A Blanket of Mucus

You are fish.  The guy above is your enemy, a Gnathiid isopod, a vicious parasitic relative of a roly-poly.  Your defense?  You cough up enough loogies to coat yourself in a protective layer of joyous mucus.

Of course you are not a fish and fish don’t need to cough 1,000’s of thick loogies.  If you were a parrotfish all you would need is to secrete a thin layer of mucus to cover yourself every evening.  You sleep and your mucus blanket protects you.  What do you care? Sure you may not be attracting the opposite sex all covered in your own slime but that is little price to pay for not getting eaten alive. Moreover, that mucus blanket costs so little.  A mere 2.5% of your daily caloric intake.  Of course you could not produce that mucus and risk a 95% chance of having flesh picked at by your friend above.  I personally pick the nice juicy mucus coat and cut my chances down to 10% of being picked off in my sleep by parasites.

Grutter, A., Rumney, J., Sinclair-Taylor, T., Waldie, P., & Franklin, C. (2010). Fish mucous cocoons: the ‘mosquito nets’ of the sea Biology Letters, 7 (2), 292-294 DOI: 10.1098/rsbl.2010.0916

Dr. M (1801 Posts)

Craig McClain is the Executive Director of the Lousiana University Marine Consortium. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Additionally, Craig is obsessed with the size of things. Sometimes this translated into actually scientific research. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (http://deepseanews.com/), a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.

3 Replies to “A Blanket of Mucus”

  1. Another theory I read was about the mucous containing or capturing the scent of the sleeping fish helping to keep it safe from predators. I had my doubts; what do you think?

  2. From the introduction of the paper

    In an early study, showing that spotted moray eels (Gymnothorax moringa) ate more of three species that do not secrete cocoons (Sparisoma radians, Sparisoma chrysopterum and Cyprinodon sp.) than a parrotfish species that does (Scarus croicensis), Winn & Bardach [6] ‘tentatively’ (p. 298) concluded that cocoons reduce predation by the spotted moray eel. However, the effect of species differences was not controlled for nor was mucous cocoon presence manipulated, and many individuals of the cocoon-producing species were still eaten during the experiment. Indeed, the role of mucous cocoons in large wrasse as defence against predators while wedged in crevices or buried in sand has been questioned [7,8].

  3. The gnathiid idea is pretty solid. Its akin to a mosquito net. Gnathiids are ubiquitous on reefs and the cumulative effect of all that blood draining can be serious. Of course, cleaner wrasse can help, but that’s a whole’nother story; cleaners aren’t nearly as altruistic as people think they are. I feel a blog post coming on…

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