Photo by Mika d’Eau
Ever seen a slug eating a salad? Well, imagine that there are cousins of these slugs underwater which bear some of the most fascinating shapes, sumptuous hues, and intricate patterns of any animal. Very logically, as these critters are slugs living in the sea, they are called sea slugs but most of the marine life enthusiasts just call them nudibranchs. Juste bear in mind that all nudibranchs are indeed sea slugs but not all sea slugs are nudibranchs. To make it easier for everyone, let’s keep it simple and call them nudibranch for now.
Nudibranchs can live up to approximately one year, some species reach a size of 60cm/24in for a weight of up to 1.5kg/3.3lb, but most of them are small (size of a thumb) and many never grow bigger than 10mm/0.4in.
There are more than 6,000 species of sea slugs from which 3,000 known species are nudibranchs and new ones are being identified almost daily. They are found throughout the world’s oceans, but are most abundant in shallow, tropical waters. Their scientific name, Nudibranchia, means naked gills, and describes the feathery gills and horns that most wear on their backs.
Sea slugs can be herbivores (veggi diet), carnivores (they eat meat) or omnivores (eat just everything). Real nudibranchs are carnivores that slowly ply their range grazing on sponges, anemones, corals, barnacles, and even other nudibranchs. To identify prey, they have two highly sensitive tentacles, called rhinophores, located on top of their heads. Nudibranchs derive their coloring from the food they eat, which helps in defense (colorful means dangerous for other marine life) and/or camouflage, and some even retain the foul-tasting poisons of their prey and secrete them as a defense against predators.
Nudibranchs are simultaneous hermaphrodites and can mate with any other mature member of their species. Their lifespan varies widely, with some living less than a month, and others living up to one year.
Nudibranchs really are beautiful animals and on would love to keep them in a fish tank. Luckily, nudibranchs are nearly impossible to keep in aquariums because it is extremely difficult to provide them with their food resource.
They are an easy catch though and are commonly used in the development of medicines such as anti-cancer or Alzheimer’s disease treatments.
The main threat is climate changes, short and long term as they depend on a complex ecosystem for their food.
There is much more to learn about these beautiful critters and SSI just released a Nudibranch Ecology Specialty which will explain everything you ever wanted to know about Nudibranchs!
Best of it is that it was written by Mika and Evelyn, our base leader couple on Rannalhi (South Male Atoll) and you can profit from all their knowledge first hand.
