A new species of Pseudoacanthocephalus (Acanthocephala: Pseudoacanthocephalidae) from Sado Island, Japan, with a report of its accidental occurrence in a marine elasmobranch.

Three species of amphibian-parasitic acanthocephalans belonging to the genus Pseudoacanthocephalus Petrochenko, 1958 have been recorded in Japan. However, only a limited number of localities have been surveyed, and the distribution of these congeners across other regions of Japan remains unclear. In this study, acanthocephalans of the genus Pseudoacanthocephalus were recovered from both definitive (Rana ornativentris Werner - type host, and Zhangixalus arboreus [Okada et Kawano]) and accidental hosts (Scyliorhinus torazame [Tanaka]) from Sado Island, Japan. Morphological analyses indicate that those specimens represent a new species, Pseudoacanthocephalus sadoensis sp. n., which may be endemic to the island. Additionally, our report of the incidental occurrence of this species in a marine elasmobranch represents the first documented case of a Pseudoacanthocephalus species found in a marine host.