Helminth parasites of Silurana tropicalis from the Okomu National Park, Edo State, Nigeria
Silurana tropicalis, the edible clawed-frog, collected from the Okomu National Park, Edo State, Nigeria, was examined for helminth parasitic infections. From 142 specimens collected, ten endo-helminth parasites spread across four classes were recovered. These included Cestoda: Cephalochlamys compactus and the cyst of a proteocephalidcestode; Trematoda: Mesocoelium monodi, Nematoda: Batrachocamallanus siluranae, Camallanus siluranae, Cosmocerca ornata, an unidentified oxyurid nematode and encysted larvae of an unidentified nematode; Acanthocephala: Centrorynchus sp. occurred only as cysthacanth. Also encountered were cysts carrying a mixed infection nematode/proteocephalid larvae Thus, Silurana tropicalis collected from the protected rainforest haboured more parasites than those of its counterpart from the derived-savanna of Edo State. Some parasites of S. tropicalis, including C. compactus, the encysted-proteocephalidcestode and C. ornata also occur in other pipid anurans. However, some other helminths such as the unidentified oxyurid nematode, the encysted larval nematodes, encysted mixed infection and the cysthcanths of Centrorynchus have no previous record in other members of the Pipidae. The presence of encysted parasites attached to some organs of the viscera is indicative of S. tropicalis having a role as a paratenic or transport host. The sharing of a common cyst by two parasites belonging to different classes is a novel parasitic adaptation ensuring an efficient delivery of multiple infections to their hosts.
Keywords: helminth parasites, Siluranatropicalis, rainforest, parasitic adaptations.