Taxonomy of the rectal endociliates of Xenopus laevis (Anura)

Abstract

Amphibians are hosts to a variety of parasite groups which include protozoans, cestodes, nematodes, acanthocephalans, monogenetic flukes, digenetic flukes, and mites. Nevertheless, of these parasite groups infecting amphibians, the protozoan gut ciliates are perhaps the most abundant, yet under-studied, group. Even in one of the world’s most widely distributed amphibian invaders and well-known model, the African Clawed Frog Xenopus laevis (Daudin, 1802) (Anura: Pipidae), the study of protozoan parasites has fallen behind that of its metazoan counterparts. Former studies that documented intestinal ciliates of amphibians from South Africa are limited and most took place decades ago. Furthermore, these studies primarily dealt with the systematics of ciliate groups whereas most did not even identify ciliates beyond the genus level. Consequently, difficulties arise when rectal endociliate assemblages are compared among populations of the host, in their native range as well as elsewhere. Therefore, the aim of this study was to document the gut ciliate diversity of X. laevis, from localities in both South Africa and France, by using an integrated taxonomic approach. Hence, for the first time, the ciliates of X. laevis were identified both morphologically and molecularly through modern as well as classic techniques. These techniques included differential interference contrast advanced microscopy, scanning electron microscopy, confocal microscopy, silver impregnation, haematoxylin staining and polymerase chain-reaction tests. The gut protozoans of X. laevis from South Africa were documented as four species namely: 1) Balantidium kirbyi, 2) Balantidium sp. 1, 3) Balantidium sp. 2 and 4) Protoopalina sp. 1. Correspondingly, the gut protozoans of X. laevis from France were documented as: 1) B. kirbyi, 2) Balantidium sp. 3, Balantidium sp. 4 and 4) Protoopalina sp. 2. Not only were molecular data of endociliates of frogs from South Africa obtained for the first time but the foundation for a working method of ciliate identification were laid by this study. Accordingly, this integrated approach will ease future ciliate identification in other anuran hosts and furthermore allow a better understanding of the host-parasite relationship, ecological role, and diversity of ciliates.