Neuroendocrine control of reproduction in the male penaeid prawn,Parapenaeopsis hardwickii (Miers) (Crustacea,Decapoda, Penaeidae)

Effects of bilateral eyestalks ablation and injections of eyestalks, (Es) brain (Br) and thoracic ganglia (ThG) extract separately on the androgenic gland and testis development of Es-ablated (Experiment 1) and normal (Experiment 2) P. hardwickii, were investigated. The androgenic gland activity increased significantly in prawns having Es-ablated (Group II), and eyestalkless (Groups VI & VII) and normal (Groups D & E) prawns received Br and ThG extracts, separately, as compared to their respective controls (Groups I & A). Injection of unboiled Es extract in eyestalkless (Group V) and normal (Group C) prawns arrested the androgenic gland activity. Simultaneously, there was a significant (p<0.05) increase in the diameter of testicular follicles, testis weight, testis index and number of mature spermatocytes per follicle in the prawns of groups II, VI & VII of experiment 1 and of groups D & E of experiment 2 when compared to their respective controls. Injection of Es extract into the eyestalkless (Group V) and normal (Group C) prawns ceased testicular development. A significant (<0.05) decrease in testicular protein and midgut gland glycogen and lipid was found in groups II, VI & VII of experiment 1 and in groups D & E of experiment 2, but the glycogen and lipid content of the testis increased. These results indicate that the hormones released from the neuroendocrine centres regulate androgenic gland activity and spermatogenesis.