Metabolic responses to thermal ramping in two endemic eurybathic amphipods of the genus Ommatogammarus from ancient Lake Baikal

Abstract

Lake Baikal harbors freshwater profundal amphipods, including the eurybathic species Ommatogammarus flavus and O. albinus. O. flavus occupies shallower habitats, including the littoral zone, which is subject to greater temperature variability. Consequently, O. flavus may demonstrate a higher degree of tolerance to temperature fluctuations in comparison with O. albinus. We compared the metabolic responses of these two amphipod species to thermal ramping. Specimens were collected from a range of depths and acclimated to a temperature of 4 °C. They were then subjected to controlled temperature up- and downshifts to assess the parameters of tissue energy status, antioxidant enzyme activity, and survival. O. flavus showed a higher degree of tolerance to warming than the deeper-dwelling O. albinus, while both species were resilient to temperature decreases. The depth of sampling had a minor effect on glycogen levels in O. flavus as well as catalase and glutathione S-transferase activity in O. albinus but had no effect on survival during experimental warming. Glucose level was shown to be the most sensitive biochemical marker to temperature variations, indicating that it could be used as a stress indicator for Baikal deep-water amphipods. This finding might provide insight into their adaptability to ambient temperature fluctuations.