Ridged Slipper Shell, Crepidula striolata

Ridged Slipper Shell, Crepidula striolata. Shell collected off the beach in Cabo San Lucas, Baja California Sur, August 2020. Size: 4.3 cm (1.7 inches) x 2.8 cm (1.2 inches).

Phylogeny: The Ridged Slipper Shell, Crepidula striolata (Menke, 1851), is a gastropod mollusk that is a member of the Calyptraeidae Family of Cup-and-Saucer and Slipper Limpets. The Crepidula Genus is one of eleven genera in the Calyptraeidae Family, and there are forty-eight species in the Crepidula Genus.

Description:  Ridged Slipper Shells have an irregular ovate outline and a low profile. The apex overhangs the shell’s margin.  A large shelf covers about one-half the shell’s interior. The exterior usually has a smooth texture however some specimens are sculpted with low radial ribs. The exterior is white in color with brown around the apex, and sometimes on the ribs. The interior is shiny white, often with brown around the margin. These shells have a shaggy yellow-brown periostracum.  Ridged Slipper Shells reach a maximum of 5.0 cm (2.0 inches) in length and 3.3 cm (1.3 inches) in height.

Habitat and Distribution: Ridged Slippers are found on, and under, stones, and on larger gastropod shells. They are found in protected waters from the lower intertidal zone to a depth of 30 m (98 feet). The Ridged Slippers 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.

Ecology and Behavior:  Ridged Slippers are suspension feeders that feed primarily on planktonic algae, which they filter from the water by use of their gills. They are protandrous hermaphrodites, beginning life as males and later becoming females. They reproduce sexually,  with internal fertilization. Ridged Slipper Shells are associated with the Pea Crab, Calyptraeotheres camposiI, in what is thought to be a commensal relationship. From a conservation perspective the Ridged 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 squama, Crepidula squama, and Crepidula strigatella.