Lettuce Sea Slug GALLERYTridachia crispata
Not a nudibranch, but a sapsucking slug.
Often the term “nudibranch” is used for all sea slugs. However, while all nudibranchs are sea slugs, not all sea slugs are nudibranchs
The skin ruffles on the body of sapsucking slugs help the animal absorb oxygen. Some nudebranchs have gills and others have rows of tubular organs, called cerata which are more like external gills.
If you are very observant, you'll see these sea slugs in areas of algae,(which they feed on) both on reefs and sandy bottoms and coral rubble. They have two fairly large rhinophores (antennae) on the head. The most common color is green with white body spots and green and white ruffles, but the ruffles can also be shades of red and blue. They can grow to about 2 inches in length.