Boreoberthella chacei (J. Q. Burch, 1944)

Description

A pleurobranchid reaching about 55 mm in length, with an oval, slightly depressed body and a thick, smooth mantle. Ground colour is translucent yellowish-white to pale orange-white, the mantle scattered with fine white spots. A slender white line runs along the mantle margin and the anterior edge of the oral veil, outlining the rim of the body. Some individuals show a slightly darker patch in the middle of the dorsum.

A thin internal shell lies beneath the mantle (typical of side-gilled slugs). The gill, with secondary lamellae arranged in multiple rows, lies in the cleft between mantle and foot on the right side of the body.

Distribution

A North-Pacific boreal-temperate species with a near-circumpacific distribution. Recorded from Japan (Hokkaidō to central Honshū on the Pacific coast), Korea, the Russian Far East (Sea of Japan, Sea of Okhotsk, Kamchatka), and North America (Alaska to Oregon). It has also been reported from deeper waters near the Galápagos Islands. It occurs from the lower intertidal of rocky shores down to a few tens of metres depth.

Etymology

The specific epithet chacei honours an American malacologist, Emery William Chace (1888-1970), or a contemporary marine biologist of the same surname.

Remarks

Originally described as Berthella chacei Marcus, 1984. Martynov & Schrödl 2009 reanalysed the Pleurobranchoidea morphologically and phylogenetically, separated a boreal lineage as the new genus Boreoberthella, and designated this species its type. The parentheses in the current author citation reflect that generic transfer.

As in other side-gilled slugs, the species is presumed to feed on sponges or encrusting tunicates. The Japanese vernacular name "Suzuyaka-fushieragai" alludes to the cool, refreshing impression made by its pale ground colour.

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References

• ベルッセラ・カリフォルニカ, 中野理枝. (2004). 本州のウミウシ. ラトルズ.
• Berthella chacei Marcus, 1984 (later transferred to Boreoberthella), Martynov A.V. & Schrödl M. (2009). The new Arctic side-gilled sea slug genus Boreoberthella (Gastropoda, Opisthobranchia): Pleurobranchoidean systematics and evolution revisited. Polar Biology. 32(1): 53-70.
• スズヤカフシエラガイ（新称）, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.
• Berthella chacei, 柏尾翔 & 山崎友資. (2021). 北海道積丹半島沿岸のウミウシ. ちりぼたん. 51(1): 1-20.
• Boreoberthella chacei comb. nov., Moles J., Brenzinger B., Berning M.I., Martynov A., Korshunova T. & Schrödl M. (2024). Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society. 202(2): zlad162. https://doi.org/10.1093/zoolinnean/zlad162