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Male Drosophila melanogaster adjust ejaculate size based on female mating status, fecundity, and age


Lüpold, Stefan; Manier, M K; Ala-Honkola, O; Belote, J M; Pitnick, S (2011). Male Drosophila melanogaster adjust ejaculate size based on female mating status, fecundity, and age. Behavioral Ecology, 22(1):184-191.

Abstract

In contrast to early predictions, it is now widely accepted that males incur substantive costs from ejaculate production. Hence, males are predicted to allocate their reproductive investments, including ejaculate size, relative to the risk of sperm competition and to female quality. The study of sperm allocation, however, has been technically challenging with nonvirgin females because sperm fromdifferent males must be discriminated within the female reproductive tract. To date, such investigations have thus largely been restricted to species that transfer sperm in spermatophores or for which females can be fitted with a harness to capture the incoming ejaculate. In this study, we examined sperm allocation using male Drosophila melanogaster that express a fluorescently labeled protein in sperm heads, allowing us to quantify sperm numbers from different males within the female reproductive tract. We found that male D. melanogaster deliver significantly more sperm to mated, large or young females compared with virgins, small or old females, respectively, whereas copulation duration was only significantly longer with large than with small females. These results provide further evidence for costly ejaculate production and consequent prudent allocation of sperm. Key words: ejaculate size, body size, female reproductive value, sperm competition, sperm number.

Abstract

In contrast to early predictions, it is now widely accepted that males incur substantive costs from ejaculate production. Hence, males are predicted to allocate their reproductive investments, including ejaculate size, relative to the risk of sperm competition and to female quality. The study of sperm allocation, however, has been technically challenging with nonvirgin females because sperm fromdifferent males must be discriminated within the female reproductive tract. To date, such investigations have thus largely been restricted to species that transfer sperm in spermatophores or for which females can be fitted with a harness to capture the incoming ejaculate. In this study, we examined sperm allocation using male Drosophila melanogaster that express a fluorescently labeled protein in sperm heads, allowing us to quantify sperm numbers from different males within the female reproductive tract. We found that male D. melanogaster deliver significantly more sperm to mated, large or young females compared with virgins, small or old females, respectively, whereas copulation duration was only significantly longer with large than with small females. These results provide further evidence for costly ejaculate production and consequent prudent allocation of sperm. Key words: ejaculate size, body size, female reproductive value, sperm competition, sperm number.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Uncontrolled Keywords:age; body size; female reproductive value; sperm allocation; sperm competition; sperm number
Language:English
Date:2011
Deposited On:28 Oct 2015 13:34
Last Modified:08 Dec 2017 14:23
Publisher:Oxford University Press
ISSN:1045-2249
Funders:Swiss National Science Foundation, National Science Foundation, Academy of Finland
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1093/beheco/arq193

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