Published online by Cambridge University Press: 19 September 2003
The subunit composition of haemocyanin (Hc) from the semiterrestrial beachflea Orchestia gammarellus exhibited less heterogeneity and less (qualitative) between-individual variation than most decapod Hcs. While between-population variation was detected, no clear trends in Hc subunit composition from four populations along a salinity gradient were observed. Salinity had no detectable effect on Hc subunit composition or HcO2 binding in the laboratory. The degree of phenotypic variation in laboratory-held beachfleas was less than that displayed by any of the natural populations examined. Furthermore, examination of the O2 binding characteristics of five of the most common Hc phenotypes showed that each phenotype had the same O2 binding properties. Differences in Hc subunit composition between individuals and between populations may exist, but it should not be automatically assumed that such variation will have consequences for intrinsic Hc O2 binding properties.