scholarly journals Sperm competition games: optimal sperm allocation in response to the size of competing ejaculates

2006 ◽  
Vol 274 (1607) ◽  
pp. 209-217 ◽  
Author(s):  
Leif Engqvist ◽  
Klaus Reinhold
Keyword(s):  
Sperm Competition ◽  
Negative Correlation ◽  
Competitive Ability ◽  
Sperm Storage ◽  
Competition Intensity ◽  
Mating Partner ◽  
Storage Model ◽  
Sperm Allocation ◽  
Competition Theory ◽  
Different Levels

Sperm competition theory predicts that when males are certain of sperm competition, they should decrease sperm investment in matings with an increasing number of competing ejaculates. How males should allocate sperm when competing with differently sized ejaculates, however, has not yet been examined. Here, we report the outcomes of two models assuming variation in males' sperm reserves and males being faced with different amounts of competing sperm. In the first ‘spawning model’, two males compete instantaneously and both are able to assess the sperm competitive ability of each other. In the second ‘sperm storage model’, males are sequentially confronted with situations involving different levels of sperm competition, for instance different amounts of sperm already stored by the female mating partner. In both of the models, we found that optimal sperm allocation will strongly depend on the size of the male's sperm reserve. Males should always invest maximally in competition with other males that are equally strong competitors. That is, for males with small sperm reserves, our model predicts a negative correlation between sperm allocation and sperm competition intensity, whereas for males with large sperm reserves, this correlation is predicted to be positive.

scholarly journals Male-derived cuticular hydrocarbons signal sperm competition intensity and affect ejaculate expenditure in crickets

2008 ◽  
Vol 276 (1655) ◽  
pp. 383-388 ◽  
Author(s):  
Melissa L Thomas ◽  
Leigh W Simmons
Keyword(s):  
Sperm Competition ◽  
Chemical Cues ◽  
Relative Concentration ◽  
Virgin Female ◽  
Male Mating ◽  
Competition Intensity ◽  
Competition Theory ◽  
Fitness Advantage ◽  
First Time ◽  
Sexual Promiscuity

Female sexual promiscuity can have significant effects on male mating decisions because it increases the intensity of competition between ejaculates for fertilization. Because sperm production is costly, males that can detect multiple matings by females and allocate sperm strategically will have an obvious fitness advantage. The presence of rival males is widely recognized as a cue used by males to assess sperm competition. However, for species in which males neither congregate around nor guard females, other more cryptic cues might be involved. Here, we demonstrate unprecedented levels of sperm competition assessment by males, which is mediated via the use of chemical cues. Using the cricket Teleogryllus oceanicus , we manipulated male perception of sperm competition by experimentally coating live unmated females with cuticular compounds extracted from males. We found that males adjusted their ejaculate allocation in response to these compounds: the viability of sperm contained within a male's ejaculate decreased as the number of male extracts applied to his virgin female partner was increased. We further show that males do not respond to the relative concentration of male compounds present on females, but rather to the number of distinct signature odours of individual males. Our results conform to sperm competition theory, and show for the first time, to our knowledge, that males can detect different intensities of sperm competition by using distinct chemical cues of individual males present on females.

scholarly journals Virility does not Imply Immensity: Testis size, Accessory Gland Size and Ejaculate depletion pattern do not Evolve in Response to Experimental Manipulation of Sex Ratio in Drosophila melanogaster

2015 ◽  
Author(s):  
◽  
Zeeshan Ali Syed ◽  
N G Prasad
Keyword(s):  
Drosophila Melanogaster ◽  
Sex Ratio ◽  
Sperm Competition ◽  
Competitive Ability ◽  
Experimental Manipulation ◽  
Reproductive Organ ◽  
Accessory Gland ◽  
Testis Size ◽  
Gland Size ◽  
Competition Theory

Sperm competition theory predicts that increase in sperm competition should result in bigger male reproductive organ(s) or higher ejaculate investment. We test this idea using experimental evolution in Drosophila melanogaster. We maintained replicate populations of Drosophila under male (M) and female (F) biased sex ratio regimes for more than a hundred generations. Males in M regime have evolved higher sperm competitive ability than those in F. We measured the testes and the accessory gland size of virgin and singly mated males from the M and F populations. The M and F males do not differ in either testis or accessory gland size. Additionally, ejaculate investment is not different in the M and F males, as measured by reduction in testis and accessory gland sizes. Thus, contrary to theoretical prediction and evidence from other species, evolved differences in sperm competitive ability is not due to evolution of testis/accessory gland size or strategic ejaculate investment in these populations.

