Temperature-Photoperiod Effects on Spermatogenesis in the Salamander Plethodon cinereus

The effects of experimentally produced light and temperature on the normal spermatogenic cycle of the salamander Plethodon cinereus were investigated. Three sets of experiments were conducted at different times in the cycle under 8 light-16 dark, 12L-12D, and 16L-8D lighting conditions at both 10° and 20° C. The normal spermatogenic cycle varied from previous descriptions only in the date of appearance of various stages. From the onset of spermatogenesis (late March), a temperature of 20° C and 16L-8D for the next 90 days accelerated the normal cycle as much as 56 days. By 26 June when the normal testis content was 65% spermatids but no spermatozoa, the testes of animals at 20° C averaged 65% spermatozoa. All photoperiod groups at 10° C had an average retarded cycle of 16 days. Experiments conducted from December 30 to March 28 indicated that temperatures of 20° C were needed to initiate the spermatogenic wave in Michigan P. cinereus. The effect of different photoperiods was also significant. Photoperiods of 16D-8D and 12L-12D advanced the spermagenic cycle more than three months by March 28, resulting in the production of spermatozoa. The 8L-16D photoperiod advanced the cycle a little more than two months with the production of few spermatids but no spermatozoa. No photoperiod-temperature effects were noted during the early quiescent period (October-December) indicating a possible refractive period in the cycle.