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1.
J Vis Exp ; (144)2019 02 07.
Artículo en Inglés | MEDLINE | ID: mdl-30799852

RESUMEN

Reptiles signal to conspecifics using lipids in their skin, primarily to enable mate tracking and assessment. The isolation of these lipids has utility in research focused on evolutionary patterns and mechanisms of chemical communication, in addition to understanding the waterproofing role of lipids in the evolution of terrestrial life. In an applied approach, such skin-based cues have potential use for wildlife managers dealing with invasive species. The main steps for quantifying reptile skin lipids in the protocol presented here include extraction, total lipid determination, and fractionation via column chromatography, the latter process resulting in purified eluates of compounds which can then either be analyzed to assign compound identifications (e.g., gas chromatography-mass spectrometry [GC-MS]) and/or used directly in more refined bioassays. Skin lipids can be extracted from living skin, shed skin, or dead whole animals, using nonpolar organic solvents (e.g., hexane, benzene, toluene). Extraction solubilizes the lipids and, then, the solvent can be evaporated to yield a measurable lipid-only extract. Fractionation involves the separation of the total lipid extract into specific eluates via traditional column chromatography. The total lipid extract is first bound to a substrate-based column (e.g., alumina) and, then, individual eluates ("fractions") of solvent at specific volumes are passed sequentially through the column to elute sets of compounds from the lipid mixture based on common polarity. The fractions progress in polarity at a standardized sequence by increasing the relative amount of polar solvent (e.g., diethyl ether) in nonpolar solvent. In this manuscript, we describe several methods for extracting skin lipids of reptiles and, then, provide a standard protocol for isolating different sets of compounds based on polarity, using traditional column chromatography. Whole lipid extracts or specific fractions can, then, be used in bioassays to determine any biological activity elicited by the compounds therein.


Asunto(s)
Lípidos/química , Reptiles , Animales , Fraccionamiento Químico , Cromatografía de Gases y Espectrometría de Masas , Solventes/química
2.
Proc Biol Sci ; 284(1852)2017 Apr 12.
Artículo en Inglés | MEDLINE | ID: mdl-28381620

RESUMEN

Life-history strategies vary dramatically between the sexes, which may drive divergence in sex-specific senescence and mortality rates. Telomeres are tandem nucleotide repeats that protect the ends of chromosomes from erosion during cell division. Telomeres have been implicated in senescence and mortality because they tend to shorten with stress, growth and age. We investigated age-specific telomere length in female and male red-sided garter snakes, Thamnophis sirtalis parietalis We hypothesized that age-specific telomere length would differ between males and females given their divergent reproductive strategies. Male garter snakes emerge from hibernation with high levels of corticosterone, which facilitates energy mobilization to fuel mate-searching, courtship and mating behaviours during a two to four week aphagous breeding period at the den site. Conversely, females remain at the dens for only about 4 days and seem to invest more energy in growth and cellular maintenance, as they usually reproduce biennially. As male investment in reproduction involves a yearly bout of physiologically stressful activities, while females prioritize self-maintenance, we predicted male snakes would experience more age-specific telomere loss than females. We investigated this prediction using skeletochronology to determine the ages of individuals and qPCR to determine telomere length in a cross-sectional study. For both sexes, telomere length was positively related to body condition. Telomere length decreased with age in male garter snakes, but remained stable in female snakes. There was no correlation between telomere length and growth in either sex, suggesting that our results are a consequence of divergent selection on life histories of males and females. Different selection on the sexes may be the physiological consequence of the sexual dimorphism and mating system dynamics displayed by this species.


