Nudibranchs/Sea Slugs

Nudibranchs/Sea Slugs

Nudibranchs, commonly known as sea slugs, are a group of shell-less marine mollusks. Their name means ‘naked gill’, referring to the breathing apparatus on the outside of their soft bodies.

Generally oblong in shape, nudibranchs can be thick or flattened, long or short, ornately colored or drab to match their surroundings. They can grow as small as 0.25 inches or as large as 12 inches long.

They are carnivores that slowly ply their range grazing on algae, 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 camouflage, and some even retain the foul-tasting poisons of their prey and secrete them as a defense against predators.

Some nudibranchs are poisonous so it’s better not to touch them. Even if they aren’t poisonous, touching one could nearly squeeze, squish, and suffocate it to near of simply, death. Some nudibranchs are poisonous while others pretend to be. They feed on stinging cells of hydrozoids and store them in the rear of their body for protection. They can also ingest toxins from sponges and become toxic and inedible.

Another great fact is that nudi’s are both genders! They aren’t exactly male or female. This comes in very handy, as finding a mate can be a very, very frustrating task for the little slugs. However, they still require a mate in order to reproduce, as they are not able to self-fertilize.

There are more than 2,000 known species of nudibranch, and new ones are being identified almost daily. In this post, I add different photos of nudibranchs I saw on the Red Sea
My favorite one is Spanish Dancer:
The most beautiful sea slug might be the Spanish Dancer.
It’s quite rare to spot one but if one’s around, you’ll know. They have bright red so they’re hard to miss. Their flashy color also indicates that Spanish Dancers are poisonous.
They quite obviously got their name from the way they swim. It’s like they are dancing in a beautiful red dress.  The Spanish Dancer is the biggest nudibranch, and even the largest sea slug on the planet!
The eggs can be distinguished from other species of nudibranchs thanks to their bright pinky coloration and rose shape.
The parents will provide the eggs with the same chemicals they extract from the sponges to protect them since they won’t care for the eggs after depositing them on the reef.
It is believed that the shape and color of the eggs are part of the romantic ritual during mating.
Sabrina Kos
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