The heat production rate of Gammarus oceanicus, a species of marine origin living in the brackishwaters (7 psu (practical salinity units)),wasexamined by direct calorimetry after acclimation to salinities of 5, 7, 14, 20 and 30 psu (at 10 °C). The mean heat dissipationwas greatest at 5 psuwith 5.64±1.60 J h−1 g−1 ww (wet weight) and decreased significantly (P < 0.05) with increasing salinity down to 2.26±1.14 J h−1 g−1 wwat 30 psu. The high inter-individual variability was of significance for the obtained results. When salinity dropped by only 2 psu from thecontrol (7 psu) the mean heat production rate raised by 18%. A salinity increase from 7 to 30 psu caused a reduction in the average metabolicrate of G. oceanicus by 53%. That means that G. oceanicus requires more energy for osmotic adjustment at lower salinities. |
