Marisa cornuarietis (Linnaeus, 1758)
Giant ramshorn snail, apple snail
The shell of this species on average measures 50 mm wide, with 3.5-4 whorls. The shell of adults generally appears flattened, as the apex does not extend above the body whorl. The juveniles' shell, on the other hand, have a more globose shape and the apex is well above the body whorl. The shell often appears to be bicolored with different color patterns on the dorsal and ventral surfaces. They almost always have 3-6 dark colored stripes; however, an unusual morph exists that is completely yellow. The body of this snail is yellow to grey with black blotches covering the entire body. The rigid structure that is used to block the opening of the shell (operculum) is very small and can be retracted entirely into the shell.
Southern and Central America
- U.S.: Alabama, Alaska, Arizona, California, Florida, Georgia, Idaho, Texas
Pacific Islands: Hawaii
This omnivorous snail can be found in standing or slow-moving water. The adults lay their orange-colored eggs, measuring 2-3 mm, below the surface of the water. The eggs are often deposited on vegetation in a gelatinous matrix. Clutch size average 210 eggs with an incubation period of approximately 8-24 days. The snail is not hermaphroditic (both sexes exist). There has been evidence of sexual dimorphism, where the males have a more rounded aperture (mouth) and a thicker shell, while the females have an oval-shaped aperture (mouth) and thinner shells. This snail is of concern because of its ability to completely decimate the vegetation in its habitat. They also are capable of outcompeting native species through direct competition and predation on their eggs and young.
Barker 2002; Rawlings et al. 2007