23 June 2012

Aestivation of Theba pisana snails

I came across a cluster of white snails at a fence post near a field of wild oats which is used for animal fodder.  The snails were all concentrated together in one area.  I carried out some research and I learnt that this is called aestivation.  Apparently, it is "a state of animal dormancy, characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions.  It takes place during times of heat and dryness, the hot dry season.  Invertebrate and vertebrate animals are known to enter this state to avoid damage from high temperatures and the risk of desiccation. Both terrestrial and aquatic animals undergo aestivation." 

It is interesting to learn that although these snails look dead and dried up they are still alive but in a dormant state to conserve their energy and avoid dessication.  These snails may be a species called Theba pisana although that is just a guess based on a photograph.  "Theba pisana, common names the white garden snail, the sand hill snail, white Italian snail, the Mediterranean coastal snail, or simply the Mediterranean snail, is an edible species of medium-sized air-breathing land snail, a pulmonate gastropod mollusk in the family Helicidae. It is native to Mediterranean region, but it is a widespread invasive species in other countries. Theba pisana is a well-known agricultural pest in many parts of the world.  It has a shell from white to yellow-brown with light brown spiral markings.  In addition to the direct negative effect of Theba pisana feeding on agricultural crops, it also has several other additional effects. It uses the stalks of cereals as aestivating sites, which in turn clogs machinery and fouls produce during mechanical harvesting.

Theba pisana snails aestivate on a fence post near a field of wild oats in Tunisia.

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