Wilmien J. Luus-Powell

Population dynamics and spatial distribution of monogeneans on the gills of Oreochromis mossambicus (Peters, 1852) from two lakes of the Limpopo River System, South Africa

An investigation was conducted into the parasitic infection of an indigenous cichlid, Oreochromis mossambicus, collected seasonally from the Nwanedi-Luphephe dams of the Limpopo River System from July 2007 to April 2009. Of 157 host specimens examined, 115 (73.25%) were infected by at least one gill parasite. In all, 1565 monogenean specimens were collected, belonging to five different species and two genera: Cichlidogyrus (C. halli, C. sclerosus, C. tilapiae and C. dossoui) and Scutogyrus (S. longicornis). Infracommunities were poor, with only 27 (17.20%) hosts harbouring four of the five species observed. Cichlidogyrus halli was the dominant species, with a prevalence of 73.25%. Prevalence values for each of the other four species were less than 50%. The mean intensities for each of the five species were low ( < 8 parasites/host). The parasite abundance and intensity levels were not influenced by either the sex or the size of the host. The abundance of all parasite species except for S. longicornis exhibited seasonal fluctuations, reaching peaks in winter and summer. The spatial distribution of each parasite was studied on different regions of the gill, and positive associations among some species were revealed.

Sharptooth catfish shows its metal: A case study of metal contamination at two impoundments in the Olifants River, Limpopo river system, South Africa

Clarias gariepinus is increasing in importance as a global aquaculture species with a 100 fold increase in production over the past decade but this species still remains one of the most important wild harvested freshwater food fish throughout rural Africa. However, this species has been shown to accumulate metals from contaminated inland waters. In this paper, the metal concentrations in muscle tissue of C. gariepinus from two main-stem impoundments in the Olifants River, Limpopo Basin, were measured and a desktop risk assessment based on the US-EPA methodology completed to evaluate whether long-term consumption of C. gariepinus from these impoundments may pose a health risk to rural communities. Our results show that metals are accumulating in the muscle tissue of C. gariepinus and have appeared to have increased in the last two decades. Risk assessment generated Hazard quotients (HQ) greater than 1 indicate that long term consumption of fish from these impoundments may cause adverse health impacts. We found that lead (HQ=9), antimony (HQ=14), cobalt (HQ=2) and chromium (HQ=1) at one impoundment and lead (HQ=2) at the other impoundment were above acceptable levels for weekly consumption of 150 g C. gariepinus muscle tissue.

Diversity of metazoan parasites of the Mozambique tilapia, Oreochromis mossambicus (Peters, 1852), as indicators of pollution in the Limpopo and Olifants River systems

Aquatic systems are affected by a variety of anthropogenic activities that decrease water quality through the introduction of organic and inorganic pollutants. To investigate the relationship between fish parasite communities and water quality, metazoan parasites were examined in 140 specimens of the Mozambique tilapia (Oreochromis mossambicus) sampled in three lakes in the Limpopo Province, namely the Luphephe-Nwanedi Dams (regarded as unpolluted), the Flag Boshielo Dam (regarded as moderately polluted) and a return water dam on a mine site (regarded as polluted). The monogenean parasites Cichlidogyrus halli, digenean larval stages of Clinostomum and Diplostomum spp. and a gryporynchid cestode were found in or on O. mossambicus in all the sampled sites. The distribution of monogeneans (Cichlidogyrus sclerosus, Cichlidogyrus dossoui, Cichlidogyrus tilapiae, Scutogyrus longicornis and three Enterogyrus spp.), metacercarial stages of two digeneans (Neascus and Acanthostomum spp.) and nematodes (an unidentified nematode, Contracaecum sp., Paracamallanus cyathopharynx and Procamallanus laevionchus) was limited to the unpolluted and moderately polluted lakes. Larval stages of Diplostomum sp. were present in O. mossambicus collected from the unpolluted and polluted sites. The variability of the calculated infection indices (prevalence, mean abundance and mean intensity) and the parameters of species richness and diversity suggest that the structure of parasite communities are affected by the pollution levels of the water. The unpolluted reference site had the highest species richness and the highest overall parasite abundance values.

