If you read my blog post from March 15, you know that many animals found in the ocean look much more like plants, than they do animals. Especially in marine communities associated with the bottom of the ocean, what are called benthic communities, many animal species have evolved to be attached to the bottom and never move. Animals of this attached sort are called sessile, and in most cases, once they attach themselves to the bottom, they never move again. Can you think of any animals found on land that are attached in one place and don't move? Plants, yes, but animals, no.
One beautiful example of a sessile animal is a sea fan, or gorgonian. Sea fans are grouped in the same category of animal as sea jellies and sea anemones, all of which have stinging cells that they use to subdue their prey. The sea anemones and sea fans are in a group that have a single body plan know as a polyp. You can think of a polyp as a sack with a ring of tentacles around the opening. In this case, the tentacles are studded with those stinging cells for capturing prey. While sea anemones are large, solitary polyps, sea fans are colonies comprised of hundreds to thousands of very small polyps. Sea fan polyps are visible to the naked eye, if you look closely when they are open to feed, but they are otherwise similar in structure to sea anemones.
The photo in today's post is a close-up view of the extended polyps of the golden gorgonian (Muricea californica) found off the California coast. Look closely and you will note that each polyp has exactly eight tentacles. This further groups then in a category of polyp-like animals called octocorals. As the name implies, octocorals have their bodies divided into eight parts.
Sea fans are colonial organisms and share a common system of internal tubes and cavities that connect each individual polyp to all of the other polyps in the colony. In this way, the food captured by one polyp is shared among all of the polyps in the colony.
While for all the world sea fans appear to be plants, they are in fact animals. Animals armed with sting cells to capture food as it floats by them on the ocean currents.
This photo was taken with a Canon EF100mm f/2.8 macro lens on a Canon EOS 10D in an Ikelite underwater housing. Lighting was provided by two Ikelite DS-125 Substrobes in eTTL mode. The exposure was set to 1/60 sec at f/11 and ISO 100.
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