Effects of alternative male mating strategies on characteristics of sperm production in the Atlantic salmon ( Salmo salar ): theoretical and empirical investigations

1995 ◽  
Vol 350 (1334) ◽  
pp. 391-399 ◽  
Keyword(s):  
Atlantic Salmon ◽  
Sperm Competition ◽  
Salmo Salar ◽  
Reproductive Traits ◽  
Fertilization Success ◽  
Mating Strategies ◽  
Male Mating ◽  
Sperm Length ◽  
Male Mating Strategies ◽  
Natural Variance

Atlantic salmon ( Salmo salar ) males mature as either tiny precocious parr before seaward migration, or as older and larger anadromous males. Anadromous males dominate the spawning redds and aggressively defend females against parr intrusions. Parr gain fertilizations by sneaking in to ejaculate while anadromous males and females spawn. Such differences in mating advantage generate asymmetries in risk of sperm competition between the male strategies. Theoretical sperm competition models predict that males typically mating in disfavoured roles (here, the parr strategy) should be selected to offset this disadvantage by investing more into spermatogenesis to achieve fertilization success. First, we present a theoretical model which analyses gametic expenditure for salmon parr and anadromous male reproductive strategies. We then use the natural variance in mating pattern within this species to compare empirically how males invest in spermatogenesis. A range of reproductive traits were measured for both male strategies. Absolutely, anadromous males have larger testes and produce greater numbers of sperm than parr males. However, results show that parr invest relatively more heavily into total spermatogenesis, and have a larger gonosomatic index than anadromous males. Relative to body size, parr produced greater numbers of sperm and volumes of stripped ejaculate. There was no difference in sperm length between the two male strategies. However, more sperm were motile in parr ejaculates, and these sperm lived longer than anadromous male sperm. Our findings may explain how male parr, under elevated risks of sperm competition and occupying a disfavoured mating role (parr weigh only 0.15% of the average body mass of anadromous males) achieve disproportionately high fertilization success.

scholarly journals Long sperm fertilize more eggs in a bird

2015 ◽  
Vol 282 (1799) ◽  
pp. 20141897 ◽  
Author(s):  
Clair Bennison ◽  
Nicola Hemmings ◽  
Jon Slate ◽  
Tim Birkhead
Keyword(s):  
Sperm Competition ◽  
Reproductive Traits ◽  
Fertilization Success ◽  
Swimming Velocity ◽  
Sperm Length ◽  
Complex Interactions ◽  
Female Reproductive Traits ◽  
Sperm Size ◽  
The Relationship ◽  
Main Factor

Sperm competition, in which the ejaculates of multiple males compete to fertilize a female's ova, results in strong selection on sperm traits. Although sperm size and swimming velocity are known to independently affect fertilization success in certain species, exploring the relationship between sperm length, swimming velocity and fertilization success still remains a challenge. Here, we use the zebra finch ( Taeniopygia guttata ), where sperm size influences sperm swimming velocity, to determine the effect of sperm total length on fertilization success. Sperm competition experiments, in which pairs of males whose sperm differed only in length and swimming speed, revealed that males producing long sperm were more successful in terms of (i) the number of sperm reaching the ova and (ii) fertilizing those ova. Our results reveal that although sperm length is the main factor determining the outcome of sperm competition, complex interactions between male and female reproductive traits may also be important. The mechanisms underlying these interactions are poorly understood, but we suggest that differences in sperm storage and utilization by females may contribute to the outcome of sperm competition.

scholarly journals Is diversification in male reproductive traits driven by evolutionary trade-offs between weapons and nuptial gifts?

2015 ◽  
Vol 282 (1807) ◽  
pp. 20150247 ◽  
Author(s):  
Xingyue Liu ◽  
Fumio Hayashi ◽  
Laura C. Lavine ◽  
Ding Yang
Keyword(s):  
Reproductive Traits ◽  
Accessory Gland ◽  
Mating Strategies ◽  
Male Mating ◽  
Nuptial Gift ◽  
Nuptial Gifts ◽  
Trade Off ◽  
Sexually Selected Traits ◽  
Trade Offs ◽  
Male Mating Strategies

