Parasite diversity and health of chiloglanis pretoriae and amphilius uranoscopus from the Limpopo River System

Abstract

The African continent has rich freshwater fish fauna, but the parasite composition of only a few species is known. Chiloglanis pretoriae Van der Horst, 1931 and Amphilius uranoscopus (Pfeffer, 1889) are among African freshwater fish endemic to South Africa with limited information about their parasite composition and health status. A total of 171 fishes, C. pretoriae (n = 127) and A. uranoscopus (n = 44) from Nwanedi, Mutshundudi, Lutanandwa and Politsi rivers within the Limpopo River System, were collected to determine their parasite diversity and health. Both ecto- and endoparasites were recovered and preserved for identification. Scanning electron microscopy and morphological, morphometric and molecular analysis were used for parasite identification. Parasite infestation indices for all parasites were calculated and compared among the four rivers. The water quality of the rivers was investigated by measuring the selected physico-chemical parameters. Subsurface water samples were collected for analysis of selected metals and nutrients. The Health Assessment Index (HAI) in conjunction with the Inverted Parasite Index (IPI), condition factor (K) and regression analysis were calculated to determine the health of fish. Species richness and parasite diversity of C. pretoriae and A. uranoscopus from the four rivers were calculated using Margalef’s richness index and Shannon-Weiner diversity index, respectively. Parasite diversity and species richness of C pretoriae and A. uranoscopus were compared to the water quality of the four localities. Three parasitic groups (Monogenea, Digenea and Hirudinea) were found from C. pretoriae which comprised of two ectoparasite species [Dactylogyridae gen. sp. (n = 56) and a leech (n = 4)] and three endoparasite species [Clinostomum sp. (n = 4), Diplostomidae gen. sp. larva (n = 143) and Cephalogonimidae gen. sp. (n = 19)]. Ectoparasites were more abundant in the Lutanandwa River with a total of 54, while endoparasites were more abundant in the Mutshundudi River with a total of 106. Diplostomidae gen. sp. from C. pretoriae in the Mutshundudi River had the highest prevalence of 57.14%, and the leech from the Nwanedi River had the lowest prevalence of 0.25%. Chiloglanis pretoriae from Nwanedi River had the highest Shannon-Weiner and Margalef’s index values of 0.53 and 0.54, respectively, indicating a healthy ecosystem. Two endoparasite groups, digeneans (Clinostomum sp., Uvulifer sp. and Cephalogonimidae gen. sp.) and nematodes (Labeonema sp., Contracaecum sp., Rhabdochona sp., Gendria sp. and Gendria cf. paski) were found in A. uranoscopus. v Uvulifer sp. was the most prevalent parasite with a 100% prevalence. Amphilius uranoscopus from Lutanandwa River had the highest Shannon-Weiner Index and Margalef’s index values of 0.26 and 0.30, respectively, and a low evenness value of 0.37 due to uneven distribution of parasite species. The highest HAI value for C. pretoriae (36.19) was recorded from the Mutshundudi River and the lowest of 28.38 was recorded from the Lutanandwa River. The highest K score for C. pretoriae of 1.08 was recorded from Nwanedi River and the lowest of 1.01 from Lutanandwa River. The HAI of A. uranoscopus from the four selected localities indicated that the fish collected from the Lutanandwa River were in poorer health state than those from the other rivers due to the higher score. The highest HAI of 99.13 was recorded from the Lutanandwa River and the lowest HAI of 36.36 was recorded from the Nwanedi River. However, the highest mean K score of 0.84 was recorded from Nwanedi River while the lowest of 0.53 was recorded from Mutshundudi River. The results of both C. pretoriae and A. uranoscopus also indicated that the parasite burden did not affect the K of the fish. Generally, water quality results indicated that the rivers were in fair condition with most parameters being within the acceptable target water quality range (TWQR) of aquatic ecosystems. These rivers therefore have good water quality and indicate an oligotrophic state, however, Nwanedi and Politsi rivers are slightly impacted by anthropogenic factors which increased their nitrate concentration compared to the other rivers (Mutshundudi and Lutanandwa rivers). During this study, fish health, parasite diversity and species richness indices were used in combination to determine the water quality of the four localities. The results represent new geographical and host records for parasites from C. pretoriae and A. uranoscopus in the Nwanedi, Mutshundudi, Lutanandwa and Politsi rivers. Since it is the first record of Cephalogonimidae gen. sp. and Dactylogyridae gen. sp., more studies should be done to investigate other possible localities within the Limpopo River System and determine the life cycle of the digenean. Since both parasites represent new genera, papers on their description and identification are in preparation. Future studies on the parasites of the two fish species should employ the use of molecular analysis for larval forms as well as the leeches. It is proposed that the HAI using A. uranoscopus and C. pretoriae should not be employed for future studies because not all variables can be used due to the small size of these fish species. It is proposed that the study should be done seasonally at all localities to detect differences in the occurrence of parasites in relation to the seasonal water quality.