Brain-gonad axis and photoperiodically-stimulated sexual maturation in the slug,Limax maximus

Summary Physiological and endocrine mechanisms mediating long-day (LD 168) triggered sexual maturation were studied in the terrestrial slug,Limax maximus. Our findings were: (1) Maturation was induced in immature slugs seeing only short days (LD 816) after implantation of whole brains from maturing donors, but no development was found in sham-operated control slugs or in animals receiving implants of muscle from mature donors (Table 1). (2) Removal of the optic tentacles did not block maturation in LD 168 or promote maturation in LD 816 (Fig. 1). (3) Gonadectomy (castration) abolished penis development in 9 of 11 slugs exposed to LD 168 for periods of up to 31 weeks (Table 2). The results are consistent with a model forLimax reproductive tract development in which the perception of long days by extraocular receptors results in the secretion of a maturation hormone by the brain followed by the production of a separate male-phase sex hormone by the developing gonad.Abbreviations ASO accessory sex organs - DB dorsal bodies - FPSH female-phase sex hormone - MH maturation hormone - MPSH male-phase sex hormone This work was supported in part by grants from NSF (BNS 78-01408) and NIH (MH 27948) to P.G.S. The assistance of Mr. T.M. Gordon, Mr. J.L. Broyles, and Mr. M. Bullock is gratefully acknowledged.