Influence of photoperiod and temperature on testicular recrudescence and body growth in the lizards, Lacerta sicula and Lacerta muralis

Abstract

With 1 plate and 16 figures in the text)Annual testicular cycles in the lizards Lacerta sicula and L. muralis appear to be regulated by the interaction between seasonal changes in body temperature and an endogenous rhythmicity in thermal responsiveness. Photoperiodism does not appear to be an important factor; i.e. testicular activity does not appear to be regulated by daylength.Following testicular regression in July, the lizards are refractory to sexual Stimulation by high temperatures (i.e. normal preferred levels) for about five months. High temperatures accelerate gonadal regression and prevent recrudescence during late summer. Reduced temperatures stimulate testicular enlargement and spermatid formation during the autumn; this recrudescence can be blocked by treatment with testosterone. Very low temperatures suppress gonadal activity during mid-winter.Maintenance of lizards at constant high temperatures (33°C) starting in July suppresses testicular recrudescence until December. Also, testicular collapse occurs in lizards transferred to high temperatures after recrudescence has started. The gonads are stimulated by exogenous gonadotropins at 33°C during the fall indicating that high temperatures reduce circulating levels of gonadotropins.The refractoriness to high temperatures is "spontaneously" terminated during midwinter (December) under a wide range of photo-thermal conditions. Low temperatures may accelerate the termination of refractoriness. Thereafter, high temperatures stimulate, and are required for the final development of the testes and accessory sexual structures, Thus, the increase in body temperature following hibernation times the onset of breeding in the spring.Temperature also has a marked influence on appetite and growth, independent of photoperiod. Weight gains are greater at 33" than at 2O"C;At 33" there is a tendency for abdominal fat bodies to enlarge but with little hepatic growth; whereas, the reverse occurs at 20°C.

Reproductive cycle of male wall lizard, <em>Podarcis vaucheri</em> (Reptilia: Sauria: Lacertidae), in Djurdjura, Northern Algeria

“…The spermatogenic cycle of Po d arcis vaucheri is of the "mixed-type", in agreement with what is the dominant pattern in temperate lizards (Licht et al, 1969;SaintGirons, 1982;Carretero, 2006), especially those belonging to the genera Lacerta s.l. and Po d arcis (Saint-Girons Duguy, 1970;Angelini et al, 1979;HraouiBloquet, 1985;Hraoui-Bloquet Bloquet, 1988;BraÑa et al, 1990;Castilla Bauwens, 1990;Galán, 1996;Amat et al, 2000;Roig et al, 2000;Carretero et al, 2006a).…”

“…Besides the environmental conditions, several studies showed reproductive cycles to be influenced also by the interaction between endogenous and exogenous factors (Licht et al, 1969;Licht, 1972;Angelini et al, 1976;Lofts, 1978;Marion, 1982;Jenssen Nunez, 1994;Carretero, 2006). On one hand, indeed, the gonadal and hormonal activity can be considered the main endogenous mechanisms controlling reproductive cycles (Díaz et al, 1994;Ikeuchi, 2004).…”

“…Specifically, for temperate regions three spermatogenic cycles were described: i) the vernal or prenuptial type, where spermatogenesis occurs during spring, immediately before or even during breeding (Licht et al, 1969;Saint-Girons, 1982;Carretero, 2006); ii) the postnuptial type, where spermatogenesis is held during summer of the previous year (SaintGirons, 1982;Carretero, 2006;HraouiBloquet et al, 2007); iii) an finally the mixed type, where spermatogenesis begins at the end of summer and is interrupted in winter (Licht et al, 1969;Saint-Girons, 1982;Carretero, 2006). However, Saint-Girons (1982) recognized two sub-types of this cycle.…”

A quantitative synthesis of and predictive framework for studying winter warming effects in reptiles

“…In dissociated breeders (i.e., where gonadal recrudescence occurs either in the fall or winter leading up to spring mating, Van Dyke 2014 ), a prolonged cold period prior to the onset of warm temperatures is a prerequisite to recrudescence and associated reproductive behaviors (Marion 1982 ; Gavaud 1991 ; Lutterschmidt 2012 ), with photoperiod having little to no effect (Aldridge 1975 , 1979 ). Even in species that do not rely on a cold period to trigger recrudescence, gradual warming in late winter and early spring is still the primary cue stimulating reproduction (Tinkle and Irwin 1965 ; Licht et al 1969 ). Evidence from laboratory manipulation experiments implicates the action of environmentally sensitive hormones in entraining biological rhythms to overwinter thermal conditions.…”