Effect of ice fraction and dilution factor on the antifreeze activity in the hemolymph of the cerambycid beetle Rhagium inquisitor.

The freezing-melting hysteresis in a given volume of hemolymph from the cerambycid beetle Rhagium inquisitor was linearly and negatively related to the logarithm of the mass fraction of ice in the sample. When the ice fraction dropped by a factor of 10, the hysteresis activity increased by about 2 degrees C. When the hemolymph was diluted, the hysteresis activity was linearly and negatively related to the logarithm of the dilution factor. Dilution of the hemolymph by a factor of 2 led to a 1 degree C reduction in hysteresis activity. In the diluted samples, the ice growth took place along the a-axes, implying that the antifreeze peptides of insects block ice growth along the c-axis, in addition to the a-axis.