Environmental influences on hormonally induced spermiation of the bullfrog, Rana catesbeiana

Frog pituitaries, human chorionic gonadotropin (HCG), luteinizing hormone (LH), follicle stimulating hormone (FSH) and gonadotropinreleasing hormone (LH/FSH‐RH) were tested to determine their effectiveness in eliciting the spermiation response in laboratory‐reared male bullfrogs ( Rana catesbeiana ). LH/FSH‐RH gave the highest percentage of positive responses and the most rapid responses. Sperm acquired by cloacal sampling after LH/FSH‐RH injections were fertile. Day length (14L:10D; 8L:16D, 25°) had no measurable effect on reproductive condition, growth or sensitivity to injections of LH/FSH‐RH. Spermiation response to LH/FSH‐RH was depressed at low temperatures (15°, 20° C) and testicular recrudescence appeared to be inhibited at warm temperature (30°C). Optimum spermiation responses were obtained at 25°C. A marked daily rhythm (unimodal) of spermiation response to LH/FSH‐RH was observable. Injections given one hour before the onset and offset of a 12L:12D photoperiod (25°C) were respectively the most and least effective in stimulating spermiation. The peak and trough of the rhythm were attributed to changes in pituitary sensitivity to LH/FSH‐RH and not changes in testicular sensitivity to LH. Age and size of bullfrogs utilized in these tests had no effect on spermiation response.