INFLUENCE OF OCULAR AND EXTRAOCULAR PHOTORECEPTION ON SPERMATOGENESISIN GAMBUSIA-AFFINIS HOLBROOKI (TELEOSTEI, POECILIIDAE)

Non-blinded and blinded male mosquito-fish (Gambusia affinis holbrooki ) were subjected to three different photoperiods (a short photoperiod of 8 hr light daily, a simulated natural photoperiod that was increase d from 12.25 to 14.50 hr of light, and a long photoperiod of 16 hr of light) at a constant mild temperature (20 degrees C) during the sperma togenesis period (March-May). Afterwards, the testes were removed and studied by quantitative histological methods, along with the testes fr om initial and final field controls. Fish exposed to simulated natural or long photoperiod (16L:8D) developed complete spermatogenesis like the final controls. Fish exposed to short photoperiod developed sperma togenesis up to the primary spermatocyte stage. Photoperiodic effects on spermatogenesis were similar in both blinded and intact males subje cted to the same photoperiodic conditions. Thus, extraocular photorece ption must be involved in photoperiodic effects on reproduction, and t he presence of the eyes is not required for spermatogenesis in this sp ecies. (C) 1994 Wiley-Liss, Inc.