Experimental reduction in dietary omega-3 polyunsaturated fatty acids depresses sperm competitivenessby M. M. Rahman, C. Gasparini, G. M. Turchini, J. P. Evans

Biology Letters

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, 20140623, published 24 September 201410 2014 Biol. Lett.

Md. Moshiur Rahman, Clelia Gasparini, Giovanni M. Turchini and Jonathan P. Evans fatty acids depresses sperm competitiveness

Experimental reduction in dietary omega-3 polyunsaturated

Supplementary data ml http://rsbl.royalsocietypublishing.org/content/suppl/2014/09/19/rsbl.2014.0623.DC1.ht "Data Supplement"

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Cite this article: Rahman MM, Gasparini C,

Turchini GM, Evans JP. 2014 Experimental reduction in dietary omega-3 polyunsaturated

Received: 7 August 2014

Accepted: 5 September 2014

Keywords: condition dependent, sexual selection, ejaculate quality, fertilization

Author for correspondence:

Jonathan P. Evans

Evolutionary biology paternity when sperm compete for fertilization, confirming that the currently on November 1, 2014rsbl.royalsocietypublishing.orgDownloaded from Electronic supplementary material is available at http://dx.doi.org/10.1098/rsbl.2014.0623 or via http://rsbl.royalsocietypublishing.org.e-mail: jonathan.evans@uwa.edu.auSubject Areas: evolutionfatty acids depresses sperm competitiveness.

Biol. Lett. 10: 20140623. http://dx.doi.org/10.1098/rsbl.2014.0623rsbl.royalsocietypublishing.orgobserved trend for reduced n-3 LC-PUFA in western diets has important implications for individual reproductive fitness. 1. Introduction

As with many traits subject to sexual selection, ejaculates can be conspicuously variable within individual species (e.g. [1–3]). While the basis for such variation remains contentious (e.g. [4]), recent work exploring the role of condition dependence in sperm traits suggests that variation among individual males in the acquisition and/or allocation of resources may constitute a considerable source of variance in ejaculate quality in polyandrous species [5–8].

The manipulation of resource availability, particularly through nutrient supplementation, offers a useful way to test for condition dependence in ejaculate traits. Accordingly, several studies have shown that males fed nutritionally enriched diets produce higher-quality ejaculates compared with those fed lowquality diets [5–9], and one study has reported significant effects of diet quality in regulating the outcome of sperm competition [5]. Among the key nutrients known to influence ejaculate quality, long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFA; namely eicosapentaenoic acid and docosahexaenoic acid) play a critical role in determining the structural properties of spermatozoa, with concomitant effects on male fertility [10–12]. Animals cannot synthesize PUFA de novo, and their ability to bioconvert dietary C18 PUFA to LC-PUFA is limited.

Animals must therefore obtain n-3 LC-PUFA from dietary sources. The experimental manipulation of dietary n-3 LC-PUFA levels therefore offers a useful way to test their effects on ejaculate ‘fitness’, and ultimately in sperm competitiveness. Despite their importance in regulating ejaculate traits [13,14], only a single study has considered fatty acids explicitly in the context of postcopulatory sexual selection [15], and no study has investigated the link between n-3

LC-PUFA intake and sperm competitiveness. & 2014 The Author(s) Published by the Royal Society. All rights reserved.Experimental reduction in dietary omega-3 polyunsaturated fatty acids depresses sperm competitiveness

Md. Moshiur Rahman1, Clelia Gasparini1, Giovanni M. Turchini2 and Jonathan P. Evans1 1Centre for Evolutionary Biology, School of Animal Biology, University of Western Australia, Crawley, 6009 Western Australia, Australia 2School of Life and Environmental Sciences, Faculty of Science, Engineering and Built Environment,

Deakin University, Warrnambool, Victoria 3280, Australia

The health benefits of diets containing rich sources of long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFA) are well documented and include reductions in the risk of several diseases typical of Western societies. The dietary intake of n-3 LC-PUFA has also been linked to fertility, and there is abundant evidence that a range of ejaculate traits linked to fertility in humans, livestock and other animals depend on an adequate intake of n-3

LC-PUFA fromdietary sources. However, relatively few studies have explored how n-3 LC-PUFA influence reproductive fitness, particularly in the context of sexual selection. Here, we show that experimental reduction in the level of n-3

LC-PUFA in the diet of guppies (Poecilia reticulata) depresses a male’s share of implications for postcopulatory sexual selection and the basis, polyandry may enhance female fitness by biasing paternity in favour of genetically superior males (reviewed rsbl.royalsocietypublishing.org

Biol.Lett.10:20140623 2 on November 1, 2014rsbl.royalsocietypublishing.orgDownloaded from (c) Paternity analyses

We used up to four microsatellite markers to assign paternity to each brood, including TTA, Pr46, KonD15 and KonD21 (Genbank accession numbers: AF164205, AF127242, AF368429, AF368430, respectively). Genomic DNA was extracted from offspring using the EDNA HISPEX extraction kit (Fisher Biotec, Subiaco,

Western Australia). PCR products were analysed on an ABI3730

Sequencer and visualized using GENEMARKER v. 1.91 (http:// www.softgenetics.com); paternity was assigned using CERVUS v. 3.0 (http://www.fieldgenetics.com). Only broods comprising three or more offspring were included in our subsequent analysis (final sample size: n ¼ 26 independent broods).In this study, we use the guppy Poecilia reticulata, a highly polyandrous livebearing fish known to exhibit condition dependence in several ejaculate traits [16–18], to explore the effects of n-3 LC-PUFA dietary manipulation on competitive fertilization success. We used controlled heterospermic artificial inseminations to show that males fed diets enriched with n-3 LC-PUFA achieved significantly higher paternity success than their counterparts fed nutritionally impaired diets, thus confirming that ejaculate ‘fitness’ in this species is highly condition dependent and functionally dependent on resource acquisition. 2. Material and methods (a) Study population and dietary treatments