What is the nudibranch related to?

Answer 1

Nudibranchs are a diverse order of marine organisms of the subclass Opisthobranchia,class gastropoda, and phylum Mollusca (Hoover, 1999). These invertebrates are commonly called sea slugs and are popular in aquariums because they are brightly colored. In general these shell-less gastropods can be found in most marine benthic waters, including the Artic (Bryan & McClintock,1998). There are even a few tropical fresh water species. Nudibranchs can be separated into distinct sub-orders. Two such suborders are Doridacea, also known as Dorids, and Aeolidaecea, also known as Aeolids. The two can be differentiated by the shapes of their mantles. Their bodies are soft and and detorted compared to their twisted relatives, the snails. Nudibranchs are defined by their exposed gills, thus the name Nudibranch which means "naked gills." Their gills are located on the outside of their body instead of hidden in a mantle cavity. In Dorid nudibranchs, the gills are in flower-like structures are called branchial plumes located on their backs. The gills surround their anal opening, and can be retracted into a gill-pocket on the mantle. The mantle is wide and typically almost entirely encompasses the foot. Aeolids do not have gills, instead they posses tentacle-like cerata made of thin mantle tissue used for respiration and defense (Picton & Morrow,1994). Nudibranchs move using a foot for crawling and by undulating of their body to swim. (Caldwell & Donovan,2003).

Sources:

Bryan P,McClintock J. (1998) Population biology and antipredator defenses of the shallow-water Antarctic nudibranch Tritoniella belli.Marine Biology.132.2.159

Caldwell S, Donovan D.(2003) Energetics of swimming and crawling in the lion nudibranch, Melibe leonina. The Velige. 45.4.355-361

Hoover JP (1999) Hawai'i's Sea Creatures: A Guide to Hawai'i's Marine Invertebrates. Mutual Publishing.

Picton B,Morrow C.(1994) A Field Guide to the Nudibranchs of the British Isles. London, England.