Stress and Reproduction in Reptiles

Tokarz, Richard R.; Summers, Cliff H.

doi:10.1016/b978-0-12-374930-7.10007-x

Cited by 10 publications

(6 citation statements)

References 288 publications

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“…Drought periods and consequently low water flow conditions are typically observed in this geographic area, and are related to reduced habitat quantity and quality (Jessop et al, 2003;Maceda-Veiga et al, 2009). Interestingly, events such as drought are known to trigger stress responses in many vertebrate species (Baker et al, 2013;Jessop et al, 2003;Tokarz and Summers, 2011;Wikelski et al, 2001). Variation in water temperature is another environmental variable that should be considered when studying wild fish, since several authors have demonstrated its influence on cortisol stress responses (Blevins et al, 2012;Cook et al, 2011;Meka and McCormick, 2005;Quinn et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

Variation in scale cortisol concentrations of a wild freshwater fish: Habitat quality or seasonal influences?

Carbajal

Talló-Parra

Monclús

et al. 2019

General and Comparative Endocrinology

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A significant body of literature suggests that aquatic pollutants can interfere with the physiological function of the fish hypothalamic-pituitary-interrenal (HPI) axis, and eventually impair the ability to cope with subsequent stressors. For this reason, development of accurate techniques to assess fish stress responses have become of growing interest. Fish scales have been recently recognized as a biomaterial that accumulates cortisol, hence it can be potentially used to assess chronic stress in laboratory conditions. We, therefore, aimed to evaluate the applicability of this novel method for cortisol assessment in fish within their natural environment. Catalan chub (Squalius laietanus) were sampled from two sites; a highly polluted and a less polluted (reference) site, in order to examine if habitat quality could potentially influence the cortisol deposition in scales. We also evaluated the seasonal variation in scale cortisol levels by sampling fish at three different time points during spring-summer 2014. In each sampling, blood was collected to complement the information provided by the scales. Our results demonstrated that blood and scale cortisol levels from individuals inhabiting the reference site were significantly correlated, therefore increasing the applicability of the method as a sensitive-individual measure of fish HPI axis activity, at least in non-polluted habitats. Since different environmental conditions could potentially alter the usefulness of the technique, results highlight that further validation is required to better interpret hormone fluctuations in fish scales. Scale cortisol concentrations were unaffected by habitat quality although fish from the polluted environment presented lower circulating cortisol levels. We detected a seasonal increase in scale cortisol values concurring with an energetically costly period for the species, supporting the idea that the analysis of cortisol in scales reveals changes in the HPI axis activity. Taken together, the present study suggests that cortisol levels in scales are more likely to be influenced by mid-term, intense energetically demanding periods rather than by long-term stressors. Measurement of cortisol in fish scales can open the possibility to study novel spatiotemporal contexts of interest, yet further research is required to better understand its biological relevance.

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Section: Discussionmentioning

confidence: 99%

Variation in scale cortisol concentrations of a wild freshwater fish: Habitat quality or seasonal influences?

Carbajal

Talló-Parra

Monclús

et al. 2019

General and Comparative Endocrinology

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“…Such a response is comparatively large (Tyrrell and Cree 1998;Tokarz and Summers 2010). In terms of the island tameness hypothesis, this result is informative in showing that fewer than a few thousand years of isolation from mainland B. constrictor populations and predators (Green 2010) have not resulted in the loss of a hormonal response to acute capture stress.…”

Section: Discussionmentioning

confidence: 81%

“…The steroid hormone concentrations of Boa constrictor imperator are very low compared to most other snakes studied. For example, baseline CORT concentrations of B. c. imperator tended to be in the range of 5-10 ng/mL, about an order of magnitude lower than most other snake species studied to date (Moore et al 2001;Tokarz and Summers 2010). Testosterone, E2, and P4 concentrations also appeared unusually low, with female T and P4 concentrations generally lower than the limits of detection, such that potential impacts of season will require further study.…”

Section: Discussionmentioning

confidence: 85%

“…For example, naive marine iguanas (Amblyrhynchus cristatus) in the Galá-pagos archipelago flee from human approach later than mainland iguanid lizards , lack adrenocortical and cardiovascular stress responses to experimental chasing by a researcher, and can be easily captured during repeated attempts Vitousek et al 2010). In particular, measuring stress reactivity-the adrenocortical response to a standardized stressor-is a fruitful way to evaluate the extent of the stress response in animals (Tokarz and Summers 2010). Animals exhibiting island tameness may lack or may have blunted stress reactivity .…”

Section: Introductionmentioning

confidence: 99%

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Wet- and Dry-Season Steroid Hormone Profiles and Stress Reactivity of an Insular Dwarf Snake, the Hog Island Boa (Boa constrictor imperator)

Holding¹,

Frazier²,

Dorr³

et al. 2014

Physiological and Biochemical Zoology

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Field endocrine studies providing new comparisons for inference into the evolutionary and ecological factors shaping organismal physiology are important, often yielding novel physiological insights. Here, we explored factors associated with the sex steroid hormone concentrations and adrenocortical response to capture stress in Hog Island boas (Boa constrictor imperator) in the Cayos Cochinos archipelago of Honduras to generate comparative field hormone data from a tropical reptile and test the island tameness hypothesis. Baseline concentrations of testosterone, corticosterone, estradiol, and progesterone were measured during the wet and dry seasons, and an acute stressor of 1 h in a cloth bag was used to assess the stress response. Plasma steroid concentrations in these snakes were generally low in comparison to other taxa. Higher testosterone concentrations in males and higher estradiol and corticosterone concentrations in females were observed during the wet season compared to the dry season, which may be indicative of mating activities and vitellogenesis during this period. Snakes displayed a 15-fold increase in corticosterone concentrations in response to capture stress, a rise that was not impacted by whether a snake had been captured during previous years. The adrenocortical stress response was greater in males and positively related to body temperature. We suggest that this system merits future inquiries into the physiology and behavior of B. c. imperator, particularly as a model for studying insular impacts on diverse life history characters.

