LAUSR

Insects’ ability to tolerate dehydration stress is understudied, yet important. The challenges of desiccating conditions confront insects in arid habitats, which can be overcome by one of four novel adaptive mechanisms: 1) reducing the rate of water loss (Gibbs et al., 1997), 2) increasing bulk water, 3) changing the phospholipid composition of epicuticular lipids (Rourke, 2000), or 4) tolerating greater amounts of water loss, that is, dehydration tolerance, (Hoffmann and Parsons, 1989; Gibbs et al., 1997; Gibbs and Matzkin, 2001). While there are several studies on dehydration tolerance and its role in desiccation resistance (Strachan et al., 2015; Weldon et al., 2016; Thorat and Nath, 2018; Ajayi et al., 2020), its significance remains controversial and there are no direct supporting evidence. It has not been extensively studied that dehydration tolerance could influence the evolution of desiccation resistance, but this aspect may play a role in diverse insect taxa. Water deficit environments can cause organisms to use different survival mechanisms. These include avoiding water loss or tolerating it. The tolerance to dehydration in dry environments consists of being able to survive internal water deficits (Scott, 2000), while dehydration avoidance is just the opposite (Pallarés et al., 2016). It is argued that avoiding dehydration should be a priority strategy, but the former lacks adequate data. Dehydration tolerance has been examined by a limited number of studies (Supplementary Data Sheet S1, Sheet 2-4), and most of those studies used selected D. melanogaster. Drosophila species adapted to desert conditions are more resistant to dehydration than their mesic counterparts (Gibbs and Matzkin, 2001); however, laboratory-selected strains showed no differences in resistance to desiccation (Gibbs et al., 1997). Comparatively, Hoffmann and Parsons (1993) reported that D (desiccation induced) flies were more dehydrated than their control group. Laboratory selection experiments generally assumed that desiccation resistance is not enhanced by dehydration tolerance (Gibbs et al., 1997). The term “dehydration tolerance” has been a topic of controversy for a long time, and the difference in terminology used by different scientists might explain this. The discrepancy in calculating dehydration tolerance might have resulted as a consequence of different formulas used by different physiologists. Table 1 shows the different formulas that were used for calculation of dehydration tolerance. OPEN ACCESS