More Like this

1. Sex differences in early transcriptomic responses to oxidative stress in the copepod Tigriopus californicus

   https://doi.org/10.1186/s12864-020-07179-5  

   Li, Ning; Flanagan, Ben A.; Partridge, MacKenzie; Huang, Elaine J.; Edmands, Suzanne (December 2020, BMC Genomics)

   null (Ed.)

   Abstract Background Patterns of gene expression can be dramatically different between males and females of the same species, in part due to genes on sex chromosomes. Here we test for sex differences in early transcriptomic response to oxidative stress in a species which lacks heteromorphic sex chromosomes, the copepod Tigriopus californicus . Results Male and female individuals were separately exposed to control conditions and pro-oxidant conditions (hydrogen peroxide and paraquat) for periods of 3 hours and 6 hours. Variance partitioning showed the greatest expression variance among individuals, highlighting the important information that can be obscured by the common practice of pooling individuals. Gene expression variance between sexes was greater than that among treatments, showing the profound effect of sex even when males and females share the same genome. Males exhibited a larger response to both pro-oxidants, differentially expressing more than four times as many genes, including up-regulation of more antioxidant genes, heat shock proteins and protease genes. While females differentially expressed fewer genes, the magnitudes of fold change were generally greater, indicating a more targeted response. Although females shared a smaller fraction of differentially expressed genes between stressors and time points, expression patterns of antioxidant and protease genes were more similar between stressors and more GO terms were shared between time points. Conclusions Early transcriptomic responses to the pro-oxidants H 2 O 2 and paraquat in copepods revealed substantial variation among individuals and between sexes. The finding of such profound sex differences in oxidative stress response, even in the absence of sex chromosomes, highlights the importance of studying both sexes and the potential for developing sex-specific strategies to promote optimal health and aging in humans. 

   more » « less
2. Prior parental experience attenuates hormonal stress responses and alters hippocampal glucocorticoid receptors in biparental rock doves

   https://doi.org/10.1242/jeb.244820  

   Farrar, Victoria S.; Morales Gallardo, Jaime; Calisi, Rebecca M. (December 2022, Journal of Experimental Biology)

   ABSTRACT In the face of challenges, animals must balance investments in reproductive effort versus their own survival. Physiologically, this trade-off may be mediated by glucocorticoid release by the hypothalamic–pituitary–adrenal axis and prolactin release from the pituitary to maintain parental care. The degree to which animals react to and recover from stressors likely affects maintenance of parental behavior and, ultimately, fitness. However, less is known about how gaining parental experience may alter hormonal stress responses and their underlying neuroendocrine mechanisms. To address this gap, we measured the corticosterone (CORT) and prolactin (PRL) stress response in individuals of both sexes of the biparental rock dove (Columba livia) that had never raised chicks versus birds that had fledged at least one chick. We measured both CORT and PRL at baseline and after an acute stressor (30 min restraint). We also measured negative feedback ability by administering dexamethasone, a synthetic glucocorticoid that suppresses CORT release, and measured CORT and PRL after 60 min. All hormones were measured when birds were not actively nesting to assess whether effects of parental experience extend beyond the breeding bout. Experienced birds had lower stress-induced and negative-feedback CORT, and higher stress-induced PRL than inexperienced birds. In a separate experiment, we measured glucocorticoid receptor subtype expression in the hippocampus, a key site of negative feedback regulation. Experienced birds showed higher glucocorticoid receptor expression than inexperienced controls, which may mediate their ability to attenuate CORT release. Together, these results shed light on potential mechanisms by which gaining experience may improve parental performance and fitness. 

   more » « less
3. Glucocorticoid-Mediated Changes in Male Green Treefrog Vocalizations Alter Attractiveness to Females

   https://doi.org/10.1093/icb/icab053  

   Leary, Christopher J; Crocker-Buta, Sarah; Holloway, Ashli; Kennedy, Joseph G (May 2021, Integrative and Comparative Biology)

