Endocrine mechanisms mediating temperature-induced reproductive behavior in red-sided garter snakes (Thamnophis sirtalis parietalis)

Lutterschmidt, Deborah I.; Mason, Robert T.

doi:10.1242/jeb.033100

Cited by 51 publications

(42 citation statements)

References 58 publications

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“…This peripheral mechanism provides an alternative to the previously described actions of gonadal steroids acting on the brain to regulate behaviour [17,18], and described actions of DHEA regulating aggression [7,16,33,41]. From a comparative perspective, this seasonal mechanism may also regulate aggression in other vertebrate species, including frogs, lizards, mammals and snakes, where melatonin also facilitates seasonal changes ( [20][21][22][23]; reviewed in [7]). …”

Section: Discussionmentioning

confidence: 95%

The agonistic adrenal: melatonin elicits female aggression via regulation of adrenal androgens

et al. 2015

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Classic findings have demonstrated an important role for sex steroids as regulators of aggression, but this relationship is lacking within some environmental contexts. In mammals and birds, the adrenal androgen dehydroepiandrosterone (DHEA), a non-gonadal precursor of biologically active steroids, has been linked to aggression. Although females, like males, use aggression when competing for limited resources, the mechanisms underlying female aggression remain understudied. Here, we propose a previously undescribed endocrine mechanism regulating female aggression via direct action of the pineal hormone melatonin on adrenal androgens. We examined this in a solitary hamster species, Phodopus sungorus, in which both sexes are highly territorial across the seasons, and display increased aggression concomitant with decreased serum levels of sex steroids in short 'winter-like' days. Short-but not long-day females had increased adrenal DHEA responsiveness co-occurring with morphological changes in the adrenal gland. Further, serum DHEA and total adrenal DHEA content were elevated in short days. Lastly, melatonin increased DHEA and aggression and stimulated DHEA release from cultured adrenals. Collectively, these findings demonstrate that DHEA is a key peripheral regulator of aggression and that melatonin coordinates a 'seasonal switch' from gonadal to adrenal regulation of aggression by direct action on the adrenal glands.

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Section: Discussionmentioning

confidence: 95%

The agonistic adrenal: melatonin elicits female aggression via regulation of adrenal androgens

et al. 2015

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“…Data were natural log-transformed where necessary to meet the assumptions required for parametric analysis. When data transformation could not correct for nonnormality and/or unequal variance, we used the nonparametric Scheirer-Ray-Hare extension of the Kruskal-Wallis analysis, as described by Lutterschmidt and Mason [2008Mason [ , 2009.…”

Section: Statisticsmentioning

confidence: 99%

Seasonal Variation in Cell Proliferation and Cell Migration in the Brain of Adult Red-Sided Garter Snakes (Thamnophis sirtalis parietalis)

2014

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Plasticity in the adult central nervous system has been described in all vertebrate classes as well as in some invertebrate groups. However, the limited taxonomic diversity represented in the current neurogenesis literature limits our ability to assess the functional significance of adult neurogenesis for natural behaviors as well as the evolution of its regulatory mechanisms. In the present study, we used free-ranging red-sided garter snakes (Thamnophis sirtalis parietalis) to test the hypothesis that seasonal shifts in physiology and behavior are associated with seasonal variation in postembryonic neurogenesis. Specifically, we used the thymidine analog 5-bromo-2′-deoxyuridine (BrdU) to determine if the rates of cell proliferation in the adult brain vary between male snakes collected during spring and fall at 1, 5, and 10 days post-BrdU treatment. To assess rates of cell migration within the brain, we further categorized BrdU-labeled cells according to their location within the ventricular zone or parenchymal region. BrdU-labeled cells were localized mainly within the lateral, dorsal, and medial cortex, septal nucleus, nucleus sphericus, preoptic area, and hypothalamus. In all regions, the number of BrdU-labeled cells in the ventricular zone was higher in the fall compared to spring. In the parenchymal region, a significantly higher number of labeled cells was also observed during the fall, but only within the nucleus sphericus and the combined preoptic area/hypothalamus. The immunoreactive cell number did not vary significantly with days post-BrdU treatment in either season or in any brain region. While it is possible that the higher rates of cell proliferation in the fall simply reflect increased growth of all body tissues, including the brain, our data show that seasonal changes in cell migration into the parenchyma are region specific. In red-sided garter snakes and other reptiles, the dorsal and medial cortex is important for spatial navigation and memory, whereas the nucleus sphericus, septal nucleus, and preoptic area/hypothalamus are central to reproductive regulation. Thus, our results provide support for the hypothesis that adult neurogenesis plays a role in mediating seasonal rhythms in migratory and reproductive behaviors.

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“…Many stressors have been observed to produce effects on CORT levels including physical factors (temperature: Lutterschmidt & Mason, 2009;Telemeco & Addis, 2014; extreme weather events: Romero & Wikelski, 2001) and biotic stressors such as predation (Thaker, Lima, & Hews, 2009), social competition (Comendant, Sinervo, Svensson, & Wingfield, 2003), and especially parasitic infections (Hanley & Stamps, 2002;Sperry, Butler, Romero, & Weatherhead, 2009).…”

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confidence: 99%

Effects of parasitic infection and reproduction on corticosterone plasma levels in Galápagos land iguanas, Conolophus marthae and C. subcristatus

Onorati

Sancesario²,

Pastore

et al. 2017

Ecology and Evolution

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In vertebrates, one main feature of stress response is the release of glucocorticoids (corticosterone in reptiles), steroid hormones whose synthesis is regulated by the hypothalamic–pituitary–adrenal axis (HPA). In the Galápagos Islands, populations of land iguanas are differentially impacted by a tick‐transmitted apicomplexan hemoparasite of genus Hepatozoon, which could cause diseases and ultimately reduce fitness. Using competitive enzyme‐linked immunosorbent assays (ELISA), we examined baseline plasma corticosterone levels of two syntopic and highly parasitized populations of the land iguana species Conolophus marthae and C. subcristatus in Wolf volcano (Isabela Island). We also used a poorly parasitized population of C. subcristatus from the same island (Bahia Urbina) as a reference. To better interpret the observed glucocorticoids patterns, we simultaneously performed the count of white blood cells (WBCs) in all individuals and investigated the reproductive status of females. We did not find evidence in support of either a positive or negative relationship between the tick load, hemoparasite infection, and glucocorticoid plasma concentration in C. marthae and C. subcristatus at Wolf volcano. The comparison between parasitized and non‐parasitized sites (V. Wolf and Bahia Urbina) would instead suggest an inverse relationship between corticosterone and parasites. Our findings support association between corticosterone plasma levels and reproduction.

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Endocrine mechanisms mediating temperature-induced reproductive behavior in red-sided garter snakes (Thamnophis sirtalis parietalis)

Cited by 51 publications

References 58 publications

The agonistic adrenal: melatonin elicits female aggression via regulation of adrenal androgens

The agonistic adrenal: melatonin elicits female aggression via regulation of adrenal androgens

Seasonal Variation in Cell Proliferation and Cell Migration in the Brain of Adult Red-Sided Garter Snakes <b><i>(Thamnophis sirtalis parietalis)</i></b>

Effects of parasitic infection and reproduction on corticosterone plasma levels in Galápagos land iguanas, Conolophus marthae and C. subcristatus

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