Nudibranch

Nudibranchs are my personal favorite type of gastropods because of their stunning colors and shapes. Nudibranchs are what people think of when  they think sea slugs (not surprisingly because of their stunning features). The name nudibranch came from the latin "nudus" (naked) and the greek "branchia" (gills). Just from the definition of their names you can tell that they have exposed gill structures on them. Nudibranchs are divided into two main kinds: dorids, which have a branchial (gill) plume, and aeolids, which have cerata speed across their backs instead of a plume.

Dorids:

Aeolids: