A comparative study of the parasitic helminth fauna of Gymnarchus niloticus (Gymnarchidae) and Heterotis niloticus (Osteoglossidae) from Lekki Lagoon, Lagos, Nigeria.

A comparative study of the gut helminthes of Gymnarchus niloticus and Heterotis niloticus were undertaken. A total of 38 fishes comprising of 20 Gymnarchus niloticus and 18 Heterotis niloticus were examined for helminth parasites. The overall prevalence of gastrointestinal helminth infections was 34.2%, which implied that 13 of the specimens examined were infected with parasites. A total of 18 parasites were recovered from the fish specimens. The male specimens of Heterotis niloticus had 38.9% prevalence of infections while the male specimens of Gymnarchus niloticus had 0% prevalence of infections. The female specimens of the two fishes had 50% prevalence of infections. Gymnarchus niloticus harboured two nematodes; Raphidascaroides species in the stomach and the Philometrids, Nilonema gymnarchi, in the intestine. Heterotis niloticus were infected with a trematode Brevimulticaecum heterotis in the liver and Tenuisentis niloticus and Sandonella sandoni in the intestine. The worm burden and intensity were low and independent of sex and age of fish with no seasonal variation in parasite intensity observed. The low prevalence of infection is possibly due to the randomness of specimens' selection.