Nudibranchs

Nudibranchs are snails without shells, basically the underwater version of a slug. Their name comes from Latin and Greek and means “naked gills.”

Every color of the rainbow can be found in the over 3,000 species of nudibranchs. A quick Google image search will show you the incredible beautify of these animals. In the animal kingdom bright colors often signify a warning, “don’t eat me, I might make you sick.” This is true for nudibranchs too as you can see in these pictures of the zebra nudibrach, Hypselodoris zebra.

Nudibranchs are carnivores. A fun fact about nudibranchs is that they often have a diet of toxin-filled animals, like sponges. Not only do the toxins not injure the nudibranch, but the nudibranch incorporates the toxins into its own skin! Some who eat animals with nematocysts (stinging cells) like anemones or jellyfish can even incorporate those into their bodies! Talk about self-defense!

I did my research project on the zebra nudibranch when I was at the Bermuda Institute of Ocean Sciences. The project didn’t work out as planned, but I got to learn a lot more about these fascinating and beautiful underwater snails.

They have horns on their head called rhinophores that are used to sense tastes or scents. Those sorts of receptors are called chemosensory organs. For protection, some nudibranchs can suck in their rhinophores to keep them safe.

One of the most interesting things about nudibranchs is their sex life. They are simultaneous hermaphrodites – both male and female at the same time! This is a benefit for the nudibranchs because if they can mate with any individual they happen to run into. After mating the nudibranchs produce a clear jelly-like band that houses their eggs. In the zebra nudibranch the eggs are bright red as seen here. They make spirals of these egg bands on hard surfaces like corals or the side of a tank like here. Then, the baby nudibranchs hatch.

You can learn more about nudibranchs by watching this great video.

Photos by Sara MacSorley