Do Male Cook Strait Giant Weta Prudently Allocate Sperm?

Kelly, Clint D.; Gwynne, Darryl

doi:10.1007/s10905-017-9622-4

Cited by 7 publications

(1 citation statement)

References 35 publications

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“…The behavior of females and their role in prolonging copulation or stimulating males to transfer larger ejaculates have not been included as potential variables here but have been suggested in some insects (Kelly & Gwynne 2017). The female role during mating is frequently assumed to be reactive, with respect to the active male, but this could be only a stereotyped vision (Perry & Rowe 2012).…”

Section: Discussionmentioning

confidence: 99%

Ejaculate allocation in Brachyura: What do males of Metacarcinus edwardsii respond to?

Pardo¹,

Riveros²,

Chaparro³

et al. 2018

Aquat. Biol.

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In polygynous species, the sperm economy hypothesis predicts that males can adjust the amount of their ejaculate during copulation in response to (1) individual traits of females according to potential female fecundity, (2) future mating opportunities, and (3) risk of sperm competition. We tested this hypothesis in the crab Metacarcinus edwardsii by performing laboratory mating experiments to compare the response of males (sperm number and ejaculate weight delivered) in 3 sex-ratio scenarios: (1) equal, 1 female:1 male; (2) male-biased, 1 female:2 males; and (3) female-biased, 2 females:1 male. First, we determined if any variable, or an interaction between variables, could explain the variation in sperm or ejaculate amount delivered under an equal sex ratio. Second, we contrasted the ejaculate allocation among different sex-ratio scenarios. Under an equal sex ratio, males of M. edwardsii did not adjust their ejaculate allocation in response to any female trait. Male size was positively related to ejaculate delivery, indicating that the pair of vasa deferentia has ejaculate reserves that scale exponentially with male size. However, larger males delivered disproportionally more seminal fluid than sperm. Under a female-biased sex ratio, males did not show plasticity in their ejaculate allocation, but they increased their ejaculate investment (23%) per female under a male-biased sex ratio (i.e. risk of sperm competition). M. edwardsii presented a low level of ejaculate allocation, responding only when competitive males were perceived. In species with trans-molt sperm retention and long ejaculate storage, the risk of sperm competition is present all the time; therefore, males do not economize ejaculate even if more receptive females are available.

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Section: Discussionmentioning

confidence: 99%