Donkey Thorn Oyster Shell, Spondylus limbatus

Donkey Thorn Oyster Shell, Spondylus limbatus. Shell provided by the commercial fishermen of the greater Los Cabos area, March 2014. Size: 5.8 cm (2.3 inches) x 5.3 cm (2.1 inches).

Phylogeny: The Donkey Thorn Oyster, Spondylus limbatus (G.B. Sowerby, II, 1847), is a bivalve mollusk that is a member of the Spondylidae Family of Spiny Oyster Shells. Spondylus is the only genus in the Spondylidae Family, and there are seventy-five species in the genus. This species is also known as the Cat’s Tongue Oyster Shell and they are known in Mexico as Almeja Burra, Callo Escarlopa and Ostra Espinosa Burricais.

Description: The Donkey Thorn Oyster shell is solidly built and oval shaped. The external surface has radiating lines with short spines; in older individuals the spines may be worn down. The exterior of the shell is pinkish-red and the interior is white, with a purplish red border. The Donkey Thorn Oyster shell  reaches a maximum of 25 cm (9.7 inches) in length and 21 cm (8.3 inches) in width.

Habitat and Distribution: Donkey Thorn Oysters are found attached to solid substrates from the intertidal zone to depths up to 53 m (175 feet). They are 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 north of San Alijo Rocks, Baja California Sur along the central and northwest coasts of the Baja Peninsula and north of San Felipe, Baja California, in the Sea of Cortez.

Ecology and Behavior:  Donkey Thorn Oysters are suspension feeders that feed primarily on planktonic algae and suspended organic matter. They are gonochoric and reproduce sexually, through broadcast spawning, 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 however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms: Spondylus calcifer, Spondylus coccineus, Spondylus lamarckii, Spondylus punicus, Spondylus radula, and Spondylus smithii.