Apple snail

Ampullariidae, whose members are commonly known as apple snails, is a family of large freshwater snails that includes the mystery snail species. They are aquatic gastropod mollusks with a gill and an operculum. These snails simultaneously have a gill and a lung as functional respiratory structures, which are separated by a division of the mantle cavity. This adaptation allows these animals to be amphibious. Species in this family are considered gonochoristic, meaning that each individual organism is either male or female.