Many male animals have evolved exaggerated traits that they use in combat with rival males to gain access to females and secure their reproductive success. But some male animals invest in nuptial gifts that gains them access to females. Both these reproductive strategies are costly in that resources are needed to produce the weapon or nuptial gift. In closely related species where both weapons and nuptial gifts are present, little is known about the potential evolutionary trade-off faced by males that have these traits. In this study, we use dobsonflies (order Megaloptera, family Corydalidae, subfamily Corydalinae) to examine the presence and absence of enlarged male weapons versus nuptial gifts within and among species. Many dobsonfly species are sexually dimorphic, and males possess extremely enlarged mandibles that they use in battles, whereas in other species, males produce large nuptial gifts that increase female fecundity. In our study, we show that male accessory gland size strongly correlates with nuptial gift size and that when male weapons are large, nuptial gifts are small and vice versa. We mapped weapons and nuptial gifts onto a phylogeny we constructed of 57 species of dobsonflies. Our among-species comparison shows that large nuptial gift production evolved in many species of dobsonfly but is absent from those with exaggerated weapons. This pattern supports the potential explanation that the trade-off in resource allocation between weapons and nuptial gifts is important in driving the diversity of male mating strategies seen in the dobsonflies, whereas reduced male–male competition in the species producing large spermatophores could be an alternative explanation on their loss of male weapons. Our results shed new light on the evolutionary interplay of multiple sexually selected traits in animals.

scholarly journals Paternity in wild ring‐tailed lemurs ( Lemur catta ): Implications for male mating strategies

2016 ◽  
Vol 78 (12) ◽  
pp. 1316-1325 ◽  
Author(s):  
Joyce A. Parga ◽  
Michelle L. Sauther ◽  
Frank P. Cuozzo ◽  
Ibrahim Antho Youssouf Jacky ◽  
Richard R. Lawler ◽  
...  
Keyword(s):  
Lemur Catta ◽  
Mating Strategies ◽  
Male Mating ◽  
Male Mating Strategies

Fertilization dynamics of sperm from different male mating tactics in bluegill (Lepomis macrochirus)

2005 ◽  
Vol 83 (12) ◽  
pp. 1638-1642 ◽  
Author(s):  
Albrecht I Schulte-Hostedde ◽  
Gary Burness
Keyword(s):  
Sperm Competition ◽  
Lepomis Macrochirus ◽  
Fertilization Success ◽  
Male Mating ◽  
Motile Sperm ◽  
Mating Tactics ◽  
Sperm Activation ◽  
Competition Theory ◽  
Sperm Density ◽  
Over Time

Sperm competition results in the evolution of ejaculate characteristics such as high sperm density, high motility, and fast sperm swimming speed. A fundamental assumption of sperm competition theory is that ejaculates with high motility and fast-swimming sperm have an advantage with respect to fertilization success. We tested this assumption by studying the fertilization dynamics of alternative mating tactics (cuckolders and parentals) of male bluegill (Lepomis macrochirus Rafinesque, 1819). Sneakers (cuckolders) have faster swimming sperm and a higher proportion of motile sperm immediately following sperm activation than do parentals; however, these variables decline more quickly over time in sneaker sperm than in the sperm of parental males. We used a controlled fertilization experiment to test the prediction that parental males will have higher fertilization success than sneakers late in the sperm activation cycle because of the reduced rate of decline in ejaculate quality over time. We found that as the time from sperm activation increases parental sperm fertilizes more eggs than the sperm of sneakers. Our results support the idea that fertilization success is higher when ejaculates contain a higher proportion of either motile sperm or faster swimming sperm, all else being equal. In addition, after controlling for time from sperm activation, we found a significant bias in fertilization success toward parental males, suggesting that cryptic female choice might play a role in fertilization dynamics.

scholarly journals Inbreeding depresses sperm competitiveness, but not fertilization or mating success in male Tribolium castaneum

2010 ◽  
Vol 277 (1699) ◽  
pp. 3483-3491 ◽  
Author(s):  
Łukasz Michalczyk ◽  
Oliver Y. Martin ◽  
Anna L. Millard ◽  
Brent C. Emerson ◽  
Matthew J. G. Gage
Keyword(s):  
Sperm Competition ◽  
Inbreeding Depression ◽  
Tribolium Castaneum ◽  
Mating Behaviour ◽  
Fertilization Success ◽  
Heterozygote Advantage ◽  
Length Variation ◽  
Sperm Length ◽  
Mating Pattern ◽  
Normal Fertilization