Asunto(s)
Factores de Edad , Colubridae/fisiología , Caracteres Sexuales , Telómero/ultraestructura , Animales , Estudios Transversales , Femenino , Masculino , Conducta Sexual Animal
3.
Parasitol Res ; 114(12): 4451-61, 2015 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-26337267

RESUMEN

Trematodes of the genus Alaria develop into an arrested stage, known as mesocercariae, within their amphibian second intermediate host. The mesocercariae are frequently transmitted to a non-obligate paratenic host before reaching a definitive host where further development and reproduction can occur. Snakes are common paratenic hosts for Alaria spp. with the mesocercariae often aggregating in the host's tail. In the current study, we used morphological examination and molecular analyses based on partial sequences of nuclear large ribosomal subunit gene and mitochondrial cytochrome C oxidase subunit 1 gene to identify larvae in the tails of red-sided garter snakes (Thamnophis sirtalis parietalis) as mesocercariae of Alaria marcianae, Alaria mustelae, and Alaria sp. as well as metacercariae of Diplostomidae sp. of unknown generic affiliation. We assessed infection prevalence, absolute and relative intensity, and associated pathological changes in these snakes. Infection prevalence was 100 % for both male and female snakes. Infection intensity ranged from 11 to more than 2000 mesocercariae per snake tail but did not differ between the sexes. Gross pathological changes included tail swelling while histopathological changes included mild inflammation and the presence of mucus-filled pseudocysts surrounding mesocercariae, as well as the compression and degeneration of muscle fibers. Our results indicate that mesocercariae can lead to extensive muscle damage and loss in both sexes which likely increases the fragility of the tail making it more prone to breakage. As tail loss in garter snakes can affect both survival and reproduction, infection by Alaria mesocercariae clearly has serious fitness implications for these snakes.


Asunto(s)
Infecciones por Cestodos/veterinaria , Colubridae/parasitología , Platelmintos/fisiología , Animales , Infecciones por Cestodos/parasitología , Femenino , Larva/crecimiento & desarrollo , Larva/fisiología , Masculino , Platelmintos/crecimiento & desarrollo , Cola (estructura animal)/parasitología
5.
J Exp Biol ; 218(Pt 9): 1410-8, 2015 May.
Artículo en Inglés | MEDLINE | ID: mdl-25954044

RESUMEN

The non-sperm components of an ejaculate, such as copulatory plugs, can be essential to male reproductive success. But the costs of these ejaculate components are often considered trivial. In polyandrous species, males are predicted to increase energy allocation to the production of non-sperm components, but this allocation is often condition dependent and the energetic costs of their production have never been quantified. Red-sided garter snakes (Thamnophis sirtalis parietalis) are an excellent model with which to quantify the energetic costs of non-sperm components of the ejaculate as they exhibit a dissociated reproductive pattern in which sperm production is temporally disjunct from copulatory plug production, mating and plug deposition. We estimated the daily energy expenditure and resting metabolic rate of males after courtship and mating, and used bomb calorimetry to estimate the energy content of copulatory plugs. We found that both daily energy expenditure and resting metabolic rate were significantly higher in small mating males than in courting males, and a single copulatory plug without sperm constitutes 5-18% of daily energy expenditure. To our knowledge, this is the first study to quantify the energetic expense of size-dependent ejaculate strategies in any species.


Asunto(s)
Metabolismo Basal , Colubridae/fisiología , Metabolismo Energético , Conducta Sexual Animal , Espermatozoides/fisiología , Animales , Masculino , Reproducción
6.
J Exp Zool A Ecol Genet Physiol ; 321(10): 603-9, 2014 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-25366702

RESUMEN

Polyandry is a source of sexual conflict and males often try to limit female promiscuity. Consequently, male manipulation of receptivity via antiaphrodisiacs and copulatory plugs that prevent female remating can be a source of sexual conflict. This sexual conflict may be intensified when females must remate for fertility insurance. Male red-sided garter snakes produce a large, gelatinous copulatory plug that has been proposed to 1) physically prevent remating and 2) contain an antiaphrodisiac that reduces female receptivity. These males may become sperm depleted because of their dissociated reproductive pattern. If a female mates with a sperm deficient male and is also rendered unreceptive to further mating, then this represents a serious conflict. We tested whether female remating frequency is affected when females are mated with a male that produces a sperm-less copulatory plug. We show that females are significantly more likely to remate after mating with vasectomized males than intact males, even though vasectomized males still produce a copulatory plug. These results suggest that the ejaculate material of the plug does not contain an antiaphrodisiac. Instead, females may use sperm as a cue for post-copulatory mate assessment and seek to remate for the direct benefit of fertility insurance if they have mated with sperm-depleted males.


