RESUMO
D-Glutamate, a novel D-amino acid found in animal tissues, exclusively exists in the male reproductive tissues of kuruma prawn, Marsupenaeus japonicus. Herein, changes in the D-glutamate content were determined in the male reproductive tissues of M. japonicus, during acclimation with breeding seawater temperature of 18°C-22°C and unilateral eyestalk ablation. The D-glutamate content in the testis increased with increasing seawater temperature, and with unilateral eyestalk ablation. This suggests that both stimulations induced D-glutamate synthesis in the testis. Although the D-alanine content in the testis increased after unilateral eyestalk ablation, it did not change with elevated seawater temperature. Furthermore, we determined the D-glutamate distribution in the M. japonicus spermatophore. This indicates that D-glutamate is crucial in prawn fertilization.
RESUMO
Some aquatic invertebrates contain free d-alanine. We previously showed copious amounts of free d-glutamate, a novel d-amino acid, in the tissue of the male reproductive organs of Marsupenaeus japonicus. Herein, we clarified the distribution and potential role of d-glutamate and d-alanine in male reproductive tissues, namely the testis, vas deferens and seminal receptacle at different growth stages of M. japonicus. The percentage of d-glutamate to total glutamate was over 50% in these tissues. In particular, the content of d-glutamate was the most abundant in the vas deferens, the ratio of d-glutamate to total glutamate was approximately 80%. In contrast, d-alanine content was the lowest in the vas deferens among these tissues. d-Glutamate content was the highest when the prawn weighed 12 g, indicating that d-glutamate is actively synthesized in the younger stage. Our findings suggest that d-glutamate plays an important role in the reproductive functions of M. japonicus.
