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Figure 2

From: Thermal reaction norms of key metabolic enzymes reflect divergent physiological and behavioral adaptations of closely related amphipod species

Figure 2

Species-specific thermal reaction norms of maximum enzyme activities. Citrate synthase (CS), cytochrome-c-oxidase (COX), 3-hydroxyacyl-CoA dehydrogenase (HADH), glutamate dehydrogenase (GDH), pyruvate kinase (PK), and lactate dehydrogenase (LDH) were extracted from tissues of E. verrucosus, E. cyaneus and G. lacustris exposed to gradual temperature increase (0.8 °C d−1). Samples of all three species were taken at 6 °C, 12.4 °C, 18.8 °C, and 23.6 °C; besides, samples of E. verrucosus were taken at 9.2 °C and 15.6 °C. Measurements were performed at the respective sampling temperatures. Enzyme activities level off at temperatures exceeding about 15 °C in the stenothermal Lake Baikal endemic amphipod species E. verrucosus (except for LDH). At the same time, they increase exponentially over the entire thermal range in the two more eurythermal species E. cyaneus (Lake Baikal, endemic) and G. lacustris (Holarctic, ubiquitous). Dots represent raw data. Solid lines represent nonlinear models (equations are summarized in Table S2; Supplement), and shaded areas display 95% confidence intervals (n = 5–7).

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