Grammonus yunokawai (Ophidiiformes: Bythitidae), a new marine cavefish from the Ryukyu Islands

Abstract

A new species of the fish genus Grammonus (Ophidiiformes: Bythitidae) is described based on a ripe female, 98 mm in standard length (SL). It was caught at the bottom of a cave at a depth of 20 m under lightless conditions in Ie-shima Island, one of the Ryukyu Islands. A comparison to the seven described species of Grammonus shows the greatest similarity to the widely distributed G. robustus, but G. yunokawai n. sp. differs from it by having fewer vertebrae (41 vs. 44–47), a greater predorsal length (41.5 vs. 32.0–39.0% SL), higher posterior margin of maxilla (8.4 vs. 5.6–7.3% SL), and greater interorbital width (10.5 vs. 5.9–7.6% SL).