First records of the rare snake eel Ophichthus exourus (Pisces: Anguilliformes: Ophichthidae) from the Northern Hemisphere

Abstract

An old museum specimen of the rare deep-sea species Ophichthus exourus McCosker, 1999 (Anguilliformes: Ophichthidae) (685 mm in total length) collected near Saipan and a recently collected example from Okinawa, Japan (634 mm in total length) represent the first Northern Hemisphere records of the species, previously known only from the southwestern Pacific in waters offNew Caledonia and Fiji, but now believed to be widely distributed in the western Pacific Ocean. A detailed morphological observation based on the above specimens and a re-examination of the holotype resulted in a revision of some species characteristics, including the number of infraorbital pores. Ophichthus exourus is distinguished from other congeners by the following combination of characters: head 8.3-10.0% of total length; upper jaw 36.1-38.1% of head length; pectoral-fin rounded, length 19.2-24.1% of head length; rear margin of eye above or slightly behind rictus; eye diameter 44.4-61.2% of snout length; horizontal length of posterior nostril dermal flap much greater than diameter of anterior nostril tube; gill opening to dorsal-fin origin greater than twice pectoral-fin length; preopercular pores 2; predorsal and total vertebrae 20-21 and 173-177, respectively; lower-jaw teeth nearly uniserial; body without bands or spots; posteriormost portion (much shorter than head length) of anal-fin membrane indistinct darkish brown. A new standard Japanese name "Gunbai-umihebi" is proposed for the species.