Spanish Shawl, Flabellinopsis iodinea

Spanish Shawl, Flabellinopsis iodinea. Underwater photographs taken in the coastal waters off San Diego, California, March 2018. Photographs courtesy of Bob Hillis, Ivins, Utah.

Spanish Shawl, Flabellinopsis iodinea. Underwater photograph taken in the coastal waters off Anacapa Island, California, February 2021. Photograph courtesy of Bob Hillis, Ivins, Utah.

Phylogeny:  The Spanish Shawl, Flabellinopsis iodinea (J. G. Cooper, 1863), is a member of the Flabellinidae family of Nudibranchs. The genus Flabellinopsis is one of only two genera in this family, and this is the only species in this genus. They are known in Mexico as Chal Español.

Morphology:  Spanish Shawl nudibranchs are soft-bodied gastropods that lose their shells during their larval phase. They have elongate, deep bodies, with a tapering tail. Their mantle forms a series of finger-like projections (cerata) along the entire back of the animal. These cerata function as gills, they assist with digestion, and they incorporate stinging cells, from their prey, as a defense mechanism. Spanish Shawls have long rhinophores (horn-like projections) on their heads. Rhinophores are chemosensory organs help them to locate food and potential mates. These nudibranchs lack complex eyes, but have photoreceptors that sense light and dark. Spanish Shawls are purple to bluish-purple in color. The cerata are bright orange, and the rhinophores are red with a white line. These beautiful nudibranchs reach up to 10.0 cm (3.9 inches) in length.

Habitat and Distribution: Spanish Shawls are found on rocks, intertidally, and to a depth of 122 m (400 feet). They are an Eastern Pacific species with a wide, but discontinuous range. In Mexican waters they are limited to the west coast of the Baja Peninsula, from the northern border to San Juanico, Baja California Sur, and they are found throughout the Gulf of California. Specimens from the Gulf are reportedly larger and more robust than California specimens. This species can be seasonally abundant.

Diet:  Spanish Shawls are predators that feed on compound ascidians and the Tree Hydroid, Eudendrium ramosum. They incorporate both the pigment, for their coloration, and the stinging cells, for defense, from this food source.

Predators: Spanish Shawls are preyed upon by the larger sea slug Navanax, Navanax inermis. They are also prey for crustaceans and sea stars.

Reproduction:  Spanish Shawls 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 bright orange ribbon, often on their hydroid prey. The eggs hatch into veliger larva and later metamorphose into adults.

Ecosystem Interactions:  Spanish Shawls are a poorly studied and understood species. There is no documentation of their involvement in commensal, parasitic, or symbiotic relationships.

Human Interactions:  Spanish Shawls have no direct impact on human activities. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms:  Aeolis iodinea and Flabellina iodinea.