Genetic coordination of sperm morphology and seminal fluid proteins promotes male reproductive success in Drosophila melanogaster

Spermatozoal morphology is highly variable both among and within species and in ways that can significantly impact fertilization success. In Drosophila melanogaster, paternity success depends on sperm length of both competing males and length of the female's primary sperm storage organ. We found that genes upregulated in long sperm testes are enriched for lncRNAs and seminal fluid proteins (Sfps). Transferred in seminal fluid to the female during mating, Sfps are secreted by the male accessory glands (AG) and affect female remating rate, physiology, and behavior with concomitant advantages for male reproductive success. Despite being upregulated in long sperm testes, they have no known function in testis tissue. We found that Sex Peptide and ovulin (Acp26Aa) knockouts resulted in shorter sperm, suggesting that Sfps may regulate sperm length during spermatogenesis. However, knockout of AG function did not affect sperm length, suggesting that AG expression has no influence on spermatogenic processes. We also found that long sperm males are better able to delay female remating, suggesting higher Sfp expression in AG. These results might suggest that long sperm males have a double advantage in sperm competition by both delaying female remating, likely through transfer of more Sfps, and by resisting sperm displacement. However, we also found that this extra advantage does not necessarily translate to more progeny or higher paternity success. Thus, we found that multiple components of the ejaculate coordinate to promote male reproductive success at different stages of reproduction, but the realized fitness advantages in sperm competition are uncertain.

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Sperm Numbers as a Paternity Guard in a Wild Bird

Cells ◽

10.3390/cells11020231 ◽

2022 ◽

Vol 11 (2) ◽

pp. 231

Author(s):

Melissah Rowe ◽

Annabel van Oort ◽

Lyanne Brouwer ◽

Jan T. Lifjeld ◽

Michael S. Webster ◽

...

Keyword(s):

Reproductive Success ◽

Sperm Competition ◽

Ecological Factors ◽

Fertilization Success ◽

Male Reproductive Success ◽

Male Mating ◽

Sexually Selected Traits ◽

Paternity Success ◽

Mating Conditions ◽

Sperm Traits

Sperm competition is thought to impose strong selection on males to produce competitive ejaculates to outcompete rival males under competitive mating conditions. Our understanding of how different sperm traits influence fertilization success, however, remains limited, especially in wild populations. Recent literature highlights the importance of incorporating multiple ejaculate traits and pre-copulatory sexually selected traits in analyses aimed at understanding how selection acts on sperm traits. However, variation in a male’s ability to gain fertilization success may also depend upon a range of social and ecological factors that determine the opportunity for mating events both within and outside of the social pair-bond. Here, we test for an effect of sperm quantity and sperm size on male reproductive success in the red-back fairy-wren (Malurus melanocephalus) while simultaneously accounting for pre-copulatory sexual selection and potential socio-ecological correlates of male mating success. We found that sperm number (i.e., cloacal protuberance volume), but not sperm morphology, was associated with reproductive success in male red-backed fairy-wrens. Most notably, males with large numbers of sperm available for copulation achieved greater within-pair paternity success. Our results suggest that males use large sperm numbers as a defensive strategy to guard within-pair paternity success in a system where there is a high risk of sperm competition and female control of copulation. Finally, our work highlights the importance of accounting for socio-ecological factors that may influence male mating opportunities when examining the role of sperm traits in determining male reproductive success.

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Male reproductive ageing: a tale of the whole ejaculate

Reproduction ◽

10.1530/rep-18-0579 ◽

2019 ◽

Vol 158 (6) ◽

pp. R219-R229 ◽

Cited By ~ 1

Author(s):

Claudia Fricke ◽

Mareike Koppik

Keyword(s):

