2023 年 49 巻 2 号 p. 75-80
The ascidian genus Culeolus (family Pyuridae) is known exclusively from deep-sea floors, being anchored by a long, thin hard stalk. A specimen of Culeolus sp. sensu Kuramochi et al. (1999), collected in 1998, was identified as C. tenuis Vinogradova, 1970, and described in detail, including some taxonomic and ecological remarks. The specimen had been one of 6 individuals observed in situ from the remote-operated submersible “KAIKO”, supported by the JAMSTEC R/V “KAIREI” (KR98-07 #79 Leg. 1), at depths of 5,726 to 5,792 m off Fukushima Prefecture, Japan, on the land-slope side of the Japan Trench. The species has been previously recorded from the NW Pacific, including the Japan Trench off Sendai, Miyagi Prefecture. The examined specimen was characterized by 6 branchial folds with 3 elongated lobed gonads on each side, and one of the left gonads within the first intestinal loop. The habitat floor off Fukushima was composed of yellowish sand mixed with black manganese-coated pebbles of olivine basalt, the bottom water likely being oxygen-rich.
