Senior lecturer and researcher of parasitology and invertebrate biology. Areas of research interest include fish parasitology and pathology, aquatic biomonitoring and ecotoxicology, and invertebrate biodiversity.
Abstract: Macrogyrodactylus spp. from the gills of Clarias gariepinus in Zimbabwe and Kenya, and C. anguillaris in Senegal were
identified using haptoral sclerite morphology and by sequencing the nuclear ribosomal DNA internal transcribed spacers
(ITS) 1 and 2, partial 18S and the complete 5.8S rRNA gene. A molecular phylogeny was constructed using all sequenced
Macrogyrodactylus species to date. Based on morphology, Macrogyrodactylus congolensis, M. heterobranchii, M. clarii, and
M. karibae were identified, with one specimen from Zimbabwe displaying morphological features that were intermediate
between M. heterobranchii and M. clarii. In the intermediate form, the partial 18S and ITS1 sequence was identical to that
of M. clarii while the remaining ITS1 and complete ITS2 region was almost identical to M. heterobranchii as was the partial
cox1 fragment, thus strongly suggesting a hybrid origin. At present, the catfish host of M. heterobranchii and M. clarii do not
co-occur in southern Zimbabwe; this hybridization event is therefore proof of historical sympatry of both fish species.
Abstract: The relationship between parasite species diversity and organic pollution in the upper Manyame catchment, Zimbabwe, was investigated between October 2006 and January 2007. The parasite assemblage comprised thirteen species in total. Species richness was high in the unpolluted sites; low in the moderately polluted sites, while only one parasite species was encountered in the polluted sites. Component community diversity, as measured by Shannon-Wiener (Hâ) decreased with increase in organic pollution. The distribution and occurrence of ectoparasites (Dolops ranarum, Lamproglena clariae, Chonopeltis fryeri, Macrogyrodactylus clarii.) and the cestode, (Lytocestus spp.) was limited to the unpolluted sites demonstrating their sensitivity to organic pollution. The prevalence of the nematodes Paracamallanus cyathopharynx, Procamallanus laevionchus and Contracaecum spp. larvae decreased along the pollution gradient showing their high sensitivity to organic pollution. The platyhelminths Diplostomulum spp. and Polyonchobothrium clarias were the most tolerant and occurred at both polluted and unpolluted sites. Proteocephalus spp. and Caryophylleaus spp. were limited to the polluted sites, probably because of high abundance of oligochaetes and copepods, their intermediate hosts, at the downstream sites due to sewage - enriched sediments. Observed results assume that the decrease in parasite diversity can be attributed to increased organic pollution. Some parasites requiring complex life histories were absent along with pollution related disappearance of their vector hosts. Further studies should address the identification of parasite life stages that are more sensitive to pollutants.
Abstract: A new proteocephalidean cestode is described from 2 catfishes, Clarias gariepinus (type host) and C. cf. anguillaris (Siluriformes: Clariidae), from Ethiopia (type locality), Sudan, Tanzania, and Zimbabwe, and a new genus, Barsonella, is proposed to accommodate it. The genus belongs to the Proteocephalinae because its genital organs (testes, ovary, vitellarium, and uterus) are situated in the medulla. Barsonella lafoni, the type and only species of the new genus, is characterized mainly by the possession of an additional opening of each sucker; circular musculature on the anterior margin of suckers, serving as a sphincter; a small thin-walled glandular apical organ; absence of well-developed osmoregulatory canals in mature, pregravid, and gravid
proglottids; and a large strobila, up to 173 mm long and 3.2 mm wide. Species of Marsypocephalus Wedl, 1861 (Marsypocephalinae), other large-sized proteocephalidean tapeworms occurring sympatrically in African catfishes (Clarias and Heterobranchus) and also possessing a sphincter-like, circular musculature on the anterior part of suckers, differ from B. lafoni in the absence of an additional sucker opening and glandular apical organ, the cortical position of the testes, well-developed osmoregulatory canals throughout the strobila, and a large cirrus sac. Proteocephalus glanduligerus (Janicki, 1928), another cestode parasitic in Clarias spp. in Africa, is much smaller than B. lafoni (maximum length 15 mm), has suckers without additional opening and circular musculature on the suckers, a large-sized glandular organ, much larger than suckers, and well-developed osmoregulatory canals. Comparison of partial sequences of the 28S rRNA gene for 7 samples of B. lafoni from 2 different hosts and 4 localities in Ethiopia, Sudan, and Tanzania has shown a very low genetic variability. In a limited phylogenetic analysis, B. lafoni formed a clade with Corallobothrium solidum Fritsch, 1886 (Proteocephalidae: Corallobothriinae), an African electric catfish parasite. This clade was the sister group of almost all Neotropical taxa from pimelodid and other catfishes.