Asunto(s)
Colubridae/fisiología , Copulación/fisiología , Semen/fisiología , Conducta Sexual Animal/fisiología , Espermatozoides/fisiología , Animales , Femenino , Masculino , Feromonas , Vasectomía
7.
Horm Behav ; 66(3): 509-16, 2014 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-25058443

RESUMEN

Vertebrates communicate their sex to conspecifics through the use of sexually dimorphic signals, such as ornaments, behaviors and scents. Furthermore, the physiological connection between hormones and secondary sexual signal expression is key to understanding their dimorphism, seasonality and evolution. The red-sided garter snake (Thamnophis sirtalis parietalis) is the only reptile for which a described pheromone currently exists, and because garter snakes rely completely on the sexual attractiveness pheromone for species identification and mate choice, they constitute a unique model species for exploring the relationship between pheromones and the endocrine system. We recently demonstrated that estrogen can activate female pheromone production in male garter snakes. The purpose of this study was to determine the mechanism(s) acting to prevent female pheromone production in males. We found that castrated males (GX) are courted by wild males in the field and produce appreciable amounts of female sex pheromone. Furthermore, pheromone production is inhibited in castrates given testosterone implants (GX+T), suggesting that pheromone production is actively inhibited by the presence of testosterone. Lastly, testosterone supplementation alone (T) increased the production of several saturated methyl ketones in the pheromone but not the unsaturated ketones; this may indicate that saturated ketones are testosterone-activated components of the garter snake's skin lipid milieu. Collectively, our research has shown that pheromone expression in snakes results from two processes: activation by the feminizing steroid estradiol and inhibition by testosterone. We suggest that basal birds and garter snakes share common pathways of activation that modulate crucial intraspecific signals that originate from skin.


Asunto(s)
Colubridae , Feromonas/metabolismo , Atractivos Sexuales/metabolismo , Conducta Sexual Animal/efectos de los fármacos , Testosterona/farmacología , Animales , Colubridae/metabolismo , Colubridae/fisiología , Cortejo , Señales (Psicología) , Implantes de Medicamentos , Sistema Endocrino/efectos de los fármacos , Sistema Endocrino/metabolismo , Estradiol/metabolismo , Femenino , Masculino , Orquiectomía/veterinaria , Conducta Sexual/efectos de los fármacos , Piel/metabolismo , Testosterona/metabolismo
8.
Proc Biol Sci ; 281(1774): 20132694, 2014 Jan 07.
Artículo en Inglés | MEDLINE | ID: mdl-24225467

RESUMEN

Sexual conflict over mating can result in sex-specific morphologies and behaviours that allow each sex to exert control over the outcome of reproduction. Genital traits, in particular, are often directly involved in conflict interactions. Via genital manipulation, we experimentally investigated whether genital traits in red-sided garter snakes influence copulation duration and formation of a copulatory plug. The hemipenes of male red-sided garter snakes have a large basal spine that inserts into the female cloaca during mating. We ablated the spine and found that males were still capable of copulation but copulation duration was much shorter and copulatory plugs were smaller than those produced by intact males. We also anaesthetized the female cloacal region and found that anaesthetized females copulated longer than control females, suggesting that female cloacal and vaginal contractions play a role in controlling copulation duration. Both results, combined with known aspects of the breeding biology of red-sided garter snakes, strongly support the idea that sexual conflict is involved in mating interactions in this species. Our results demonstrate the complex interactions among male and female traits generated by coevolutionary processes in a wild population. Such complexity highlights the importance of simultaneous examination of male and female traits.


