By Abel Munoz
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)
Biogeographic Regions:
nearctic 
; atlantic ocean .
Habitat
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)
These animals are found in the following types of habitat:
saltwater or marine .
Aquatic Biomes:
coastal ; brackish water .
Wetlands: marsh .
Other:
estuarine ; intertidal or littoral .
Physical Description
(0.75 to 1.26 in)
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)
Some key physical features:
ectothermic ; heterothermic ; bilateral symmetry .
Development
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)
Reproduction
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)
Key reproductive features:
sexual ; fertilization (internal ); oviparous .
Females lay eggs and no parental investment is involved thereafter.
Parental investment:
pre-fertilization (provisioning).
Behavior
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, Williams, and McBride, 1993)
Key behaviors:
motile .
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, Calzetta, and Rittschof, 1994; Hamilton, 1982; Hamilton, Ardizzoni, and Penn, 1983)
Communicates with:
chemical .
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, Atmospheric Administration, and Environmental Protection Agency, 2004; Purchon, 1968; Wilbur and Vonge, 1964)
Primary Diet:
herbivore (algivore); detritivore .
Plant Foods:
algae.
Other Foods:
detritus ; microbes.
Predation
- fish (Actinopterygii)
- crabs (Decapoda)
- blue crabs (Calinectes sapidus)
- sea urchins (Echinoidea)
- small mammals (Mammalia)
- diamondback terrapin (Malaclemys terrapin)
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, 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, Atmospheric Administration, and Environmental Protection Agency, 2004)
Key ways these animals impact their ecosystem:
biodegradation .
Economic Importance for Humans: Positive
Periwinkles are sensitive to toxic agents and are used for toxicology studies. (National Oceanic, Atmospheric Administration, and Environmental Protection Agency, 2004)
Ways that people benefit from these animals:
research and education.
Conservation Status
IUCN Red List: [link]:
Not Evaluated.
US Federal List: [link]:
No special status.
CITES: [link]:
No special status.
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For More Information
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Contributors
Abel Munoz (author).
Troy Ladine (editor), East Texas Baptist University.
Renee Sherman Mulcrone (editor).
