Oryzatus Worm Shell, Thylacodes oryzatus

Oryzatus Worm Shell, Thylacodes oryzatus. Shell provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, May 2008. Size: 28 cm (11 inches).

Phylogeny: The Oryzatus Worm Shell, Thylacodes oryzatus (Morch, 1862), is a gastropod mollusk that is a member of the Vermetidae Family of Worm Shells. The genus Thylacodes is one of twelve genera in this family, and there are forty species in this genus.

Description: Oryzatus Worm Shells are loosely spiraled only for the short section of their length that attaches to rock. The remainder of the shell is straight or gently curved. The shell increases in diameter as it gets farther from the attachment end. The exterior is covered with small bumps, nodules, and scales. The interior is smooth and slightly glossy. This glossy interior allows these shells to be distinguished from the similar shells of annelid worms which are dull and chalky. These shells are whitish in color. Oryzatus Worm Shells are long and can reach a maximum of 47 cm (19 inches) in length.

Habitat and Distribution: Oryzatus Worm Shells are found attached to rocks and other hard surfaces, in protected waters. They live in the intertidal zone, and to depths up to 35 m (115 feet). They are a subtropical to tropical Eastern Pacific specie that are endemic to Mexico, where they have a limited range. They are found from Mazatlán, Sinaloa south to Guatemala along the west coast of the mainland. They are found from La Paz to Cabo San Lucas, Baja California Sur on the East Coast of Baja and from Guaymas, Sonora south to Mazatlán in the Sea o Cortez. They have not been documented from the west coast of the Baja Peninsula.

Ecology and Behavior:  Oryzatus Worm Shells are suspension feeders, which feed by extruding mucous nets into the water column to collect plankton and then withdrawing the net to feed. In turn they are preyed upon by crabs, fish, and mollusks. They are gonochoric and reproduce sexually, through spermcast spawning, with internal fertilization. The eggs  are brooded in egg-capsules, stored in the mantle cavity. 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.

Synonyms: Serpulorbis oryzata and Thylacodes oryzata.