scholarly journals Genotype-by-environment interactions for seminal fluid expression and sperm competitive ability

2019 ◽  
Author(s):  
Bahar Patlar ◽  
Steven A. Ramm
Keyword(s):  
Sperm Competition ◽  
Natural Variation ◽  
Competitive Ability ◽  
Seminal Fluid ◽  
Expression Level ◽  
Mating Partner ◽  
Genotype By Environment Interactions ◽  
Genotype By Environment ◽  
Genetic And Environmental Factors ◽  
Paternity Success

AbstractSperm competition commonly occurs whenever females mate multiply, leading to variation in male paternity success. This can be due to variation in the various traits that might affect sperm competitive ability, which itself depends on both genetic and environmental factors, as well as on genotype-by-environment interactions (GEI). Seminal fluid is a major component of the male ejaculate that is often expected to mediate sperm competition, where different genotypes can differ in their seminal fluid expression as a response to different level of sperm competition (i.e., exhibit GEI). We therefore here focussed on testing for GEI in expression of two recently identified seminal fluid transcripts,suckless-1andsuckless-2, which potentially modulate sperm competitive ability in the simultaneously hermaphroditic flatwormMacrostomum lignanovia their effects on manipulating post-mating partner behaviour and ultimately the fate of transferred ejaculates. In addition, we sought to test for GEI in sperm competitive ability, to investigate the relationship between natural variation in the expression of these seminal fluid transcripts generated through GEI and relative paternity success. To do so, we manipulated social group size, which has been shown to successfully alter sperm competition level inM. lignano, in a set of inbred lines (genotypes) and then measured both the expression level ofsuckless-1andsuckless-2in focal worms together with their relative paternity success in a standardised sperm competition (P1&P2) assay. We found GEI for the expression level ofsuckless-1andsuckless-2, as well as for sperm competitive ability. Moreover, we found a positive relation between the expression ofsuckless-1and paternity success. This suggests that natural variation in the expression of this seminal fluid transcript indeed can influence sperm competition outcomes inM. lignano.

scholarly journals Functional morphology of immature mating in a widow spider

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Lenka Sentenská ◽  
Aileen Neumann ◽  
Yael Lubin ◽  
Gabriele Uhl
Keyword(s):  
Sperm Competition ◽  
Storage Conditions ◽  
Sperm Storage ◽  
Sperm Transfer ◽  
Costs And Benefits ◽  
Micro Computed Tomography ◽  
Mating Tactics ◽  
Adult Females ◽  
Storage Organs ◽  
Widow Spider

Abstract Background Mating generally occurs after individuals reach adulthood. In many arthropods including spiders, the adult stage is marked by a final moult after which the genitalia are fully developed and functional. In several widow spider species (genus Latrodectus), however, immature females may mate a few days before they moult to adulthood, i.e. in their late-subadult stage. While the “adult” mating typically results in cannibalism, males survive the “immature” mating. During both “immature” and “adult” matings, males leave parts of their paired copulatory organs within female genitalia, which may act as mating plugs. To study potential costs and benefits of the two mating tactics, we investigated female genital morphology of the brown widow spider, L. geometricus. Light microscopy, histology and micro-computed tomography of early-subadult, late-subadult and adult females were conducted to determine the overall pattern of genital maturation. We compared genitalia of mated late-subadult and adult females to reveal potential differences in the genitalic details that might indicate differential success in sperm transfer and different environments for sperm storage and sperm competition. Results We found that the paired sperm storage organs (spermathecae) and copulatory ducts are developed already in late-subadult females and host sperm after immature mating. However, the thickness of the spermathecal cuticle and the staining of the secretions inside differ significantly between the late-subadult and adult females. In late-subadult females mating plugs were found with higher probability in both spermathecae compared to adult females. Conclusions Sperm transfer in matings with late-subadult females follows the same route as in matings with adult females. The observed differences in the secretions inside the spermathecae of adult and late-subadult females likely reflect different storage conditions for the transferred sperm which may lead to a disadvantage under sperm competition if the subadult female later re-mates with another male. However, since males mating with late-subadult females typically transfer sperm to both spermathecae they might benefit from numerical sperm competition as well as from monopolizing access to the female sperm storage organs. The assessment of re-mating probability and relative paternity will clarify the costs and benefits of the two mating tactics in light of these findings.

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.