Metal bioaccumulation in the fish of the Olifants River, Limpopo province, South Africa, and the associated human health risk: a case study of rednose labeo Labeo rosae from two impoundments

The Olifants River, Limpopo River system, is now one of the most polluted rivers in South Africa. The concentrations of metals in fish muscle tissue from two impoundments on the Olifants River, Flag Boshielo Dam and Phalaborwa Barrage, were measured and a human health risk assessment conducted to investigate whether it was safe to consume Labeo rosae from these impoundments. Labeo rosae is one of the most common pan-fish in these impoundments and is frequently available to rural communities. Metals are accumulating in the muscle tissue of L. rosae even though the populations appear to be healthy. At Flag Boshielo Dam the recommended hazard quotient (HQ) of 1 was exceeded for lead and chromium in all L. rosae analysed, and 53% exceeded that for antimony. At Phalaborwa Barrage almost all L. rosae analysed exceeded the recommended HQ for lead, and <25% exceeded that for arsenic. Weekly consumption of 150 g of L. rosae muscle tissue from these impoundments may pose an unacceptable health risk to rural communities.

Ecology of metazoan parasites of Clarias gariepinus (Osteichthyes: Clariidae) from the Nwanedi-Luphephe Dams of the Limpopo River System, South Africa

A total of 7748 parasites, belonging to 17 metazoan species, was recorded from 45 specimens of Clarias gariepinus (Burchell, 1822) caught from the Nwanedi-Luphephe Dams, Limpopo River System, South Africa. All host specimens were parasitized by one or more metazoan parasite species. The parasite species included five monogeneans (Gyrodactylus rysavyi, Macrogyrodactylus clarii, Macrogyrodactylus congolensis, Quadriacanthus clariadis and Q. aegypticus), four digeneans (Diplostomum type 3, Tetracotyle sp. metacercaria, Acanthostomum sp. and Glossidium pedatum), two nematodes (Contracaecum larvae and Paracamallanus cyathopharynx), two cestodes (Proteocephalus glanduligerus and Tetracampos ciliotheca), two branchiurans (Chonopeltis inermis and Dolops ranarum), one copepod (Lamproglena clariae) and one unidentified leech. Eleven parasites were satellite species, with low prevalence (<33%) and mean abundance (<12.9 parasites per host). The nematode larvae (L3) of Contracaecum sp. were the dominant species, constituting 56% of the total metazoans (100% prevalence, mean abundance and mean intensity 96.3). Infra- and component community species richness and diversity were high. The dominance of hostspecific parasite species in the sharptooth catfish confirms that its metazoan fauna has a considerable degree of specificity. This study indicates the importance of ecological determinants of richness in metazoan communities of the sharptooth catfish from dams in an oligotrophic state.

Monogenean parasites from fishes of the Vaal Dam, Gauteng Province, South Africa. I. Winter survey versus summer survey comparison from Labeo capensis (Smith, 1841) and Labeo umbratus (Smith, 1841) hosts.

Indigenous South African Labeo spp. show promise with regard to development of semi-intensive aquaculture, yet little research on their monogenean fauna has been conducted. Ecological aspects of monogenean fauna of the moggel Labeoumbratus (Smith 1841) and the Orange River mudfish Labeo capensis (Smith 1841), as recorded during both winter and summer sampling surveys, are reported here. Fish were collected using gill nets, euthanized and gills removed and examined to both quantify parasite numbers and distribution on the gills. Results obtained support the hypothesis that gill site preference is not due to active choice for a particular attachment site, but rather a result of water flow over gills during respiration in conjunction with fish behaviour and habitat use. Interaction between individual elements investigated (temperature effects, parasite population dynamics and host population dynamics) may be largely responsible for seasonal differences in infection statistics of monogenean parasites. Such interactions should be investigated in future large scale ecological studies, in combination with experimental studies, to further elucidate these effects.

