Black Murex Shell, Muricanthus nigritus

Black Murex Shell, Muricanthus nigritus. Size: 6.6 cm (2.6 inches) x 4.6 cm (1.8 inches). Shell collected within the intercoastal waterway, Puerto Adolfo Lopez Mateos, Baja California Sur, April 2017.

Phylogeny: The Black Murex, Muricanthus nigritus (R. A. Phillipi, 1845), is a gastropod mollusk that is a member of the Muricidae Family of Rock Shells.  The genus Muricanthus is one of one hundred ninety-eight genera in this family, and there are five species in this genus. This species is also known as the Northern Radix  or the Black and White Murex.  They are known in Mexico as Busano Negro and Caracol Burro Negro.

Description: Black Murex shells are solid and fairly globose. They have six whorls, a low to  moderate pointed spire, and a long, mostly enclosed, siphon canal. They have raised varices with short, pointed, open, spines. The Black Murex can be confused with the Ambiguous Murex Shell, Muricanthus ambiguus (longer, less pointed and more frilled spines). The exterior of the shell is white with black stripes and varices, with the amount of black coloration varying between specimens. The interior is porcelaneous white. Black Murexes reach a maximum of  20.0 cm (7.8 inches) in length and 14.0 cm (5.5 inches) in height.

Habitat and Distribution: Black Murexes live on rock, gravel, and sand bottoms. They are found from the intertidal zone to depths up to 61 m (200 feet). They are a tropical Eastern Pacific species. In Mexican waters they range from Magdalena Bay, Baja California Sur, to Guatemala. They are found throughout the Gulf of California.

Ecology and Behavior:  Black Murexes are predators that feed primarily on bivalves and barnacles. They are preyed upon by crabs, fish, and sea stars.  They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. The eggs are laid in protective capsules. Black Murexes are known to host multiple species of epibionts, including algae, gastropods, bivalves, and brittle stars. This is because they are sometimes the only hard surface in a sandy environment. This species does face significant fishing pressure and populations are declining. From a conservation perspective they have not been formally evaluated.

Synonyms: Hexaplex (Muricanthus) nigritus, Hexaplex nigritus, Murex (Phyllonotus) melanoleuca, Murex nigrita, and Murex nigritus.