title: Rapid effects of humidity acclimation on stress resistance in Drosophila melanogaster.
abstract: We tested the hypothesis whether developmental acclimation at ecologically relevant humidity regimes (40% and 75% RH) affects desiccation resistance of pre-adults (3rd instar larvae) and adults of Drosophila melanogaster Meigen (Diptera: Drosophilidae). Additionally, we untangled whether drought (40% RH) acclimation affects cold-tolerance in the adults of D. melanogaster. We observed that low humidity (40% RH) acclimated individuals survived significantly longer (1.6-fold) under lethal levels of desiccation stress (0-5% RH) than their counter-replicates acclimated at 75% RH. In contrast to a faster duration of development of 1st and 2nd instar larvae, 3rd instar larvae showed a delayed development at 40% RH as compared to their counterparts grown at 75% RH. Rearing to low humidity conferred an increase in bulk water, hemolymph content and dehydration tolerance, consistent with increase in desiccation resistance for replicates grown at 40% as compared to their counterparts at 75% RH. Further, we found a trade-off between the levels of carbohydrates and body lipid reserves at 40% and 75% RH. Higher levels of carbohydrates sustained longer survival under desiccation stress for individuals developed at 40% RH than their congeners at 75% RH. However, the rate of carbohydrate utilization did not differ between the individuals reared at these contrasting humidity regimes. Interestingly, our results of accelerated failure time (AFT) models showed substantial decreased death rates at a series of low temperatures (0, -2, or -4°C) for replicates acclimated at 40% RH as compared to their counter-parts at 75% RH. Therefore, our findings indicate that development to low humidity conditions constrained on multiple physiological mechanisms of water-balance, and conferred cross-tolerance towards desiccation and cold stress in D. melanogaster. Finally, we suggest that the ability of generalist Drosophila species to tolerate fluctuations in humidity might aid in their existence and abundance under expected changes in moisture level in course of global climate change.
authors.affiliation: Institute of Evolution, University of Haifa, Haifa, Israel. ddgenetics@gmail.com
authors.forename: Dau Dayal
authors.initials: DD
authors.lastname: Aggarwal
authors.forename: Poonam
authors.initials: P
authors.lastname: Ranga
authors.forename: Bhawna
authors.initials: B
authors.lastname: Kalra
authors.forename: Ravi
authors.initials: R
authors.lastname: Parkash
authors.forename: Eugenia
authors.initials: E
authors.lastname: Rashkovetsky
authors.forename: Leonidas E
authors.initials: LE
authors.lastname: Bantis
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D003080:Cold Temperature; D003890:Desiccation; D004331:Drosophila melanogaster / Q000254:growth & development / Q000502:physiology*; D055864:Droughts; D004734:Energy Metabolism; D005260:Female; D006813:Humidity; D007814:Larva / Q000254:growth & development; D008954:Models, Biological; D011679:Pupa / Q000254:growth & development; D013312:Stress, Physiological; D016019:Survival Analysis; D013696:Temperature; D014882:Water-Electrolyte Balance
keywords: Carbohydrate content; Cold tolerance; D. melanogaster; Desiccation resistance; Developmental acclimation at 40% and 75% RH; Duration of development