Effects of androgenic gland ablation on male primary and secondary sexual characteristics in the Malaysian prawn, Macrobrachium rosenbergii (de Man) (Decapoda,Palaemonidae), with first evidence of induced feminization in a nonhermaphroditic decapod

Male Macrobachium rosenbergii (de Man), categorized into three developmental stages according to possession of male gonopore complexes, appendixes masculina, and mature chelipeds, were subjected to bilateral androgenic gland ablation (andrectomy). Andrectomized males initially lacking appendixes masculina and mature chelipeds do not develop them; those initially possessing appendixes masculina and mature chelipeds do not lose them. Growth rate of the appendixes masculina, however, is reduced. Andrectomized males are unable to redifferentiate amputated or accidentally lost appendixes masculina and mature chelipeds. Instead, the appendages regenerate as immature forms. Andrectomized M. rosenbergii possess atrophied testes and vasa deferentia. Histological sections of the testes revealed a reduction in number of spermatogenic lobules. Spermatogonia and primary spermatocytes were commonly found; secondary spermatocytes and spermatids were found only occasionally. Andrectomy appears to inhibit but not prevent meiosis. Feminization occurred in five andrectomized males. Complete feminization, including initiation of oogenesis and development of oviducts and female gonopores, occurred in males andrectomized in the youngest developmental stage. Males andrectomized in later developmental stages were either partially feminized or not feminized. Reimplantation of androgenic glands reverses the effects of andrectomy. Remasculinization, as evidenced by differentiation of appendixes masculina, was noted after the first postimplantation molt. The testes of remasculinized males were normal in gross anatomy and spermatogenic ability. The data indicate a uniform function for the androgenic glands with respect to male primary and secondary sexual characteristics among the Amphipoda, Isopoda, and Decapoda. Past theories on androgenic gland function are modified in light of the present information.