Chill susceptible Drosophila species lose hemolymph volume in the cold.
(A) Hemolymph volume before cold exposure (circles, solid line) and immediately following 4 h at 0 °C (squares, dashed line) in five Drosophila species. The shaded grey area denotes the magnitude of hemolymph volume loss during cold exposure (lines illustrate no significant interaction between species and treatment). All values are means ( ± sem). (B) The relative disturbance of hemolymph volume correlated positively with cold tolerance (shown as LTe50). Error bars that are not clearly visible are obscured by the symbols. All values are means ( ± sem). (C) The mean percent increase in hemolymph [K+] in relation to the proportion of hemolymph volume lost. Cold exposure caused D. birchii, D. equinoxialis and D. melanogaster to lose K+ balance in excess of what is expected from the concentrating effect of hemolymph volume loss alone (dashed line), implying additional K+ leak into the hemocoel from the tissues and/or gut lumen. By contrast, D. montana and D. persimilis reduced hemolymph [K+], despite a small reduction in hemolymph volume, suggesting these two species are removing net K+ from the hemolymph at 0 °C.