Intraspecific variation in resistance to desiccation and climatic gradients in the distribution of the bush‐dwelling land snail Trochoidea simulata

Abstract

Resistance to desiccation was examined in six populations of the Israeli bush‐dwelling snail Trochoidea simulata, a desert species distributed mainly between the 100–200 mm isohyets. The present study revealed significant intraspecific differences in resistance to desiccation which are correlated with habitat and climatic gradients within the distribution range of the species. Populations from more arid sites were more resistant to desiccation and heat exposure than those from more mesic areas. However, the population from the Rift Valley (an extremely arid region) was surprisingly poorly resistant. Rates of population water loss under the controlled experimental conditions in the laboratory generally matched the calculated water losses during natural summer aestivation.

Physiological adaptations to high intertidal life involve improved water conservation abilities and metabolic rate depression in Littorina saxatilis

“…Hence, alanine accumulation during air exposure in intertidal molluscs seems to be unrelated to the need for maintenance of the osmotic balance. This is probably due to the fact that water is evenly lost from extracellular and intracellular compartments during air exposure in molluscs (Arad et al 1992(Arad et al , 1993, thus reducing the necessity for iso-osmotic cell volume regulation. Despite significant anaerobic end-product accumulation, the main energy supplying pathways in Littorina saxatilis were aerobic, with aerial oxygen consumption accounting for > 95% of the total ATP turnover during air exposure at elevated temperatures.…”

Natural annual cycle of heat shock protein expression in land snails: desertversusMediterranean species ofSphincterochila

“…Comparative studies in land snails have revealed that, in general, resistance to heat and aridity is correlated with distribution patterns and with abiotic environmental variation (Cameron, 1970;Machin, 1967). A series of studies on water relations and resistance to experimental desiccation of Israeli land snails have demonstrated that Mediterranean snails are less resistant than desert species and populations, and that the distribution pattern of each species and its microhabitat are related to its ability to cope with desiccating conditions (Arad, 2001;Arad, 2009;Arad et al, 1989;Arad et al, 1992;Arad et al, 1993). In addition, interspecific differences were found that stem from a variety of morphological, behavioral and physiological adaptations, such as snail size, epiphragm thickness, site selection and lifestyle, and osmoregulatory capacities.…”

Ontogeny of resistance to desiccation in the bush‐dwelling snail Theba pisana (Helicidae)

“…During both, the experimental desiccation and during the dry season in the ®eld, water loss was mainly attributed to the extra-pallial compartment which, thus, serves as a reservoir for water loss before body water content is compromised. The osmotic changes revealed in aestivating and in desiccated snails help in moderating extreme changes in the`mileu interieur' of the snail (Prior, 1980;Arad, 1990;Arad et al, 1992Arad et al, , 1993a. The effectiveness of osmoregulation changes seasonally in the ®eld: during summer the osmotic concentration of the¯uids almost doubled compared to winter values (327±335 vs. 173±206 mosmol/1 in July±September and November±February, respectively), indicating that aestivation initiates the establishment of an osmotic gradient in favour of water preservation.…”