Radiant Button Shell, Pusula radians

Radiant Button Shell, Pusula radians. Shell collected off the beach of El Mezquital, Baja California Sur, December 2022. Size: 2.2 cm  (0.9 inches) x 1.1 cm (0.4 inches) x 1.1 cm (0.4 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Radiant Button Shell, Pusula radians. Shell collected off the beach of El Mezquital, Baja California Sur, December 2022. Size: 2.3 cm  (0.9 inches) x 1.7 cm (0.7 inches) x 1.1 cm (0.4 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny: The Radiant Button Shell, Pusula radians (Lamarck, 1810), is a gastropod mollusk that is a member of the Triviidae Family of Trivia Shells. The genus Pusula is one of sixteen genera in this family, and there are eight species in this genus. They are also known as the Radiating Trivia Shell and in Mexico as the Trivia Radiante.

Description: Radiant Button Shells look like cowry shells in that they are ovate, have a toothed aperture that runs the length of the shell, and, as adults, lack an obvious spire. They visibly differ from cowries in that they are sculpted with strong ribs. The rib ends are beaded where the dorsal furrow cuts through them. The ribs on the base continue into the aperture, giving it a toothed appearance. They may be pinkish, gray, or brown in color, often with brown spots or blotches.  Radiant Button Shells reach a maximum of 2.3 cm (0.9 inches) in length and 1.7 (0.7 inches) in diameter. The Radiant Button Shell is very similar to the Coffee Bean Shell, Pseudopusula californiana, which is smaller and has ribs that cross the dorsum.

Habitat and Distribution: Radiant Buttons reside attached to, and under, rocks in the intertidal zone. They 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 north of Magdalena Bay, Baja California Sur, along the central and northwest coasts of the Baja Peninsula.

Ecology and Behavior: Radiant Buttons are predators that feed primarily on ascidians (sea squirts). They are gonochoric and reproduce sexually, with internal fertilization. The eggs are laid in protective capsules. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. The Radiant Button Shell has not been formally evaluated from a conservation perspective however, they are fairly common with a relatively wide distribution and should be considered to be of Least Concern.

Synonyms: Cypraea radians and Trivia (Pusula) radians.