Pay attention to the ladies: female aggressive behavior and weapon allometry provide clues for sexual selection in freshwater anomurans (Decapoda: Aeglidae)

Dalosto, Marcelo M.; Ayres-Peres, Luciane; Araujo, Paula Beatriz; Santos, Sandro; Palaoro, Alexandre V.

doi:10.1007/s00265-019-2741-5

Cited by 13 publications

(12 citation statements)

References 68 publications

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“…Therefore, there may be no specific selection towards disproportionately stronger weapons in males as hypothesized. As already noted, females can fight for resources (Dalosto et al, 2019), which may already increase the selective pressure on the female weapon. Hence, investigating the correlations between components that share the same developmental pathway might lend us insights into sexual dimorphism patterns.…”

Section: Discussionmentioning

confidence: 94%

“…Given that the females of A. abtao do not have the tubercles (b in Figure 1), and we are uncertain whether A. abtao females engage in contests, we removed A. abtao from this analysis. Therefore, we only measured the mechanical advantage of the claws of A. longirostri because in this species both males and females have tubercles, and both engage in contests (Dalosto et al, 2019). By standardizing function (claw use) and tubercle presence in both sexes, we provided a reliable test of whether males' claws are more mechanically efficient than females' claws.…”

Section: Methodsmentioning

confidence: 99%

“…During fights, they grasp their rival's claw and squeeze it until the loser decides to retreat (Palaoro, Dalosto, Costa, & Santos, 2014). Despite males and females fighting similarly, females have proportionally smaller weapons than males (Dalosto, Ayres‐Peres, Araujo, Santos, & Palaoro, 2019). Higher reproduction costs for females have already been pointed out as an explanation for the smaller claw of females (Dalosto et al, 2019), but there are no measures of female claw muscle content or mechanical efficiency.…”

Section: Introductionmentioning

confidence: 99%

“…Despite males and females fighting similarly, females have proportionally smaller weapons than males (Dalosto, Ayres‐Peres, Araujo, Santos, & Palaoro, 2019). Higher reproduction costs for females have already been pointed out as an explanation for the smaller claw of females (Dalosto et al, 2019), but there are no measures of female claw muscle content or mechanical efficiency. Claw biomechanics is important during aeglid male fights because winners of male contests have stronger claws than losers (Palaoro et al, 2014), but we do not have similar information for females.…”

Section: Introductionmentioning

confidence: 99%

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Harder, better, faster, stronger: Weapon size is more sexually dimorphic than weapon biomechanical components in two freshwater anomuran species

Palaoro

Muniz

Santos

2020

Journal of Morphology

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Sexual selection influences the evolution of morphological traits that increase the likelihood of monopolizing scarce resources. When such traits are used during contests, they are termed weapons. Given that resources are typically linked to monopolizing mating partners, theory expects only males to bear weapons. In some species, however, females also bear weapons, although typically smaller than male weapons. Understanding why females bear smaller weapons can thus help us understand the selective pressures behind weapon evolution. However, most of our knowledge comes from studies on weapon size, while the biomechanics of weapons, such as the size of the muscles, efficiency, and shape are seldom studied. Our goal was to test if the theoretical expectations for weapon size sexual dimorphism also occur for weapon biomechanics using two aeglid crab species. Males of both species had larger claws which were also stronger than female claws. Male claws were also more efficient than females' claws (although we used only one species in this analysis). For weapon shape, though, only one species differed in the mean claw shape. Regarding scaling differences, in both species, male claws had higher size scaling than females, while only one species had a higher shape scaling. However, male weapons did not have higher scaling regarding strength and efficiency than females. Thus, males apparently allocate more resources in weapons than females, but once allocated, muscle and efficiency follow a similar developmental pathway in both sexes. Taken together, our results show that sexual dimorphism in weapons involves more than differences in size. Shape differences are especially intriguing because we cannot fully understand its causes. Yet, we highlight that such subtle differences can only be detected by measuring and analysing weapon shape and biomechanical components. Only then we might better understand how weapons are forged.