The Occurrence of Metazoan Endoparasites of Schilbe intermedius Rüppell, 1832 from the Nwanedi-Luphephe Dams in the Limpopo River System, South Africa

The present study deals with the survey of endoparasites from Schilbe intermedins (silver catfish) at the Nwanedi-Luphephe Dams from July 2009 to May 2010. The hosts (n = 60) were collected using gill nets and examined for endoparasites. The following parasites were recorded: three species of trematodes, i.e. Clinostomum metacercariae in the body cavity (prevalence 40%), an unidentified adult digenean in the small intestine (prevalence 33.3%) and Diplostomum metacercariae from the eye (prevalence 1.7%), and two species of nematodes, i.e. Contracaecum larvae in the body cavity (prevalence 95%) and Paracamallanus cyathopharynx from the intestine (prevalence 63.3%). None of the fish examined during this study was in a notably poor state of health due to parasitism. Correlations between endoparasite infection and host size, as well as seasonal variation in their infection dynamics associated with environmental changes, were detected.

A comparative assessment of the health status of feral populations of Clarias gariepinus from three dams in the Limpopo and Olifants river systems, Limpopo province, South Africa, using the fish health assessment index protocol

An evaluation of the health status of feral populations of the freshwater catfish Clarias gariepinus was carried out between 2009 and 2010 at three dams in the Limpopo and Olifants river systems with varying levels of human impact. Fish health was assessed using a modified health assessment index (HAI) protocol, with the inclusion of the inverted parasite index (IPI) and condition factor (K). These biomonitoring tools provide relatively simple and rapid indications of how well fish are coping in their environment. To verify the biomonitoring results, water quality analyses were included in the study. The nutrients and mining-related pollutants in the three dams differed to a great extent and showed an increasing trend in the order: Luphephe–Nwanedi Dams < Flag Boshielo Dam < Return Water Dam. The HAI score varied across the three sampling sites, with individual mean values of 93.3, 84 and 42.7 at the Return Water Dam, Flag Boshielo Dam and Luphephe–Nwanedi Dams, respectively. The top six metrics that correlated best with fish health scores were the levels of ectoparasites, haematocrit values and the condition of the gills, liver, skin and fins. Although the HAI successfully differentiated among the three localities, which differed in water quality, it was non-specific in response to contaminants. Notably, the premise set forth by the IPI that endoparasites increase with a decrease in water quality was not supported.

Distribution of Contracaecum (Nematoda: Anisakidae) Larvae in Freshwater Fish from the Northern Regions of South Africa

A total of 1 847 fishes (16 species) from 14 reservoirs in northern and north-eastern regions of South Africa were collected and examined for larval Contracaecum spp. between 2005 and 2013. This study, the first to examine several potential second intermediate hosts, found Clarias gariepinus, Coptodon rendalli, Cyprinus carpio, Hydrocynus vittatus, Labeobarbus marequensis, Marcusenius macrolepidotus, Micropterus salmoides, Oreochromis mossambicus and Schilbe intermedius infected with the third-stage larvae. Coptodon rendalli, Marcusenius macrolepidotus and Micropterus salmoides are new host records for South Africa. A generalised linear model identified locality as the main factor affecting parasite burden.

Monogenean Parasite Species Descriptions from Labeo spp. Hosts in the Vaal Dam, South Africa

Specimens of Labeo capensis (n = 13) and Labeo umbratus (n = 26) from the Vaal Dam (South Africa) were collected and examined for gill and skin monogenean parasites. Three new Dactylogyrus and one new Dogielius species are described. Dactylogyrus iwani n.sp. (longer inner root on anchor and predominates onL. capensis) and D. larindae n.sp. (shorter inner root on anchor and predominates on L. umbratus) show similarities in male copulatory organ (MCO) and anchor structure with representatives of the D. pseudanchoratus group. Dactylogyrus nicolettae n.sp. differs completely with regard to anchor morphology (stout with a curved inner root and reduced outer root), yet MCO morphology (curved penis and simple accessory piece structure of similar shape and size) are similar in all three species described. Dogielius intorquens n.sp. was collected from both hosts. Two forms, corresponding to host species and differing in anchor and MCO size but not shape, are described. This brings the number of Dactylogyrus species described from African Labeo spp. to 29, with D. intorquens n.sp. constituting the 16th Dogielius species from African Labeo spp. hosts.