Species Description: The checkered nerite, Nerita tessellata, is a common intertidal gastropod in southeast Florida. The snail is named for the black and white checkered pattern on the shell, which covers a series of coarse irregular spiral ridges on 4-5 whorls (Andrews 1994, Abbott & Morris 1995, Bovbjerg 1984). The calcareous operculum is black, closing around an aperture which displays numerous small teeth on the interior of the inner and outer lips (Abbott & Morris 1995). Members of this family (Neritidae) are also characterized by a small, pointed hook at the end of the operculum (Abbott & Morris 1995).
Potentially Misidentified Species: Several other species of small gastropods occur in the intertidal areas of the IRL where N. tessellata is abundant. Of these, the two species that are most closely related to the checkered nerite are: the Antillean nerite, Nerita fulgurans; and the four-tooth nerite, N. versicolor. Both species are roughly the same size as N. tessellata.
The shell of the Antillean nerite is dark gray to yellowish gray, black, or mottled brown (Andrews 1994, Abbott & Morris 1995). Markings are occasional and generally less distinct than N. tessellata, but the shell has the same 4-5 whorls. The aperture is more prominently toothed than the checkered nerite, with two larger teeth on the inside of the outer tip and the inner lip toothed throughout (Andrews 1994). Unlike the checkered nerite, the operculum of N. fulgurans is yellowish gray. This species is reported to prefer brackish waters (Abbott & Morris 1995).
The shell of the four-tooth nerite is slightly more elongate than N. tessellata or N. fulgurans (Andrews 1994), with about four whorls (Abbott & Morris 1995). Coarse spiral threads mark the outside of the shell, which is dirty white with red and black spots or bars. The outer lip is toothed within, and the interior of the inner lip bears four prominent teeth. Fine dimples are present on the dark gray operculum (Abbott & Morris 1995). The four-tooth nerite is reported to be most abundant in oceanic rocky intertidal areas (Andrews 1994). In some locations where N. tessellata and N. versicolor occur together, the four-tooth nerite retreats farther from the water line; whereas, the checkered nerite can be found at the air-water interface (Bovbjerg 1984).
Regional Occurrence & Habitat Preference: The range of N. tessellata extends from southern Florida to Brazil and Bermuda, with rare sightings in northern Florida (Andrews 1994, Russell 1941). It is a rocky intertidal species that is most abundant at or just below the water line, though seldom deeper than 0.5 m (Bovbjerg 1984). Migration occurs over the course of the day to maintain this position with the tidal cycle.
IRL Distribution: Though little information exists on the distribution of the checkered nerite in the IRL, it is most likely more abundant in the southern areas of the lagoon. Populations can be found in rocky shorelines near inlets, jetty rocks and seawalls.
Age, Size, Lifespan: The checkered nerite has a length of approximately 1.9 to 2.5 cm (Andrews 1994). The average shell length for populations in the Florida Keys was measured at 1.9 cm (Bovbjerg 1984).
Abundance: Abundance estimates for populations of N. tessellata in the IRL are unknown. However, checkered nerites have been recorded at densities of: 24 m-2 in Pigeon Key, Florida (Bovbjerg 1984); 40 m-2 in Key Largo, Florida (Kolipinski 1964); and between 93 and 220 m-2 in Barbados (Hughes 1971, McLean 1967).
Reproduction: Like other species of Nerita, N. tessellata copulates at night. The male transfers sperm-filled sacs, called spermatophores, to the female via a gelatinous tube that is extended from the tip of the penis into the mantle cavity of the female (Chislett 1969). Mature females continually carry spermatophores (Chislett 1969). Once the eggs are fertilized, the female deposits them in water-filled depressions of rocks or other sheltered areas around the mean tide level where they are somewhat protected from direct sun exposure until hatching (Hughes 1971). The reproductive season seems to be tied somewhat to location. Populations in Florida have been reported to spawn mainly in the summer months (Kolipinski 1964); whereas, those in Barbados are reproductively active year-round (Hughes 1971). Individuals are sexually mature at a length of about 1.7 cm (Kolipinski 1964).
Embryology / Larval Development: The 1mm long egg capsules of N. tessellata are oval and covered with calcium carbonate bumps (Andrews 1935). Each capsule contains approximately 111 eggs, which hatch after about 21 days (Kolipinski 1964). Like many other mollusks, the checkered nerite reproduces via a planktonic larva called a veliger (Kolipinski 1964). These larvae remain in the water column until they reach the final stage, or pediveliger, at which time they search for a suitable location to settle and metamorphose into juvenile snails. The average female N. tessellata lays about 160 egg capsules per year (Kolipinski 1964).
Temperature & Salinity: Little information exists describing the environmental tolerances of N. tessellata. However, the distribution and range of most populations suggests the species prefers oceanic to highly saline brackish, warm coastal waters. Lewis (1960, 1963) suggested that the intertidal zonation patterns of the checkered nerite were related to its evaporative cooling abilities at tropical and subtropical latitudes.
Trophic Mode: The checkered nerite feeds mostly at night, grazing along rocks at lateral distances of up to 23 m over a 2-day period (Bovbjerg 1984). Microscopic organisms composing the biofilm (slime layer) are the dominant food source scraped from rock surfaces, including: algae, detritus, flagellates, diatoms and nematodes (Bovbjerg 1984).
Predators: Documented accounts of predation on N. tessellata are scarce. However, checkered nerites are likely preyed upon by a variety of birds, fishes and invertebrates. In particular, crabs, pufferfishes and the common octopus, Octopus vulgaris, have been cited as dominant predators of neritid snails (Bovbjerg 1984, Vermeij 1978).
Associated Species: No known obligate associations exist for N. tessellata. However, checkered nerites are associated with several organisms common to rocky intertidal habitats. For extensive lists of species found in this habitat and others throughout the IRL, please refer to the links at the left of this page.
Abbott, RT & PA Morris. 1995. A field guide to shells: Atlantic and Gulf coasts and the West Indies, 4th edition. Houghton Mifflin Co. Boston, MA. USA.
Andrews, EA. 1935. The egg capsules of certain Neritidae. J. Morph. 57: 31-59.
Andrews, J. 1994. A field guide to shells of the Florida coast. Gulf Publishing Co. Houston, Texas. USA. 182 pp.
Bovbjerg, RV. 1984. Habitat selection in two intertidal snails, genus Nerita. Bull. Mar. Sci. 34: 185-196.
Chislett, GR. 1969. Comparative aspects of the ecology of three Nerita (Mollusca: Gastropoda) species from different locations in Barbados. Master's Thesis. McGill University. Montreal, Quebec. Canada.
Hughes, RN. 1971. Ecological energetic of Nerita (Archaeogastropoda, Neritacea) populations on Barbados, West Indies. Mar. Biol. 11: 12-22.
Kolipinski, MC. 1964. The life history, growth and ecology of four intertidal gastropods. PhD Dissertation. University of Miami. Miami, FL. USA.
Lewis, JB. 1960. The fauna of rocky shores of Barbados, West Indies. Can. J. Zool. 28: 391-435.
Lewis, JB. 1963. Environmental and tissue temperatures of some tropical intertidal marine animals. Biol. Bull. 124: 277-284.
McLean, RF. 1967. Measurements of beachrock erosion by some tropical marine gastropods. Bull. Mar. Sci. 17: 551-561.
Russell, HD. 1941. The recent mollusks of the family Neritidae of the western Atlantic. Bull. Mus. Comp. Zool. Harvard. 88: 347-404.
Vermeij, GJ. 1978. Biogeography and adaptation, patterns of marine life. Harvard University Press. Cambridge. 332 pp.