Triopha modesta Bergh, 1880

Location: Rousokuiwa, Rausu, Hokkaido, Japan
Date: 2015/05/30
Length: 12mm
Depth: 10.0m
Water temperature: 5.0℃

Description

Ground colour translucent white, occasionally tinged with pale brown. The dorsum bears scattered tubercles of orange to orange-red, often forming a median series running between and behind the rhinophores. Branched papillae of the same translucent white as the body fringe the mantle margin, each tipped vividly with orange; similar branching papillae line the frontal veil. The rhinophores have a translucent white base and orange clavus, and the tripinnate gills are translucent white with orange tips. Northern Japanese specimens commonly reach 45-50 mm, with maximum size around 70 mm.

Distribution

Widely distributed across the North Pacific. The type locality is the Shumagin Islands, Alaska. The species ranges along Hokkaido and northern Honshu, the Russian Far East, the eastern coast of the Korean Peninsula, and across to Alaska, British Columbia, Washington, Oregon, and California, predominantly in cold-current regions. the 1957 study first reported it from northern Japan (Shirikishinai and Hirota), and it has since been recorded along Hokkaido including the Shakotan Peninsula.

Etymology

From the Latin modestus (modest, unassuming), reflecting the comparatively subdued appearance of Bergh's original Alaskan specimens relative to congeners described in the same work.

Remarks

Triopha modesta was long treated as a junior synonym of the eastern Pacific Triopha catalinae (Cooper, 1863), and the North Pacific population was regarded as a single trans-Pacific species. Martynov et al. 2015 reinstated T. modesta as valid for Russian Far Eastern material, and Korshunova et al. 2020 confirmed the western and eastern Pacific lineages as distinct species using combined morphological and molecular evidence. Records published by the 1957 study under "Triopha carpenteri (Stearns)" from northern Japan are referable to T. modesta, and the Japanese name "Hanasaki-umiushi" was coined in the same work. Like other members of the genus, it is reported to feed on bryozoans.