The relationship between plasma steroid hormone concentrations and the reproductive cycle in the Northern Pacific rattlesnake, Crotalus oreganus

Abstract

The Relationship Between Plasma Steroid Hormone Concentrations and the Reproductive Cycle in the Northern Pacific Rattlesnake, Crotalus oreganusCraig M. LindTo gain a better understanding of the role of steroid hormones in vertebrate reproduction, we quantified steroid hormone concentrations in a free ranging population of the Northern Pacific rattlesnake, Crotalus oreganus. Plasma steroid hormone concentrations were quantified for both male and female snakes throughout the active season (Mar-Oct). We measured testosterone (T), 5α-dihydrotestosterone (DHT), and corticosterone (B) concentrations in male and female snakes. 17β-estradiol (E2) and progesterone (P) were measured in females only. We also observed breeding behaviors (e.g. consortship, courtship, and copulation) in the field and measured testis and follicle size in male and female snakes from museum collections. Our results indicate that C. oreganus in central California utilizes a bimodal pattern of breeding, with mating and agonistic behavior occurring in the spring and the late summer/fall. Each breeding season corresponds with elevated or highly variable androgen (T and DHT) levels. Several female snakes had high E2 concentrations in the spring and fall, coincident with vitellogenesis and mating. Females with high E2 concentrations also had high T and DHT concentrations. Corticosterone concentrations in males are not related to either time of year or concentrations of any other hormones quantified. This suggests that the breeding season in this population may not demand a significant increase in energy mobilization by glucocorticoids. Measurements of testis volume show that testes are regressed in the spring when the majority of breeding was observed in this population and reach peak volume in August and September during spermatogenesis. Multiple regression analyses revealed that in female snakes, P is positively correlated with T and DHT, and E2 is correlated with T. Since these results are strictly descriptive, experimental studies are needed to identify the functional significance of these results.

Environmental and physiological correlates of the severity of clinical signs of snake fungal disease in a population of pigmy rattlesnakes,Sistrurus miliarius

“…3 A), and snakes sampled during the autumn scored significantly lower on bactericidal assays. Males may also experience increased concentrations of testosterone during the autumn because this time coincides with the onset of the breeding season, a life-history stage when elevated testosterone is observed in most crotaline snakes ( Schuett et al ., 1997 , 2005 ; Taylor et al ., 2004 ; Lind et al ., 2010 ; Lind and Beaupre, 2015 ). Increased testosterone can be immunosuppressive and could render males more susceptible to infection at the onset of the breeding season ( Roberts et al ., 2004 ; Martin et al ., 2008 ; Ruiz et al ., 2010 ).…”

How do host sex and reproductive state affect host preference and feeding duration of ticks?

“…Blood samples were centrifuged for 5 min at 10,000 rpm, and plasma was extracted and frozen at −20°C. Plasma samples were quantified by radioimmunoassay according to the methods of Lind et al (2010). All samples were run in the same assay.…”

Androgen-related sperm storage in oviduct of Chinese Soft-Shelled Turtle in vivo during annual cycle

“…In the male lizard ( Sceloporus undulates ), androgens were highly correlated with size and weight of the epididymis, and the stored spermatozoa were lost from regressing epididymis 38 . Furthermore, high circulating levels of androgen were also present in the blood of female reptiles and amphibians during certain periods of their seasonal reproductive cycles 39 40 . In the present study, the concentrations of circulating T and DHT were examined in female P. sinensis during sperm storage, showing relatively higher levels of these hormones during the hibernation season (from November to the next April) than during the non-hibernation season (July).…”