Nudibranchs are an amazing group of colorful and diverse creatures that can be found throughout the world's reefs. They can vary in size from that of your fingernail to the big boys that bear a striking resemblance to certain Hawaiian sumo wrestlers. They are also known as "sea slugs" and belong to the mollusk group. Closely related to snails with shells, nudibranchs actually have a residual shell when young and shed it during adulthood. Beautiful coloration is their most striking feature and serves either as camouflage or a warning to potential predators that they are poisonous.

The name "nudibranch" means naked gills and the tail end of most sport a tuft of feathery objects that are the exposed gills that allow oxygen exchange. The front end is set off by a pair of feelers that are called rhinophores and are exquisitely sensitive chemical receptors for prey, dangers or potential mates.

The shell of the mollusk provides the obvious function of passive protection, allowing the snail to quickly pull inside and slam the door if any threat such as a Frenchman with a small dish of garlic butter approaches. In shedding the shell during the evolutionary process, the nudibranch has derived the benefits of being able to slip into the small spaces throughout the reef without the impediment of pulling a shell along. More interesting to marine observers is the necessity of developing defensive measures to take the place of the shell that was left behind eons ago.

Nudibranchs have perfected the technique of making themselves unpalatable to any potential predator. Their bodies are often covered on top by small projections called papillae that can secrete a number of noxious chemicals, including sulfuric acid! Studies have shown that predator fish have an intense aversion to anything with an acidic taste. I have often seen a nudibrach fall through the water, be gulped down by a passing fish and almost immediately spit back out. The fish has a facial expression remarkably like that of my wife when offered a piece of sushi. Certain nudibranchs feed on hydroids that contain stinging cells called nematocysts. They have the ability to separate the stinging cells from the digestible hydroid in their digestive tract and actually move the stinging cells into their own skin for protection!

"Pretty interesting", you say...."but get to the sex part!" OK, Nudibranchs are kinky little creatures and are both male and female, true hermaphrodites. They carry both eggs and sperm and cross fertilize each other. The mating process is very much like that in certain drinking establishments in South Florida. A Nudibranch who is in the mood for love can be seen with the upper body raised, searching for other like minded nudibranchs. When they make contact, one follows the other nose to tail for a while and then pulls up side to side, head to tail and a small tube protrudes from the side of one to the other and sperm is passed back and forth. After smoking very small cigarettes and exchanging telephone numbers, the two critters head their separate ways to deposit their fertilized eggs and wait for their future tax exemptions to arrive.


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Phillip Slosberg.
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