{{Short description|Species of gastropod}} {{Speciesbox | image = Janolus fuscus 3.jpg | taxon = Janolus fuscus | authority = O'Donoghue, 1924 }}
'''''Janolus fuscus''''' is a species of sea slug, or more accurately a nudibranch, a marine gastropod mollusc in the family Janolidae.
==Distribution== The species ''Janolus fuscus'' is found from the Kenai Peninsula, Alaska to central California and also in northern Japan.<ref>{{cite web|url=http://www.seaslugforum.net/factsheet.cfm?base=janofusc |publisher=Sea Slug Forum |title=''Janolus fuscus'' |access-date=24 December 2006 |url-status=dead |archive-url=https://web.archive.org/web/20070713073500/http://www.seaslugforum.net/factsheet.cfm?base=janofusc |archive-date=13 July 2007 }}</ref>
==Habitat== This species of nudibranch is found in intertidal and subtidal zones. These areas are shallow and rocky, and Janolus fuscus do not inhabit spaces deeper than 30m.<ref name="centralcoastbiodiversity.org">{{Cite web |title=White-and-orange-tipped nudibranch • Janolus fuscus |url=https://www.centralcoastbiodiversity.org/white-and-orange-tipped-nudibranch-bull-janolus-fuscus.html |access-date=2022-10-25 |website=Biodiversity of the Central Coast |language=en}}</ref>
==Description== thumb|left|''Janolus fuscus'', head end towards the top The bodies of nudibranchs in this species are semi-translucent and whitish-grey, and reach lengths of about 35mm. The body is covered in short cerata with brown cores, and the exterior fades to orange and then white at the tip. Its rhinophores have around 20 lamellae and are also white tipped.<ref name=":0">{{Cite book |last1=California Malacozoological Society. |url=https://www.biodiversitylibrary.org/item/134152 |title=The veliger |last2=Society |first2=California Malacozoological |last3=Club |first3=Northern California Malacozoological |date=1981 |publisher=California Malacozoological Society |volume=24 |location=Berkeley, CA}}</ref> The cerata in front of the rhinophores (as well on the standard back of them) are a distinguishing factor between it and other nudibranch species' that are similar in appearance.<ref name="centralcoastbiodiversity.org"/>
==Life habits== ''Janolus'' species feed on Bryozoa, specifically ''Bugula californica'' and ''Tricellaria.''<ref name=":0" /> The fuscus species live for approximately five months.<ref name=":1">{{Cite journal |last1=Wolf |first1=Maya |last2=Young |first2=Craig M. |date=May 2014 |title=Impacts of an endoparasitic copepod, Ismaila belciki, on the reproduction, growth and survivorship of its nudibranch host, Janolus fuscus |url=http://dx.doi.org/10.1016/j.ijpara.2014.02.002 |journal=International Journal for Parasitology |volume=44 |issue=6 |pages=391–401 |doi=10.1016/j.ijpara.2014.02.002 |pmid=24590063 |issn=0020-7519|url-access=subscription }}</ref> thumb|left|''Janolus fuscus''
==Predators== In California, ''Navanax'' is a known predator of ''Janolus''. ''Navanax'' tracks the slime of ''Janolus'' by using chemoreceptors. When ''Janolus'' is about to be caught, it rolls into a ball, leaving its cerata exposed. If there is a water current, as if often the case, the sea slug may then be passively rolled away from the predator.
==Parasitic threats== ''Janolus fuscus'' can be infected with a parasitic crustacean called ''Ismaila belciki.'' This is fairly common, and in some monitored populations of the nudibranchs such as Coos Bay, Oregon's, the rate of infection is up to 80%. When I. belciki is present in this species, it is covertly located inside the body cavity so the only portion that can be seen from the outside are egg sacs. The parasite does not interfere with the growth of its host, but it poaches off the sea slug for many functions including taking the nudibranch's resources that it uses for egg production to use for I. belciki's own egg production, making reproduction slow for the host and the survival rate lower as a whole.<ref name=":1" />
==References== {{Reflist}}
==External links== * Sea Slug Forum info at: [https://web.archive.org/web/20070715023333/http://www.seaslugforum.net/display.cfm?id=9060] * SlugSite info: [http://slugsite.us/bow/nudwk148.htm]
{{Taxonbar|from=Q1120035}} {{Use dmy dates|date=May 2017}}
Category:Nudibranchs Category:Taxa named by Charles Henry O'Donoghue