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 (1619 Posts)

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, created to facilitate research to address fundamental questions in evolutionary science. He has conducted deep-sea research for 11 years and published over 40 papers in the area. He has participated in dozens of expeditions taking him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses mainly on marine systems and particularly the biology of body size, biodiversity, and energy flow. He focuses often on deep-sea systems as a natural test of the consequences of energy limitation on biological systems. He is the author and chief editor of Deep-Sea News, a popular deep-sea themed blog, rated the number one ocean blog on the web and winner of numerous awards. Craig’s popular writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.





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3 comments on “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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