Asunto(s)
Colubridae/fisiología , Copulación/fisiología , Conducta Sexual Animal , Anestésicos/farmacología , Animales , Bupivacaína/farmacología , Cloaca/efectos de los fármacos , Colubridae/anatomía & histología , Conflicto Psicológico , Copulación/efectos de los fármacos , Femenino , Masculino , Factores de Tiempo
9.
J Exp Biol ; 215(Pt 5): 723-30, 2012 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-22323194

RESUMEN

Vertebrates indicate their genetic sex to conspecifics using secondary sexual signals, and signal expression is often activated by sex hormones. Among vertebrate signaling modalities, the least is known about how hormones influence chemical signaling. Our study species, the red-sided garter snake (Thamnophis sirtalis parietalis), is a model vertebrate for studying hormonal control of chemical signals because males completely rely on the female sex pheromone to identify potential mates among thousands of individuals. How sex hormones can influence the expression of this crucial sexual signal is largely unknown. We created two groups of experimental males for the first experiment: Sham (blank implants) and E2 (17ß-estradiol implants). E2 males were vigorously courted by wild males in outdoor bioassays, and in a Y-maze E2 pheromone trails were chosen by wild males over those of small females and were indistinguishable from large female trails. Biochemically, the E2 pheromone blend was similar to that of large females, and it differed significantly from Shams. For the second experiment, we implanted males with 17ß-estradiol in 2007 but removed the implants the following year (2008; Removal). That same year, we implanted a new group of males with estrogen implants (Implant). Removal males were courted by wild males in 2008 (implant intact) but not in 2009 (removed). Total pheromone quantity and quality increased following estrogen treatment, and estrogen removal re-established male-typical pheromone blends. Thus, we have shown that estrogen activates the production of female pheromone in adult red-sided garter snakes. This is the first known study to quantify both behavioral and biochemical responses in chemical signaling following sex steroid treatment of reptiles in the activation/organization context. We propose that the homogametic sex (ZZ, male) may possess the same targets for activation of sexual signal production, and the absence of the activator (17ß-estradiol in this case) underlies expression of the male phenotype.


Asunto(s)
Colubridae/fisiología , Estrógenos/metabolismo , Feromonas/metabolismo , Conducta Sexual Animal , Maduración Sexual , Animales , Estradiol/metabolismo , Femenino , Cetonas/metabolismo , Masculino , Preferencia en el Apareamiento Animal
10.
J Chem Ecol ; 38(1): 71-80, 2012 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-22231473

RESUMEN

During the breeding season, female red-sided garter snakes (Thamnophis sirtalis parietalis) produce and express a sexual attractiveness pheromone that elicits male courtship behavior. Composed of a homologous series of saturated and monounsaturated methyl ketones, this pheromone is expressed in female skin lipids. Recent studies have shown that the sexual attractivity of unmated female garter snakes declines as the breeding season progresses. Here, we investigated whether temporal changes in the quantity and/or quality of the female sexual attractiveness pheromone are responsible for the observed loss of attractivity. Female red-sided garter snakes were collected immediately following spring emergence and held under natural conditions for the duration of the breeding season. Behavioral experiments confirmed that unmated females become significantly less attractive to males within two weeks of emergence from hibernation. Additionally, these females had lower estradiol concentrations at two weeks post-emergence. Subsequent chemical analyses revealed qualitative variation between the pheromone profiles of newly emerged females and those of females at two weeks post-emergence. Together, these results support the hypothesis that changes in the female sexual attractiveness pheromone are responsible for declining post-emergence female attractivity in garter snakes.


Asunto(s)
Colubridae/metabolismo , Estaciones del Año , Atractivos Sexuales/metabolismo , Atractivos Sexuales/farmacología , Conducta Sexual Animal/efectos de los fármacos , Animales , Estradiol/metabolismo , Estrógenos/metabolismo , Femenino , Masculino
11.
Physiol Behav ; 102(5): 532-7, 2011 Mar 28.
Artículo en Inglés | MEDLINE | ID: mdl-21195723

