Montagnei Horn Shell, Cerithideopsis montagnei

Montagnei Horn Shell, Cerithideopsis montagnei. Shell collected off the beach in the greater Los Cabos area, Baja California Sur, June 2021. Size: 3.0 cm (1.2 inches) x 1.4 cm (0.6 inches).

Phylogeny: The Montagnei Horn Shell, Cerithideopsis montagnei (A. d’Orbigny, 1839), is a gastropod mollusk that is a member of the Potamididae Family of Horn Shells. The genus Cerithideopsis is one of twenty-six genera in this family, and there are fourteen species in this genus. They are  known in Mexico as Caracol  Cuerno de Montagne.

Description: The Montagnei Horn Shell has a narrow cone-shaped profile and consists of ten to fifteen strong convex whorls. This shell has a large round aperture and lacks a siphon canal. The whorls are sculpted with curved, lengthwise, ribs.  The base has spiral grooves. The exterior of the shell a glossy chocolate brown color, often with pale bands running around the whorls. The interior can be white, to reddish brown or dark brown. Montagnei Horn Shells reach a maximum of 3.8 cm (1.5 inches) in length and 1.8 cm (0.7 inches) in height.

Habitat and Distribution: Montagnei Horn Shells are found on and within muddy substrates in the intertidal zone of estuaries. They are often associated with mangroves, and may be found in large groups attached to mangroves. They are a subtropical to tropical Eastern Pacific species that in Mexican waters of the Pacific Ocean are found from San Ignacio Lagoon, Baja California Sur south to Guatemala.  They are found in the Sea of Cortez from Santa Rosalia to the greater Cabo San Lucas area, Baja California Sur.

Ecology and Behavior: Montagnei Horn Shells are grazers that feed primarily on micro algae and detritus. They are gonochoric and reproduce sexually. Montagnei Horn Shells are known to host endo parasitic trematodes. There is no mention in the available literature of them engaging in any types of  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 considered to be of Least Concern.

Synonyms:  Cerithidea montagnei, Cerithium montagnei, and Cerithium reevianum.