title: Physiological responses to salinity changes of the isopod Idotea chelipes from the Baltic brackish waters.
abstract: Survival, haemolymph osmolality and the specific metabolic rate of the isopod Idotea chelipes from the brackish waters of the southern Baltic Sea (salinity 7 psu) were investigated after acclimation to different salinities in the range of 3-30 psu keeping other parameters constant (T=15 degrees C, full air saturation). Haemolymph osmolality of I. chelipes increased from 379+/-33 mmol kg(-1) at 3 psu to 935+/-12 mmol kg(-1) at 30 psu. In the salinity range of 3-11 psu I. chelipes exhibited a hyperosmotic pattern of haemolymph regulation, whereas from 14 to 25 it behaved like an osmoconformer. Isoosmosis occurred at 28.5 psu (920 mmol kg(-1)). The specific metabolic rate of I. chelipes was significantly (P<0.05) related to salinity, with maximum (2.4+/-0.8 J g(-1) wm h(-1)) and minimum values (0.6+/-0.3 J g(-1) wm h(-1)) at 7 and 20 psu, respectively. The changes in the specific metabolic rate and in the difference between the osmolality of haemolymph and external medium were significantly correlated for I. chelipes (P<0.05). Rates of change per salinity unit were, however, unequal varying according to salinity transition. These differences indicate that osmotic adjustment may be a more or less costly in terms of energy according to salinity.
authors.affiliation: Department of Experimental Ecology of Marine Organisms, Institute of Oceanography, The University of Gdańsk, Al. Marszałka J. Piłsudskiego 46, 81-378 Gdynia, Poland.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Lapucki
authors.forename: Monika
authors.initials: M
authors.lastname: Normant
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001454:Baltic States; D001481:Basal Metabolism; D001835:Body Weight; D006458:Hemolymph / Q000378:metabolism; D033321:Isopoda / Q000502:physiology*; D008297:Male; D054712:Salinity; D012623:Seawater; D013534:Survival