Adaptation of Gammarus tigrinus Sexton, 1939 to new environments—Some metabolic investigations

The heat dissipation rates of the invasive amphipod Gammarus tigrinus Sexton, 1939 of the southern Baltic Sea were measured by means of direct calorimetry at the habitat salinity of 7‰ (males and females) and after gradual acclimation (only males) to lower (3‰) and higher (13‰ and 19.5‰) values (T = 18 °C). The mean specific metabolic rate at 7‰ amounted to 1.67 ± 0.86 mW g−1 ww (n = 25, average wet weight 10.9 ± 5.1 mg). Due to the sexual dimorphism and the smaller size of the females their specific metabolic rates were two-fold higher than that of males. Animals exposed to lower than habitat salinity insignificantly increased their specific metabolic rate by 42.5%. A reduction of 37.5% was observed when they were subjected to the highest examined salinity (19.5‰). G. tigrinus was thus able to change its metabolic rate by 56% in the studied salinity range from 3‰ to 19.5‰