Protective effects of ectoine on heat-stressed Daphnia magna

Abstract

Ectoine (ECT) is an amino acid produced and accumulated by halophilic bacteria in stressful conditions in order to prevent the loss of water from the cell. There is a lack of knowledge on the effects of ECT in heat-stressed aquatic animals. The purpose of our study was to determine the influence of ECT on Daphnia magna subjected to heat stress with two temperature gradients: 1 and 0.1 °C/min in the range of 23–42 °C. Time to immobilisation, survival during recovery, swimming performance, heart rate, thoracic limb movement and the levels of heat shock protein 70 kDa 1A (HSP70 1A), catalase (CAT) and nitric oxide species (NOx) were determined in ECT-exposed and unexposed daphnids; we showed protective effects of ECT on Daphnia magna subjected to heat stress. Time to immobilisation of daphnids exposed to ECT was longer when compared to the unexposed animals. Also, survival rate during the recovery of daphnids previously treated with ECT was higher. ECT significantly attenuated a rapid increase of mean swimming velocity which was elevated in the unexposed daphnids. Moreover, we observed elevation of thoracic limb movement and modulation of heart rate in ECT-exposed animals. HSP70 1A and CAT levels were reduced in the presence of ECT. On the other hand, NOx level was slightly elevated in both ECT-treated and unexposed daphnids, however slightly higher NOx level was found in ECT-treated animals. We conclude that the exposure to ectoine has thermoprotective effects on Daphnia magna, however their mechanisms are not associated with the induction of HSP70 1A.

Influence of maternal age on the effects of seleno-l-methionine in the model organism Daphnia pulex under standard and heat stress conditions

“…For instance, Daphnia dually exposed to cadmium and elevated temperature exhibited increased sensitivity 45 . Recorded responses of Daphnia to elevated temperatures include changes in swimming behavior, immobilization, and death 46 . The effect of SeMet on thermal stress has not yet been evaluated in Daphnia.…”

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“…There are also results on effects induced by ECT in aquatic animals. Our previous studies revealed its low toxicity with the modulatory influence on heart activity, thoracic limb movement in Daphnia magna and protective effects in heat-stressed daphnids (Bownik et al, 2014;Bownik et al, 2015).…”

“…Microorganisms such as Marinococcus sp. ECT1 synthesize and accumulate intracellular ECT in response to osmotic stress during unfavourable environmental conditions, such as high temperature, salinity (Wei et al, 2011;Bownik et al, 2014). This amino acid protects bacterial cell membranes, enzymes and nucleic acids against dehydration (Galinski et al, 1985).…”