RESUMEN

During the breeding season, two distinct male phenotypes are exhibited by red-sided garter snakes (Thamnophis sirtalis parietalis), with courtship behavior being directed not only toward females, but also toward a sub-population of males called she-males. She-males are morphologically identical to other males except for a circulating androgen level three times that of normal males and their ability to produce a female-like pheromone. As in other vertebrates, limbic nuclei in the red-sided garter snake brain are involved in the control of sexual behaviors. For example, an intact anterior hypothalamus pre-optic area (AHPOA) is essential for the initiation and maintenance of reproduction. To determine if brain morphology varies among the three behavioral phenotypes (i.e., males, she-males, and females) during the breeding season, we examined the volume, cell size and cell density of the AHPOA as well as a control region, the external nucleus of the optic tract (ENOT). We used Luxol Fast Blue and Ziehl's Fuchsin to visualize neurons and glial cells, respectively. No significant differences were observed among the three behavioral phenotypes in the volume, cell size or density in the control region. In contrast, the volume, cell size and density of the AHPOA of she-males were significantly greater than those of both male and female snakes. While the volume of the AHPOA was significantly greater in females compared to males, no differences were observed in cell size or density. These differences in brain morphology suggest a possible underlying mechanism for phenotypic-specific behavioral patterns.


Asunto(s)
Colubridae/anatomía & histología , Neuronas/citología , Área Preóptica/citología , Prosencéfalo/citología , Diferenciación Sexual/fisiología , Animales , Recuento de Células , Tamaño de la Célula , Femenino , Masculino , Neuroglía/citología , Fenotipo , Conducta Sexual Animal/fisiología
12.
Gen Comp Endocrinol ; 169(1): 11-7, 2010 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-20603122

RESUMEN

Circadian and circannual rhythms in physiology and behavior are temporally organized via hormonal signals that reflect changing environmental cues. Interactions between endocrine signals are in turn important for integrating multiple physiological and behavioral rhythms. In the present study, we examined interactions between melatonin, the hypothalamus-pituitary-adrenal (HPA) axis, and corticosterone in a well-studied population of red-sided garter snakes (Thamnophis sirtalis parietalis). We demonstrate that 4h of capture stress significantly increased photophasic melatonin and decreased scotophasic melatonin concentrations of male snakes. Treatment with exogenous corticosterone (15 and 60 µg) did not mimic the effects of stress on diel melatonin rhythms. To determine if capture stress decreases scotophasic melatonin by depleting the precursors necessary for melatonin synthesis, we used a paradigm in which snakes were treated with the melatonin precursor 5-hydroxytryptophan (0.6 and 1.2mg) to elevate melatonin concentrations. Pretreatment of snakes with both capture stress and exogenous corticosterone blocked the effect of 5-hydroxytryptophan on scotophasic melatonin. Thus, although corticosterone itself does not influence melatonin rhythms of snakes, corticosterone can inhibit the synthesis of melatonin from 5-hydroxytryptophan. These experiments suggest that the initial versus later phases of an acute physiological stress response have temporally distinct effects on melatonin synthesis: activation of the sympathoadrenal system increases melatonin, while increased glucocorticoids can inhibit melatonin synthesis. Collectively, we demonstrate that a physiological coupling between melatonin, glucocorticoids, and the sympathoadrenal system is conserved in this ectothermic model and propose that such interactions may mediate stress-induced changes in physiology and behavior.


Asunto(s)
Antiinflamatorios/farmacología , Colubridae/fisiología , Corticosterona/farmacología , Melatonina/metabolismo , Periodicidad , Estrés Fisiológico/efectos de los fármacos , Estrés Fisiológico/fisiología , Animales , Masculino
13.
Artículo en Inglés | MEDLINE | ID: mdl-20585786

RESUMEN

The role of pheromones in orchestrating social behaviors in reptiles is reviewed. Although all reptile orders are examined, the vast majority of the literature has dealt only with squamates, primarily snakes and lizards. The literature is surprisingly large, but most studies have explored relatively few behaviors. The evolution of chemical signaling in reptiles is discussed along with behaviors governed by pheromones including conspecific trailing, male-male agonistic interactions, sex recognition and sex pheromones, and reptilian predator recognition. Nonreptilian prey recognition by chemical cues was not reviewed. The recent literature has focused on two model systems where extensive chemical ecology studies have been conducted: the reproductive ecology of garter snakes and the behavioral ecology of Iberian lacertid lizards. In these two systems, enough is known about the chemical constituents that mediate behaviors to explore the evolution of chemical signaling mechanisms that affect life history patterns. In addition, these models illuminate natural and sexual selection processes which have lead to complex chemical signals whose different components and concentrations provide essential information about individuals to conspecifics. Reptiles provide excellent candidates for further studies in this regard not only in squamates, but also in the orders where little experimental work has been conducted to date.


