 0.005 mu M) but reformed after two days in griseofulvin-free medium.
Abstract: Actin rings are demonstrated for the first time in florideophyte red algae in Audouinella botryocarpa (Acrochaetiales) and Tiffaniella snyderae and Griffithsia pacifica (Ceramiales). Rings formed a complete circle in the peripheral cytoplasm prior to the development of the septum by furrowing. In the uninucleate A. botryocarpa, ring formation precedes mitosis. In all species F-actin initially has a diffuse to longitudinal alignment throughout the cell. The actin realigns and then contracts to form a dense actin ring. Following cell division, aggregations of actin are maintained along the transverse wall in at least G. pacifica and A. botryocarpa, and a dense ring of actin was observed around a pit plug in T. snyderae. The occurrence of actin rings in cell division of members of the Acrochaetiales and Ceramiales is consistent with ultrastructural observations on red algal unicells and suggests that actin rings are part of the ancestral cytokinetic mechanism in red algae.
Abstract: The shapes of 51 fronds from three species of brown algae (Fucus vesiculosus, Fucus serratus and Ascophyllum nodosum) were evaluated by computing the fractal dimensions (D) of their outlines. There was no difference in fractal dimension among mature fronds of the three species, and D tvas highly correlated with both developmental stage and structural complexity. With increasing age the plants grew not only larger but also more complex in form. Fractal dimension increased systematically with increasing complexity of shape from about 1 to 1.6. Fractal dimension thus provides a useful quantitative measure for the elaboration of shape complexity during plant development.
Abstract: Laboratory studies were carried out with Ascophyllum nodosum (L.) Le Jolis in which zygotes were either infected or not with its mycobiont Mycosphaerella ascophylli Cotton. Zygotes were continuously immersed or desiccated for 1, 2, 4 or 8 h per day. The survival, growth and morphology were examined after 12 weeks. Infection with M. ascophylli improved zygote growth at 1 h desiccation relative to non-infected thalli and non-desiccated thalli. In non-desiccating conditions, zygotes infected with M. ascophylli had lower rhizoid numbers; however, the 1 and 2 h desiccation treatments increased rhizoid production to levels in non-infected thalli. These results suggest that M. ascophylli has a role in protecting A. nodosum zygotes from desiccation, and that desiccation influences rhizoid production.
Abstract: The first developmental studies of Ascophyllum nodosum are presented in which zygote development is compared in thalli with and without endophytic Mycosphaerella ascophylli. In cultures where 24 h A. nodosum zygotes were inoculated with ascospores of M. ascophylli, 20-50% of the zygotes developed differently from control cultures without ascospores, with later infections (at 1-3 weeks) having little effect. Morphological differences were apparent within one month when infected thalli were ovoid and non-infected thalli were clavate. In addition, infected thalli were longer, had greater apical diameters, more apical hairs, and fewer and shorter rhizoids than non-infected thalli, the development of which more closely resembled other fucoid species. Differences between infected and non-infected individuals became more pronounced with development. After eight months there was a four-fold difference in thallus length, and morphologically transformed thalli had endophytic fungi. This transformation provides the first experimental evidence for an obligate, mutualistic symbiosis between A. nodosum and M. ascophylli.
Abstract: Vegetative and reproductive development of some European and Californian species of Laurencia Lamouroux (Ceramiales, Rhodophyta), L. obtusa (Hudson) Lamouroux, L. spectabilis Postels et Ruprecht, L. crispa Hollenberg, L. osmunda (S.G. Gmelin) Maggs et Hommersand, L. pinnatifida (Hudson) Lamouroux and L. truncata Kutzing, is investigated on the basis of liquid-preserved and herbarium specimens. The latter five species share several features, but they differ distinctly from L. obtusa, the lectotype of the genus, in essential anatomical characters of vegetative and male reproductive structures and tetrasporangial development. In these five species each vegetative axial segment produces two rather than four pericentral cells, and spermatangial branches (filaments) are produced in apical pits of branchlets from apical and epidermal cells rather than from trichoblasts arising from axial cells. The spermatangial branches are usually branched alternately and usually terminate in a cluster of several large sterile vesicular cells, rather than being branched dichotomously and terminating in a single, or occasionally a row of two, large sterile vesicular cells as in L. obtusa. Apical spermatangial pits of fertile male branchlets (except for those in L. truncata) are pocket- (or urn)-shaped, with an ostiole-like upper opening, rather than cup- (or bowl)-shaped. In these five species tetrasporangia are produced laterally from random epidermal cells rather than abaxially from particular pericentral cells (the third and fourth ones) as in L. obtusa, and the two presporangial cover cells are aligned parallel rather than transverse to the stichidial axis in surface view. These important differences strongly suggest that L. spectabilis, L. crispa, L. osmunda, L. pinnatifida and L. truncata occupy a phylogenetically different position from L. obtusa, and lead to the conclusion that the genus Osmundea Stackhouse, which was based on 0. expansa Stackhouse, nom. illeg. (= Laurencia osmunda) and which has been a nomen rejiciendum as an earlier facultative synonym of Laurencia, should be resurrected. Emendations of the generic criteria of Laurencia and Osmundea are proposed here, and relevant nomenclatural changes for several Laurencia species are also included.
