Littorina irroratamarsh periwinkle

Geographic Range

Littorina irrorata is found in salt marshes that extend from Long Island, New York, south along the coast to central Florida. L. irrorata is also found of west of Florida extending along the Gulf Coast to Texas. (Emerson and Jacobson, 1976; Rehder, 1981)


Littorina irrorata is found in brackish water marshes and can be found on marsh grass living at or above the water level. It is usually associated with marsh plants in the genus Spiratina. (Rehder, 1981)

Physical Description

The shell size of Littorina irrorata ranges from 19 mm to about 32 mm high. The shell is thick and broad. The aperture is oval in shape. The shell is shaped like an elongated cone, being longer than wide. Usually a grayish white color, it has tiny, short streaks of reddish brown on the spiral ridges. The shell is also opaque and dull. The columella and callus is usually a pale reddish brown color and the outer lip of the shell is stout, sharp and usually has tiny regular grooves on the inside edge. The inside of the sharp outer lip is marked with red-brown streaks. The whorls on the shell are almost flat and it has about 8 to 10 whorls, which gradually increase. The shell may have a greenish tinge from fine algal growth. (Andrews, 1981; Rehder, 1981)

  • Range length
    19 to 32 mm
    0.75 to 1.26 in


Nothing was documented about the species but about the genus. In a closely related species, Littorina littorea, the embryo hatches as a veliger larva. The planktonic distributive larval stage has been eclipsed. Littorina neritoides and L. littorea eggs are set free singly into the plankton hatching as veligers. In L. littoralis, the eggs are laid in gelatinous layers attached to the substratum, hatching at the crawling stage. In L. saxatlis, the young merge at the crawling stage as viviparous forms and the young remain protected within the maternal body. In L. angulifera, a veliger larva is expelled. (Purchon, 1968)


Information is not known.

Most of what is known about reproduction is for the genus Littorina. In some species of Littorina, the males are not only smaller than the females but their shell has a more elongated spire and narrow aperture. In this genus fertilization occurs internally. The delivery of the spermatozoa into the mantle city of the female would be rendered more efficient if the ciliated pathway were extended on to a projection from the body of the male. It is natural, therefore, that a penis bearing a lateral ciliated seminal groove should develop on the right side of the male. In many mesogastropods and in the hermaphrodites in which exchange of sperm cannot be reciprocal since male and female aperture are widely separate, the partners orientate themselves in the same direction and the male may the female, settle on the right side of the body, and even be carried about by her, as in Littorina spp. Some Littorina spp. (e.g. L. littorea, L. neritoides) have pelagic capsules extruded from an ovipositor situated near the genital aperture in a position comparable to that of the penis. Here the capsule receives its final form and its outer layers harden the contact with seawater. The ventral wall of the pallial oviduct usually fails to develop glands and so provides an easy pathway for the sperm. The female L. irrorata is known to produce floating egg capsules. (Rehder, 1981; Wilbur and Vonge, 1964)

Females lay eggs and no parental investment is involved thereafter.

  • Parental Investment
  • pre-fertilization
    • provisioning


When the tide is out, L. irrorata withdraws into its shell which may remain dry and exposed to the sun for hours. This snail is usually found on marsh grass where it leaves a mucus trail.

Littorina irrorata climbs marsh grasses as water temperatures rise. This probably serves two functions: obtaining more oxygen (since warmer waters have less oxygen) and avoiding predators. (Andrews, 1981; Henry, et al., 1993)

Communication and Perception

The eye structure of Littorina irrorata have been described. Eyes are lateral to the cephalic tentacle. The animal is able to detect light and motion.

