Mollusc’ means soft bodied, in Latin. Molluscs belong to the second largest group of animals on the earth after arthropods, with more than 1.5 lakh described species, and many more still awaiting discovery. They occur in a wide range of habitats, from the deepest oceans to high altitudes in the Himalayas and the Alps. The marine environment is the richest, followed by terrestrial and freshwater, in terms of described species. Terrestrial snails (snails and slugs) belong to the class Gastropoda and have 35,000 described species till date.
Land snails (also known as terrestrial snails, terrestrial gastropods or land gastropods) are an important component in a forest’s ecosystem. They help in recycling nutrients and are the prey base for rodents, birds, snakes and reptiles, and for some invertebrates too. This is because they are a rich calcium source for these organisms. Land snails also serve as an indicator of ecological conditions, and are very sensitive to climatic and ecological change, as they depend on moisture for their survival.
A large part of Indian terrestrial mollusc fauna is still poorly known. India has 1129 species within its political boundaries. The Western Ghats and North-east India have the highest number of species, with more than 80 percent endemic to these regions. Karnataka has nearly 100 species with endemicity of 80 percent. The greatest diversity is found in the Western Ghats region. Some of the terrestrial snails such as Deroceras laeve , Laevicauli salte, Macochlymus indica, etc. are serious pests to horticultural and agricultural systems.
Cryptozona bistrilis : A common snail found in dry regions of Karnataka. These snails aestivate during dry periods, in the soil as well as in crevices in trees.
Macrochlymus indica : This species is one of the commonest terrestrial snails of India. At times, this species can become a serious pest to agricultural and horticultural crops.
Ariophanta immerita : Unlike other relatives of the family Ariophantidae, all the species of this genus have shells which are coiled left-wards.
Indrella ampulla : An endemic and monotypic land snail endemic to evergreen forests of the Western Ghats. At times, this species can be seen in plantations such as coffee, areca and cardamom. Apart from feeding on decaying organic matter, it also feeds onmushrooms
Euplecta indica : Closely related to Ariophanta and Cryptozona. Though endemic to the Western Ghats, it is widely distributed in wet regions of Karnataka.
Mariaella dussumieri : A common slug of the Western Ghats. It is a generalist species found not only in forests but also in houses, plantations, home gardens etc. during the monsoon. Sometimes, it is a pest to horticultural crops.
Perrottetia peroteti : A carnivorous snail, it feeds on other small snails and soil organisms. This belongs to only carnivorous family of Indian snails – Streptaxide. This cryptic snail is found under dead logs and rotting vegetation. Mostly seen in wet forests of the Western Ghats.
Glessula sp.: Small, conical-shelled, terrestrial mollusc found in leaf litter and on tree trunks. One of the most difficult groups to identify in the field.
Succinia sp.: An amphibious snail, most common near Myristica swamps. Their shell is thin and translucent.
Rachis punctatus : Common snail in dry parts of Karnataka. The shell shows polymorphism and can easily be confused as a different species.
Laevicaulis alte : Common slug of Karnataka, found mostly in human-dominated areas. Believed to be an introduced species and can be a serious pest to horticultural crops.
Deroceras laeve : A European slug, introduced to India. A serious pest to horticultural crops and nurseries.