epigean) crustacean Gammarus fossarum acclimated to 12°C, 3°C and –2°C. With decreasing temperature, G. fossarum significantly increased its alanine and glutamine

The capacity to survive a temporary or permanent cold environment is a crucial challenge for ectotherms. Many physiological and biochemical mechanisms are known to extend the survival of freeze-susceptible species at subzero temperatures by avoiding injuries induced by the formation of ice crystals in tissues (Zachariassen, 2000). However, low but positive temperatures may also induce severe damage (Turnock, 1991, 1993; Tanaka and Udagawa, 1993; Ramløv, 2000; Hochachka and Somero, 2002; Renault et al., 2004). The mechanism of chill injury is not well understood, although it may be related to protein denaturation (Carpenter and Crowe, 1988; Ramløv, 2000; Hochachka and Somero, 2002), phase changes in membrane lipids and/or a complex metabolic disorder (Grout and Morris, 1987; Ramløv, 2000; Hochachka and Somero, 2002). Such injuries may induce chill coma and even death (Vannier, 1987; Renault et al., 1999; Ramløv, 2000). There are several low-molecular-mass sugars and polyols that may be accumulated and may prevent lethal injuries (Kostal et al., 2001; Slachta et al., 2002). The importance of glycerol, mannitol, trehalose and sucrose is widely recognized in insects during thermal acclimation and cold exposure (Salt, 1961; Ring and Danks, 1998). Although the importance of free amino acids (FAA) during cold exposure has been less investigated, authors found a positive correlation between the increase in content of a few FAAs (i.e. proline, alanine, leucine) in insects’ body fluids and their acclimation to cold (Storey, 1984, 1997; Fields et al., 1998). Although the literature on insect cold hardiness is overwhelming, very few studies deal with cold adaptations in crustaceans. An accumulation of trehalose and myo-inositol was found in the terrestrial isopod Porcellio scaber (Tanaka and Udagawa, 1993). Moreover, the FAA composition is known to widely vary with season in this taxon (Graney and Giesey, 1986). Alanine, arginine, leucine and glycine are the Journal of Experimental Biology 208, 2923-2929 Published by The Company of Biologists 2005 doi:10.1242/jeb.01737