Experiments found the snails preferred vertical bars over horizontal bars, suggesting they can see and sense plant stems, where they are usually found in nature. Another study found L. irrorata positively reponds to plant odors found in its environment. (Duval, et al., 1994; Hamilton, 1982; Hamilton, et al., 1983)

Food Habits

Littorina irrorata is an herbivore that feeds mainly on algae. It grazes over the surface of marsh grass, usually Spiratina species. Members of the genus Littorina are known to move in response to chemical emanation from food at a distance. (Andrews, 1981; National Oceanic and Atmospheric Administration and Environmental Protection Agency, 2004; Purchon, 1968; Wilbur and Vonge, 1964)

  • Plant Foods
  • algae


Littorina irrorata is preyed on by fish, crabs (particularly blue crabs), birds, sea urchins, and small mammals. In Connecticut, research found diamondback terrapins also fed on this species. (National Oceanic and Atmospheric Administration and Environmental Protection Agency, 2004; Snyder, 2001; Whitelaw, 2000)

Ecosystem Roles

When predators are removed, periwinkles feed heavily and negatively impact Spartina, a marsh plant. (National Oceanic and Atmospheric Administration and Environmental Protection Agency, 2004)

Economic Importance for Humans: Positive

Periwinkles are sensitive to toxic agents and are used for toxicology studies. (National Oceanic and Atmospheric Administration and Environmental Protection Agency, 2004)

  • Positive Impacts
  • research and education

Conservation Status


Renee Sherman Mulcrone (editor).

Abel Munoz (author), Troy Ladine (editor), East Texas Baptist University.


Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map


living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


helps break down and decompose dead plants and/or animals

brackish water

areas with salty water, usually in coastal marshes and estuaries.


uses smells or other chemicals to communicate


the nearshore aquatic habitats near a coast, or shoreline.


an animal that mainly eats decomposed plants and/or animals


particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.


union of egg and spermatozoan


An animal that eats mainly plants or parts of plants.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.


marshes are wetland areas often dominated by grasses and reeds.


having the capacity to move from one place to another.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


uses touch to communicate


uses sight to communicate


Andrews, J. 1981. A field guide: Texas shells. Austin: University of Texas Press.

Duval, M., A. Calzetta, D. Rittschof. 1994. Behavioral responses of Littorina irrorata (SAY) to water-borne odors. Journal of Chemical Ecology, 20: 3321-3334.

Emerson, W., M. Jacobson. 1976. American The Museum of Natural History: guide to shells: land, freshwater and marine, from Nova Scotia to Florida. New York: Alfred A. Knopf.

Graça, M., S. Newell, R. Kneib. 2000. Grazing rates of organic matter and living fungal biomass of decaying Spartina alterniflora by three species of salt-marsh invertebrates. Marine Biology, 136: 281-289.

Hamilton, P. 1982. Behavioral responses to visual stimuli by the snail, Littorina irrorata. Animal Behaviour, 30: 752-760.

Hamilton, P. 1976. Predation on Littorina irrorata by Callinectes sapidus (Crustacea: Portunidae). Bulletin of Marine Science, 26: 403-409.

Hamilton, P., S. Ardizzoni, J. Penn. 1983. Eye structure and optics in the intertidal snail Littorina irrorata. Journal of Comparative Physiology: A. Sensory neural and behavioral physiology, 152: 435-446.

Henry, R., A. Williams, C. McBride. 1993. Responses of the marsh periwinkle, Littoraria (littorina) irrorata to temperature, salinity and desiccation, and the potential physiological relationship to climbing behavior. Marine Behavior and Physiology, 24: 45-54.

Hyman, L. 1967. The invertebrates. New York: McGraw-Hill Book Company.

National Oceanic and Atmospheric Administration, , Environmental Protection Agency. 2004. "Periwinkle (Littorina irrorata)" (On-line). N. C. Plant and Animal Species Fact Sheets. Accessed January 03, 2005 at

Pechnik, J. 2000. Biology of the invertebrates. Boston: McGraw-Hill Book Company.

Purchon, R. 1968. The biology of the Mollusca. London: Pergamon Press.

Rehder, H. 1981. The Audubon Society field guide to North America seashells. New York: Alfred A. Knopf.

Snyder, R. 2001. "Salt Marsh Molluscs" (On-line). Flora and Fauna of Northwest Florida. Accessed December 22, 2004 at

Whitelaw, D. 2000. "Prey availability for the diamondback terrapin population of Milford Marsh, Connecticut" (On-line). Research Conducted at the University of New Haven, Connecticut, 1999. Accessed January 03, 2005 at

Wilbur, K., C. Vonge. 1964. Physiology of Mollusca. New York: Academic Press.