CHANGES IN SUPERCOOLING WITH BODY-SIZE, SEX, AND SEASON IN THE LONG-LIVED MILLIPEDE POLYZONIUM-GERMANICUM (DIPLOPODA, POLYZONIIDAE)

The supercooling points (SCPs) of a held population of Polyronium germ anicum were measured at different stages in the life cycle. There was no post-freezing survival under the experimental conditions used. The mean SCP was -26.2 degrees C for eggs and increased to -18.2 degrees C for juveniles of stadium III experiencing their first winter. From st adium V onwards, SCP varied considerably among individuals, ranging fr om -22.7 to -4.7 degrees C. SCP was shown to increase significantly wi th body size in both sexes. Seasonal changes also occurred in males, S CP being lower in autumn-winter than in spring-sumner. Measurements fr om a sample starved in the laboratory showed that the winter decrease could result from starvation affecting a proportion of males in the he ld. There was no relationship between the SCP and relative water conte nt of individuals. After starvation in the laboratory, however, there was a relationship between the SCP and relative fat content of males. The results show that freezing is not a significant threat to the held population studied, with the possible exception of the largest overwi ntering females.