Notes: This genus of tapeworm was given in honour of Maxwell Barson, fish parasitologist from Zimbabwe who first discovered this tapeworm in Lake Chivero, Harare, during his masters project, but wrongly identified is as a Proteocephalus species.
Abstract: Dynamics of flooding and drying resulting in fragmentation of lotic habitats are a yearly phenomenon in subtropical floodplain rivers but theirecological significance is not known for invertebrate communities. We studied the response of zooplankton and macroinvertebrate communities in 48 dry season river pools in the Save-Runde river system (Lowveld, Zimbabwe). Patterns and ecological processes influencing invertebrate communities, taxon richness and macroinvertebrate functional richness were investigated with focus on the role of regional (connectivity) and local processes (habitat characteristics). Local factors accounted for 15% of the variability in the zooplankton community but only 3.4% for the macroinvertebrate community. Important factors affecting zooplankton densities in the pools were depth, vegetation cover and presence of fish (planktivorous and omnivorous). The presence of fish in pools can infer predation risk. Macroinvertebrate abundances were affected by the presence of fish only. Zooplankton densities increased in pools with fish while macroinvertebrate densities declined in the presence of fish. Macroinvertebrates could exert top-down pressure on zooplankton either by competition for resources or predation in pools. Regional factors significantly explained zooplankton but not macroinvertebrate community variability. Connectivity had no significant effect on local pool habitat characteristics. There were no significant differences in water quality variables between flowing river sites and the pools. Zooplankton and macroinvertebrate a- and c-diversity in dry-season pools was higher than in the flowing river. Species additions rather than species replacements by processes that include dispersal and possibly dormancy may explain increased zooplankton and macroinvertebrate taxon diversity in pools. Functional feeding group (FFG) analysis showed that the proportion of macroinvertebrate predator taxa increased significantly in pools compared to the flowing river. Pools create a more suitable and diverse habitat for these widely dispersing taxa. The other FFG were comparable between the river and pools. The pools are strongly heterotrophic. Our results confirm that habitat fragmentation may actually be beneficial for zooplankton and macroinvertebrate biodiversity in dryland rivers.
Abstract: Infestation of fish by the crustacean ectoparasite Lernaea cyprinacea Linnaeus, 1758 was investigated to establish the extent of infestation, potential effects of the parasite and its ecological adaptations. Fish samples were collected from impoundments in the Malilangwe Wildlife Reserve in the southeastern lowveld of Zimbabwe and these included the cichlids Oreochromis mossambicus, Oreochromis placidus and Tilapia rendalli, the cyprinids Labeo altivelis and Barbus paludinosus, the clariid Clarias gariepinus, the centrarchid Micropterus salmoides and the characid Hydrocynus vittatus. All the cichlids and one cyprinid (L. altivelis) were infested with L. cyprinacea. The two Oreochromis species exhibited prevalence as high as 100% and mean intensity up to 149 parasites per fish. Lernaea cyprinacea exhibited an aggregated distribution in host populations and were attached mostly to the ventral and caudal regions of hosts, while the head was the least preferred attachment site. With a few exceptions, there was no significant correlation between parasite prevalence and intensity with host size, sex, condition factor, gonadosomatic index or fecundity.
Abstract: Two freshwater fish species, Clarias gariepinus and Oreochromis mossambicus were collected from pans, dry-season pools and tributaries of the Save and Runde Rivers in the south-eastern lowveld of Zimbabwe from December 2004 until June 2006. Helminth parasites infecting these fish were isolated from the gills, skin, muscles, body cavity, gall bladder, stomach and intestines, and were examined microscopically. Adult helminths were collected from the darter, Anhinga melanogaster, a piscivorous bird, to compare and possibly link them to the larvae recovered from fish. Stomach contents of the birds were analyzed and their prey fish species were identified. Larval helminths collected include digenean metacercariae (clinostomes and strigeids), larval cestodes (gryporhynchids) and juvenile nematodes (Contracaecum). Adult worms include the monogeneans Macrogyrodactylus clarii, Macrogyrodactylus karibae and Macrogyrodactylus. congolensis, the digenean Clinostomum complanatum, the nematodes Paracamallanus cyathopharynx, Contracaecum rudolphi, Contracaecum multipapillatum and Contracaecum rodhaini; and the cestodes Polyonchobothrium clarias and Echinorhynchotaenia tritesticulata. Many of these observations are the first record of that particular parasite species in Zimbabwe or southern Africa. Morphological measurements were made and compared with the original species description; and some unique morphological features are here described.
