Four-tooth Nerite Shell, Nerita versicolor
Four-tooth Nerite Shell, Nerita versicolor. Underwater photograph taken in coastal waters off Cozumel Island, Quintana Roo, March 2021. Photograph and identification courtesy of Marina Sutormina, Stockholm, Sweden.
Phylogeny: The Four-tooth Nerite Shell, Nerita versicolor (Gmelin, 1791), is a gastropod mollusk that is a member of the Neritidae Family of Nerite Shells. The genus Nerita is one of thirteen genera in this family, and there are seventy-four species in this genus. They are also known as the Four-toothed Nerite, the Plicate Nerite and the Variegated Nerite.
Description: The Four-tooth Nerite Shell is thick and heavy, with a large globose body whorl. They have with a short spire. The shell is sculpted with spiral grooves. Most specimens are slightly wider than tall. Their columella is lunate with a straight edge. The aperture is wide and thick with yellow tinges. The inner lip of the aperture has four large teeth (occasionally five), for which this species is named. The exterior of Four-tooth Nerite Shells varies in coloration and pattern. Most shells are off-white in color with black and red dots and/or bars, in straight or zigzag patterns. The outer lip of the aperture normally has black, red, and white pigmentation. Their operculum is rounded, stiff, brittle, and curves inward. The operculum is the thickness of a fingernail, is gray-brown in color, and is covered with small fine bumps. The living animal has a stout body with a short, blunt, head. The animal is dark gray to black in color, with pale gray to white undersides. Four-tooth Nerite Shells reach a maximum of 22.1 cm (8.7 inches) in length. The majority are approximately 2.54 cm (1.0 inch) in height and 2.54 cm (1.0 inch) in width. The Four-tooth Nerite is similar to the Bloody Tooth Nerite, Nerita peloronta (lacks the four distinct teeth and is rust-red in color).
Habitat and Distribution: Four-tooth Nerite Shells are found on rocks and rock benches along the shoreline. They are often found in crevasses and small pits. They are also on branches of littoral trees overhanging the water. The live in the intertidal zone. They are mobile and follow the high tide water level. They have the ability to withstand periods of heat and desiccation. They are a tropical Western Atlantic species. The Four-tooth Nerite is a resident of all Mexican waters of the Atlantic Ocean, including the Gulf of Mexico and the east coast of the Yucatán Peninsula in the Caribbean.
Ecology and Behavior: Four-tooth Nerite Shells are nocturnal grazers and detritivores, which utilize long major tentacles that extend outwards on either side of the head to gather food. They feed on detritus, algae, flagellates, diatoms and nematodes. 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. Four-tooth Nerite Shells are popular with the aquarium trade because they are easy to maintain. 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: Nerita (Nerita) versicolor, Nerita (Ritena) versicolor, Nerita amplisulcata, Nerita flammea, Nerita hertweckorum, Nerita musica, Nerita nigrocincta, Nerita pica, Nerita selot, Nerita tricolor, Nerita variegata, and Nerita versicolor f. nigrocincta.