Acanthodoris atrogriseata O'Donoghue, 1927

Location: Oyashirazu, Niigata, Japan
Date: 2022/04/22
Length: 14mm
Depth: ??m
Water temperature: 12.0℃

Description

Body coloration is highly variable, ranging from yellowish-white to gray, smoky gray, black, and golden brown. The dorsum is densely covered with conical papillae tipped with yellow, a feature that reflects the generic name Acanthodoris ("spiny Doris"). The rhinophores are long and bend backwards. The non-retractile gill circle is set well back on the body. Adults typically measure around 30 mm in length, with the largest individuals reaching about 50 mm. It occurs from the lower intertidal zone into shallow rocky habitats, on bryozoan-encrusted substrates.

Distribution

Northeastern Pacific, recorded from Kiska Island in the Aleutians, Alaska, south to Morro Bay, California. The type locality is False Narrows, Nanaimo, Vancouver Island, Canada; WoRMS lists a neotype from Puget Sound, Washington. Some North Pacific records previously assigned to Acanthodoris pilosa, including specimens from waters around northern Japan, are now considered likely referable to this species.

Etymology

From Latin atro- ("dark, black") and griseata ("gray"), referring to the smoky gray to dark coloration documented in the original description.

Remarks

A bryozoan-feeder, found on encrusting bryozoan colonies on rocks and floats. The species was long treated as a synonym of the trans-boreal Acanthodoris pilosa (Abildgaard, 1789). A 2016 revision showed through molecular phylogenetics that the northeastern Pacific population represents a distinct lineage, reinstating A. atrogriseata, originally described by O'Donoghue in 1927 from material treated together with the Laguna Beach nudibranch fauna. The Japanese name "Toge-umiushi", first proposed by Kikutaro Baba in 1957 for North Japanese material then identified as A. pilosa, has carried over to this species under the current taxonomy.