Abstract: Catfish, Clarias gariepinus, from the Rietvlei Dam near Pretoria, South Africa were examined for nem atode parasites. Two species, Procamallanus laeviconchus in the stomach and Contracaecum spp. larvae in the abdominal cavity, were found. The morphology of these species, based on light and scanning electron microscopy, and how they compare with previously described specimens are discussed. Infection rates were mild compared to previous surveys although Contracaecum spp. had a high prevalence of 86 %.
Abstract: Sharptooth catfish, Clarias gariepinus, from the Rietvlei Dam near Pretoria, South Africa were examined for internal platyhelminth parasites. Two adult cestodes, Polyonchobothrium clarias (stomach) (prev alence 71 %, mean intensity = 5, n = 7) and Proteocephalus glanduliger (anterior intestine) (prevalence 14 %, mean intensity = 2, n = 7), were found in the gut while metacercariae of one larval digenean, Ornithodiplostomum sp. (prevalence 14 %, mean intensity = 140, n = 7), were found encysted in the muscles. The morphology of these species, based on light and scanning electron microscopy as well as histological analysis, and how they differ from previously described specimens, are discussed. Ornithodiplostomum is a new record in southern Africa. Infection levels of the host fish were mild compared to records from previous surveys.
Abstract: Clarias gariepinus were collected from Lake Chivero, Zimbabwe, and examined for nematode parasites from November 2000 to May 2002. Of the 202 specimens collected, 42.6 % were infected with third-stage larvae of Contracaecum sp. in the body cavity. The intensity of the infection was 1â7 worms per fish (mean intensity = 2.2). Seasonal variation in the prevalence of the parasite was not obvious and there was no significant difference in the prevalence of infection between males and
females (Ï2 = 2.228; P > 0.05). No significant relationship between host size and prevalence was established. There was also no significant relationship between intensity and the body condition factor (r = 0.11; P > 0.05). The low parasite prevalence may have been caused by the disruption of the infection cycle since piscivorous birds, which are the final hosts of the parasite, do not feed on C.
gariepinus in Lake Chivero.
Abstract: Endoparasites of fish-eating birds, Phalacrocorax africanus, P. carbo, Anhinga melanogaster and Ardea cinerea collected from Lake Chivero near Harare, Zimbabwe, were investigated. Adult Contracaecum spp. were found in the gastrointestinal tract (prevalence 100%in P. africanus, P. carbo and A. melanogaster; 25 % in A. cinerea). Parasite intensity was 11â24 (mean 19) in
P. africanus, 4â10 (mean 7) in P. carbo, 4â56 (mean 30) in A. melanogaster and 2 (mean 0.5) in A. cinerea. The cormorants fed mainly on cichlid fishes and carp; the darters and the grey herons on cichlids. All these fishes are intermediate hosts of Contracaecum spp. Scanning electron microscopy revealed that Contracaecum rudolphii infected both cormorant species and darters; C. carlislei infected only the cormorants while C. tricuspis and C. microcephalum infected only the darters. Parasites from the grey heron were not identified to species because they were still developing larvae. These parasites are recorded in Zimbabwe for the first time.
Abstract: We compared abundance and diversity of phytoplankton, zooplankton, and fishes among limnetic (P: always without macrophytes) and littoral habitats with (L+) and without (L-) hyacinths in Lake Chivero, a man-made hypertrophic reservoir near Harare (Zimbabwe). In addition, the littoral macrophyte community, and macro-invertebrates associated with hyacinth mats were inventoried. The phytoplankton community was dominated by blue-green algae (mainly Microcystis aeruginosa), typical for a hyper-eutrophic lake. Total absolute densities were about 10 to 30 times higher at the L+ sites than at the unvegetated L- and P sites. On the basis of relative species abundances the L- zones were more similar to the P than to the L+ zones. There was an increasing importance of chlorophytes (Staurastrum sp. and Pandorina morum) and diatoms (Cyclotella meneghiniana and pennales) and a decreasing dominance of Mycrocystis along the discriminant axis from L+, L- to P. The zooplankton community was most dense in the unvegetated zones. Daphnids and bosminids were more abundant in the pelagic than in both littoral zones. Calanoids and Diaphanosoma were dominantly represented in the unvegetated zones. The two littoral zones were characterised by higher densities of chydorids, while they could be discriminated by the dominance of cyclopoids in the vegetated site. Seventeen different fish species were captured by at least one of the different fishing methods. Apparent habitat preferences differed ac1 cording to fishing method. Generally, Oreochromis niloticus and Pharyngochromis acuticeps preferred the vegetated sites, while mature specimens of Clarias gariepinus were caught in deeper water at pelagic sites. Barbus paludinosus and Labeo cylindricus preferred the rocky shores of the lake. The smaller size classes of O. niloticus, Tilapia sparrmanii and P. acuticeps preferred the littoral zone rather than the open waters. Water hyacinth mats generally seem to have a positive effect on taxon diversity only in fishes and were the preferred sites for only a limited number of groups, mainly zooplankton (cyclopoids and Daphnia laevis) and fishes (O. niloticus and P. acuticeps). The most important function of this weed could be to offer shelter and feeding grounds for small fishes.
