Chinese Hat Slipper Shell, Calyptraea mamillaris

Chinese Hat Slipper Shell, Calyptraea mamillaris.  Shell collected off the beach in the greater Punta Chivato area, Baja California Sur, December 2022.  Size: 2.7 cm (1.1 inches) x 1.2 cm (0.5 inches). Photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Chinese Hat Slipper Shell, Calyptraea mamillaris. Shell collected off the beach in the greater Punta Chivato area, Baja California Sur, December 2022. Size: 3.1 cm (1.2 inches) x 1.3 cm (0.5 inches). Photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny: The Chinese Hat Slipper Shell, Calyptraea mamillaris (Broderip, 1834), is a gastropod mollusk that is a member of the Calyptraeidae Family of Cup-and-Saucer and Slipper Limpet Shells. The Calyptraea Genus is one of eleven genera in the Calyptraeidae Family, and there are twenty-one species in the Calyptraea Genus.

Description: The Chinese Hat Slipper Shell has an irregular circular outline and a high conical profile.  The apex is central and spiraled.  These shells are thin in construction. The exterior may be smooth or sculpted with commarginal ridges or striae. The internal “shelf” is broad and often forms a cup at the center of the shell. The exterior color is white to tan, often with brown or purple blush at the apex. The interior is shiny white, though sometimes the outside color shows through the shell. Chinese Hat Slipper Shells reach a maximum of 3.7 cm (1.4 inches) in length.

Habitat and Distribution: Chinese Hat Slipper Shells are found attached to rocks and stones, often in mudflats and near mangroves.  They live in the intertidal zone, and to  depths of 81 m (266 feet). Chinese Hat Slipper Shells are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from the west coast of the Baja Peninsula, north of Magdalena Bay, Baja California Sur.

Ecology and Behavior:  Chinese Hat Slipper Shells are suspension feeders that feed primarily on planktonic algae, which they filter from the water by use of their gills. They are prey for crabs and gastropods. Chinese Hat Slipper Shells are protandrous hermaphrodites, beginning life as males and later becoming females. They reproduce sexually, with internal fertilization. Their engagement in any type of commensal, parasitic, or mutualistic relationship has not been documented. From a conservation perspective the Chinese Hat Slipper Shell has not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be considered to be of Least Concern.

Synonyms: Calyptraea regularis, Galerus sinensis var. fuscus, and Trochita solida.