Festive Murex Shell, Pteropurpura festiva 

Festive Murex Shell, Pteropurpura festiva. Shell collected offshore, San Diego, California, October 2019. Size: 5.9 cm (2.3 inches) x 3.0 cm (1.2 inches). Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Festive Murex, Pteropurpura festiva (Hinds, 1844), is a gastropod mollusk that is a member of the Muricidae Family of Rocks Shells. The genus Pteropurpura is one of one hundred ninety-eight genera in this family, and there are sixteen species in this genus. They are known in Mexico as Murícido Festivo.

Description: The Festive Murex shell consists of six whorls, and a moderately high spire. They have three varices that are uniquely rolled back. There is a strong knob, on the body whorl,  between each varix. They have a closed, curved, short, siphon canal. The aperture is large and oval-shaped, with fine dentition (teeth) along the outer lip. The exterior of the shell is white to tan in color, with very fine, dark brown, spiral lines. The interior is white to bluish-white. Festive Murex Shells reach a maximum of 6.7 cm (2.6 inches) in length and 3.4 cm (1.3 inches).

Habitat and Distribution: Festive Murexes are found attached to rocks, on mud substrate between rocks, and on vegetation. They live in the intertidal zone, and to depths up to 25 m (82 feet). They are a temperate Eastern Pacific species. In Mexican waters they have a limited range. They are found on the west coast of the Baja Peninsula, from the northern border, to Magdalena Bay, Baja California Sur.

Ecology and Behavior: Festive Murexes are predators that feed primarily on barnacles, mussels, clams, limpets, and other gastropods, including Gould’s Bubble Shell, Bulla gouldiana. They are gonochoric and reproduce sexually, with internal fertilization. The eggs are laid as a mass, on rocks or other hard substrates. They reproduce year-round, with a peak between May and August.  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:  Murex (Jaton) gaza, Murex festivus, Murex gaza, Pteropurpura (Pteropurpura) festiva and Shaskyus festivus.