Pacific Coast Angel Wing Shell, Pholas chiloensis

Pacific Coast Angel Wing Shell, Pholas chiloensis. Shell collected within Magdalena Bay, Baja California Sur, October 2019. Size: 5.7 cm (2.2 inches) x 1.5 cm (0.6 inches). Identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Pacific Coast Angel Wing, Pholas chiloensis (Molina, 1782), is a bivalve mollusk that is a member of the Pholadidae Family of Angel Wing Shells. The genus Pholas is one of sixteen genera in this family, and there are five species in this genus. The word Pholas is a Latin word, borrowed from Greek, meaning “to bore”, or “lying in a hole”. This refers to this family’s behavior of boring into rock or wood.

 Description: Pacific Coast Angel Wings are equivalve with an elongated oval profile. Both ends are sharply rounded. The anterior third of the shell has imbricated radial sculpting. The remainder of the shell has concentric sculpting. Their hinge does not have teeth. There are three adductor muscle scars inside the shell. Their siphons are long and united. Their foot is circular, truncated, and forms a sucker. The shell is thin and fragile. These shells are white in color and often stained with brown. Pacific Coast Angel Wings reach a maximum of 13.1 cm (5.2 inches) in length and 3.4 cm (1.4 inches) in height.

Habitat and Distribution: Pacific Coast Angel Wings are found within burrows in soft rock and wood within the intertidal zone, and to depths up to 150 m (492 feet). 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 from north of Scammon’s Lagoon (Laguna Ojo de Liebre), along the west coast of Baja California.

Ecology and Behavior:  Pacific Coast Angel Wings 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 wide distribution and should be considered to be of Least Concern.

Synonyms:  Pholas (Thovana) chiloensis, Pholas chiloensis var. parva, Pholas dilecta, Pholas laqueata, and Pholas retifer.