Biology and ecology

Snails: juvenile vs. adult

It is sometimes difficult to determine if a snail of a given species is a juvenile based solely on its shellShell:
A hard, inflexible, calcareous or chitinous structure that vary in size and may either completely encasing the animal, covering some part of it or be internal.
. In many cases observation of the genitaliaGenitalia:
The reproductive structures of an animal. May refer to either male or female structure.
, through dissection of the specimen, is required. As a general rule, the shells of juveniles tend to have brittle apertural lips, whereas the apertural lips of adult specimens are often thickened, rigid, and may be reflected in some species (e.g., Otala spp. and Eobania vermiculata). Also, the baseBase:
This is the lower or underside of the shell; opposite of apical.
of the juvenile apertureAperture:
The major opening of a shell that the body of the animal may be retracted.
curves downward, whereas in adult specimens the apertural lips generally curve outward, rather than downward.