Mechanism of blood coagulation in common carp (Cyprinus carpio)

In vitro, carp blood was anticoagulated by using MgSO₄ at a final concentration of 22.2 mmol L^?1 and sodium citrate at a final concentration of 11.8 mmol L^?1. The coagulation times for carp plasma diluted by ion‐free water (1:1), and that of carp plasma to which thrombocytes and small lymphocytes were added, were measured at 23 °C using standard methods, and then contrasted with the coagulation times for plasma obtained from chickens and rabbits. The shapes of the thrombocytes and small lymphocytes, which were either wet mounted or stained with hematoxylin and eosin, were observed under a light microscope. We found that: (i) the coagulation reaction of carp blood was significantly (P < 0.01) accelerated by the addition of ion‐free water; (ii) the three types of blood cells (thrombocytes, small lymphocytes and red blood cells) promoted plasma coagulation to a similar extent (P > 0.05); (iii) in carp Mg²⁺ plasma and K₂C₂O₄ plasma, the thrombocytes were usually morphologically normal, but many small lymphocytes were destroyed and became aggregated; (iv) in the citrate plasma, thrombocytes were often aggregated, but the small lymphocytes were usually morphologically normal; and (v) the coagulation time for chicken and rabbit plasma was significantly extended by adding ion‐free water.