Slender Triton Shell, Monoplex macrodon
Slender Triton Shell, Monoplex macrodon. Shell collected off the beach in the greater Los Cabos area, Baja California Sur, March 2016. Size: 4.6 cm (1.8 inches) x 2.5 cm (1.0 inch).
Slender Triton Shell, Monoplex macrodon. Shell collected off the beach in the greater Agua Verde area, Baja California Sur, March 2020. Size: 6.9 cm (2.7 inches) x 3.7 cm (1.5 inches). Collection, photograph and identification courtesy of Barry Mastro, Escondido, California.
Phylogeny: The Slender Triton Shell, Monoplex macrodon (Valenciennes, 1832), is a gastropod mollusk that is a member of the Cymatiidae Family of Triton Shells. The genus Monoplex is one of twenty-three genera in this family, and there are twenty-seven species in this genus. They are also known as the Hairy Triton and in Mexico as Tritón Esbelto. The species name macrodon means “large teeth”, and refers to the teeth around the interior of the aperture.
Description: Slender Triton Shells are strongly built, spindle-shaped, and consist of six or seven robust whorls. Each whorl is sculpted with a strong varix, and the shell is sculpted with fine spiral cords. They have a long spire that is equal in length or longer than the aperture. The aperture is elongated and has raised white teeth marking the inner and outer lips. The exterior of the shell may be dark brown, light brown, orange-brown, reddish brown, or yellowish-brown in color, with white spiral banding. The interior is usually rust or reddish-brown. Live specimens are covered with a “hairy” brown periostracum. Slender Triton Shells reach a maximum of 9.0 cm (3.5 inches) in length and 4.8 cm (1.9 inches) in height.
Habitat and Distribution: Slender Tritons are found attached to rocks and within coral and rubble. They live in the intertidal zone, and to depths up to 78 m (255 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 Cedros Island, Baja California along the central and northwest coasts of the Baja Peninsula. This species has historically been confused with other global “Hairy Tritons” and thus range and depth records for this species may be inaccurate because of confusion regarding species.
Ecology and Behavior: Slender Tritons are a poorly studied and understood species. There is very limited documentation of their diet, predation, reproduction or ecosystem interactions. Other species in the Cymatiidae Family are predators that feed primarily on ascidians, bivalves, gastropods, sea cucumbers, sea stars, and urchins. They sense their prey with chemoreceptors and utilize chemicals in their saliva to anesthetize and pre-digest their prey. In turn they are preyed upon by crabs, fish, predatory mollusks and sea stars. Slender Triton Shells are gonochoric and reproduce sexually. Some sources state that they reproduce through broadcast spawning, with external fertilization, and other sources state they have internal fertilization. Triton species are generally known for having a long larval phase. Consequently, they can drift, as plankton, for long distances before settling to the bottom. Their engagement in any type of commensal, parasitic, or symbiotic relationships has not been formally documented. From a conservation perspective Slender Triton Shells 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: Cymatium (Monoplex) macrodon, Cymatium (Monoplex) pileare, and Tritonium macrodon.