Morphometric analysis of monogenean parasites of cichlid and cyprinid fish in Lake Naivasha, Kenya

Abstract

Fish diseases and parasitic infections have been recognized as detrimental and limiting factors in the development of capture fisheries and aquaculture. Research on monogeneans parasitizing fish from Lake Naivasha, Kenya is scanty. This study aimed to identify the species of monogenean parasites of some cichlid and cyprinid fish in Lake Naivasha, Kenya. Fifty specimens of each fish species comprising: Oreochromis niloticus, O. leucostictus, Tilapia zillii and Barbus paludinosus were captured using a fleet of gill nets with mesh sizes 2, 2.5, 3 and 4 inches from December 2014 to January 2016. The fish were transported alive to the laboratory in the Department of Biological Sciences, Egerton University, Njoro, where they were killed by severing the spinal cord followed by a dissection. Using parasitological examination procedures, the fish gills were examined for the presence of monogeneans. The parasites were identified using morphometric analysis with the help of identification keys. From this study the following parasites were recovered: O. leucostictus had Scutogyrus gravivaginus with a prevalence (P) = 2%, Cichlidogyrus sclerosus (P = 100 %), C. tilapiae (P = 6%), C. halli (P = 4 %). From O. niloticus, C. sclerosus (P = 8 %) and C. tilapiae (P = 12%) were identified. From T. zillii, C. digitatus (P = 42%), C. yanni (P = 2 %), C. aegypticus (P = 2 %), C. arthracanthus (P = 2 %), C. sclerosus (P = 2 %), C. tilapiae (P = 2%); and C. vexus (P = 4%) were identified. From the cyprinid B. paludinosus a new species of Dactylogyrus (P = 22%) was found. All these species are reported for the first time from Lake Naivasha, and form the first monogenean biogeographical records from the Republic of Kenya and therefore adds to our knowledge of the biodiversity. It was also concluded that Lake Naivasha harbours the ancyrocephalids and dactylogyrids on the gill filaments of the cichlids and cyprinid fishes and recommend that further studies on their ecology, seasonality and water quality should be carried out to determine whether they facilitate the spread of these monogenean parasites. Additionally, more studies should be done to identify monogeneans infecting the other fish species which were not part of the present study.