Nephelo Top Shell, Calliostoma nepheloide

Nephelo Top Shell, Cillistoma nepheloide.  Shell provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, August 2019. Size 2.5 cm (1.0 inch) x 2.6 cm (1.0 inch).

Phylogeny: The Nephelo Top, Calliostoma nepheloide (Dall, 1913) is a gastropod mollusk that is a member of the Calliostomatidae Family of Noble Top Shells. The genus Calliostoma is one of thirty-two genera in this family, and there are three hundred seventy-five species in this genus. Theis species is also known as the Cloud Top Shell. The name of this family is derived from the Greek words kallos (beautiful) and stoma (mouth), referring to the pearly aperture found in most species. The common name Nephelo comes from a Greek word meaning “cloudy”, the root word for nebula.

Description: Nephelo Top Shells have an almost straight-sided cone-shape, with the bottom whorl being slightly convex.  The shell is is sculpted with finely beaded spiral strands. The exterior of the shell yellowish brown to olive brown in color, with darker specks or flammules.  Nephelo Top Shells reach a maximum of 2.8 cm (1.1 inches) in length and 2.9 cm (1.1 inches) in height.

Habitat and Distribution:  Nephelo Top Shells are found on and within mud substrate at depths between 73 m (240 feet) and 180 m (590 feet). They are a subtropical to tropical Eastern Pacific species that are found in Mexican waters of the Pacific Ocean from San Ignacio Lagoon, Baja California Sur south to Guatemala. They are absent from the Sea of Cortez.

Ecology and Behavior: Because they are a deep-water species, Nephelo Top Shells are a poorly studied and understood species. There is very limited documentation of their diet, predation, reproduction or ecosystem interactions. Other species in Family Calliostomatidae are very diverse in their diets. They may be detritovores, algae eaters, scavengers, or predators that eat sessile invertebrates. They are gonochoric and reproduce sexually,  with external fertilization. The eggs are laid in a ribbon-like mass and then fertilized. 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 an uncommon species.

Synonyms:  Calliostoma nepheloides