Reproductive Success ◽

Conformational Changes ◽

Seminal Fluid ◽

Reproductive Capacity ◽

Male Reproductive Success ◽

Seminal Fluid Proteins ◽

Area Of Interest ◽

General Decline ◽

Age Dependent ◽

The Impact

Ageing is nearly ubiquitous and encompasses all biological functions. We here focus on age-dependent changes in male reproductive capacity across a broad range of animal taxa. While there has been a long-standing focus on mating ability and overall reproductive success, we here highlight the underlying mechanisms that explain loss in fertilisation capacity in ageing males. Fertilisation is mediated by not only the presence of sperm, but also the cocktail of seminal fluid proteins that ensure sperm survival, capacitation and interaction with female physiology. Sperm ageing has received much attention in studies of male reproductive senescence; however, post-mating processes include a number of interlocked steps that together cumulate in successful fertilisation. As such we consider male ability to elicit female post mating responses such as uterine conformational changes, sperm storage and ovulation and the components within the ejaculate that mediate these post-mating processes. For the latter seminal fluid proteins are key and hence we reflect on age-dependent changes in quality of the entire ejaculate and its consequences for male reproductive capacity. While first studies accrue and highlight that changes in the non-sperm fraction can explain substantial variation in senescent male reproductive success and male ability to induce post-mating responses necessary for fertilisation many open questions still remain that warrant further investigations. One being what the potential age-dependent changes in composition are or whether there is a general decline and how this interacts with sperm to affect fertilisation success. Further, the impact females might have to ameliorate these changes will be an area of interest.

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A genome-wide analysis of courting and mating responses in Drosophila melanogaster females

Genome ◽

10.1139/g04-050 ◽

2004 ◽

Vol 47 (5) ◽

pp. 900-910 ◽

Cited By ~ 129

Author(s):

Mara KN Lawniczak ◽

David J Begun

Keyword(s):

Gene Expression ◽

Drosophila Melanogaster ◽

Seminal Fluid ◽

Differentially Expressed ◽

Male Reproductive Success ◽

Female Side ◽

Accessory Gland Proteins ◽

Seminal Fluid Proteins ◽

A Genome ◽

Immune Related Genes

In Drosophila melanogaster, seminal fluid proteins influence several components of female physiology and behavior, including re-mating rates, ovulation and oviposition, and sperm use. It is well-known that female flies are not simply passive vessels and that female-mediated interactions with male products are important to female (and thus male) reproductive success. While the population genetics, molecular evolution and physiological effects of seminal fluid proteins have been examined, the genetics and evolution of the female side of these post-mating interactions is unexplored in spite of work showing that female genotype and female-by-male genotype interactions are important determinants of sperm competition outcomes. Here we use microarrays to identify candidate genes involved in the female side of post-mating sexual interactions. We report the results of a whole-genome oligonucleotide chip experiment that reveals 23 genes differentially expressed between virgin females exposed and unexposed to courting males, and 38 genes differentially expressed between virgin and recently mated females. Immune related genes are overrepresented among the mating-influenced candidates. We use quantitative reverse-transcriptase PCR to independently assess gene expression changes for roughly half of the mating-affected candidate genes.Key words: reproduction, gene expression, Drosophila immune related genes, serine proteases, accessory gland proteins.

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Sperm wars and the evolution of male fertility

Reproduction ◽

10.1530/rep-12-0285 ◽

2012 ◽

Vol 144 (5) ◽

pp. 519-534 ◽

Cited By ~ 210

Author(s):

Leigh W Simmons ◽

John L Fitzpatrick

Keyword(s):