Abstract: Cestode parasites were collected from Barbus paludinosus from Munwahuku Dam near Harare, Zimbabwe over a period of 13
months. Plerocercoids of Ligula intestinalis were found in 7.2% of the fish. The majority of the infected fish carried one parasite,
with 3.1% having two and 1.6% with three. There was a positive correlation (r = 0.59, P < 0.05) between the weight of L. intestinalis and that of their host, but there was no significant relationship between the condition factor of the fish and the weight of the parasite, and the parasite index was low (7.97 ± 3.38) compared to previous studies in South Africa. The gonads of all infected fish were atrophied. The prevalence of L. intestinalis in B. paludinosus was high between July and September 2000 and low thereafter. There was no clear seasonal variation in the occurrence of the parasite, although the lengthy dry season might have had an effect on the prevalence.
Abstract: The Rietvlei Dam near Pretoria, South Africa, provides drinking water for the city and for the wild life in the Rietvlei Nature Reserve, and is also used for recreational fishing. The dam is part of the Sesmyl Spruit system, which has a history of pollution, the major sources of which are industrial, agricultural and sewage from informal human settlements upstream of the reserve. With a large wetland separating the upstream Marais Dam and the Rietvlei Dam, the system has a high conservation priority status because of the high number of bird species that breed and roost in the various habitats. As part of a big aquatic health project in the Zoology Department, Rand Afrikaans University, aimed at finding suitable biomarkers for water quality monitoring in the system, this study was done to identify the major internal helminth parasites of the sharptooth catfish, Clarias gariepinus, that can be used in fish health assessment studies, and to determine their prevalence and intensity in the Rietvlei Dam. Fish were collected during one sampling survey and examined for endoparasites, also noting any ectoparasites that are recorded in routine fish health studies. Five species of helminths were identified: the adult cestodes, Polyonchobothrium clarias (intestine and stomach), Proteocephalus glanduliger (anterior intestine), the adult nematode Procamallanus laevionchus (stomach), larvae of the nematode Contracaecum sp. and many trematode metacercariae encysted in the muscles, of which only Ornithodiplostomum sp. was successfully excysted and identified. This trematode is recorded in South Africa for the first time, but could not be specifically identified because the reproductive system was still immature. Examination of piscivorous birds in the area or experimental infection of young birds are the only means by which the adult trematodes can be obtained. The adult cestodes and nematodes had specialised structures for attachment to the stomach and/or intestinal mucosa, adaptations associated with pathological effects in the host. Polyonchobothrium clarias had a crown of 26-30 hooks on its rostellum, and this number differs from those of specimens described from catfish in other African countries. Scanning electron microscopy showed that the rostellum of the P. clarias specimens from Rietvlei Dam was different from that of specimens from other localities in South Africa. Proteocephalus glanduliger in C. gariepinus from Rietvlei Dam differed in strobila size and size of glandular organ from specimens described by Janicki (Egypt) and Mashego (South Africa), the present specimens being much longer but with smaller glandular organs. Procamallanus laevionchus is a common parasite of catfish from many African countries, including South Africa, and scanning electron microscopy showed some form of transverse markings and presence of papillae-like structures at the posterior end of female specimens, an observation which was not described in previous studies. Larval Contracaecum are also common in C. gariepinus and other fish species, and adults have been identified in several species of fish-eating birds from South Africa. The sample size of fish collected in this survey was too low for a full health assessment index (HAI) study to be undertaken. Polyonchobothrium clarias and Contracaecum, however, were highly prevalent in the host species, and Contracaecum and Ornithodiplostomum occurred at high intensity (up to 44 and 140 respectively). Endoparasites of C. gariepinus can therefore be used in the fish HAI as a bioindicator of water quality. Only two ectoparasitic species were found on C. gariepinus: Argulus japonicus (skin and fins) and Lamproglena clariae (gills). Most water quality variables from the dam were within the target limits recommended by the Department of Water Affairs and Forestry, but the levels of inorganic nitrogen (nitrate and ammonia) and phosphorus (orthophosphate) exceeded the limit. If uncontrolled, these may lead to eutrophication of the dam. With the parasite species and diversity known, it is recommended that fish health assessments should be conducted along pollution gradients in the system to determine whether it can be incorporated into the suite of biomarkers for water quality monitoring of the Sesmyl Spruit system.
