Eunuchs are better fighters

Kralj‐Fišer, Simona; Gregorič, Matjaž; Zhang, Shichang; Li, Daiqin; Kuntner, Matjaž

doi:10.1016/j.anbehav.2011.02.010

Cited by 39 publications

(72 citation statements)

References 43 publications

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“…Hence, the gloves-off hypothesis [12] is supported as a possible mechanism behind eunuchs' better fighting abilities [14].…”

Section: Discussionmentioning

confidence: 94%

“…(a) Study subjects Subadult N. malabarensis males were collected in Singapore and housed in a laboratory under controlled environment, kept individually in vials and fed with Drosophila melanogaster twice a week [14]. They were monitored daily until adulthood to control for their virginity and post-maturity age (defined as days elapsed from the final moult until the day of trial).…”

Section: Methodsmentioning

confidence: 99%

“…Because eunuchs are effectively sterile, emasculation seems maladaptive. Nevertheless, adaptive hypotheses for the eunuch phenomenon do exist, including the mating plug hypothesis [8], the better fighter hypothesis [8,12] and the remote copulation hypothesis [13][14][15]. These three hypotheses have been experimentally tested and supported in Nephilengys malabarensis, a highly sexually dimorphic and cannibalistic nephilid spider known for obligate self emasculation during mating and intense post-copulatory mate guarding in surviving eunuchs [12,14,15].…”

Section: Introductionmentioning

confidence: 99%

“…In a recent study, about 25 per cent of N. malabarensis males survived mating, became half-eunuchs (one palp emasculated) or full-eunuchs (both palps emasculated), continued guarding the females intensively, and these eunuchs were found to win contests against intact males [14]. However, proximate mechanisms behind better fighting abilities in eunuchs remain unknown.…”

Section: Introductionmentioning

confidence: 99%

“…Tidarren sisyphoides males emasculate one palp before mating, whereas N. malabarensis males break off their palps during mating. It is unclear whether N. malabarensis eunuchs' superior fighting abilities [14] are also directly related to increased endurance capacity after the removal of their disproportionately large palps [16], i.e. the 'gloves-off ' hypothesis [12].…”

Section: Introductionmentioning

confidence: 99%

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Emasculation: gloves-off strategy enhances eunuch spider endurance

Lee

Kralj‐Fišer

et al. 2012

Biol. Lett.

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Males of sexually cannibalistic spiders commonly mutilate parts of their paired genitals (palps) during copulation, which may result in complete emasculation or the ‘eunuch phenomenon’. In an orb-web nephilid spider, Nephilengys malabarensis , about 75 per cent of males fall victim to sexual cannibalism, and the surviving males become half-eunuchs (one palp emasculated) or full-eunuchs (both palps emasculated). While it has been shown that surviving eunuchs are better fighters compared with intact males when guarding the females with which they have mated, mechanisms behind eunuchs’ superior fighting abilities are unknown. The previously proposed ‘gloves-off’ hypothesis, attributing eunuchs’ enhanced locomotor endurance to the reduction in total body weight caused by genital mutilation, is plausible but has remained untested. Here, we tested the gloves-off hypothesis in N. malabarensis by comparing the time until exhaustion (i.e. endurance) of intact males with half- and full-eunuchs created experimentally. We found that by reducing body weight up to 4 per cent in half-eunuchs and 9 per cent in full-eunuchs through emasculation, endurance increases significantly in half-eunuchs (32%) and particularly strongly in full-eunuchs (80%). Our results corroborate the gloves-off hypothesis and further point towards the adaptive significance of male emasculation.

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“…Hence, the gloves-off hypothesis [12] is supported as a possible mechanism behind eunuchs' better fighting abilities [14].…”

Section: Discussionmentioning

confidence: 94%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Emasculation: gloves-off strategy enhances eunuch spider endurance

Lee

Kralj‐Fišer

et al. 2012

Biol. Lett.

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Sex differences in the genetic architecture of aggressiveness in a sexually dimorphic spider

Kralj‐Fišer

Laskowski

García‐González

2019

Ecology and Evolution

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Sex differences in the genetic architecture of behavioral traits can offer critical insight into the processes of sex‐specific selection and sexual conflict dynamics. Here, we assess genetic variances and cross‐sex genetic correlations of two personality traits, aggression and activity, in a sexually size‐dimorphic spider, Nuctenea umbratica. Using a quantitative genetic approach, we show that both traits are heritable. Males have higher heritability estimates for aggressiveness compared to females, whereas the coefficient of additive genetic variation and evolvability did not differ between the sexes. Furthermore, we found sex differences in the coefficient of residual variance in aggressiveness with females exhibiting higher estimates. In contrast, the quantitative genetic estimates for activity suggest no significant differentiation between males and females. We interpret these results with caution as the estimates of additive genetic variances may be inflated by nonadditive genetic effects. The mean cross‐sex genetic correlations for aggression and activity were 0.5 and 0.6, respectively. Nonetheless, credible intervals of both estimates were broad, implying high uncertainty for these estimates. Future work using larger sample sizes would be needed to draw firmer conclusions on how sexual selection shapes sex differences in the genetic architecture of behavioral traits.

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Beyond spider personality: The relationships between behavioral, physiological, and environmental factors

Duran

Wilson

Briffa

et al. 2021

Ecology and Evolution

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Spiders are useful models for testing different hypotheses and methodologies relating to animal personality and behavioral syndromes because they show a range of behavioral types and unique physiological traits (e.g., silk and venom) that are not observed in many other animals. These characteristics allow for a unique understanding of how physiology, behavioral plasticity, and personality interact across different contexts to affect spider's individual fitness and survival. However, the relative effect of extrinsic factors on physiological traits (silk, venom, and neurohormones) that play an important role in spider survival, and which may impact personality, has received less attention. The goal of this review is to explore how the environment, experience, ontogeny, and physiology interact to affect spider personality types across different contexts. We highlight physiological traits, such as neurohormones, and unique spider biochemical weapons, namely silks and venoms, to explore how the use of these traits might, or might not, be constrained or limited by particular behavioral types. We argue that, to develop a comprehensive understanding of the flexibility and persistence of specific behavioral types in spiders, it is necessary to incorporate these underlying mechanisms into a synthesized whole, alongside other extrinsic and intrinsic factors.

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Eunuchs are better fighters

Cited by 39 publications

References 43 publications

Emasculation: gloves-off strategy enhances eunuch spider endurance

Emasculation: gloves-off strategy enhances eunuch spider endurance

Sex differences in the genetic architecture of aggressiveness in a sexually dimorphic spider

Beyond spider personality: The relationships between behavioral, physiological, and environmental factors

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