Sea slugs may be nature’s “best-dressed” marine animals, as the Red Sea creatures on article attest. Unlike their gardenpest cousins, they come in a dazzling array of shapes, sizes, colors and patterns, and they are definitely not slimy. In addition, they may offer scientists maps to new drugs through the chemical compounds they produce. Sea slugs, scientifically known as opisthobranchs (“rear gills” in Latin), are highly evolved relatives of marine snails. Primitive sea slugs retain a thin external or internal shell, but advanced ones, like the nudibranchs, or “naked gills,” pictured in this gallery, have none. Living without this protection means they have had to develop other methods of defense, expressed in a wide display of adaptations seen in sub-orders such as dorids (which have gills near the tail and two sensory horns near the head), dendronotids (thosewith tree-like gills in pairs along their backs) and aeolids (those covered with fingerlike projections). Their bright colors and bold patterns warn predators of their noxious taste.
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| The chromodorids are
probably the most colorful and easiest sea slugs to recognize. Doris was a
Greek goddess, the daughter of Oceanus, and chromo means color, so they are
the colorful goddesses of the sea. Their colors and patterns are limitless,
although their basic body plan remains the same. Chromodoris geminus Rudman, 1987 is found in
the Red Sea and Indian Ocean and is truly beautiful underwater—its ocellated
spots are almost luminescent. Like many spotted species, it flaps the edges of
its mantle in a kind of rhythm, and the spots above and below glow.
Of the 4000-plus species of nudibranchs worldwide, more than 175 are found in the Red Sea and nearly one quarter of these live only there. This almost self-contained waterway—running some 2100 kilometers (1300 mi) from the Gulf of Suez in the north to the narrow Bab al-Mandab in the south—is a very special place, hosting endemic fish, sea urchins, worms, slugs and snails, and myriad other animals. It has been isolated for approximately five million years, and its fauna has suffered partial extinctions with several glaciations, the most recent 20,000 to 15,000 years ago, which substantially lowered sea levels. The Red Sea’s southern gateway opened around five million years ago—at the time land uplifts closed off its shallow link to the Mediterranean—and has never shut, so its fauna is Indo-Pacific. |
