Salinity modulates thermotolerance, energy metabolism and stress response in amphipods Gammarus lacustris.

Kseniya P Vereshchagina,Egor Zadereev,Maxim Timofeyev,Inna Sokolova,Denis V Axenov-Gribanov,Anton Gurkov,Elizaveta S Kondrateva,Daria Bedulina,Yulia A Lubyaga,Boris Baduev,Zhanna Shatilina,Mikhail Gubanov

doi:10.7717/peerj.2657

Abstract

Temperature and salinity are important abiotic factors for aquatic invertebrates. We investigated the influence of different salinity regimes on thermotolerance, energy metabolism and cellular stress defense mechanisms in amphipods Gammarus lacustris Sars from two populations. We exposed amphipods to different thermal scenarios and determined their survival as well as activity of major antioxidant enzymes (peroxidase, catalase, glutathione S-transferase) and parameters of energy metabolism (content of glucose, glycogen, ATP, ADP, AMP and lactate). Amphipods from a freshwater population were more sensitive to the thermal challenge, showing higher mortality during acute and gradual temperature change compared to their counterparts from a saline lake. A more thermotolerant population from a saline lake had high activity of antioxidant enzymes. The energy limitations of the freshwater population (indicated by low baseline glucose levels, downward shift of the critical temperature of aerobic metabolism and inability to maintain steady-state ATP levels during warming) was observed, possibly reflecting a trade-off between the energy demands for osmoregulation under the hypo-osmotic condition of a freshwater environment and protection against temperature stress.

Highlights

Temperature and salinity are important abiotic factors affecting survival and performance of aquatic invertebrates and setting limits to their geographical distribution (Kinne, 1971; Nelson, 1977; Pörtner and Farrell, 2008)
Median mortality times (LT50) during acute exposure to 30°C were significantly higher in amphipods from the saline Lake Shira (LT50 = 22.8 h) compared to their counterparts from a freshwater Lake in Irkutsk (LT50 = 7.7 h) (Fig. 1). 100% mortality during gradual warming was observed at 31°C in Irkutsk population and 33°C in Shira population
Our study shows that adaptation to different salinity regimes can influence thermotolerance and modulate key characteristics of cellular metabolism and stress responses in Holarctic amphipods G. lacustris Sars

Summary

Introduction

Temperature and salinity are important abiotic factors affecting survival and performance of aquatic invertebrates and setting limits to their geographical distribution (Kinne, 1971; Nelson, 1977; Pörtner and Farrell, 2008). Recent data indicate the effect of the global climate change to surface waters including lakes worldwide (O’Reilly et al, 2015). The bulk of aquatic organisms are ectothermic, that makes them responsive to one of the main effects of global climate change: the increased variability in temperature, due to the dependency of their body temperature and the metabolic processes from the ambient water temperature. Environmental stress (including salinity and temperature stress) can significantly influence the energy balance of living organisms due to the additional energy required to restore and maintain homeostasis, which can put a strain on the energy acquisition, transformation and conservation systems

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