Giant Ramshorn (Marisa cornuarietis) Breeding Guide

Marisa cornuarietis has separate sexes and, unlike other apple snails, lays gelatinous disk-shaped egg clutches below the waterline. It eats soft plants and can become invasive.

Overview

Marisa cornuarietis is a large flat-coiled apple snail of the family Ampullariidae. It is a gonochoric species, so it has separate sexes rather than being hermaphroditic. It consumes large amounts of plant matter and is not suited to planted aquariums.

Sexing

Because the species has separate sexes, a breeding group must include both a male and a female. As with related apple snails, external sexing is unreliable, so a small group is the practical way to ensure both sexes are present.

Egg-laying / Reproduction

Unlike most apple snails, Marisa cornuarietis lays its eggs below the waterline. The clutches are characteristic disk-shaped gelatinous masses that adhere to plants, glass and other submerged substrates, so no air gap is required for successful reproduction.

Juvenile Care

Juveniles hatch directly into the water and graze on aquatic plants, algae and decaying matter, including dead fish and snails. Given the species' capacity to spread, surplus snails should never be released into natural waters.

Common Challenges

The species feeds heavily on aquatic vegetation and has been used to retard the growth of water hyacinth and to control Biomphalaria snails that vector schistosomiasis. Its appetite for plants and its invasive establishment in Florida mean it can outcompete and damage planted or natural systems.