Taxonomic review and general biology of the genus Eupolystoma (Monogenea: Polystomatidae)

Abstract

Polystomes are parasitic flatworms infecting mainly anuran hosts. Of the 21 known polystome genera only Eupolystoma, Metapolystoma, Polystoma and Protopolystoma are known from Africa. Although the genus Polystoma has a world wide distribution, Metapolystoma and Protopolystoma are limited to Africa while Eupolystoma is limited to Africa and India. The genus Eupolystoma currently consists of five species. These species include Eupolystoma anterorchis parasitic in Amietophrynus pantherinus, E. vanasi from Schismaderma carens, E. alluaudi from A. regularis, A. gutturalis, Nectophrynoides malcomi and Pyxicephalus adspersus from Africa. Two species, E. chauhani from an unidentified Bufo sp. and E. rajai from an unidentified Rana sp., are both known from India. Eupolystoma produce both ciliated and unciliated oncomiracidia. Ciliated oncomiracidia leave the host and infect post-metamorphic naive hosts. The oncomiracidium enters the cloaca; migrate to the kidney, then to the Mulerian ducts and to the bladder where the parasites then reach maturity. Because the hosts are usually explosive breeders, parasite transmission may be risky. Eupolystoma also produce non-ciliated oncomiracidia. They do not leave the parent host but attach alongside the parent to develop into mature parasites. Due to large intraspecies variation and limited interspecies variation, huge emphasis is placed on morphometric measurements of sclerotised parts and in particular the marginal hooklets. A set of 13 measurements were taken of the sclerotised marginal hooklets of the Eupolystoma species. Through mathematical modelling the combination of measurements with the highest classification potential was determined for the genus Eupolystoma. The best combination of measurements did not produce a significantly better result as the protocol for the genus Polystoma. We thus suggest that the Polystoma protocol be used for the genus Eupolystoma.