Female-biased sex ratios are associated with higher maternal testosterone levels in nutria (Myocastor coypus)

Fishman, Ruth; Vortman, Yoni; Shanas, Uri; Koren, Lee

doi:10.1007/s00265-018-2517-3

Cited by 14 publications

(13 citation statements)

References 93 publications

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“…Previously we found that in nutrias litter size did not influence sex ratios, and that heavier females had male-biased sex ratios [64]. We also found that male fetuses in the last stages of pregnancy were heavier and longer than female fetuses [64]. It is possible that a successful strategy for having many male fetuses is to include an equal number of female fetuses.…”

Section: Discussionmentioning

confidence: 56%

Cortisol advantage of neighbouring the opposite sex in utero

et al. 2018

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Population sex ratios naturally fluctuate around equality. It is argued that the production of an equal number of male and female offspring by individual parents should be favoured by selection, if all costs and benefits are equal. Theoretically, an even sex ratio should yield the highest probability for a fetus to be adjacent to a fetus of the opposite sex in utero. This may cause developmental costs or benefits that have been overlooked. We examined the physiological and developmental parameters associated with in utero sex ratios in the nutria (Myocastor coypus), an invasive wildlife species with a strong reproductive output. Using hair testing, we found that litters with even sex ratios had the highest average cortisol levels. Fetuses neighbouring the opposite sex exhibited longer trunks than those neighbouring the same sex, which might imply better lung development. Our results are the first, to our knowledge, to link intra-utero sex ratios and fetal cortisol and suggest that fetal cortisol might be a mechanism by which even sex ratios are maintained via developmental advantages.

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Section: Discussionmentioning

confidence: 56%

Cortisol advantage of neighbouring the opposite sex in utero

et al. 2018

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“…Thus, the final sample comprised of 91 fetuses (44 males and 47 females) with gestational ages of 110 - 138 days, belonging to 16 litters. Estimation of gestational age followed Newson’s formula (Newson, 1966) cross-validated with multiple fetal morphometric measurements (Fishman et al, 2018). Fetal sex determination was performed using anatomical and molecular tools as described in (Fishman et al, 2018).…”

Section: Methodsmentioning

confidence: 99%

“…Estimation of gestational age followed Newson’s formula (Newson, 1966) cross-validated with multiple fetal morphometric measurements (Fishman et al, 2018). Fetal sex determination was performed using anatomical and molecular tools as described in (Fishman et al, 2018). Testosterone was extracted and quantified from fetal hair as previously described (Fishman et al, 2019).…”

Section: Methodsmentioning

confidence: 99%

“…In adults, male body size is strongly associated with testosterone levels, however, this association does not exist in females (Fishman et al, 2022). Moreover, higher testosterone levels in females are related to lower fitness (Fishman et al, 2018). Based on these past findings, we predict that there might be sex-differences in the genetic architecture for testosterone levels in the nutria.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative genetic study suggests sex-specific genetic architecture for fetal testosterone in a wild mammal

Fishman

Kralj‐Fišer

Marglit

et al. 2022

Preprint

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Testosterone plays a critical role in mediating fitness-related traits in many species. Although it is highly responsive to environmental and social conditions, evidence from several species show a heritable component to its individual variation. Despite the known effects that in utero testosterone exposure have on adult fitness, the heritable component of individual testosterone variation in fetuses is mostly unexplored. Furthermore, testosterone has sex-differential effects on fetal development, i.e., a specific level may be beneficial for male fetuses but detrimental for females. The above mentioned may lead to a different genetic structure underlying the heritability of testosterone between the sexes. Here, we used a wild animal model, the feral nutria, quantified testosterone using hair-testing and estimated its heritability between parent and offspring from the same and opposite sex. We found that in utero accumulated hair testosterone levels were heritable between parents and offspring of the same sex. However, there was a low additive genetic covariance between the sexes, and a relatively low cross-sex genetic correlation, suggesting a potential for sex-dependent trait evolution, expressed early on, in utero.

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“…In the laboratory, we extracted and quantified steroid hormones from female wild boar using standard protocols ( Fishman et al , 2018 ). The mass of the samples varied depending on the availability.…”

Section: Methodsmentioning

confidence: 99%

Do boars compensate for hunting with higher reproductive hormones?

Davidson

Malkinson

Schonblum

et al. 2021

Conservation Physiology

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The predation-stress hypothesis has been proposed as a general mechanism to explain the negative effect of predation risk on reproduction, through a chronic activation of the stress response. However, in some cases, stress appears to augment the reproductive potential of mammals. Wild boar (Sus scrofa) populations are on a rise worldwide, despite the high hunting pressure that they are exposed to. This hunting pressure instigates, among other effects, earlier sexual maturity in juvenile females, leading to the shortening of wild boars’ generation time. The mechanism that underlies this earlier sexual maturity under high hunting pressure has not been examined to date. To explore the physiological effects that hunting has on the reproductive system and whether the stress response is involved, we examined steroid hormone levels in the hair of female wild boars in northern Israel, comparing populations exposed to high and low hunting pressure. Furthermore, we compared steroid levels in the hair of female wild boars that were roaming alone or as a part of a group. We found no hormonal signs of stress in the hunted boars. Cortisol levels were low in both the high and low hunting-pressure groups. Yet, progesterone levels were higher in females that were exposed to high hunting pressure. Females roaming in a group also had higher progesterone levels compared to females that were alone, with no distinguishable differences in cortisol levels. These elevations in reproductive hormones that were associated with hunting may lead to a higher reproductive potential in female wild boars. They further show that high hunting pressure does not necessarily lead to chronic stress that impairs the reproductive potential of female wild boars. This data suggests that a reproductive hormonal response may be one of the factors leading to the rapid wild boars population growth worldwide, despite the high hunting pressure.

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Female-biased sex ratios are associated with higher maternal testosterone levels in nutria (Myocastor coypus)

Cited by 14 publications

References 93 publications

Cortisol advantage of neighbouring the opposite sex in utero

Cortisol advantage of neighbouring the opposite sex in utero

Quantitative genetic study suggests sex-specific genetic architecture for fetal testosterone in a wild mammal

Do boars compensate for hunting with higher reproductive hormones?

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