Chubby Simnia Shell, Simnia avena

Chubby Simnia Shell, Simnia avena. Size: 2.2 cm (0.9 inches) x  0.8 cm (0.3 inches). Shell collected from Islas de los Coronados, Baja California. October 1998. Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Chubby Simnia, Simnia avena (Sowerby, 1833), is a member of the Ovulidae Family of False Cowry Shells. The genus Simnia is one of forty-four genera in this family, and there are thirteen species in this genus. This species is also known as the Gorgonian Spindle Shell. In Mexico they are called Ovúlido Avena.

Description: The Chubby Simnia shell is shorter and stouter than most Simnias, but it is still an elongated, narrow, thin (to the extent that some shells are translucent), spindle-shaped shell. The exterior of the shell may be smooth or marked with very fine, spiral, lines. The aperture is very long and it grows wider at its lower end. The shells vary in color and can be brownish-lavender, lavender, orange, rose or white. The canal ends are usually a darker yellow or orange. The living animal varies in color to match its gorgonian host. Common colors include white, yellow, pink, red, or purple, with darker spots. They also exhibit raised papillae. The Chubby Simnia shell reaches a maximum of  2.4 cm (0.9 inches) in length and 0.9  cm (0.3 inches) in height.

Habitat and Distribution: Chubby Simnias are found attached to gorgonians at depths between 5 m (15 feet) and 76 m (250 feet). They are a temperate to tropical Eastern Pacific species. They are found along the entire Pacific coast of Mexico, including throughout the Gulf of California.

Ecology and Behavior: Chubby Simnias are predators that feed on feed on the polyps and flesh of their gorgonian hosts, including  Eugorgia, Muricea, and Psammogorgia. They are gonochoric and reproduce sexually. The eggs are laid at the base of their host gorgonian. There is no mention in the available literature of them engaging in any types of parasitic, commensal, or symbiotic relationships. 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: Delonovolva aequalis, Delonovolva aequalis aequalis, Neosimnia avena, Neosimnia avena avena, Neosimnia capitia, Neosimnia formicaria, Neosimnia spelta capitia, Ovula hordacea, Ovulum aequale, Ovulum avena, Ovulum lividum, Ovulum seminulum, Ovulum simile, Simnia aequalis, and Simnia rufa var. inflexa. 

Note:  the Chubby Simnia Sea Snail is currently presented within a sister Web-site, Mexican-marine-life.org under Mexican-marine-life.org/chubby-simnia.