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Section: Discussionmentioning

confidence: 94%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Harder, better, faster, stronger: Weapon size is more sexually dimorphic than weapon biomechanical components in two freshwater anomuran species

Palaoro

Muniz

Santos

2020

Journal of Morphology

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“…Bearing a large weapon usually increases the fitness of the sex that engages in territorial contests (Husak, Lappin, & Bussche, 2009;Lailvaux & Husak, 2014). As such, weapons are typically under stronger selection in males compared to females, generating sexual dimorphism in weaponry (but see Dalosto, Ayres-peres, Araujo, Santos, & Palaoro, 2019;Stankowich & Caro, 2009). One of the most common forms of weapon sexual dimorphism comes from the disproportional increase in sizes of preexisting structures or appendages.…”

Section: Introductionmentioning

confidence: 99%

Performance, but not size, of hindleg weaponry is sexually dimorphic in the giant mesquite bug (Thasus neocalifornicus)

Graham

Kaiser

Palaoro³

2020

Preprint

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In many species, males possess specialized weaponry that have evolved to confer a benefit during aggressive interactions. Because male weaponry is typically an exaggerated or extreme version of pre-existing body parts, females often possess reduced or weaponry. Although much research has investigated sexual dimorphism in the sizes of such weapons, other weapon components, such as weapon performance or alternative weapon forms can also explain the evolution of weapon sexual dimorphisms. Here, we investigated the allometry and variation of multiple weapon components of hindleg weaponry in the male and female giant mesquite bugs, Thasus necalifornicus. Despite theory predicating greater allocation in male weaponry, we found that females allocated more into the lengths of their hindlegs compared to males. Despite this allocation, males possess relatively wider hindlegs, which likely increase area of muscle mass. Indeed, the squeezing performance of male hindlegs was much greater than that of female hindlegs. Lastly, we also described the allometry and variation in a male weapon component, prominent tibial spines, which likely are used to damage competitors during aggressive interaction. Overall, our findings highlight the intricacies of weapon sexual dimorphism and demonstrate the importance of measuring multiple weapon components and not a single measure.

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Reproductive season‐based plasticity in the size and strength of female crayfish (Faxonius obscurus) claws

Graham

Stubbs

Loughman

2023

Journal of Morphology

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Animal weapons are morphological traits that improve the fighting ability of the wielder and are associated with competition. These traits are typically sexually dimorphic, with males possessing weaponry and females lacking weaponry. However, in some cases, like in many crustaceans, both males and females wield enlarged claws, which may function as weapons. Further, animal weapons may vary in their size, shape, and performance, with theory predicting that selection pressure for weaponry should be the highest when the importance of fights is the greatest, such as during a reproductive season. However, the degree and direction of selection may vary based on sex and season, with females potentially benefiting from wielding larger weapons during nonreproductive seasons. Crayfishes offer an ideal system to investigate how weapon phenotypes change across reproductive seasons since both males and females undergo a form alteration associated with reproduction. Thus, we investigated whether female Allegheny crayfish, Faxonius obscurus, claws change in size, shape, or pinching strength based on whether a female is in a reproductive or nonreproductive form. We found that female F. obscurus claws are larger and stronger during the reproductive season. These findings align with previous research on males of the same species. We discuss how predictions about the relationship between seasonality and weapon investment may differ based on sex.

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Pay attention to the ladies: female aggressive behavior and weapon allometry provide clues for sexual selection in freshwater anomurans (Decapoda: Aeglidae)

Cited by 13 publications

References 68 publications

Harder, better, faster, stronger: Weapon size is more sexually dimorphic than weapon biomechanical components in two freshwater anomuran species

Harder, better, faster, stronger: Weapon size is more sexually dimorphic than weapon biomechanical components in two freshwater anomuran species

Performance, but not size, of hindleg weaponry is sexually dimorphic in the giant mesquite bug (Thasus neocalifornicus)

Reproductive season‐based plasticity in the size and strength of female crayfish (Faxonius obscurus) claws

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