Effects of sulphide and thiosulphate on the respiratory properties of the haemocyanin of the benthic crustaceans Calocaris macandreae Bell, Nephrops norvegicus (L.) and Carcinus maenas (L.)

The addition of sulphide and thiosulphate (final concentration of 1 mmol l( -1)) to the haemolymph of the benthic decapod crustaceans Calocaris macandr eae Bell, Nephrops norvegicus (L.) and Carcinus maenas (L.) had no effect o n the ability of the haemocyanin to combine with oxygen in vitro. The addit ion of sulphite resulted in the deoxygenation of the haemocyanin but this c ould be reversed by exposure to air. There were pronounced differences betw een the species in both the oxygen affinity of the haemocyanin (P-50 at pH 7.8, 10 degrees C = 1.4 Torr, 8.6 Torr and 21 Torr in C. macandreae, C. mae nas and N. norvegicus, respectively) and in the magnitude of the Bohr coeff icient (-1.12, -0.84 and -1.15 in C. macandreae, C. maenas and N. norvegicu s, respectively). The addition of thiosulphate at concentrations between 0. 5 and 1.5 mmol l(-1) to the haemolymph of C. maenas and N. norvegicus had n o effect on the oxygen affinity of the haemocyanin. This was also true for the haemolymph of C. macandreae except that at the highest concentration us ed (1.5 mmol l(-1)) there was a slight but significant reduction in the P-5 0 value. The addition of thiosulphate to the haemolymph had no effect on th e Bohr coefficient or on the cooperativity of the haemocyanin in these spec ies. Even though C. macandreae may be exposed to sulphide in the burrows th at it constructs in sublittoral mud sediments, it would appear unlikely tha t the thiosulphate that accumulates in the haemolymph resulting from the ox idation of sulphide entering the body has a significant effect on the respi ratory properties of the haemocyanin. (C) 1999 Elsevier Science B.V. All ri ghts reserved.