O2-BINDING PROPERTIES OF HEMOCYANIN FROM THE SANDHOPPER TALITRUS-SALTATOR (MONTAGU, 1808) (CRUSTACEA, AMPHIPODA)

The common sandhopper of British shores, Talitrus saltator (Montagu, 1808), occupies a narrow vertical range around the high water mark on predominantly sandy beaches. During the winter, adults burrow deep into the sand where they remain in an inactive state ("torpor") for extended periods. This study examined the possibility of seasonal acclimation in haemocyanin (Hc) O2; affinity in this hopper. Despite marked differences in haemolymph ionic composition between hoppers collected at different times of the year (torpid hoppers had low Na+ and Cl- and an exceptionally high Mg2+, concentration), there were no significant differences in the Hc O2 affinities of the respective haemolymphs in vitro: the Hc O2 affinity was low [p50 = 17.6 Torr (2.35 kPa) at pH = 7.8, T = 10 °C; gf = - 0.749] and in each case was temperature dependent over the range of temperatures examined (5-20 °C). Values for heats of oxygenation (ΔH) were high, ranging from -24 to -38kJ·mol-1. Resuspended Hc was largely insensitive to changes in the concentrations of those organic (l-lactate, urate) and inorganic (Ca2+, Cl-) ions which are known to affect the O2-binding properties of many other crustacean Hc's, with the possible exception of Mg2+ which increased Hc O2; affinity slightly [ ΔlogP50 Δlog (Mg2+) = 0.10]. In general, these results explain the absence of any changes in the O2; affinity of the haemolymph of T. saltator despite marked "seasonal" changes in many of the haemolymph ions. © 1990.