Kelp Top Shell, Callistoma bonita
Kelp Top Shell, Callistoma bonita. Shell collected off the beach of Punta Chivato, Baja California Sur, March 2025. Size: 1.8 cm (0.7 inches) x 1.8 cm (0.7 inches) x 2.1 cm (0.8 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.
Kelp Top Shell, Callistoma bonita. Shell collected off the beach of Punta Chivato, Baja California Sur, March 2025. Size: 2.2 cm (0.9 inches) x 2.2 cm (0.9 inches) x 2.1 cm (0.8 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.Phylogeny: The Kelp Top Shell, Callistoma bonita, A. M. Strong, G. D. Hanna & Hertlein, 1933, 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. 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.
Description: The Kelp Top Shell is roughly as tall as it is wide, and consists of 5 – 7 concave whorls. The spire is relatively high and sharp. The exterior is sculpted with smooth spiral threads. The aperture is round, with no folds or teeth. The exterior is white to tan in color, with darker dashes on the spiral threads. Sometimes the dashes are arranged so as to appear as radiating bands or blotches. The interior is a pearly white. Most specimens have a purple groove adjacent to the inner lip. Kelp Top Shells reach a maximum diameter of around 2.7 cm ( 1.1 inches). The similar looking Palmer’s Top Shell, Callistoma palmeri, is squattier and less angular in profile.
Habitat and Distribution: Kelp Top Shells are found on rock and rubble substrates. Some sources state that they live at depths between 0 m and 100 m (328 feet). Other sources limit the depth range to between 37 m (121 feet) and 73 m (239 feet). They are a subtropical to tropical Eastern Pacific species. In Mexican waters they range from Bahía San Carlos, Sonora to Guatemala.
Ecology and Behavior: Kelp 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. 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: None