Purple-ring Top Snail, Calliostoma annulatum

Purple-ring Top Snail, Calliostoma annulatum. Shell collected from coastal waters of Monterey, California, October 2009. Size: 3.0 cm (1.2  inches) x 2.8 cm (1.1 inches). Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny:  The Purple-ring Top Snail, Calliostoma annulatum (Lightfoot, 1786) is a member of the Calliostomatidae Family of Noble Top Snails. The genus Calliostoma is one of twenty-eight genera in this family, and there are two hundred and ninty-six species in this genus. It is also known as the Blue- ringed Top Shell, the Jeweled Top Snail and the Ringed Top. The name Calliostoma comes from the Greek words for “beautiful mouth”, referring to the iridescent aperture.

Description:  Purple-ringed Top Snails have a conical profile with seven to nine flattened whorls. The exterior is marked with beaded ridges.  The shell is yellow-brown to gold, with darker brown dashes on the ridges. The sutures are purple or pink in color, as is the apex. The rhomboidal aperture is oblique and there is no umbilicus. The interior is yellowish, with pink or green iridescence.  The living animal is orange with black speckles. Purple-ringed Top Snails reach a maximum of 4.9 cm (1.5 inches) in height.

Habitat and Distribution:  Purple-ringed Top Snails are found on rocks in the upper half of kelp plants. They can climb kelp at up to 6.0m (20 feet) in a day. They reside in the lower intertidal zone and to depths of 42 m (140 feet). They are a temperate Eastern Pacific Species that in Mexican waters of the Pacific Ocean they have a limited range, from the United States border south to San Geronimo Island, Baja California.

Ecology and Behavior:  Purple-ringed Top Snails are opportunistic omnivores. They consume  bryozoans, carrion, copepods, diatoms, detritus and kelp. In turn they are preyed upon shore birds, crabs, fish and other mollusks. Purple-ringed Top Snails are gonochoric (male or female for life), and reproduction is sexual, through broadcast spawning. Any form of commensal, parasitic, or symbiotic relationships have not been documented. 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:  Trochus annulatus.