Potpourri columns began a few months ago when I observed that from time to time I’d make an observation or come across a tidbit of information that, while interesting, would be difficult to flesh-out into a full column. At other times I’ve had to leave information out of columns because of word count limitations and thought this a good format to visit those subjects again. So here we go.
Mistaken Identity: Bryozoans provide us with one of the more interesting and wide spread examples of what you see may not be what it appears to be. Among the most ubiquitous yet disarmingly subtle marine creatures, bryozoans fall into that category.
Appearing for all the world to be mosses or alga, the 5,000 extant species of bryazoa are actually colonial animals made up of individual zooids.
A colony begins when a single larval zooid settles on a hard substrate and cements itself in place. Known as the ancestrula, after the completion of its larval metamorphosis, it begins to asexually reproduce by a process known as clonal budding. As the colony grows the succeeding zooids, though genetically identical to the to the ancestrula, may be polymorphic and produce a variety of shapes for specific functions within the colony.
While the vast majority of zooids of the thousands of bryozoan species measure a mere .5mm, the intricacy and variety of morphology exhibited between and within the two or three, depending on source material, major groups prohibits all but a most cursory and general description of what meets the eye.
Some bryozoans are dense encrusting organisms; think of paint spatters, velcro fuzz or the fried coating on a corndog as visual references. Others are delicate feathery creatures of great beauty (magnification usually required). All are of a kind you should find most interesting should you choose to pursue them on the web.
Sea Caterpillars: Or at least that’s what they remind me of. More commonly, if less generously, called sea slugs; nudibranchs form the largest suborder of the order Opisthobranchia of the class Mollusca with more than 3,000 known species and new ones being discovered with regularity. They may best be described as snails without shells.
It should be pointed out that while all nudibranchs are sea slugs, not all sea slugs are nudibranchs. There are a number of other suborders of opisthobranchia whose members are also called sea slugs.
Ranging in size fro 6mm to 31cm and found primarily in shallow waters of all the worlds oceans, nudibranchs are among the most wildly diverse animal groupings found on earth. Color and form ranges from the bland and basic to the psychedelic and highly complex, I suggest you google nudibranchs and check out the photo galleries. It gives a whole new meaning to words like bizarre and ostentation.
Virtually all nudibranchs are carnivores. Depending on species they feed on sponges, hydroids, bryozoans, anemones, barnacles and more. Some feed on other sea slugs and some are cannibalistic within their species.
The showy colors of some nudibranchs are a warning to would be predators. Many species that feed on anemones are able to ingest the stinging cells without triggering the firing pins and then transport those cells to their own epidermis. Others produce chemicals imparting a foul smell or taste.
Sad to say but the one species I regularly observe locally falls into the bland and basic category. They are gray in color, a half inch or so long with numerous fleshy spike-like appendages and may be seen beginning in early spring winding their white thread-like egg cases in the stems of hydroids growing on area dock floats.
All in all, nudibranchs are quite interesting critters. Speaking of critters, make plans to join us at the newly renovated Lowcountry Estuarium for our inaugural “Critter Fest – A Celebration of Creatures of the Estuary” from noon to 5 on May 30th.