Tolerance to desiccation stress in Chironomus Ramosus through plasticity in homeostatic control

Abstract

Desiccating environments pose physiological challenges to organisms, especially those experiencing them on recurring basis. Several desiccation-tolerant organisms are known to withstand loss of body water in response to seasonal dehydration patterns through adaptations that facilitate their sustenance in the dry state followed by recovery upon return of favourable hydrating conditions. In the present study, we have chosen Chironomus ramosus, an aquatic midge species as a laboratory model system towards the exploration of its desiccation tolerance ability. We confirm that upon desiccation exposure at low relative humidity, larvae of C. ramosus exhibited rapid water loss and could revive upon rehydration. Moreover, the revived individuals underwent successful metamorphosis; albeit delayed. This heterochrony in the developmental calendar was experimentally verified by the investigation of ecdysone levels which suggested an altered pattern of ecdysis in response to the stress. These data suggested the organism's plasticity in developmental homeostasis when confronted with dehydration stress. Furthermore, spectrofluorometric assays indicated the occurrence of thiol damage in the larvae. Investigation of Hsp70, the evolutionarily conserved stress responsive gene suggested that Hsp70 was indeed up-regulated during the rehydration period, thus facilitating recovery of the larvae from dehydration. In summary, several lines of evidence involving cellular, physiological and developmental adaptations revealed the ability of C. ramosus larvae to minimize the diverse categories of damage caused by desiccation stress through plasticity in their homeostatic mechanism.

High-throughput mass spectrometry analysis revealed a role for glucosamine in potentiating recovery following desiccation stress in Chironomus

“…The exploration of other desiccation-induced biomolecules was out of scope of the present study, however, their involvement cannot be ruled out. Nevertheless, we have previously reported the role of Hsp70 during larval desiccation tolerance in C. ramosus 15 .

Figure 2Desiccation-induced trehalose synthesis in the larvae. ( A–D ) Representative UPLC-QToF-MS chromatograms indicating the detection of trehalose in the midge larvae.

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Changes in Microbiota Composition Along the Metamorphosis Developmental Stages of Chironomus transvaalensis

“…Chironomids lay their egg masses on the water’s edge, and in the summertime, the egg masses are exposed to high temperatures and UV radiation. Chironomids are known to be temperature‐ and UV radiation-tolerant ( Thorat and Nath, 2015 , 2016 ). Thus, Deinococcus-Thermus bacterial species may play a role in protecting the egg masses from extreme conditions; however, the direct effect of Deinococcus-Thermus on chironomid survival under high temperature and UV radiation has not yet been studied.…”

“…Chironomids are the most widely dispersed aquatic insects in freshwater habitats ( Ferrington, 2008 ). They can tolerate extreme temperature, pH, salinity, depth, and current velocity, and even dehydration and UV and gamma radiation ( Ali, 1991 ; Senderovich and Halpern, 2012 , 2013 ; Thorat and Nath, 2015 , 2016 ). Chironomids are an important component of the food chain as a food source for invertebrates, fish, and birds ( Floss et al, 2013 ).…”

Insects With Survival Kits for Desiccation Tolerance Under Extreme Water Deficits

“…In the case of the oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae), desiccation does not exert significant effects on the average eclosion time (Xie and Zhang, 2007). In C. ramosus and D. melanogaster , modulations in 20-hydroxyecdysone affect recovery patterns and are linked with the desiccation-mediated delay in metamorphosis (Thorat and Nath, 2015; Thorat et al, 2016b). Interestingly, in D. melanogaster , despite the developmental heterochrony, the overall duration of postembryonic development of the life cycle remains almost unaltered.…”