Creature feature: Opalescent Nudibranch

One of the more beautiful creatures we find in our tidepools is the Opalescent Nudibranch or Hermissenda Crassicornis.  This organism has several adaptations (some of which I mentioned in an earlier post on Mollusks) that make it particularly interesting.  Most impressive is the nudibranch's ability to 'steal' stinging cells from its prey and pass them untriggered to the tips of its cerrata (the orange tipped structures on its back).    

Click to enlarge

As they live less than a year, they must go through their life cycle quickly and seem to do so without respect for the seasons.  Being hermaphrodites, nudibranchs can self-fertilize or mate with any other nudibranch of the same species though they usually choose the latter option (presumably to ensure the diversity of their gene pool).  

Another species, the Barnacle-eating Nudibranch, seen out of water

When tide-pooling, we often find opalescent nudibranchs close to the water line tucked away in rock crevices or sticking to pieces of kelp.  Searching amongst hydroids, one of their main food sources, is another way to increase the chances of an encounter with this nudibranch.  If you do find a sea slug and it is out of water, it is nice to have a small specimen jar or large clam shell that you can fill so as to observe the nudibranch in all its glory.  Be careful though, nudibranchs are delicate animals and cannot withstand rough handling.

Sources:
Monterey bay aquarium
Puget Sound Sealife