RELATIVE IMPORTANCE OF HUMIDITY AND TEMPERATURE ON MICROHABITAT USE BY LAND SNAILS IN ARID VERSUS HUMID ENVIRONMENTS
Authors: Gregorio Moreno-Rueda, Antonio Ruiz-Ruiz, Eloísa Collantes-Martín and José Ramón Arrébola
Abstract: Dry environments, characterized by high temperatures and low humidity, impose restrictive living conditions on animals, which are especially critical for hydrophilic animals such as terrestrial gastropods. In order to successfully inhabit arid zones, snails show a suite of adaptations, such as the selection of microhabitats to minimize dehydration risk. When dehydration risk is high, protective microhabitats should be selected, and therefore, microhabitat selection should be regulated by weather conditions. Moreover, the weather factor more restrictive for snail life (humidity or temperature) should be the primary one regulating microhabitat selection. Here, we analyze this with two sympatric arid-dwelling snails from southeastern Spain, Iberus gualtieranus and Sphincterochila candidissima, and compare the results with two other sympatric landsnails, Theba pisana and Otala lactea, from a humid Mediterranean zone. For the four snails, microhabitat use is affected by weather, but differences occurred between sites. In humid environments, only temperature regulates microhabitat selection by T. pisana and O. lactea, and these snails climb to vegetation when temperature is high in order to escape from heat shocks. Meanwhile, in arid environments, humidity is also an important variable regulating snail behavior, especially for I. gualtieranus, which is sheltered in karstic fissures when humidity is low. In contrast to this species, S. candidissima prefers to climb to vegetation to escape from dehydration. In sum, snails respond to adverse weather conditions selecting the most protective microhabitats, although the response varies with climatic conditions and among species.