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“…Stress reactions, the complex physiological processes that occur in response to increased activity of the adrenal gland, can have marked impacts on development, reproduction, behaviour, and immune function (Dhabhar, 2014;Greenberg & Wingfield, 1987;Guillette et al, 1995;Tokarz & Summers, 2011). However, the severity of physiological stress responses varies significantly depending on factors such as taxa, sex, season, body condition, reproductive stage, and duration of the stressor (Angelier et al, 2007;Baker et al, 2013;Cote et al, 2010;Greenberg & Wingfield, 1987;Seddon & Klukowski, 2012;Simmons, 2012).…”

Section: Introductionmentioning

confidence: 99%

Reproductive Fitness in Male Tuatara (Sphenodon punctatus) and its Implications

Lamar¹

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Sexual selection and variation in mating success in the mate-limited sex provide the underpinning for the evolution of many unique traits. Understanding the evolutionary costs of and relationships among these traits can inform our knowledge of sexual selection across the tree of life and provide species-specific improvements in conservation practices. Despite facing an ongoing extinction crisis, the evolution of sexual traits and variation in reproductive fitness is understudied in reptiles. Tuatara (Sphenodon punctatus) are culturally significant reptiles endemic to Aotearoa New Zealand. The sole survivors of the once widespread reptile order Rhynchocephalia, they are of extreme evolutionary, and thus conservation, importance. While many conservation successes have been achieved since tuatara were at their lowest numbers following severe human-associated range restrictions, we still know very little about reproductive fitness in males of this species. Thus, I undertook a large study investigating male sperm quality, dietary intake, immune function, morphological characteristics, and the relationship among these factors in a population of tuatara living on Takapourewa (Stephens Island). I provide the first description of tuatara, and thus Rhynchocephalian, mature sperm, including: summary statistics of sperm head length, midpiece length, tail length, percent viability, and curvilinear velocity. I found that tuatara sperm are long and fast but have poor viability relative to other reptile species. I did not find any significant trade-off between percent viability and curvilinear velocity in male tuatara, but there was weak support for the influence of tail length and midpiece length on sperm swim speed. Tail length was positively associated with faster sperm swim speeds, while midpiece length was negatively associated with faster sperm swim speeds. I also carried out preliminary work exploring the efficacy of different buffers and cryopreservatives at maintaining sperm cell membrane integrity and swim speed after freezing and thawing. I found that PBS was an effective buffer and that Lake’s cryoprotectant is not suitable for use in this species. Next, I used morphological measurements and stable isotope analyses (Δ13C and Δ15N) to establish that tuatara with larger gapes have higher levels of marine-associated (seabird) carbon in their diets. Additionally, tuatara with larger gapes tended to have better overall body condition, be longer (larger snout-vent length), and have larger caudal fat stores. Tuatara are sexually dimorphic, with males being larger and larger males dominating mating opportunities. These results indicate that male tuatara most likely to mate consume a disproportionately larger amount of seabird material on Takapourewa. Using historical blood smears collected from tuatara living on both Takapourewa and a resource-restricted island (North Brother Island), I established reference intervals for tuatara leukocyte profiles for the first time and explored the factors influencing tuatara immune function. I found that tuatara leukocytes display circannual rhythm and that the source population and date of sample collection were the most consistent predictors of leukocyte profile makeup in this species. Interestingly, I found that individuals from a resource-restricted, inbred population with poor body condition and showing evidence of chronic stress (determined via increased heterophil: lymphocyte ratio) were still able to mount responses to immune challenge, as measured by nitric oxide production. Finally, I looked at the trade-off between the many factors explored in this thesis: morphological characteristics known or thought to be under selection from female mate choice (body condition, gape size, and dorsal and nuchal spine number/area), dietary intake (Δ13C and Δ15N), immune status (heterophil:lymphocyte ratio, total number of leukocytes, and ectoparasite load), and sperm quality (viability and curvilinear velocity). I found evidence of an immunocompetence handicap, with both measures of sperm quality being negatively associated with body condition and the ratio of heterophils:lymphocytes. These relationships are likely the result of testosterone-induced immunosuppression and an increase in metabolic rate. I also found evidence of signal dishonesty in relation to tuatara sperm swim speed. Faster sperm were associated with smaller spine area, a trait known to be negatively associated with female mate choice. Lastly, I found evidence of the effects of diet on tuatara sperm swim speeds. Tuatara with higher (less negative) Δ13C values had slower swimming sperm, possibly a consequence of oxidation damage associated with marine-derived dietary items. These results combine to provide support for a trade-off between immune and endocrine system investment, mediated by diet, in this unique reptile. This work expands our understanding of sexual selection and the costs of reproductive fitness to a new order and provide important context for future conservation practices in this species.

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Stress and Reproduction in Reptiles

Cited by 10 publications

References 288 publications

Variation in scale cortisol concentrations of a wild freshwater fish: Habitat quality or seasonal influences?

Variation in scale cortisol concentrations of a wild freshwater fish: Habitat quality or seasonal influences?

Wet- and Dry-Season Steroid Hormone Profiles and Stress Reactivity of an Insular Dwarf Snake, the Hog Island Boa (Boa constrictor imperator)

Reproductive Fitness in Male Tuatara (Sphenodon punctatus) and its Implications

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