Sperm Competition ◽

Swimming Speed ◽

Male Fertility ◽

Seminal Fluid ◽

Future Research ◽

Sperm Length ◽

Seminal Fluid Proteins ◽

Control Male ◽

Form And Function ◽

And Function

Females frequently mate with several males, whose sperm then compete to fertilize available ova. Sperm competition represents a potent selective force that is expected to shape male expenditure on the ejaculate. Here, we review empirical data that illustrate the evolutionary consequences of sperm competition. Sperm competition favors the evolution of increased testes size and sperm production. In some species, males appear capable of adjusting the number of sperm ejaculated, depending on the perceived levels of sperm competition. Selection is also expected to act on sperm form and function, although the evidence for this remains equivocal. Comparative studies suggest that sperm length and swimming speed may increase in response to selection from sperm competition. However, the mechanisms driving this pattern remain unclear. Evidence that sperm length influences sperm swimming speed is mixed and fertilization trials performed across a broad range of species demonstrate inconsistent relationships between sperm form and function. This ambiguity may in part reflect the important role that seminal fluid proteins (sfps) play in affecting sperm function. There is good evidence that sfps are subject to selection from sperm competition, and recent work is pointing to an ability of males to adjust their seminal fluid chemistry in response to sperm competition from rival males. We argue that future research must consider sperm and seminal fluid components of the ejaculate as a functional unity. Research at the genomic level will identify the genes that ultimately control male fertility.

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Divergent allocation of sperm and the seminal proteome along a competition gradient in Drosophila melanogaster

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1906149116 ◽

2019 ◽

Vol 116 (36) ◽

pp. 17925-17933 ◽

Cited By ~ 24

Author(s):

Ben R. Hopkins ◽

Irem Sepil ◽

Marie-Laëtitia Thézénas ◽

James F. Craig ◽

Thomas Miller ◽

...

Keyword(s):

Drosophila Melanogaster ◽

Sperm Competition ◽

Seminal Fluid ◽

Sperm Transfer ◽

Male Mating ◽

Compositional Change ◽

Seminal Fluid Proteins ◽

Allocation Rules ◽

Offspring Production ◽

Component Allocation

Sperm competition favors large, costly ejaculates, and theory predicts the evolution of allocation strategies that enable males to plastically tailor ejaculate expenditure to sperm competition threat. While greater sperm transfer in response to a perceived increase in the risk of sperm competition is well-supported, we have a poor understanding of whether males (i) respond to changes in perceived intensity of sperm competition, (ii) use the same allocation rules for sperm and seminal fluid, and (iii) experience changes in current and future reproductive performance as a result of ejaculate compositional changes. Combining quantitative proteomics with fluorescent sperm labeling, we show that Drosophila melanogaster males exercise independent control over the transfer of sperm and seminal fluid proteins (SFPs) under different levels of male–male competition. While sperm transfer peaks at low competition, consistent with some theoretical predictions based on sperm competition intensity, the abundance of transferred SFPs generally increases at high competition levels. However, we find that clusters of SFPs vary in the directionality and sensitivity of their response to competition, promoting compositional change in seminal fluid. By tracking the degree of decline in male mating probability and offspring production across successive matings, we provide evidence that ejaculate compositional change represents an adaptive response to current sperm competition, but one that comes at a cost to future mating performance. Our work reveals a previously unknown divergence in ejaculate component allocation rules, exposes downstream costs of elevated ejaculate investment, and ultimately suggests a central role for ejaculate compositional plasticity in sexual selection.

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Effects of two seminal fluid proteins on post-mating behavior in the simultaneously hermaphroditic flatwormMacrostomum lignano

10.1101/734301 ◽

2019 ◽

Author(s):

Michael Weber ◽

Bahar Patlar ◽

Steven A. Ramm

Keyword(s):