Asunto(s)
Comunicación Animal , Conducta Animal/fisiología , Feromonas/fisiología , Reptiles/fisiología , Conducta Social , Animales , Olfato/fisiología
14.
Horm Behav ; 58(3): 485-92, 2010 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-20420841

RESUMEN

We investigated regional and seasonal variations in neural aromatase activity (AA), the enzyme that converts androgens into estrogens, to examine a possible indirect role of testosterone (T) in mediating spring reproductive behavior of red-sided garter snakes, a species exhibiting a dissociated reproductive pattern. Neural AA in male snakes varied significantly among brain regions. Additionally, there were significant interactions between brain region and season. In the spring, actively courting males had greater AA in the olfactory region (O) compared to the septum/anterior-hypothalamus preoptic area (S/AHPOA), nucleus sphericus (NS) and midbrain (Mb). Fall animals collected as they returned to the den prior to winter dormancy had significantly greater AA in the S/AHPOA compared to all other regions. These findings were consistent using either regional (gross) dissection or punch microdissection, which allowed us to separate the S and AHPOA. There were no significant differences in AA production between the S and AHPOA. This study provides the first documentation of seasonal and regional variations in AA in a snake brain and suggests that aromatization of androgens may play a role in regulating reproduction in red-sided garter snakes. During spring mating, elevated AA in the O may activate pathways essential for detection of courtship pheromones, while increased AA in the S and AHPOA of fall animals suggests that circulating androgens play an indirect role in programming critical neural pathways involved in reproduction. Thus, as in many other vertebrates, estrogenic metabolites of testosterone may be a critical hormonal component regulating reproductive behavior in this dissociated breeder.


Asunto(s)
Aromatasa/metabolismo , Encéfalo/enzimología , Colubridae/metabolismo , Animales , Aromatasa/análisis , Encéfalo/fisiología , Cortejo , Femenino , Masculino , Estaciones del Año
15.
J Chem Ecol ; 35(10): 1234-41, 2009 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-19904571

RESUMEN

Low temperature dormancy is a necessary requirement of the annual cycle of most nonmigratory, temperate vertebrates. The red-sided garter snake, Thamnophis sirtalis parietalis, overwinters in communal dens during its prolonged winter dormancy (8 mo), and upon emergence, reproductive behavior of both sexes is maximal. Previous work on this species showed that male courtship behavior is maximally induced after simulated low temperature dormancy. The purpose of this study was to determine whether low temperature dormancy affects the pheromone profiles of individual female red-sided garter snakes. We collected females in the fall at den sites in Manitoba, Canada, and extracted pheromones from individuals at three different time points: fall (field), winter (lab), and spring (lab). Total skin lipid and pheromone fraction masses increased from fall to spring, and pheromone profiles were distinctly different in the fall and spring. Pheromone profiles became dominated by the long-chain, unsaturated methyl ketone components of the blend by the time snakes emerged in the spring. Further, the amounts of both saturated and unsaturated components increased from fall to spring, suggesting significant sex pheromone synthesis was induced by low temperature dormancy.


Asunto(s)
Frío , Colubridae/fisiología , Hibernación/fisiología , Atractivos Sexuales/biosíntesis , Atractivos Sexuales/farmacología , Animales , Femenino , Lípidos/análisis , Masculino , Estaciones del Año , Atractivos Sexuales/análisis , Atractivos Sexuales/química , Conducta Sexual Animal , Piel/química , Factores de Tiempo
16.
J Exp Biol ; 212(19): 3108-18, 2009 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-19749103

