Nerita versicolor Gmelin, 1791
Family: Neritidae
Common names: Four-tooth Nerite,  more...
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Species Description: Nerita versicolor have shells approximately 1 inch in both length and height as adults (Morris 1975; Abbot 1954). The shell is thick, heavy, and rounded, with grooves following the spiral of the shell (Smith, 1951). There are about four rounded spires on the shell (Morris, 1975; Abbot 1954). The base color of the shell is off-white, with a variety of different pigments and patterns that can appear over it; most commonly there are black and red dots and bars in straight or zigzag patterns, though other colors such as purple have also been observed (Morris, 1975; Abbot, 1954).

The aperture of the shell is thick and sometimes more yellow than the base color of the shell. The inner lip of the shell has four large teeth, and the outer lip tends to have red, white and black pigmentation (Morris, 1975; Abbot, 1954). Nerita versicolor possesses a rounded operculum, which is gray-brown in color. The stiff, brittle operculum curves inward and is covered in small, fine bumps. It is about the thickness of a fingernail (Abbot, 1954). The body of the snail is stout with a short blunt head and dark gray to black in color, with pale gray-white undersides. The major tentacles are long and extend outwards on either side of the head (Smith, 1951). It is similar in appearance to Nerita peloronta, the Bloody Tooth Nerite, but can be differentiated from it by N. versicolor's four distinct “teeth” as well as N. peloronta's characteristic rust-red coloration on the underside of the shell.

Habitat & Regional Occurrence: Nerita versicolor's range extends through southern Florida and the Caribbean (Morris 1975; Smith, 1951), as well as the Bahamas (Northrop, 1910), and South America as far as Para, Brazil (Chislett, 1969). Its distribution within the Indian River Lagoon, FL is unknown.

N. versicolor is found in higher, less frequently inundated portions of the intertidal zone than other gastropods in the same general habitat, including other Nerita. (Bobvjerg, 1984; Gilinsky, 1984; Chislett, 1969). In the Florida Keys, Nerita versicolor is common in the grey (higher) zone of the supralittoral rocky intertidal but may reach their greatest numbers in the black (middle) zone, with some found at times in the higher part of the yellow zone. On sea walls the same pattern holds, but less strictly. (Stephenson and Stephenson, 1950).

Physical Tolerances: N. versicolor is nocturnal, showing photonegative behavior and becomes inactive during the day (Bobvjerg, 1984). It will retreat into rock crevices to avoid wave action and high temperatures and emerge once the stressful conditions are gone (Chislett, 1969). Many species of Nerita including N. versicolor have the ability to adapt to higher temperatures, which may be related to their higher position in the intertidal relative to other intertidal gastropods (Chislett, 1969; Fraenkel 1968). N. versicolor and some of its close relatives can withstand high turbidity with no apparent effects on respiration (Gilinsky, 1984).

Size, Lifespan & Reproduction: Nerita versicolor reaches sexual maturity at 16 to 19 millimeters, and achieves a maximum size of about 25 millimeters (Chislett, 1969). Factors affecting the growth rate of N. versicolor include crowding and temperature. Crowding and lower temperatures decrease the growth rate while more space and warmer temperatures increase it. Heavy wave action causing snails to retreat into crevices, as opposed to spending more time feeding, could also have an effect on growth rate (Chislett, 1969).

Immature female gonads of this species are pale yellow in color and more compacted than mature gonads, which are a richer yellow with a loose texture. Ripe eggs are somewhat ovoid spheres 250 by 300 nanometers in size. Immature male gonads are light brown, and darken to an orange, then a red-brown color as they mature (Chislett, 1969).

When mating, the male nerite climbs onto the female's shell, and is turned slightly right with respect to the female. The male then extends the cephalic penis around and under the female's shell to the right side of the mantle, and a tube forms between the tip of the penis and the female nerite's genital aperture. The male transfers spermatophore packets to the female, which the female then stores for later use. Mature females in at least one study had some spermatophore packets stored at all or almost all times (Chislett, 1969).

N. versicolor is capable of breeding year round in warm, hospitable environments (Chislett, 1969) similar to those found around the Indian River Lagoon. Smaller peaks in breeding occur but are different for different locations (Chislett, 1969). N. versicolor is known to incorporate protective inorganic rounded objects, called spherulites, into its egg sacs (Andrews, 1937). Juveniles of the species have been observed sheltering under material washed into large, semi-permanent tide pools, separated from the rocky intertidal environment preferred by the adults (Bobvjerg, 1984).

Abbot, R. T. 1954. American Seashells. D. Van. Nostrand Company Inc. Toronto, New York, London

Andrews, E. A. 1937. Spherulites as Specific Characters in Certain Gastropods. Transactions of the American Microscopical Society, 56:2 237-242

Bovbjerg, R. V. 1984. Habitat Selection in Two Intertidal Snails, Genus Nerita. Bulletin of Marine Science, 34:2, 185-196

Chislett, G. R. 1969. Comparative Aspects of the Ecology of Three Nerita (Mollusca: Gastropoda) Species From Different Locations in Barbados, W.I. MS thesis. McGill University, Montreal.

Fraenkel, G. 1968. The Heat Resistance of Intertidal Snails at Bimini, Bahamas; Ocean Springs, Mississippi; and Woods Hole, Massachusetts. University of Chicago Press, Physiological Zoology, 41:1 1-13

Gilinsky, N. L. 1984. Does Archaeogastropod Respiration Fail in Turbid Water? Palaeobiology, 10:4, 459-468

Morris, P. A. 1975. A Field Guide to Shells; Atlantic and Gulf Coasts and the West Indies (The Peterson Field Guide Series) 3rd Ed. Houghton Mifflin Co. Boston, New York.

Northrop, J. I. 1910. A Naturalist in the Bahamas. The Columbia University Press, New York, New York.

Smith, M. 1951. East Coast Marine Shells, 4th Ed. Edwards Brothers Inc. Ann Arbor, Michigan

Stephenson, T. A., and A. Stephenson. 1950. Life between Tide Marks in North America: the Florida Keys. Journal of Ecology, 38:2, 354-402

Wodinsky, J. 1969. Penetration of the Shell and Feeding on Gastropods by Octopus. Oxford University Press, American Zoologist, 9: 3, 997-1010