   Synopsis Adrenal glucocorticoids (GCs) are increasingly recognized as important modulators of male courtship signals, suggesting that circulating levels of these steroids can play a central role in sexual selection. However, few studies have examined whether GC-mediated effects on male sexual signals actually impact mate choice by females. Here, we examine how corticosterone (CORT)-mediated changes in the vocalizations of male green treefrogs, Dryophytes cinereus, influence attractiveness to females. In this species, agonistic acoustic signaling between rival males competing for mates increases circulating CORT levels in contest losers. Acute elevations in CORT, in turn, decrease the duration of male advertisement calls and increase the latency between successive calls, resulting in a net reduction in vocal effort (the amount of signaling per unit time) that occurs independently of changes in circulating androgens. Based on known preferences for acoustic features in D. cinereus, and other anuran species, the direction of CORT-mediated effects on temporal call characteristics is expected to compromise attractiveness to females, but whether they are of sufficient magnitude to impact female mate choice decisions is unclear. To examine whether CORT-mediated effects on male advertisement calls reduce attractiveness to females, we broadcast vocalizations in dual speaker playback experiments approximating the mean and 1 SD above and below the mean call duration and vocal effort values (the two primary vocal features impacted by elevated CORT) of males with low and high CORT levels. Results revealed strong preferences by females for the calls characteristic of males with low CORT in tests using the approximate mean and 1 SD above the mean call duration and vocal effort values, but females did not show a preference for calls of males with low CORT in trials using call values approximating 1 SD below the mean. Overall, females preferred males with signal traits predictive of low CORT, however this effect was nonlinear with attenuated preferences when signal alternatives differed only marginally indicating a possible thresholding effect. Specifically, females appeared to discriminate between males with low versus high CORT based primarily on differences in call rates associated with CORT-mediated changes in call duration and vocal effort. Our results highlight that changes in circulating CORT during male–male vocal interactions can decrease attractiveness to females, suggesting that circulating levels of CORT can play a critical role in both intra- and intersexual selection. 

   more » « less
4. Uncovering the Sex-Specific Endocrine Responses to Reproduction and Parental Care

   https://doi.org/10.3389/fendo.2021.631384  

   Austin, Suzanne H.; Krause, Jesse S.; Viernes, Rechelle; Farrar, Victoria S.; Booth, April M.; Harris, Rayna M.; Angelier, Frédéric; Lee, Candice; Bond, Annie; Wingfield, John C.; et al (November 2021, Frontiers in Endocrinology)

   Hormones mediate physiological and behavioral changes in adults as they transition into reproduction. In this study, we characterize the circulating levels of five key hormones involved in reproduction in rock doves ( Columba livia ): corticosterone, progesterone, estradiol, testosterone, and prolactin using univariate and multivariate approaches. We show similar patterns as previous studies in the overall patterns in circulating levels of these hormones, i.e., testosterone (males) and estradiol (females) high during nest-building or egg-laying, prolactin increasing at mid-incubation and peaking at hatching (both sexes), and elevated corticosterone levels in later incubation and early nestling development. In our investigation of hormone co-variation, we find a strong correlation between prolactin and corticosterone across sampling stages and similarities in earlier (early to mid-incubation) compared to later (late incubation to nestling d9) sampling stages in males and females. Finally, we utilized experimental manipulations to simulate nest loss or altered caregiving lengths to test whether external cues, internal timing, or a combination of these factors contributed most to hormone variation. Following nest loss, we found that both males and females responded to the external cue. Males generally responded quickly following nest loss by increasing circulating testosterone, but this response was muted when nest loss occurred early in reproduction. Similar treatment type, e.g., removal of eggs, clustered similarly in hormone space. These results suggest internal drivers limited male response early in reproduction to nest loss. In contrast, circulating levels of these hormones in females either did not change or decreased following nest manipulation suggesting responsiveness to external drivers, but unlike males, this result suggests that reproductive processes were decreasing. 

   more » « less
5. Revisiting the specific and potentially independent role of the gonad in hormone regulation and reproductive behavior

   https://doi.org/10.1242/jeb.247686  

   Farrar, Victoria S (November 2024, Journal of Experimental Biology)

   ABSTRACT Gonadal sex steroid hormones are well-studied modulators of reproductive physiology and behavior. Recent behavioral endocrinology research has focused on how the brain dynamically responds to – and may even produce – sex steroids, but the gonadal tissues that primarily release these hormones receive much less attention as a potential mediator of behavioral variation. This Commentary revisits mechanisms by which the reproductive hypothalamic–pituitary–gonadal (HPG) axis can be modulated specifically at the gonadal level. These mechanisms include those that may allow the gonad to be regulated independently of the HPG axis, such as receptors for non-HPG hormones, neural inputs and local production of conventional ‘neuropeptides'. Here, I highlight studies that examine variation in these gonadal mechanisms in diverse taxa, with an emphasis on recent transcriptomic work. I then outline how future work can establish functional roles of gonadal mechanisms in reproductive behavior and evaluate gonad responsiveness to environmental cues. When integrated with neural mechanisms, further investigation of gonadal hormone regulation can yield new insight into the control and evolution of steroid-mediated traits, including behavior. 

   more » « less