Ejaculate allocation in Brachyura: What do males of Metacarcinus edwardsii respond to?
| Autor: | Luis Miguel Pardo, Oscar R. Chaparro, Marcela P. Riveros, Katrin Pretterebner |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
0106 biological sciences
Ecology QH301-705.5 010604 marine biology & hydrobiology media_common.quotation_subject Zoology Aquatic Science Biology Oceanography Microbiology 010603 evolutionary biology 01 natural sciences QR1-502 Metacarcinus edwardsii Biology (General) Reproduction Sperm competition Ecology Evolution Behavior and Systematics Invertebrate media_common |
| Zdroj: | Aquatic Biology, Vol 27, Pp 25-33 (2018) |
| ISSN: | 1864-7790 1864-7782 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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