Trapdoor Snail (Bellamya chinensis) is a large freshwater snail with gills and an operculum, an aquatic gastropod mollusk in the family Viviparidae.
The Japanese variety of this species is black and usually a dark green, moss-like algae covers the shell.
The name, "trapdoor snail" refers to a hinged fingernail-like plate or operculum that the snail can use to seal the aperture of the shell, thus providing some resistance to drought and predation.
This species prefers freshwater lakes with soft, muddy or silty bottoms, reservoirs, slow-moving freshwater rivers, streams, paddy fields, and ponds with aquatic grass, creeping at the bottom of the water or on aquatic grasses.
The optimal water temperature for it to grow and develop is between 20 and 28°C. It will hibernate while water temperature is lower than 10-15 °C or higher than 30 °C.