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 Shell and the Ringed Top Shell. The name Calliostoma comes from the Greek words for “beautiful mouth”, referring to the iridescent aperture.

Description:  Purple-ringed Top Snail Shell has 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 Snail Shells 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 to subtropical Eastern Pacific species that  are found in Mexican waters of the Pacific Ocean on a limited basis being found north of San Geronimo Island, Baja California, along the west coast of the Baja Peninsula.

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 shorebirds, crabs, fish and other mollusks. Purple-ringed Top Snails are gonochoric (male or female for life), and reproduction is sexual, through broadcast spawning. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. The Purple-ringed Top Snail has not been formally evaluated from a conservation perspective, however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms:  Trochus annulatus.