As populations decline to levels where reproduction among close genetic relatives becomes more probable, subsequent increases in homozygous recessive deleterious expression and/or loss of heterozygote advantage can lead to inbreeding depression. Here, we measure how inbreeding across replicate lines of the flour beetle Tribolium castaneum impacts on male reproductive fitness in the absence or presence of male–male competition. Effects on male evolution from mating pattern were removed by enforcing monogamous mating throughout. After inbreeding across eight generations, we found that male fertility in the absence of competition was unaffected. However, we found significant inbreeding depression of sperm competitiveness: non-inbred males won 57 per cent of fertilizations in competition, while inbred equivalents only sired 42 per cent. We also found that the P 2 ‘offence’ role in sperm competition was significantly more depressed under inbreeding than sperm ‘defence’ (P 1 ). Mating behaviour did not explain these differences, and there was no difference in the viability of offspring sired by inbred or non-inbred males. Sperm length variation was significantly greater in the ejaculates of inbred males. Our results show that male ability to achieve normal fertilization success was not depressed under strong inbreeding, but that inbreeding depression in these traits occurred when conditions of sperm competition were generated.

Influence of density and major histocompatibility genotype on sexual selection in a salmonid alternative mating strategy

2012 ◽  
Vol 69 (4) ◽  
pp. 670-680 ◽  
Author(s):  
Laura K. Weir ◽  
Jeffrey A. Hutchings ◽  
Daniel D. Heath
Keyword(s):  
Sexual Selection ◽  
Salmo Salar ◽  
Fertilization Success ◽  
Mating Strategy ◽  
Male Mating ◽  
Salmonid Fishes ◽  
Major Histocompatibility ◽  
Main Determinant ◽  
Alternative Mating Strategy

Various mechanisms of sexual selection can occur at both the whole organism and gamete levels. Fertilization success in salmonid fishes is largely determined by behavioural competition within and between “fighter” and “sneaker” male strategies, but is also influenced by interactions among gametes. We investigated the influence of density, fighter male presence, and major histocompatibility (MH) genotype on patterns of fertilization success in sneaker Atlantic salmon ( Salmo salar ). At low density and in the absence of fighter males, monopolization by single sneaker males occurred, suggesting that male–male competition was the main determinant of fertilization success. By contrast, at high density and (or) in the presence of fighter males, several sneakers succeeded in fertilizing eggs. Our study, the first to investigate the role of MH-mediated fertilization for a genetically based alternative male mating strategy, suggests that a larger proportion of eggs were fertilized by sneakers whose MH genotypes were more similar to those of the female than expected by chance. These findings highlight the importance of examining sexual selection under different competitive conditions.

scholarly journals Atlantic salmon eggs favour sperm in competition that have similar major histocompatibility alleles

2008 ◽  
Vol 276 (1656) ◽  
pp. 559-566 ◽  
Author(s):  
Sarah E Yeates ◽  
Sigurd Einum ◽  
Ian A Fleming ◽  
Hendrik-Jan Megens ◽  
René J.M Stet ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Sperm Competition ◽  
Fertilization Success ◽  
Class I ◽  
Egg Recognition ◽  
Major Histocompatibility ◽  
Sperm Velocity ◽  
Paired Male ◽  
Unexpected Findings

Polyandry and post-copulatory sexual selection provide opportunities for the evolution of female differential sperm selection. Here, we examined the influence of variation in major histocompatibility (MH) class I allelic composition upon sperm competition dynamics in Atlantic salmon. We ran in vitro fertilization competitions that mimicked the gametic microenvironment, and replicated a paired-male experimental design that allowed us to compare differences in sperm competition success among males when their sperm compete for eggs from females that were genetically either similar or dissimilar at the MH class I locus. Concurrently, we measured variation in spermatozoal traits that are known to influence relative fertilization success under these conditions. Contrary to the findings demonstrating mechanisms that promote MH complex heterozygosity, our results showed that males won significantly greater relative fertilization success when competing for eggs from genetically similar females at the MH class I. This result also showed covariation with the known influences of sperm velocity on relative fertilization success. We discuss these unexpected findings in relation to sperm–egg recognition and hybridization avoidance mechanisms based upon immunogenetic variation.

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