- Sunday, January 16, 2011

Land Snails of Sri Lanka

Lecture done at the YBA meeting on 04.01.2011 by Dilshan De Silva

Land snails is one of the taxa that Sri Lanka has a very high diversity. A total number of 246 land snails has been recorded from the island so far.Out of that 218 species are endemic to Sri lanka.

Land Snail Classification
Kingdom : Animalia
Phyllum : Mollusca
Class : Gastropoda
Sub Classes : Prosobranchia
Pulmonata

Some main differences between Subclasses Pulmonata and Prosobranchia
Prosobranchians have a single pair of tentacles while the Pulmonates have two pairs of tentacles.CaCo3 % in the Prosobranchian shell is higher than the protein %.Therefore the shell is much harder.Pulmonates have more protein in their shells.So they have softer shells.
Prosobranchians have an operculum (a lid like structure that covers
the shell opening when the snail's body is inside the shell) Pulmonates don't have an operculum.

Tree Snails of Sri Lanka
The snails that live mainly on trees are called tree snails.Sometimes they can be found in the leaf litter too.All the tree snails in Sri Lanka belongs to the family Acavidae.

Genus
Acavus
This Genus is endemic to Sri Lanka.There are 3 species classified under the Genus Acavus and all of them are comparatively large and colorful.These species has a very hard shell and normally they feed on fungus,mosses and degrading fruits.
  • Acavus phoenix : Most common Acavus species.It has a rosy brown shell and a black colored body. The lateral edge of the largest ring of it's shell is round. A.Phoenix is distributed in the wet zone of the country.













  • Acavus superbus : This species has a greenish shell and a rosy brown body. The lateral edge of the largest ring of it's shell is sharp. It's eggs has an average diameter of 10 mm. A.superbus is distributed in the South Western part of the Wet zone of Sri Lanka.
  • Acavus haemastoma : A.haemastoma has a rosy/dark brown shell and sometimes there are white or dark lateral lines on the shell.it's body color is brown. There are 2 sub species of A.haemastoma. They are, A.h.melanotragus and A.h.haemastoma
Genus Oligospira
The snails belongs to this genus are also large like the Acavus species but they have less conical shells with flat tops.


  • Oligospira polei : This species has a orange brown shell and a white shell lip. The shell of the juveniles is yellowish. They live close to the ground.













  • Oligospira skinneri : A shiny light brown/rosy shell with some small white spots on it. Lip of the shell is meat red.
  • Oligospira waltoni : This species has a rosy brown shell with a dark brown lip.