ABSTRACT
Recently the presence and metabolism of steroids in female sea stars have been studied rather extensively. The presence of progesterone and oestrone in ovaries and pyloric caeca has been established beyond doubt and the main pathways in steroid metabolism have been outlined. This study showed the presence of progesterone and oestrone in the gonads and pyloric caeca of male sea stars and estimated the levels throughout the reproductive cycle. The onset of a new reproductive cycle, taking the abrupt decrease of the pyloric caeca-index as a marker, coincides with a strong decrease of the progesterone level and an increase of the eostrone level in the pyloric caeca of the male sea star.
