SEASONAL-CHANGES IN BLOOD IGM LEVELS IN GOLDFISH, WITH SPECIAL REFERENCE TO WATER TEMPERATURE AND GONADAL MATURATION

Plasma IgM levels were monitored bimonthly for three years in individu al male and female goldfish reared under natural conditions, with spec ial reference to water temperature and seasonal reproductive cycle. Se xual maturation of the experimental fish occurred normally in the spri ng of each year as judged by rises in plasma levels of-gonadal steroid s. Plasma IgM levels showed clear seasonal change, both in males and f emales: values became elevated during the period between spring and su mmer, and declined from autumn to winter. These changes are related, a t least in part, to gonadal maturation in spring, since plasma IgM inc reased concurrently with the rise of steroid hormones, i.e., estradiol -17 beta and testosterone in females, and 11-ketotestosterone and test osterone in males. IgM levels also showed positive correlations with w ater temperature. An artificial increase in water temperature, from 5 degrees C to 15 degrees C or 25 degrees C within one day, was seen to induce an acute rise in plasma IgM. These results suggest that the sea sonal changes in plasma IgM levels in goldfish are related to both gon adal maturation and water temperature.