Deep-water ascidians (Tunicata : Ascidiacea) from the northern and western Pacific

摘要

Bathyal and abyssal ascidians from the northeast Pacific (Alaska Gulf and Aleutian Islands) and ultra-abyssal species from the deep-water trenches in the west Pacific (Kurile-Kamchatka, Ryukyu, Philippine, and Volcano Trenches) are discussed. Six abyssal species recorded for the first time from the north Pacific were previously known from the southern hemisphere including Antarctica, the Indian Ocean, and the Atlantic, confirming the cosmopolitan distribution of many abyssal species. Three new species are described and three previously known species are recorded at depths exceeding 7000 m.