What’s a Nudibranch?

A nudibranch belongs, not surprisingly, to an order of invertebrates called Nudibranchia. They are called nudibranchs because, well, because they are nude. You have to admit it’s a more elegant term than just calling them sea slugs, which is what they actually are.  These guys are considered naked because they do not have a shell or mantle cavity. Both sea slugs and the garden slugs sliding around your backyard are gastropods, a word originating from Latin meaning “stomach foot.”  They are members of the Mollusca phylum, a huge and fascinating group of animals that also includes octopus, squids, clams, oysters, limpets, and a host of others.

Nudibranchs pretty much have the basic slug shape and move about just as you’d expect, they just do underwater in a marine environment. They boast a wide variety unique appendages from spiky tentacles to flowery gills. They’re not the cuddliest creatures on earth but in the looks department many species possess an exotic beauty that far outshines their land dwelling cousins. Vivid hues of pink, blue, orange, purple; every color and design imaginable. This beauty disguises a predatory lifestyle, however. They eat everything from barnacles to sponges, just about anything they can creep up on is considered dinner.

But one of the best things about these fascinating animals is how easy they are to observe. Unlike many oceanic mysteries nudibranch watching does not require a huge investment in diving gear or effort. All you have to do is head down to your nearest boat marina and check out the docks. It’s one of their favorite hangouts. Squat down and look closely. There among the mussels, anemones, and seaweed you’ll see a translucent, brilliantly colored, ghostly creature gliding along. That’s your nudibranch.