RESUMEN

We investigated the mechanisms by which temperature induces seasonal reproductive behavior in red-sided garter snakes (Thamnophis sirtalis parietalis). Specifically, we addressed whether elevated temperatures during winter dormancy influence (1) diel melatonin and corticosterone rhythms; (2) sex steroid hormone and corticosterone profiles; and (3) the expression of reproductive behavior following emergence. Elevated hibernation temperatures (i.e. 10 degrees C versus 5 degrees C) significantly increased overall melatonin and decreased corticosterone concentrations of snakes. The temperature-induced differences in melatonin rhythms between the 5 degrees C and 10 degrees C treatment groups persisted even after both groups were again acclimated to 10 degrees C, indicating that cold temperature exposure has a lasting influence on melatonin rhythms. Elevated hibernation temperatures also significantly altered androgen and corticosterone profiles of snakes, providing a potential mechanism to explain reported annual variation in steroid hormones. Although previous studies indicate that male red-sided garter snakes exhibit a dissociated reproductive strategy, we demonstrate the presence of intersexual variation in sex steroid hormone profiles, as estradiol concentrations of female snakes increased significantly prior to spring mating activity. Importantly, the percentage change in body mass did not differ significantly between snakes in the hibernation treatments, indicating that the observed changes in hormone profiles are indeed temperature induced and not simply an indirect result of significant changes in the energy balance of snakes. Finally, in males maintained at 10 degrees C during winter dormancy the onset of courtship behavior following emergence was delayed. Our results suggest that environmental temperatures induce reproductive behavior, in part, via changes in diel melatonin and/or corticosterone rhythms in this seasonally breeding reptile.


Asunto(s)
Colubridae/fisiología , Conducta Sexual Animal , Temperatura , Animales , Colubridae/metabolismo , Corticosterona/metabolismo , Sistema Endocrino/fisiología , Femenino , Hormonas Esteroides Gonadales/metabolismo , Hibernación , Masculino , Melatonina/metabolismo , Fotoperiodo
17.
J Comp Physiol B ; 179(6): 747-57, 2009 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-19363617

RESUMEN

Data addressing adrenocortical modulation across taxonomic groups are limited, especially with regard to how female reproductive condition influences the sensitivity of the hypothalamus-pituitary-adrenal axis. We investigated seasonal and reproductive variation in basal and stress-induced hormone profiles in a population of free-ranging timber rattlesnakes (Crotalus horridus) in north-central Pennsylvania during spring (i.e., May), summer (i.e., July), and early fall (i.e., September). Baseline corticosterone concentrations varied seasonally and were significantly lower during the summer sampling period in July. We observed a significant negative relationship between baseline corticosterone and testosterone in male snakes, while baseline corticosterone and estradiol tended to be positively correlated in females. Treatment of snakes with 1 h of capture stress significantly increased corticosterone across all seasons. However, there was a significant interaction between corticosterone responses to capture stress and season, suggesting that adrenocortical function is modulated seasonally. Because elevated corticosterone may be associated with reproduction, we asked whether hormonal stress responses vary with female reproductive condition. Although sample sizes are low, reproductive snakes had significantly higher baseline and stress-induced corticosterone concentrations than non-reproductive or post-parturient females. Further, despite similar baseline corticosterone concentrations between non-reproductive and post-parturient rattlesnakes, post-parturient females responded to capture stress with a significantly higher increase in corticosterone. Collectively, these data suggest that the sensitivity of the hypothalamus-pituitary-adrenal axis varies both seasonally and with changing reproductive states.


Asunto(s)
Crotalus/fisiología , Ambiente , Estadios del Ciclo de Vida , Estaciones del Año , Estrés Fisiológico , Análisis de Varianza , Animales , Peso Corporal , Corticosterona/sangre , Crotalus/crecimiento & desarrollo , Estradiol/sangre , Femenino , Manejo Psicológico , Inmovilización , Masculino , Pennsylvania , Análisis de Regresión , Reproducción , Caracteres Sexuales , Telemetría , Testosterona/sangre , Árboles
18.
Physiol Biochem Zool ; 81(6): 810-25, 2008.
Artículo en Inglés | MEDLINE | ID: mdl-18937566

