Antiopella fusca (O'Donoghue, 1924)

Description

Usually 30 to 50 mm in body length, with British Columbia specimens sometimes exceeding 100 mm. The body is semi-translucent yellowish white to pale grey, with an orange longitudinal line running from the interrhinophoral crest along the dorsal midline and a white line along the midline of the tail. The dorsum and sides bear numerous long cerata; each ceras shows the brown digestive gland duct internally, an orange subapical band, and an opaque white tip. The rhinophores carry roughly 20 lamellae and have white tips. The presence of cerata anterior to the rhinophores distinguishes this species from similar northeastern Pacific aeolids.

Distribution

Type locality is the Vancouver Island region of British Columbia, Canada. The species ranges along the northeastern Pacific from the Kenai Peninsula, Alaska to central California, and is also recorded from northern Japan and the Russian Far East (Sea of Japan coast). It inhabits rocky intertidal and shallow subtidal zones to about 30 m depth.

Etymology

From the Latin fuscus, meaning dark brown or dusky.

Remarks

A specialised predator of arborescent bryozoans, feeding mainly on Bugula pacifica and species of Tricellaria. Northeastern Pacific populations are commonly infected by the host-specific endoparasitic copepod Ismaila belciki, which can sterilise its host. The species was originally described as Janolus fuscus O'Donoghue, 1924 from material from the Vancouver Island region. Following the resurrection of Janolidae and the generic rearrangement by a 2019 revision, it was transferred to Antiopella, and Antiopella fusca is the currently accepted name.

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References

• Janolus fuscus n.sp., O'Donoghue C.H. (1924). Notes on the nudibranchiate Mollusca from the Vancouver Island region. IV. Additional species and records. Transactions of the Royal Canadian Institute, 15(1): 1-33, plates 1-2.
• 高岡生物研究会. (2002). 日本海のウミウシ. 第2版.
• ハナヤギウミウシ, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.
• Pola M., Hallas J.M. & Gosliner T.M. (2019). Welcome back Janolidae and Antiopella : Improving the understanding of Janolidae and Madrellidae (Cladobranchia, Heterobranchia) with description of four new species. Journal of Zoological Systematics and Evolutionary Research. 57(2): 345-368. https://doi.org/10.1111/jzs.12257
• Antiopella fusca, Behrens D.W., Hermosillo A., Fletcher K. & Jensen G.C. (2022). Nudibranchs & Sea Slugs of the Eastern Pacific. Molamarine.