Modulation of haemocyanin oxygen affinity in the prawn, Palaemon elegans (Rathke) under environmental salinity stress

Abstract

The effects of salinity acclimation on the oxygen-transporting properties of the blood of the intertidal prawn Palaemon elegans (Rathke) have been examined. Although there was considerable variation in the haemocyanin content of the haemolymph between individual animals, an inverse relationship was obtained between the haemocyanin content of the blood and the salinity to which the animals were acclimated. This resulted in an increase in the oxygen-carrying capacity of the haemocyanin from 1.2 mmol · 1 ∮-1 to 1.48 mmol · 1 −1 in prawns acclimated to salinities of 30 and 10%., respectively. No significant differences were observed in either the oxygen affinity ( P 50 = 31.3–34.0 Torr, pH = 7.8, temperature = 10 °C) or in the size of the Bohr effect (mean value of Φ = −0.74) of the haemocyanin in animals maintained in salinities of 10, 20, and 30%., but blood from animals kept in water having a salinity of 40%. had both a higher oxygen affinity ( P 50 = 11.8 Torr, pH = 7.8) and a higher Bohr value (Φ = −1.26). These increases were primarily due to changes in the concentration of ions (mainly Mg 2+) in the blood of these animals. The co-operativity of the haemocyanin, however, did not differ significantly between the four groups of prawns. Similarly, the effect of l-lactate on the modulation of haemocyanin oxygen affinity was found to be unaffected by changes in the ionic composition of the blood associated with acclimation to differing salinities.