Many of the species of littorinids common to the western Atlantic are found in the IRL, including: the marsh periwinkle, Littorina irrorata; slender periwinkle, L. angustior; lineolate periwinkle, L. lineolata; white-spot periwinkle, L. meleagris; and the zebra periwinkle, L. ziczac. All of these species share a similar shell shape and an intertidal distribution. The marsh periwinkle attains a shell length of about 3.2 cm, and is elongate conic in shape, longer than it is wide (Andrews 1994). Coloration of the shell is dull grayish white with tiny dashes of reddish brown on the ridges of the spiral. Eight to ten gradually increasing flat whorls comprise the shell, with the body whorl measuring about half of the total height. The aperture is oval with a sharp outer tip and regular grooves on the inside edge.The slender periwinkle is relatively small, reaching a length of about 0.8 cm (Abbott 1974). The upper whorls of the shell are marked with 6-9 spiral lines, the sides of the foot are mottled black and gray, and the operculum is mostly round in shape. The lineolate periwinkle reaches a length of about 1.2 to 2.5 cm, has a gray background color on the shell with oblique zigzag lines of dark brown, and an apex of reddish brown (Andrews 1994). The shell is composed of 6-8 gradually increasing whorls, with the body whorl spanning more than half of the total length, and the suture between whorls is well marked. The pear-shaped aperture has a sharp, thin outer lip meeting the body whorl at an acute angle. Males are smaller and more strongly sutured then females.The white-spot periwinkle is also small like the slender periwinkle, measuring about 0.8 cm in length (Abbott 1974). The shell has a pointed spire with a thin periostracum or organic covering. The aperture is reddish brown and the exterior of the shell is brown with large, irregular white spots, often arranged in spiral roles.The zebra periwinkle has a shell length of about 1.3 cm, and is whitish with dark brown or black wavy stripes (Andrews 1994). The aperture is small and oval, and the operculum is chitinous. This species is often confused with L. lineolata, but has a lighter colored shell with a narrower apical angle than the lineolate periwinkle. Regional Occurrence & Habitat Preference: The range of the mangrove periwinkle extends from Florida to Brazil, throughout the Caribbean and Bermuda (Abbot & Morris 1995, Tanaka & Maia 2006). The species is also found in the eastern Atlantic from Senegal to Angola (Merkt & Ellison 1998). As its common name implies, L. angulifera is a common inhabitant of mangrove forests, mainly above the water line on trunks and prop roots of the red mangrove, Rhizophora mangle (Kaplan 1988, Merkt & Ellison 1998).
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