Role of light and temperature in the regulation of reproduction in the red-sided garter snake, Thamnophis sirtalis parietalis

The influence of photoperiodic manipulation on sexual behavior and ovarian recrudescence of male and female red-sided garter snakes (Thamnophis sirtalis parietalis) was examined over a 4-year period. Snakes were exposed to photoperiodic manipulations before, during, and after a 17-week cold temperature dormancy; sexual behavior of males and females and ovarian recrudescence were observed after emergence from cold temperature dormancy. In the 1st year (1982), males were exposed to two conditions representing minimum and maximum exposure to daylight: (i) 6 weeks of a short-day prehibernation period (10L:14D, 28:18 °C), followed by 17 weeks of hibernation in complete darkness (0L:24D, 4 °C) and emergence into warm dark conditions (0L:24D, 28:18 °C); and (ii) 6 weeks of a long-day prehibernation period (14L:10D, 28:18 °C), followed by 17 weeks of hibernation with exposure to light (12L:12D, 4 °C) and emergence into warm, long days (14L:10D, 28:18 °C). Males in both conditions exhibited intense courtship behavior on emergence from hibernation. Females in 1982 were significantly influenced only by long-day prehibernation conditions (14L:10D, 28:18 °C); under these conditions, ovarian recrudescence on emergence was inhibited. Long prehibernation photoperiod did not significantly influence female receptive behavior on emergence, indicating that neuroendocrine control of ovarian activation and sexual behavior may be separate in this species. In three subsequent years (1983, 1984, 1985) none of the photoperiodic conditions significantly influenced male or female sexual behavior or ovarian recrudescence. Slight differences in experimental protocol in these subsequent years that may account for differences in results from 1982 are discussed. Finally, ovarian development was found to be clearly tied to the duration of cold temperature dormancy in this species. Females receiving 7 or 17 weeks of exposure to cold (4 °C) underwent vitellogenesis at similar frequencies. Most females receiving 0 or only 4 weeks of exposure to cold (4 °C) did not become vitellogenic. Mating on emergence was not a requirement for the initiation of vitellogenesis in this study.

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Control of length of the courtship season in the red-sided garter snake, Thamnophis sirtalis parietalis: the role of temperature

Canadian Journal of Zoology ◽

10.1139/z89-142 ◽

1989 ◽

Vol 67 (4) ◽

pp. 987-993 ◽

Cited By ~ 3

Author(s):

Randolph W. Krohmer ◽

David Crews

Keyword(s):

Courtship Behavior ◽

Temperature Fluctuations ◽

Thamnophis Sirtalis ◽

Garter Snakes ◽

Ambient Temperatures ◽

Thamnophis Sirtalis Parietalis ◽

Laboratory Populations ◽

Influence Of Temperature On ◽

The Central Nervous System

The influence of temperature on the length and intensity of the courtship season was examined in both field and laboratory populations of red-sided garter snakes (Thamnophis sirtalis parietalis) over a 2-year period. Snakes were exposed to fluctuations in temperature following emergence from hibernation and activation of courtship behavior. In the field, males were exposed to four temperature regimens: extended hibernation (0L:24D, 4 ± 1.5 °C), cool (14L:10D, 12 ± 2.3° C), warm (14L:10D, 28 °C:ambient), or control (ambient temperatures and light). Control animals exhibited courtship behavior fluctuating in intensity with daily ambient temperatures. Animals exhibited high intensity courtship behavior when exposed to warm conditions following emergence from either natural hibernation or a secondary period of laboratory hibernation. Animals placed in the cool regimen were active but exhibited very little courtship behavior. Animals maintained under the cool regimen for 14 days did not initiate courtship behavior when placed in the warm regimen. Studies conducted in the laboratory support the field results. However, whereas animals maintained under the cool regimen for 14 days and then placed in the warm regimen exhibited dramatically reduced courtship behavior, animals placed in the warm regimen after 21 days under the cool regimen initiated courtship of normal intensity and duration. Following the end of all courtship behavior, males exposed to conditions of hibernation for a brief period reinitiated courtship behavior. These data suggest that the areas of the central nervous system critical for the perception of temperature fluctuations and initiation of courtship behavior remained sensitive in late spring. Following the end of the courtship season, females exposed to a brief period of hibernation also reinstated courtship behavior in noncourting males. These data suggest that the length of the courtship season ultimately may be controlled by the presence of attractive females.

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