Nudibranchs are mostly very colorful, and depending on the species, the color denotes danger (foul tasting) or is cryptic. Having evolved from shelled, torted ancestors, they have completely lost all vestiges of shell, and their bodies have de-torted. At the anterior end is a pair of tentacles (rhinophores), which are chemo-sensory structures, and near the posterior end are the gills (pseudobranchia).
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature