Fig. 1. Hemolymph pH varies as a function of acclimation temperature. Symbols represent mean (± s.e.m.) values for pH measured in lobsters acclimated to the indicated temperatures in artificial seawater in the laboratory (filled symbols) or to the ambient temperature of natural seawater in Woods Hole (MA, USA) in February (open symbols, WH) and in Salisbury Cove (ME, USA) in July (open symbols, SC). Numbers of samples measured under each condition are indicated. Inset: heart rates (mean ± s.e.m.) averaged over a period of 1 min in quiescent lobsters acclimated in the laboratory to water temperatures of 4 and 20°C.