Flabellinidae Family of Nudibranchs

Two Nudibranchs of the Flabellinidae Family can be found in this  website:

Phylogeny:  Flabellinidae Nudibranchs of the Flabellinidae Family are Aeolids that belong to the Phylum Mollusca. They are in the class Gastropoda, the subclass Heterobranchia, the infraclass Euthyneura, the subterclass Ringipleura, the  superorder Nudipleura, the order Nudibranchia, the suborder Aeolidina, and the superfamily Aeolidioidea. The Flabellinidae Family is one ten families in this superfamily. The Flabellinidae Family contains six genera and around thirty-nine species. The name Flabellinidae is derived from the Latin word for “fan” or “whisk” and probably refers to the cerata found on these nudibranchs.

Morphology:   Flabellinidae Nudibranchs are Aeolid nudibranchs. As such they are soft-bodied gastropods that lose their shells during their larval phase. Aeolids have a mantle that forms a series of finger-like projections (cerrata) along the entire back of the animal. Flabellinidae Nudibranchs that have an elongated, high, tapering, profile, usually with a pointed tail.  The oral tentacles are long and tapering The rhinophores can be either smooth, or have clubs that are papillate or lamellate but there are no basal sheaths. The anterior corners of the foot are rounded or form short tentacles. The mantle has a ridge that runs down the middle of the dorsal surface. The cerata, set in rows or clusters, are long and tapering and can be raised on lobes. Flabellinidae Nudibranchs have rhinophores (horn-like projections) on their heads that are chemosensory organs that help them to locate food and potential mates. They  lack complex eyes, but have photo-receptors at the base of their rhinophores. Many species in this family are brightly colored. They derive the pigments for their color from the food they eat. Most species in this family reach a length of 1 cm (0.4 inches) – 4 cm (1.4 inches). The largest species exceed 6 cm ( 2.3 inches).

Distribution:  Flabellinidae Nudibranchs are found on, or under, rocks, in crevasses, and on vertical and overhanging surfaces. They live in the intertidal zone and 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. Flabellinidae Nudibranchs are found worldwide, in tropical to temperate waters, however, these nudibranchs are best represented in colder waters. At least eleven species from this family are found in  Mexican waters.

Reproduction:  Flabellinidae Nudibranchs are simultaneous hermaphrodites (having male and female reproductive organs). They reproduce sexually by hypodermic insemination. This occurs when both mating partners dart their penis toward each other to induce one to act as a male and the other as the female. The victorious one to penetrate the body wall is the dominant male. The eggs are laid as a mass on the bottom stratum. The eggs hatch into veliger larva and later metamorphose into adults.

Ecosystem Roles:  The Flabellinidae Nudibranchs feed exclusively on hydroids. In turn they are preyed upon by other nudibranchs. They can store stinging cells (nematocysts) that they obtain from the food they eat in cnido-sacks that are located at the end of their cerata as a defense mechanism.