Rhian Williams ‘25
What do you picture when you read the words: sea slug? Some form of a gewy, slimy, worm? Would it surprise you to find that sea slugs can be cute? Forget cute, what even is a sea slug?
Nudibranchs, commonly known as sea slugs, are gastropods who live in the shallow waters of world oceans. There are 2,000 species of sea slug, and the largest a sea slug can get is around three feet and two inches, while the smallest gets no larger than one inch.
And without further ado, let’s meet some of the cute, colorful, and sometimes dangerous sea slugs that are top on my favorites list.
The Sea Sheep (Costasiella Kuroshimae)
(Cover Image)
The sea sheep was discovered in 1993 off the coast of the Japanese island Kuroshima. They grow up to only one inch long and are mainly found near Japan, Indonesia, and the Philippines. What makes these little guys interesting is the fact that they are kleptoplastic. This means that they can photosynthesize even though they aren’t plants! How do they do this? Well, sea sheep and other organisms who can perform the process of kleptoplasty have the ability to take the plastids (Chloroplasts) from an aquatic plant like algae and store it in their own body.
Pikachu Sea Slug (Thecacera pacifica)
The Pikachu slug is mainly found in the Indian Ocean and the Western Pacific Ocean. These guys are not seen too often, so it’s considered very special when one is spotted! Full grown adults are usually only 0.8 Inches long, or about two centimeters. This slug gained popularity due to its close resemblance to the famous Pokémon character, Pikachu.
Sea Bunny (Jorunna parva)
The Sea Bunny was discovered in 1938 by Japanese biologist Kikutaro Baba. They grow up to about one inch long and are found mainly in the Philippines, Tanzania, Papua New Guinea, and Australia. The appendages on their head, or the “bunny ears” that gave them their common name, are actually used to detect changes in chemicals and currents. Though these guys are cute, don’t hug them! They are very toxic. They absorb the toxins from prey (like toxic sponges) and use it as their own defense. Sea bunnies may be small, but they can put up a fight. To defend themself against predators, they will grab stingers from jellyfish and use them as weapons.
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Blue Dragon (Glaucus atlanticus)
The Blue Dragon was discovered in 1777 and only grows to about 1.2 inches. These little guys float on their backs, an air bubble in its stomach helping keep the buoyancy.. Their stomach is a silvery-gray which blends in with the bright surface of the sea, and their backs are a darker blue to blend in with the ocean. Just like the pikachu slug above, no touching please! They feed on aquatic animals who float close to the surface. They steal stinging Hematocystsl from their favorite foods (Portuguese Man o’ War) and store them in their fingers like appendages. Though they can’t kill you, their sting does hurt!
Black-margined Nudibranch (Glossodoris Atromarginata)
The Black-Margined Nudibranch is native to the Pacific and Indian Oceans. They grow to around an inch and a half, and are commonly found closer to the surface of the waters. They are a rather docile species, spending most of their life “crawling” on rocks and reefs, or curled up on some pre organism like a sponge. What makes this form of slug so fascinating is the way it moves or “crawls”. The outer parts of their body move in a wave, making it an entrancing motion.
If you made it this far, thank you for reading! I hope you learned that little weird things like sea slugs can be pretty and deadly too.