Abstract: Considerable progress has been made recently, based on classical morphological characters and newly described ultrastructural features, in understanding the phylogenetic relationships of the tracheophytes to the green algae and bryophytes. Recent technological advances in molecular biology, particularly the advent of the polymerase chain reaction (PCR), have allowed nucleotide sequence data relevant to such large-scale phylogenetic questions to accumulate, especially ribosomal RNA gene sequences (both the large and small subunits) from the nucleus and the chloroplast. We present synthetic cladistic analyses of the green plants that combine and compare available morphological and molecular data sets. Although the resulting phylogenies are poorly resolved in some areas at present, certain conclusions are supported: (1) The green plants are composed of two major monophyletic groups, one containing the ââcharophyteâ green algae and the land plants (i.e., ââbryophytesâ plus tracheophytes), the other containing the bulk of the classically delimited ââgreen algaeâ (chlorophytes, pleurastrophytes, and ulvophytes). (2) The land plants are a well-supported monophyletic group, but neither the specific outgroup for the land plants nor the precise relationships among basal lineages of land plants are clear. In many analyses (including the combined molecular and morphological analysis) the three major lineages (i.e., liverworts, hornworts, and mosses) appear to be paraphyletic with respect to the tracheophytes, with an indication that the mosses alone may be the sister group of the tracheophytes; however, in other analyses the ââbryophytesâ are supported as a monophyletic group. (3) The ulvophytes, chlorophytes, and pleurastrophytes are each supported as monophyletic (with the exception of a few taxa that may be misplaced in the current classification), with the topology: [ulvophytes [chlorophytes + pleurastrophytes]]. Combined analyses of molecular and morphological data offer the greatest potential for resolving these relationships.
Abstract: Spore production and viability were studied in Chondrus crispus based on monthly samples from June to October 1991 at Tor Bay on the Atlantic coast of Nova Scotia. Random collection of fronds showed a gametophyte : tetrasporophyte ratio of about 3 : 1. Two reproductive periods were distinguished based on number and diameter of cystocarps and number of tetrasporic sori g-1 frond weight, with reproductive fronds in June and July having larger and fewer cystocarps, and fewer tetrasporic sori g-1 than fronds collected from August to October. The pattern of daily spore release was variable among months. Spore viability varied between monthly means of 4-16% for carpospores and 6-26% for tetraspores, with maximum viability in June and August for carpospores and tetraspores, respectively. Variation in spore viability occurred at all levels: among cystocarps or tetrasporangial sori on the same frond, among different fronds, and among months. Such variation provides additional levels of complexity that need to be more fully explored if the extent and timing of spore production to actual reproductive success in C. crispus (or any other seaweed) is to be fully understood.
Abstract: Lindenmayer systems (L-systems) are used to model the structure and development of several species of seaweed. The agreement between the images produced by the models and the actual plants is very good. Two species exhibit the fractal property of self-similarity to at least four levels of recursion. The possibility of a relation between the L-systems coding and the biological coding mechanism is noted.
Abstract: Rhodamine-phalloidin was used to label F-actin in unfixed cells of 13 species of filamentous and blade-forming red algae from the three families Ceramiaceae, Acrochaetiaceae and Bangiaceae. Labelling was achieved only after treatment with either beta-glucuronidase or a combination of cellulase and an extract of snail gut enzyme. Different species required different enzyme treatments and incubation times for successful labelling. All species examined showed extensive arrays of F-actin which generally are confined to the peripheral cytoplasm and are oriented longitudinally. Transverse arrays are present beside the crosswalls of Griffithsia pacifica, and Audouinella species show actin concentrations at the tips of apical cells and in developing branch initials.
Abstract: A cladistic analysis was carried out to resolve phylogenetic pattern among bryophytes and other land plants. The analysis used 22 taxa of land plants and 90 characters relating to male gametogenesis. Coleochaete or Chara/Nitella were the outgroups in various analyses using HENNIG 86, PAUP, and MacClade, and the land plant phylogeny was unchanged regardless of outgroup utilized. The most parsimonious cladograms from HENNIG 86 (7 trees) have treelengths of 243 (C.I. = 0.58, R.I. = 0.82). Bryophytes are monophyletic as are hornworts, liverworts, and mosses, with hornworts identified as the sister group of a liverwort/moss assemblage. In vascular plants, lycophytes are polyphyletic and Selaginella is close to the bryophytes. Lycopodium is the sister group of the remaining vascular plants (minus Selaginella). Longer treelengths (over 250) are required to produce tree topologies in which either lycophytes are monophyletic or to reconstruct the paraphyletic bryophyte phylogeny of recent authors. This analysis challenges existing concepts of bryophyte phylogeny based on more classical data and interpretations, and provides new insight into land plant evolution.
