Hemolymph levels of vertebrate-type steroid hormones in female kuruma prawn Marsupenaeus japonicus (Crustacea: Decapoda: Penaeidae) during natural reproductive cycle and induced ovarian development by eyestalk ablation

摘要

The occurrence of vertebrate-type steroid hormones in the hemolymph and ovaries has been reported in several crustacean species; however, their physiological roles are not sufficiently understood. In the present study, correlations between hemolymph levels of the vertebrate-type steroid hormones and ovarian development in female kuruma prawn Marsupenaeus japonicus were examined. In the first experiment, hemolymph samples were taken in November (non-reproductive period) and June (maturing and spawningperiod) and the hemolymph levels of estradiol-17β estriol, progesterone, testosterone, and 11-ketotestosterone were found not to be significantly related to the ovarian development (gonadosomatic index, 0.80-9.39). In the second experiment, ovarian development was induced by bilateral eyestalk ablation in the non-reproductive period. The hemolymph levels of estradiol-17β estriol, and progesterone did not significantly differ between the control female prawn and the eyestalk-ablated female prawn, which underwent vitellogenesis. If the examined steroid hormones were vitellogenesis-stimulating hormones as in fish, their hemolymph levels would be expected to show significant correlations with ovarian development. However, the present study found no significant correlations between hormone levels and ovarian development. This suggests that based on the available data, the examined vertebrate-type steroid hormones do not play an important role in ovarian development in M. japonicus.