The effects of water availability on the life history of the desert snail,Trochoidea seetzeni

Abstract

In the Negev desert of Israel, the pulmonate land snailTrochoidea seetzeni is active, grows and reproduces in the month following the torrential winter rains. Thereafter, these snails estivate until the following year's rains. By experimental supplementation of water in the field, we examined the ability of these snails to alter their life histories. Specifically, we measured changes in feeding activity, overall activity levels, movement patterns and reproductive output. We found that snails on artificially-watered plots stopped feeding on higher plants and fed on soil-surface algae growing as a result of increased water availability. Most snails moved onto the watered plots, and reduced the total amount of movement once there, in response to increased food availability. Snails on the watered plots grew more and remained active for a longer period into the summer months than did snails on control plots. However, we found little evidence for the ability of these snails to alter their reproductive outputs in response to increased water (and hence food) availability. There was also no carry-over effect of high water availability in one season enhancing reproduction in the following season. We postulate that the low level of phenotypic plasticity recorded here is a consequence of an adaptive conservative strategy to maintain a high reproductive output under extremely unpredictable desert conditions.

Development and reproduction in Bulimulus tenuissimus (Mollusca: Bulimulidae) in laboratory

“…Reproductive seasonality similar to that shown here was found in Trochoidea simulata (Ehrenberg, 1831) (Helicidae), which has very well defined seasonal reproduction, apparently generated by environmental conditions of temperature and humidity (WARD & SLOTOW 1992). Mastus olivaceos (Philippi, 1845) and Mastus crelensis (Pfeiffer, 1846) (Bulimulidae) also have well-defined reproductive periods, also due to variable environmental conditions.…”

Flux balance models for the oxygen and carbon isotope compositions of land snail shells

“…The main activity phase of a snail appears to be during and immediately following a rain event (Wells, 1944;Heatwole and Heatwole, 1978;Ward and Slotow, 1992). Hence rainwater would be the main source of water for land snails that are wholly subaerial (as opposed to semiaquatic).…”

“…Therefore, land snails are commonly active during and immediately following rainfall and in the evening -times when relative humidity is comparatively high (Howes and Wells, 1934;Wells, 1944;Heatwole and Heatwole, 1978;Ward and Slotow, 1992;Thompson and Cheny, 1996). In the European locations (Lécolle, 1985) of interest to this study, the average maximum relative humidity (h) for the days that it rained ranged from ϳ0.87 to 0.96 (decimal fractions).…”

“…Both of these times represent the known activity periods of snails (Wells, 1944;Edelstam and Palmer, 1950;Newell, 1966;Gelperin, 1974;Heatwole and Heatwole, 1978;Cook, 1979;Ward and Slotow, 1992). However, high values of h associated with air temperatures outside the usual range of snail activity (below 10°C or above 27°C) were excluded.…”

Considerations Regarding the Land Snails from the Upper Timiş River Valley (Banat, Romania)

“…Some of the terrestrial gastropod species have developed physiological mechanisms to overcome desiccation, but most of them need large amounts of water in order to survive (Burton, 1983;Ward and Slotow, 1992). As they are animals with low mobility, the land snails are among the most vulnerable to the habitat fragmentation, process that has been rapidly accelerated by human activities (Nekola, 1999;Lindenmayer and Fischer, 2006;Mysák and Horsák, 2011).…”