RESUMEN

Transduction of environmental cues into endocrine signals that synchronize physiology and behavior with optimal environmental conditions is central to an animal's timekeeping system. Using a common garden approach, we investigated possible geographic variation in timekeeping systems by comparing 24-h melatonin and corticosterone rhythms and reproductive behavior among three populations of garter snakes with very different life histories: red-sided garter snakes (Thamnophis sirtalis parietalis) from Manitoba, Canada; red-spotted garter snakes (Thamnophis sirtalis concinnus) from western Oregon; and eastern garter snakes (Thamnophis sirtalis sirtalis) from southern Florida. Melatonin and corticosterone cycles differed significantly among the three snake populations in a majority of the sampling periods. Population differences were observed across a wide range of acclimatization conditions and were themselves plastic (i.e., one snake population was not consistently different from the others). Changes in courtship behavior during emergence also varied significantly among populations. Our data support the hypothesis that endogenous timekeeping systems have evolved in the presence of unique environmental conditions. Further research is necessary to determine whether this geographic variation results from inherent genetic differences or whether it is a product of development. These studies provide insight into the evolution of timekeeping systems and may aid in understanding the potential effects of environmental perturbations on seasonal physiology and behavior.


Asunto(s)
Colubridae/fisiología , Ecosistema , Aclimatación , Animales , Ritmo Circadiano , Colubridae/sangre , Corticosterona/sangre , Femenino , Hibernación , Masculino , Melatonina/sangre , Fotoperiodo , Estaciones del Año , Conducta Sexual Animal/fisiología
19.
Gen Comp Endocrinol ; 155(3): 607-12, 2008 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-17897644

RESUMEN

The body condition index is a common method for quantifying the energy reserves of individual animals. Because good body condition is necessary for reproduction in many species, body condition indices can indicate the potential reproductive output of a population. Body condition is related to glucocorticoid production, in that low body condition is correlated to high concentrations of corticosterone in reptiles. We compared the body condition index and plasma corticosterone levels of brown tree snakes on Guam in 2003 to those collected in 1992/1993 to determine whether that population still showed the chronic stress and poor condition apparent in the earlier study. We also examined the relationship between fat mass, body condition and plasma corticosterone concentrations as indicators of physiological condition of individuals in the population. Body condition was significantly higher in 2003 than in the earlier sample for mature male and female snakes, but not for juveniles. The significantly lower levels of corticosterone in all three groups in 2003 suggests that although juveniles did not have significantly improved energy stores they, along with the mature males and females, were no longer under chronic levels of stress. Although the wet season of 2002 was unusually rainy, low baseline levels of corticosterone measured in 2000 indicate that the improved body condition of snakes in 2003 is likely the result of long-term changes in prey populations rather than annual variation in response to environmental conditions.


Asunto(s)
Constitución Corporal/fisiología , Corticosterona/sangre , Indicadores de Salud , Serpientes/fisiología , Factores de Edad , Animales , Animales Salvajes/sangre , Animales Salvajes/fisiología , Femenino , Masculino , Lluvia , Estaciones del Año , Serpientes/sangre , Factores de Tiempo
20.
Toxicon ; 50(6): 810-5, 2007 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-17689581

RESUMEN

Ring-necked snakes (Diadophis punctatus) are suspected of being venomous because their Duvernoy's gland secretions have high levels of phospholipase activity, which is characteristic of many viperid and elapid venoms, and because anecdotal reports of feeding behavior are consistent with the use of a venom. We tested the toxicity of northwestern ring-necked snake oral secretions to a natural prey species, northwestern garter snakes (Thamnophis ordinoides), by injecting 2-35 microl of oral secretions intraperitoneally. All doses were 100% lethal within 180 min. The dose significantly affected the time to loss of a righting response. Neither injection of saline nor denatured oral secretions resulted in loss of a righting response or any visible detrimental effects. We suggest that northwestern ring-necked snakes may have evolved venom to subdue larger prey items than the snake would otherwise be capable of taking.


Asunto(s)
Colubridae/fisiología , Venenos de Serpiente/toxicidad , Animales , Animales Recién Nacidos , Conducta Animal/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Contenido Digestivo , Inyecciones Intraperitoneales , Longevidad/efectos de los fármacos , Equilibrio Postural/efectos de los fármacos , Conducta Predatoria/fisiología , Reflejo/efectos de los fármacos , Reflejo/fisiología , Venenos de Serpiente/metabolismo , Pruebas de Toxicidad Aguda
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