A redescription of Pseudorhabdosynochus epinepheli (Yamaguti, 1938), the type-species of Pseudorhabdosynochus Yamaguti, 1958 (Monogenea: Diplectanidae), and the description of P. satyui n. sp. from Epinephelus akaara off Japan.

Pseudorhabdosynochus epinepheli (Yamaguti, 1938) has been recorded from a variety of hosts, mainly groupers. All type-specimens of Diplectanum epinepheli Yamaguti, 1938, Pseudorhabdosynochus epinepheli Yamaguti, 1958 and Cycloplectanum hongkongensis Beverley-Burton & Suriano, 1981 are figured: it is concluded, as did Kritsky & Beverley-Burton (1986), that the three species are synonymous. In addition, numerous monogenean specimens from a deep-sea grouper, Epinephelus chlorostigma, collected off New Caledonia, South Pacific, were prepared using various methods and described. These specimens are also conspecific with P. epinepheli (Yamaguti, 1938) and represent a new geographical record. This species has a sclerotised vagina with a very characteristic primary chamber. The simultaneous presence of P. lantauensis (Beverley-Burton & Suriano, 1981) and P. epinepheli was noted in both type-slides of D. epinepheli from Japan (host: E. akaara) and C. hongkongensis from Hong Kong (host: E. bruneus). Several causes are suspected for the alleged 'generalist' character of P. epinepheli, including the misidentification of either fish or monogeneans and the accidental exchanges of monogeneans between fishes of different species kept alive in the same tank. Finally, the confirmed list of hosts of P. epinepheli includes E. akaara, E. awoara and E. chlorostigma; it is suggested that the latter, a widespread deep-sea fish, serves as a reservoir for the infection of the other species, which are associated with shallow waters. P. satyui n. sp. is described from two specimens found on slides from E. akaara (from the Inland Sea of Japan) deposited by Yamaguti; the new species has a sclerotised vagina with characteristic spherical chambers.