Facelinidae Family of Nudibranchs

Las Cruces Acolid, Phidiana lascrucensis. A representative of the Facelinidae Family of Nudibranches.

Phylogeny:  Nudibranchs of the Facelinidae Family are Sea Slugs in the Phylum Mollusca. These Chromodorids are separated into two main classifications, the Aeolids and the Dorids. The Aeolids have a mantle that forms a series of finger-like projections (cerrata) along the entire back of the animal; these cerrata function as gills that assist with digestion, and they can incorporate stinging cells, from their prey, that they utilize for defense. The Dorids have a thick mantle on their back (dorsal surface) that extends over the foot; their gills consist of feathery plumes that encircle the anus. and the Order Nudibranchia. Facelinidae Nudibranchs are Aeolid Nudibranchs. They are in the Class Gastropoda and the Order Nudibranchia.

Distribution:  Facelinidae Nudibranchs are found worldwide, in tropical and temperate waters. There are approximately one hundred thirty members in the Facelinidae Family of which at least four species are found along the west coast of Mexico. Facelinidae Nudibranchs are found on, or under, rocks, in crevasses, and on vertical and overhanging surfaces. Most are found intertidally or subtidally at depths up to 30 m (98 feet), either because it is the actual depth limit, or because most observations are made by SCUBA divers.

Morphology:  Facelinidae are soft-bodied gastropods that They have an elongated deep body, often with a tapering tail. These nudibranchs have regular rows of cerata, which may be club-tipped, coiled, curved, tapering or tubular. They have long oral tentacles and rhinophores. Their rhinophores have numerous rings or collars and the radula has a single row of teeth. The anterior end of the foot is angular. The anus is more anterior than Aeolididae Nudibranchs. All nudibranchs have rhinophores (horn-like projections) on their heads that are chemosensory organs that help them to locate food and potential mates.  They lose their shells during their larval phase.  Nudibranchs lack complex eyes, but have photo-receptors that sense light and dark. 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. They range in size from less than 1.0 cm (0.4 inches) to more than 8.0 cm (3.1 inches).

Ecosystem Roles:  Facelinidae Nudibranchs are relatively fast moving, aggressive, predators feeding on algae, coral polyps and other cnidarians, and sea slug eggs. In turn they are preyed upon by other nudibranchs. Some species store the stinging cells (nematocysts) from their food in cnidosacs at the end of their cerata, that they utilized to provide defense. Other species are zooxanthellate that have a symbiotic relationship with single-cell dinoflagellates, known as zooxanthellae. Zooxanthellae live within certain coral polyps, jellyfish, nudibranchs and sea anemones. The zooxanthellae produce energy, during daylight, by means of photosynthesis. This energy is passed along to their hosts, sometimes providing up to 90% of the host’s total energy needs. In return, the host provides nutrients, carbon dioxide, and a secure, sunlit, platform for the zooxanthellae.