How biases in sperm storage relate to sperm use during oviposition in female yellow dung flies

2021 ◽  
Author(s):  
Marco Demont ◽  
Paul I Ward ◽  
Wolf U Blanckenhorn ◽  
Stefan Lüpold ◽  
Oliver Y Martin ◽  
...  
Keyword(s):  
Sperm Competition ◽  
Sperm Storage ◽  
Adaptive Plasticity ◽  
Strongly Correlated ◽  
Scathophaga Stercoraria ◽  
General Importance ◽  
Copula Duration ◽  
Mixed Paternity ◽  
Paternity Success ◽  
The Relationship

Abstract Precise mechanisms underlying sperm storage and utilization are largely unknown, and data directly linking stored sperm to paternity remain scarce. We used competitive microsatellite PCR to study the effects of female morphology, copula duration and oviposition on the proportion of stored sperm provided by the second of two copulating males (S2) in Scathophaga stercoraria (Diptera: Scathophagidae), the classic model for sperm competition studies. We genotyped all offspring from potentially mixed-paternity clutches to establish the relationship between a second male’s stored sperm (S2) and paternity success (P2). We found consistent skew in sperm storage across the three female spermathecae, with relatively more second-male sperm stored in the singlet spermatheca than in the doublet spermathecae. S2 generally decreased with increasing spermathecal size, consistent with either heightened first-male storage in larger spermathecae, or less efficient sperm displacement in them. Additionally, copula duration and several two-way interactions influenced S2, highlighting the complexity of postcopulatory processes and sperm storage. Importantly, S2 and P2 were strongly correlated. Manipulation of the timing of oviposition strongly influenced observed sperm-storage patterns, with higher S2 when females laid no eggs before being sacrificed than when they oviposited between copulations, an observation consistent with adaptive plasticity in insemination. Our results identified multiple factors influencing sperm storage, nevertheless suggesting that the proportion of stored sperm is strongly linked to paternity (i.e., a fair raffle). Even more detailed data in this vein are needed to evaluate the general importance of sperm competition relative to cryptic female choice in postcopulatory sexual selection.

Current Sperm Competition Determines Sperm Allocation in a Tephritid Fruit Fly

Ethology ◽  
2015 ◽  
Vol 121 (5) ◽  
pp. 451-461 ◽  
Author(s):  
Solana Abraham ◽  
M. Teresa Vera ◽  
Diana Pérez-Staples
Keyword(s):  
Sperm Competition ◽  
Fruit Fly ◽  
Sperm Allocation

Multiple Matings and Sperm Competition

2020 ◽  
pp. 332-363
Author(s):  
Carola Becker ◽  
Raymond T. Bauer
Keyword(s):  
Genetic Diversity ◽  
Sperm Competition ◽  
Mate Guarding ◽  
Sperm Storage ◽  
Internal Fertilization ◽  
Multiple Matings ◽  
Storage Organs ◽  
Anatomical Adaptations ◽  
Multi Level ◽  
Molecular Aspects

In polyandrous mating systems, females mate multiple times and males have evolved adaptations for sperm competition which increase the number and fitness of their offspring. Mate guarding is a widespread monopolization strategy in groups where female receptivity is temporally restricted and often associated with the molt. Precopulatory guarding occurs in branchipods, copepods, peracarids and decapods. Postcopulatory guarding is notable in numerous brachyurans with males protecting females until her exoskeleton has hardened. During copulation, male success in fertilization depends on an effective sperm transfer mechanism, the precise placement of ejaculates closest to where female gametes are fertilized. Male copulatory systems are highly diverse and strongly adapted to these tasks, especially the structures that interact with the female genital ducts. The elaborate tips of brachyuran gonopods are supposed to act in the displacement, possibly even in the removal of rival sperm masses; however, sperm removal is only evident in crayfish: males eat spermatophores previously deposited by other males. During copulation of several crustacean groups, males transfer secretions that harden and form a sealant. These sperm plugs, plaques and gel layers may protect their own sperm, prevent remating or seal off rival sperm from the site of fertilization. Several groups of isopods and decapods have internal insemination, elaborate sperm storage organs and some exhibit internal fertilization. The intensity of sperm competition increases with the latency between the processes of insemination and fertilization. This chapter gives on overview on mate guarding, male sealants and the anatomical adaptations to sperm competition in crustaceans. We also briefly discuss the consequences of multiple matings for the genetic diversity of broods, i.e., single vs. multiple paternities. There is still a lack of data for many crustacean groups. Moreover, it is often hard to assess how successful a male strategy to ensure paternity actually is as many studies focus on either the behavioral, anatomical, or molecular aspects, while comprehensive multi-level studies on crustacean sperm competition are virtually absent from the literature.

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