Abstract: Cytoskeletal components have been visualized for the first time in red algae using fluorescent labelling. Rhodamine-phalloidin was used to stain actin in a variety of filamentous species: Griffithsia pacifica, Tiffaniella snyderae, Ceramium strictum, Antithamnion kylinii (Ceramiales) and Audouinella dasyae (Acrochaetiales). immunofluorescent labelling of microtubules was obtained only in Griffithsia pacifica. In both procedures, successful labelling was achieved only after wall digestion with glucuronidase and protocols using cellulase resulted in no labelling. Both microfilaments and microtubules formed extensive arrays in the peripheral cytoplasm of Griffithsia. Microtubules were associated with nuclei in these highly multinucleate cells, suggesting that they maintain the extremely regular nuclear arrangement. Dense labelling of microfilaments occurred at rhizoid apices, however, this was not observed in apical cells, suggesting that two distinct mechanisms of tip growth may be present. Of the algae studied, only Griffithsia formed extensive peripheral arrays of microfilaments in all cells; the remaining genera showed actin labelling in a variety of different structures including, long and short âropesâ of varying thicknesses, basket-like structures and âspikesâ. In Griffithsia extensive actin staining was often associated with the pit plugs between adjoining cells. Cytoskeletal components often showed a polar distribution with denser labelling towards the bases or apices of cells. In dividing apical cells of Griffithsia, a band of microfilaments was observed prior to deposition of the new cross wall. These preliminary results suggest that cytoskeletal studies will provide important insights into understanding development and cell function in red algae.
Abstract: Experiments were conducted to examine the survival of spores, sporelings and apical fragments of Polysiphonia lanosa and the interactions between P. lanosa and potential fucoid hosts (Ascophyllum nodosum and Fucus species). In culture there was no dependency of P. lanosa on A. nodosum for spore germination. Apical fragments of P. lanosa survived longer (half life of over 194 versus 85 days and 119 versus 85 days) in cultures in which fragments of A. nodosum or Fucus vesiculosus were present. Thus substances from fucoids are likely involved in this improved survival. When apical fragments of P. lanosa were artificially attached to fragments of A. nodosum, F. vesiculosus and F. serratus, these survived longer than free-living fragments in the same tank (half lives of 68, 89, 89, 20 days, respectively). Similar survival rates of sporelings of P. lanosa artifically attached to the three fucoids support our previous conclusion that host specificity of P. lanosa is based on ecological factors that restrict recruitment on to Fucus spp., rather than a biochemical dependency that requires A. nodosum.
Abstract: Four fluorescent brighteners (Fluorescent Brightener 28, Fluostain 1, Fluostain II and Cellufluor) were examined with respect to their binding affinity, toxicity (their ability to stunt growth), and teratogenic effects on the red alga Antithannion kylinii. Maximum binding occurred with FB-28 and F-II but these stains showed the greatest inhibition of growth when plants were exposed to concentrations of 0.01% for 30 min. Filaments incubated in low stain concentrations (0.0005%) showed cell abnormalities with all stain types, with FB-28 producing the most extreme deformations of both intercalary and apical cells. The experiments suggest that extensive experimentation is required to develop protocols for vital cell wall stains that minimize toxicity and maximize binding.
Abstract: Antithamnion makroklonion sp. nov. is described from Elat, Gulf of Aqaba (Gulf of Elat) in the Red Sea, where vegetative, spermatangial, and tetrasporangial specimens were found growing in the upper sublittoral zone. The new alga belongs to a group of Antithamnion species characterized by distichous-alternate ramification of branches, sessile tetrasporangia, and decussately arranged laterals along the bearing axis. It shows a unique combination of distinctive features, including the proximal development of gland cells on elongate branchlets that overtop the parent branch. In addition to the characteristic position, and in contrast to congeners, gland cells of A. makroklonion often have a large and prominent cytoplasmic band and one or two vacuoles. Morphological features of A. makroklonion and eight related species are tabulated and the characteristics of the new species are discussed.
Abstract: A cladistic analysis of the orders of Rhodophyta is presented. Sixteen taxa and 34 characters comprise the data matrix. Included in the analysis are biochemical and ultrastructural features of pigments, cell walls, cell organelles, mitosis and pit connections as well as vegetative and reproductive characters. The traditional recognition of two classes or subclasses, Bangiophycidae and Florideophycidae, is not supported regardless of whether Porphyridiales, Rhodochaetales or Bangiales is designated the outgroup. Florideophycidae, however, appears to be monophyletic with Bangiales as its sister group. Relationships among taxa with one or two plug cap layers, i.e. Acrochaetiales, Palmariales, Corallinales, Nemaliales, Batrachospermales, Gelidiales and Hildenbrandiales are unresolved. Rhodochaetales, Bangiales and possibly Erythropeltidales are monophyletic, but Porphyridiales is polyphyletic. The class Cyanidiophyceae is not recognized and the included genera are considered to be unicellular red algae belonging to Porphyridiales. Taxa that have been proposed as sister groups for red algae, including Cyanobacteria, Cryptophyta, Glaucophyta and Chlorophyta, and Ascomycetes and Basidiomycetes are discussed in relation to the proposed phylogeny of Rhodophyta.
