Profiles of progesterone- and estradiol-like substances in the hemolymph of female Pandalus kessleri during an annual reproductive cycle.

The changes in GSI and HSI of Pandalus kessleri were monitored during an annual reproductive cycle. GSI reached a peak when ovaries were composed of yolky oocytes and decreased sharply during the spawning season. HSI followed a similar pattern. The changes in the concentrations of progesterone- and estradiol-17 beta-like substances in the hemolymph were also investigated. Progesterone levels increased at the onset of vitellogenesis and decreased during vitellogenesis. In contrast, estradiol concentrations rose during the peak of vitellogenesis and dropped after the release of mature eggs from the gonad.