Photoperiodic activation of brains in castrates and the role of the gonad in reproductive maturation ofLimax maximus

Summary Results obtained with castration and gonad implantation verify that a factor(s) from the gonad is required for development of the female accessory sex organs (ASO) inLimax maximus. In addition, they show that a gonadal factor promotes rapid gonadal growth and sperm production, and gradual or incomplete development of the penis. Although an immature slug that is castrated and then switched to inductive photoperiods fails to exhibit reproductive tract maturation, in two differently designed experimental tests, the brains of such animals were able to promote sexual maturation when subsequently paired with an immature gonad. We interpret the results of these experiments as evidence for photoperiodic induction of secretion of maturation-inducing factor (MH) by the brain in the absence of the gonad. One or more gonadal hormones appear to be both necessary and sufficient for production of sperm and for development of ASO, but they are not required for the photoperiodic stimulation of MH release.Abbreviations ASO accessory sex organs - MH maturation hormone