The blood of Halicryptus spinulosus (Priapulida)

Abstract

The blood of the priapulid Halicryptus spinulosus was investigated by protein electrophoresis and electron microscopy. Two cell types were encountered: irregularly shaped amoebocytes and spherical erythrocytes. In vitro, the former efficiently phagocytized bacteria and tended to coagulate. A 12-kilodalton polypeptide was the major molecule in erythrocytes, amounting to 20–30% of total erythrocytic proteins. It contained iron and probably formed complexes of higher molecular mass in the cells. These findings support suggestions that Halicryptus contains a haemerythrin-like pigment. Blood colour ranged from pink to black, probably depending on the hydrogen sulphide or oxygen concentration of the medium. Haematocrit values averaged 15.6%, and 58 000 erythrocytes were typically counted per microlitre of body fluid. The major blood constituent was a water-clear serum containing at least 20 proteins at very low and fairly variable concentrations; the molecular masses have been determined for 14 of these. A 46-kilodalton protein was prominent among serum proteins. Superoxide dismutase activity was demonstrated in erythrocyte lysates.