A New Find of the Whale-fall Lancelet <i>Asymmetron inferum</i> (Cephalochordata) near a Hydrothermal Vent at Oomuro-dashi Submarine Volcano in the Izu Islands, Pacific Coast of Japan, as a Possible Case to Prove the Stepping-stone Hypothesis

Abstract

Two mature specimens of the whale-fall lancelet Asymmetron inferum Nishikawa, 2004, were collected in 2016 from reducing gravel bottom near a hydrothermal vent, 196 m deep, at Oomuro Hole of Oomuro-dashi submarine volcano in the Izu Islands, Pacific coast of Japan by using the ROV Hyper-Dolphin during the RV Shinsei-maru KS-16-6 cruise of JAMSTEC. This species has so far been known exclusively from whale-fall communities off Cape Nomamisaki, SW Kyushu, Japan, 219-254 m deep. The new find suggests the dispersal stepping-stone hypothesis of whale-fall communities for the origin of vent and/or seep fauna.