Discodorid Family of Nudibranchs

San Diego Dorid, Diaulula sandiegensis. A representative of the Discodorid Family of Sea Slugs.

Phylogeny:  Discodorid Nudibranchs are Sea Slugs in the Phylum Mollusca. They are in the Class Gastropoda and the Order Nudibranchia.

Distribution:  Discodorids are found globally in tropical, temperate waters. They are found on, or under, rocks, in crevasses, and on vertical or overhanging surfaces. Most are found intertidally or subtidally, but some are found at depths greater than 200 m (656 feet). The Discodorid Nudibranch Family is large with three hundred and six individuals of which sixteen are found along Mexico’s Pacific Coast.

Morphology:  Discodorids Nudibranchs are soft-bodied Dorids. They usually have an oval very flattened profile. Some actually resemble Flatworms more than nudibranchs. Their mantle is wide and thick, with the skirt extending over the foot covering the entire animal. The mantle may be smooth, ridged, tuberculate or pustulose in texture. Their foot is large relative to the animal. All nudibranchs have rhinophores (horn-like projections) on their heads which are chemosensory organs help them to locate food and potential mates. Their rhinophores are lamellate, often with raised sheaths and can be completely retracted into separate pockets. Their gills consist of feathery plumes that encircle the anus that are set posteriorly and can be retracted. Nudibranchs lack complex eyes but have photoreceptors that sense light and dark. They lose their shells during their larval phase. Despite their inability to see color, nudibranchs are some of the most brightly colored of all animals. They derive the pigments for their color from the food they eat.

 Ecosystem Roles:  Discodorids are specialized predators that consum sponges, with most species preferring only one species of sponge. This family exhibits a variety of dense mechanisms. Some Discodorids can shed a piece of their mantle to distract predators long enough to escape. The mantle will then regenerate. Others can secrete acid through their mantle. This acid provides a citrus scent to some species. Some can also swim to avoid predation. The primary predators of these nudibranchs are other nudibranchs.