Janolus fuscus
O'Donoghue, 1924

Suborder: ARMININA
Family: Zephyrinidae


Alaska to California. Also northern Japan [m12680].


Upper: Eastbourne Wall, Keats Island, in Howe Sound, British Columbia, Canada. Photo: Marli Wakeling. Lower: Coronation Island, Alaska, Depth 12m, Length approx 50mm. July, 2002 Photo: Clinton Bauder

In Nth America, Janolus fuscus ranges from the Kenai Peninsula, Alaska (Goddard & Foster, 2002) to central California (Behrens, 1991). It is also known from nthn Japan. It preys on arborescent bryozoans, including Bugula pacifica and species of Tricellaria (Goddard, 1998). It overlaps in distribution with the more southerly Janolus barbarensis, but the two species can be distinguished externally by ceratal differences; Janolus fuscus having unbranched digestive gland ducts and orange and white tips and Janolus barbarensis having branched digestive gland ducts and orange and blue tips (Gosliner, 1982; Behrens, 1991). Janolus fuscus hatch from irregularly coiled, cylindrical egg masses as planktotrophic veligers with type 1 shells 138 microns long (Goddard, 2001).

See message describing parasite, Ismaila belciki.

• Behrens, D.W. (1991) Pacific Coast Nudibranchs. Sea Challengers: Monterey, California.
• Goddard J.H.R. (1984) The opisthobranchs of Cape Arago, Oregon, with notes on their biology and a summary of benthic opisthobranchs known from Oregon. The Veliger, 27: 143-163.
• Goddard, J.H.R. (1998) A summary of the prey of nudibranch mollusks from Cape Arago, Oregon. Opisthobranch Newsletter, 24: 11-14.
• Goddard J.H.R. (2001) Mollusca: Gastropoda. Pp. 86-128. In: A. L. Shanks (ed.), An Identification Guide to the Larval Marine Invertebrates of the Pacific Northwest. Oregon State University Press: Corvallis, Oregon 314 pp.
• Goddard J.H.R. & Foster, N.R. (2002) Range extensions of sacoglossan and nudibranch molluscs to Alaska. The Veliger, 45: 331-336.
• Gosliner, T.M. (1982) The genus Janolus (Nudibranchia: Arminacea) from the Pacific coast of North America, with a reinstatement of Janolus fuscus O'Donoghue, 1924. The Veliger, 24: 219-226.
• O'Donoghue, C.H. (1924). Nudibranchiate mollusca from the Vancouver Island region. 4. Additional species and records. Transactions of the Royal Canadian Institute, Toronto, 15(1): 1-33.

Authorship details
Goddard, J.H.R., 2003 (February 1) Janolus fuscus O'Donoghue, 1924. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/janofusc

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  2. Janolus fuscus from northern Japan
    From: Nishina Masayoshi, July 9, 2004
  3. Janolus fuscus from Puget Sound
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  4. Additional information on Janolus fuscus
    From: Jeff Goddard, February 3, 2003
  5. Janolus fuscus from Alaska
    From: Clinton Bauder, August 8, 2002
  6. Janolus fuscus from British Columbia
    From: Marli Wakeling, June 4, 2000

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