January 2006
Streetwise Magazine |
Sluggish Times |
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Nudibranch, you might say! (And the same to you too). This is not a new form of Andalucia greeting, or something you find on the Cantarrijan naturist beach. It is in fact a very colourful name for a very colourful species of “Sea Slug” There are over 3000 species of Nudibranch in the world and they are some of the most beautiful creatures I have seen. |
They are essentially snails without shells, and the name means “naked gill. In most species the gills are prominently displayed on their backs and are used for respiration and in some cases for defence. They live on the ocean floor from tidal zones to over 700 metres deep.
All nudibranchs are carnivores, feeding on a variety of animals, which include sponges, anemones, barnacles, corals and sometimes on other nudibranchs. Each species tend to be selective feeders and may only eat one type of prey |
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As these creatures have no protective shell nature has provided an alternative defence system. The strikingly bright colours warn potential predators that they contain distasteful or toxic substances. We are lucky enough to have a very large specimen here on our local shores commonly called a “sea hare” ( Aplysia punctata) which changes colour according to that of its seaweed diet. Usually here they are a beautiful purple colour, growing up to 20cm in length.
Nudibranchs are simultaneous hermaphrodites, which means that they possess both male and female sex organs at the same time. Self-fertilization is very rare, but this strategy increases the probability of finding a mate, since every mature individual of the same species is a potential partner. (Well it would wouldn't it)? After mating, nudibranchs lay their egg masses either on or near the organism on which they feed.
Egg development can take between 5 and 50 days, and is strongly influenced by temperature. Warmer waters generally result in a shorter embryonic period. The eggs develop first into a larval form, which drifts in the ocean currents as plankton. Specific environmental conditions trigger the larvae to settle and metamorphose into the adult form. This larval dispersal is important in the successful exploitation of new areas. |
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If you find nudibranchs while snorkelling or diving, please do not attempt to pick them up or touch them. These creatures are very delicate and easily damaged, and you may hurt them inadvertently. Adult nudibranchs move very slowly and cannot travel long distances; I know just how they feel! Sluggish takes on a whole new meaning!!! |
Dave
ScubaDoo
Photos by D Graves, J Jensen, G Fairhurst.
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