Arminidae Family of Sea Slugs

Striped Nudibranch, Armina californica. A representative of the Arminidae Family of Nudibranchs.

Phylogeny:  The Arminidae are nudibranchs that are members of the Arminidae Family of Sea Slugs. There are ninety-eight members in the Arminidae Family of which four species are found along the west coast of Mexico. They belong to the Phylum Mollusca. They are in the Class Gastropodia and the Order Nudibranchia. Arminidae Nudibranchs are Dorid Nudibranch that fall 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. The Dorids have a thick mantle on their dorsal surface that extends over the foot.

Distribution:  Arminidae Nudibranchs are found worldwide in tropical and temperate seas. They are found over and within sand and mud substate from the intertidal zone or subtidally at depths up to 30 m (98 feet). A few species are known to depths of greater than 200 m (660 feet).

Morphology:  Arminidae Nudibranchs have an elongated oval flattened profile with soft bodies that lose their shells during their larval phase. They have a thick mantle, with ridges that run lengthwise, that tapers gradually to a pointed or rounded tail. Some of the Arminidae have mantles that are pustules or smooth. Their dorsal surfaces do not have cerrata; they have numerous cnidosac around the margins of their mantles and are distinguished by having an oral veil. The Aeolids have “naked gills” exposed on their dorsal side that assist with digestion. They have have ability to incorporate stinging cells from their prey which they use to avoid predation. Dorids have gills that consist of feathery plumes that encircle the anus. Their retractable rhinophores have vertical lamellae that are set close together and well forward.  Arminidae reach a maximum of 20 cm (7.9 inches) in length but most are much smaller. 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 prey they consume. All nudibranchs have rhinophores(horn-like projections) on their heads that are chemosensory organs that help them to locate food and potential mates. Nudibranchs lack complex eyes, but have photo-receptors that sense light and dark.

Ecosystem Roles:  Arminidae Nudibranchs feed on soft coral, sea anemones, sea pens, and sea pansies. They have the ability to store toxins from their prey in their mantle that provides them with a defense against predation.