Representatives of Batrachocamallanus n. g. (Nematoda: Procamallaninae) from Xenopus spp. (Anura: Pipidae): geographical distribution,host range and evolutionary relationships

The great majority of the Procamallaninae occur in teleosts from tropical regions; however, representatives of this group are also frequent parasites of aquatic clawed toads (Xenopus spp.) in Africa. The taxonomic status of procamallanines from different Xenopus spp. and their geographical distribution is reviewed. Batrachocamallanus n. g. is created to include forms from amphibians with large numbers of mucrons on the female tail and relatively small body size. B. occidentalis n. sp. and B. siluranae n. sp. are described, while Procamallanus brevis Kung, 1948, originally recorded from an unidentified African amphibian, is considered a synonym of B. slomei (Southwell & Kirshner, 1937) n. comb. Due to the presence of spiral thickenings on its buccal capsule, B. xenopodis (Baylis, 1929) n. comb. has previously been placed in the genus Spirocamallanus Olsen, 1952. However, this species shares the apomorphic presence of numerous mucrons on the female tail, and almost identical cephalic morphology, male caudal structures and female reproductive system with other procamallanines from clawed toads. This suggests that they represent a monophyletic grouping. There is also only limited morphometric differentiation between B. xenopodis and the other proposed representatives of Batrachocamallanus (supported by a multivariate analysis of male and female specimens), which further indicates a close relationship between them. Great variability in the presence and type of buccal capsule thickenings occurs within Batrachocamallanus. Members of this genus most closely resemble the African species Procamallanus laeviconchus (Wedl, 1862), which exhibits a smooth buccal capsule similar to that of B. siluranae. Buccal capsule thickenings of the remaining Batrachocamallanus spp. probably arose independently from those described in other procamallanines. Such characters may be evolutionarily unstable and an unsuitable basis for generic classification in this subfamily. Although B. siluranae is the only Batrachocamallanus species to occur in X. tropicalis-like hosts (which represent a separate lineage from other clawed toads), its distribution, and that of its congeners, may be determined more by host-independent ecological or biogeographical factors than by an association with host phylogeny. Thus, B siluranae occurs in Xenopus spp. from tropical rain forest (including those from other host lineages) while the other forms are typically found in savanna or montane forest, and in the cases of B. slomei and B. xenopodis at least, do not show narrow host specificity to particular clawed toad taxa. Although more than one Batrachocamallanus spp. were found in X. laevis, X. muelleri and X. fraseri-like clawed toads, co-existence at the same locality never occurred, perhaps indicating a high degree of interspecific ecological segregation.