Redescription of Pseudanthobothrium hanseni Baer, 1956 and description of P. purtoni n. sp. (Cestoda: Tetraphyllidea) from different pairs of rajid skate hosts, with comments on the host-specificity of the genus in the Northwest Atlantic.

During a parasitological survey of Leucoraja erinacea, L. ocellata, Malacoraja senta and Amblyraja radiata from Passamaquoddy Bay and waters surrounding the West Isles of the Bay of Fundy, NB, Canada, seven species of cestodes were recovered. Examination of these skates revealed the presence of two distinct species of Pseudanthobothrium Baer, 1956: one was retrieved from M. senta and A. radiata, identified as P. hanseni Baer, 1956 and redescribed herein; the other was retrieved from L. erinacea and L. ocellata and differs from previously described species. The new species is described herein as P. purtoni n. sp. on the basis of the degree of apolysis, the maximum width of the strobila, the length of the cirrus-sac and the number of testes. Additionally, the distinctiveness of both species of Pseudanthobothrium is supported by the characterisation of a 643 base-pair nuclear marker, which includes most of the D2 variable region of the large subunit ribosomal DNA (LSU). The recovery of two different tetraphyllidean species, each from two different host species, challenges the oioxeny (strict host-specificity) of echeneibothriine cestodes and can be explained, at least in part, by the similarities in diet and substrate preference within each host pair.