Nudibranchs are invertebrates that live in the ocean and look like colorful slugs. Belonging to the phylum Mollusca, the term Nudibranch, comes from the Greek for “naked gills”. 3000 known species have been found and scientists estimate that is only half.
These animals can be very poisonous. In fact, their poison can be so potent that they will kill almost anything in a 50 cm radius. Although some make their own poison, most eat the poisonous thing in the ocean, which in turn makes them more poisonous. Some Nudibranchs eat and absorb sting cells, which they use for defense. Some are completely harmless and pretending to be deadly.
All nudibranches eat different species of hydroid colonies and sponges, and they will even eat each other. Some nudibranchs make use of photosynthesis, by eating certain hydroids, the nudibranchs take in zooxantelles (microscopic plants) and use them symbiotically to acquire food through their photosynthesis.
Nudibranch anatomy is relatively simple with three main parts head, foot, and visceral mass. Rhinomphore, caryophllidia, gills and eyes are all parts of the Nudibranch as well. Caryophllidia are an external nervous system for the Nudibranch and can be found extending all around the surface of the Nudibranch. The head contains the mouth, eyes, and rhinophores. The rhinophores are the main sensory origin for the Nudibranch. The mouth is on the under side of the head. The rhinophores are so important because the nudibranch’s eyes are poor. They only can sense dark and light. Not only are they a weak sensory organ but are buried under a layer of skin. The boundary
of the head is usually defined by the eye placement which is towards the back of the head.
The rest of the body is really the visceral mass that sits on top of the foot. The gills and cerata are located in this area. The cerata aid in respiration and, in some species, help with defense because they have nematocysts on them.
These amazing animals are helping with everything with satisfying someone’s need to collect things to fighting cancer. As you just saw, these are truly eye opening animals.