“Nudibranchs crawl through life as slick and naked as a newborn. Snail kin whose ancestors shrugged off their shell millions of years ago, they are just skin, muscle, and organs sliding on trails of slime across ocean floors and coral heads the world over.” This is how National Geographic magazine presents these tiny sea animals in just a few lines. You may have passed them by without noticing them, snorkeling in a coral reef area, in Kuwait or elsewhere in the world.
Nudibranch means “naked gill”. Members of the gastropod class, and more broadly the mollusks, these mostly finger-d animals live “nude” and without a shell, their gills forming tufts on their backs. During its research missions on islets Qaru and Umm Al-Maradim, and sponsored by TOTAL Foundation and TOTAL Kuwait, the Kuwait Turtle Conservation Project, in cooperation with the Voluntary Work Center and The Scientific Center, met with a number of nudibranchs and their cousins, the flatworms, realizing how their presence contributes to the biodiversity of the reef habitats of the islets. The ringed chromodorid (Chromodoris annulata) was encountered a number of times in Qaru and Umm Al-Maradim, especially in the shallows, the long and graceful Flabellina bicolor was seen once moving gracefully on the seabed among coral and a number of Bedford’s flatworms (Pseudobiceros bedfordi) were photographed by KTCP divers in waters no deeper than three meters in Qaru in October 2009.
Found from sandy shallows and reefs to the murky seabed nearly a mile down and their family probably hosting the most colorful creatures on earth, nudibranchs thrive in waters both warm and cold and even around billowing deep-sea vents. Although they can release their muscular foothold to tumble in a current—a few can even swim freely—they are rarely in a hurry.
So why, in habitats swirling with voracious eaters, aren't nudibranchs picked off like shrimp at a barbecue? The 3,000-plus known nudibranch species, it turns out, are well equipped to defend themselves. Not only can they be tough-skinned, bumpy, and abrasive, but they've also traded the family shell for less burdensome weaponry: toxic secretions and stinging cells. Some feed on toxic sponges and others hoard capsules of tightly coiled stingers, called nematocysts, ingested from fire corals, anemones, and hydroids. Immune to the sting, the slugs deploy the stolen artillery along their own extremities.
In Qaru, the team observed several dozen species of carnivore fish bypass nudibranchs without considering going closer. Nature knows its ways. And these animals, commonly known as “sea slugs” are practically in no danger of predators, other than the human eye that can occasionally become nasty. As every other sea organism, nudibranchs and flatworms highly depend on healthy coral reefs, which in turn, are susceptible and vulnerable to pollution. Degradation of the reef means we may soon not be able to sea ornate nudibranchs while snorkeling in Kuwait. Do we really want that?
Humans have studied sea slugs' simple nervous systems for clues to learning and pharmaceuticals. Scientists today are isolating chemicals that may help ailing hearts, bones, and brains. A sea hare (cousin to the nudibranch) recently offered up a cancer-fighting compound that made it into clinical trials.
Still, nudibranchs have hardly given up all their secrets. Scientists estimate that they've identified only half of all nudibranch species, and even the known ones are elusive. Most live no more than a year and then disappear without a trace, their boneless, shell-less bodies leaving no record of their brief, brilliant lives.
In conclusion, nudibranchs and other sea slug species are not only gorgeous to view on a diving or snorkeling expedition, but are very useful to the sea as they enhance its biodiversity and their existence may prove more important than we think for the production of all kinds of medicine curing human disease. They are small but important. Beautiful but toxic. Watch with admiration and avoid any handling. Experts are there to do that, if necessary.