Reproductive Success ◽

Sperm Competition ◽

Mating Behavior ◽

Competitive Ability ◽

Seminal Fluid ◽

Genetic Correlations ◽

Complex Mixture ◽

Mating Frequency ◽

Seminal Fluid Proteins ◽

Knock Down

AbstractAlong with sperm, in many taxa male ejaculates also contain a complex mixture of proteins, peptides and other substances found in seminal fluid. Once seminal fluid proteins (SFPs) are transferred to the mating partner, they play crucial roles in mediating post-mating sexual selection, since they can modulate the partner’s behavior and physiology in ways that influence the reproductive success of both partners. One way in which sperm donors can maximize their own reproductive success is by changing the partners’ (sperm recipient’s) postcopulatory behavior to prevent or delay re-mating, thereby decreasing the likelihood or intensity of sperm competition. We therefore adopted a quantitative genetic approach combining gene expression and behavioral data to identify candidates that could mediate such a response in the simultaneously hermaphroditic flatwormMacrostomum lignano. We identified two putative SFPs - Mlig-pro46 and Mlig-pro63 - that exhibit a negative genetic correlation between transcript expression and mating frequency. Importantly, however, in one of the two different group sizes, differing in their sperm competition level, in which we measured genetic correlations, these same two transcripts are also linked to a second post-mating behavior inM. lignano, namely the ‘suck’ behavior of recipients in which, upon ejaculate receipt, the worm places its pharynx over its female genital opening and appears to attempt to remove ejaculate components. To therefore investigate directly whether these two candidates manipulate partner behavior, and test whether this impacts on competitive fertilization success, we performed a manipulative experiment using RNA interference-induced knockdown to ask how loss of Mlig-pro46 and Mlig-pro63 expression, singly and in combination, affects mating frequency, partner suck propensity and both defensive and offensive sperm competitive ability (P1andP2, respectively). None of the knock-down treatments impacted strongly on mating frequency or sperm competitive ability, but the knock-down of Mlig-pro63 resulted in a significantly decreased ‘suck’ propensity of mating partners. This suggests that Mlig-pro63 may normally act as a cue in the ejaculate to trigger recipient suck behavior, though the functional and adaptive significance of these two seminal proteins from a donor perspective remains enigmatic.

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Plastic responses of male Drosophila melanogaster to the level of sperm competition increase male reproductive fitness

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2008.1878 ◽

2009 ◽

Vol 276 (1662) ◽

pp. 1705-1711 ◽

Cited By ~ 154

Author(s):

Amanda Bretman ◽

Claudia Fricke ◽

Tracey Chapman

Keyword(s):

Drosophila Melanogaster ◽

Reproductive Success ◽

Sperm Competition ◽

Reproductive Fitness ◽

Male Reproductive Success ◽

Mating Duration ◽

Contrast Exposure ◽

Plastic Responses ◽

Paternity Share

Evolutionary and plastic responses by males to the level of sperm competition (SC) are reported across widespread taxa, but direct tests of the consequences for male reproductive success in a competitive context are lacking. We varied male perception of SC to examine the effect on male competitive reproductive success and to test whether the outcomes were as predicted by theory. Exposure to rival males prior to mating increased a male's ejaculate investment (measured as mating duration); by contrast, exposure to rival males in the mating arena decreased mating duration. The results therefore suggested that SC intensity is important in shaping male responses to SC in this system, although the patterns were not strictly in accord with existing theory. We then tested whether males that responded to the level of SC had higher reproductive fitness in a competitive context. We found that males kept with rivals prior to mating again mated for longer; furthermore, they achieved significantly higher paternity share regardless of whether they were the first or second males to mate with a female. The plastic strategies employed by males therefore resulted in significantly increased reproductive success in a competitive context, even following subsequent rematings in which the majority of sperm were displaced.

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Post-Copulatory Sexual Selection

Evolutionary Biology ◽

10.1093/obo/9780199941728-0131 ◽

2021 ◽

Author(s):

Patricia L.R. Brennan ◽

Dara N. Orbach

Keyword(s):

