10/21/2026
They say you are what you eat, but some nudibranchs take that saying to the next level. Can you spot the nudibranch hiding on this Common Sea Fan?
Nudibranch sea slugs are closely related to snails, however they do not need a shell for protection. At less than half an inch long, Hamner’s Tritonia uses its small size, striped patterning, and bumpy protrusions to blend into its surroundings. This species is found only on Common Sea Fans, surviving by exclusively eating its polyps.
But Hamner’s Tritonia doesn’t just eat its food, it steals its abilities! Instead of digesting the sea fan, this nudibranch retains the fan’s stinging cells in its body. This gives it a powerful defense, becoming stinging and distasteful to predators that may try to eat it.
Next time you are out exploring the reef, slow down and look closely: there may be a nudibranch hiding in plain sight!
NPS Photos 1-2 (Bella McCracken): A tiny, pale, striped nudibranch is visible on the purple, net-like pattern of a sea fan as it crawls across its surface. Brown polyps dot parts of the sea fan, but none are present directly surrounding the nudibranch.