Sexual Selection ◽

Sperm Competition ◽

Female Choice ◽

Reproductive Tract ◽

Seminal Fluid ◽

Fertilization Success ◽

Female Reproductive Tract ◽

Cryptic Female Choice ◽

Trade Offs ◽

Morphological Criteria

The field of post-copulatory sexual selection investigates how female and male adaptations have evolved to influence the fertilization of eggs while optimizing fitness during and after copulation, when females mate with multiple males. When females are polyandrous (one female mates with multiple males), they may optimize their mating rate and control the outcome of mating interactions to acquire direct and indirect benefits. Polyandry may also favor the evolution of male traits that offer an advantage in post-copulatory male-male sperm competition. Sperm competition occurs when the sperm, seminal fluid, and/or genitalia of one male directly impacts the outcome of fertilization success of a rival male. When a female mates with multiple males, she may use information from a number of traits to choose who will sire her offspring. This cryptic female choice (CFC) to bias paternity can be based on behavioral, physiological, and morphological criteria (e.g., copulatory courtship, volume and/or composition of seminal fluid, shape of grasping appendages). Because male fitness interests are rarely perfectly aligned with female fitness interests, sexual conflict over mating and fertilization commonly occur during copulatory and post-copulatory interactions. Post-copulatory interactions inherently involve close associations between female and male reproductive characteristics, which in many species potentially include sperm storage and sperm movement inside the female reproductive tract, and highlight the intricate coevolution between the sexes. This coevolution is also common in genital morphology. The great diversity of genitalia among species is attributed to sexual selection. The evolution of genital attributes that allow females to maintain reproductive autonomy over paternity via cryptic female choice or that prevent male manipulation and sexual control via sexually antagonistic coevolution have been well documented. Additionally, cases where genitalia evolve through intrasexual competition are well known. Another important area of study in post-copulatory sexual selection is the examination of trade-offs between investments in pre-copulatory and post-copulatory traits, since organisms have limited energetic resources to allocate to reproduction, and securing both mating and fertilization is essential for reproductive success.

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Copulation order, density cues and variance in fertilization success in a cestode

Parasitology ◽

10.1017/s0031182014000043 ◽

2014 ◽

Vol 141 (7) ◽

pp. 934-939

Author(s):

D. ANDREOU ◽

D. P. BENESH

Keyword(s):

Reproductive Success ◽

Intermediate Host ◽

Fertilization Success ◽

Final Host ◽

Fish Host ◽

Multiple Infection ◽

Single Infection ◽

Male Reproductive Success ◽

Mating Order ◽

Potential Partner

SUMMARYSimultaneous hermaphrodites maximize their fitness by optimizing their investment into male or female functions. Allocation of resources to male function (tissues, traits, and/or behaviours increasing paternity) is predicted to increase as density, and the associated level of sperm competition, increases. We tested whether the simultaneous hermaphroditic cestode Schistocephalus solidus uses cues of potential partner densities in its fish intermediate host to improve its male reproductive success in the final host. We had two worms, one originating from a multiple infection in the fish intermediate host and one from a single infection, sequentially compete to fertilize the eggs of a third worm. The fertilization rates of the two competitors nearly always differed from the 50–50 null expectation, sometimes considerably, implying there was a ‘winner’ in each experimental competition. However, we did not find a significant effect of density in the fish host (single vs multiple) or mating order on paternity. Additional work will be needed to identify the traits and environmental conditions that explain the high variance in male reproductive success observed in this experiment.

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Seminal fluid and accessory male investment in sperm competition

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2020.0068 ◽

2020 ◽

Vol 375 (1813) ◽

pp. 20200068

Author(s):

Steven A. Ramm

Keyword(s):

Sperm Competition ◽

Seminal Fluid ◽

Complex Mixture ◽

Internal Fertilization ◽

Animal Evolution ◽

Male Investment ◽

Trade Offs ◽

Fluid Production ◽

Alternative Routes ◽

Paternity Success

Sperm production and allocation strategies have been a central concern of sperm competition research for the past 50 years. But during the ‘sexual cascade’ there may be strong selection for alternative routes to maximizing male fitness. Especially with the evolution of internal fertilization, a common and by now well-studied example is the accessory ejaculate investment represented by seminal fluid, the complex mixture of proteins, peptides and other components transferred to females together with sperm. How seminal fluid investment should covary with sperm investment probably depends on the mechanism of seminal fluid action. If seminal fluid components boost male paternity success by directly enhancing sperm function or use, we might often expect a positive correlation between the two forms of male investment, whereas trade-offs seem more likely if seminal fluid acts independently of sperm. This is largely borne out by a broad taxonomic survey to establish the prevailing patterns of seminal fluid production and allocation during animal evolution, in light of which I discuss the gaps that remain in our understanding of this key ejaculate component and its relationship to sperm investment, before outlining promising approaches for examining seminal fluid-mediated sperm competitiveness in the post-genomic era. This article is part of the theme issue ‘Fifty years of sperm competition’.

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