7,763 research outputs found
Female control over multiple matings increases the opportunity for postcopulatory sexual selection
No full textIt is widely acknowledged that in most species sexual selection continues after mating. Although it is generally accepted that females play an important role in generating paternity biases (i.e., cryptic female choice), we lack a quantitative understanding of the relative importance of female-controlled processes in influencing variance in male reproductive fitness. Here we address this question experimentally using the guppy Poecilia reticulata, a polyandrous fish in which pre- and postcopulatory sexual selection jointly determine male reproductive fitness. We used a paired design to quantify patterns of paternity for pairs of rival males across two mating contexts, one in which the female retained full control over double (natural) matings and one where sperm from the same two males were artificially inseminated into the female. We then compared the relative paternity share for a given pair of males across both contexts, enabling us to test the key prediction that patterns of paternity will depend on the extent to which females retain behavioural control over matings. As predicted, we found stronger paternity biases when females retained full control over mating compared to when artificial insemination was used. Concomitantly, we show that the opportunity for postcopulatory sexual selection (standardised variance in male reproductive success) was greater when females retained control over double matings compared to when artificial insemination was used. Finally, we show that the paternity success of individual males exhibited higher repeatability across successive brood cycles when females retained behavioural control of matings compared to when AI was used. Collectively, these findings underscore the critical role that females play in determining the outcome of sexual selection and to our knowledge provide the first experimental evidence that behaviourally moderated components of cryptic female choice increase the opportunity for sexual selection
Chiral dynamics from AdS space
No full textWe study the low energy dynamics of pions in a gravity dual of chiral symmetry breaking. The string theory construction consists of a probe D7 brane in the Constable-Myers nonsupersymmetric background, which has been shown to describe chiral symmetry breaking in the pattern of QCD. We expand the D7 brane's Dirac-Born-Infeld action for fluctuations that correspond to the Goldstone mode and show that they take the form of a nonlinear chiral Lagrangian. We numerically compute the quark condensate, pion decay constant, and higher order Gasser-Leutwyler coefficients. We find their form is consistent with naive dimensional analysis estimates. We also explore the gauging of the quark's chiral symmetries and the vector meson spectrum. <br/
R v Evans (Gemma) [2009] EWCA Crim 650, Court of Appeal
No full textEssential Cases: Criminal Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in R v Evans (Gemma) [2009] EWCA Crim 650, Court of Appeal. The document also included supporting commentary from author Jonathan Herring.</p
Evans, Daniel-Residence, Lehi P.1
No full text8513 Daniel Evans house, Lehi, Utah. Gift of Jonathan Fairbanks
Extreme fertilization bias towards freshly inseminated sperm in a species exhibiting prolonged female sperm storage
No full textThe storage of sperm by females across successive reproductive cycles is well documented in internal fertilisers, yet the fate of stored sperm when they compete with ‘new’ sperm to fertilise a female’s eggs has rarely been considered. This gap in our understanding is likely due to the logistical difficulties of controlling behavioural interactions during or after mating, which in turn may influence how many sperm are inseminated and how stored sperm are ultimately utilised during successive bouts of sperm competition with freshly inseminated sperm. Here, we use artificial insemination (AI) in guppies (Poecilia reticulata), a polyandrous livebearing poeciliid fish exhibiting prolonged sperm storage by females, to overcome these challenges. The use of AI enables us to control potential differential maternal effects (e.g. behaviourally mediated cryptic female choice) and specifically test for post-copulatory paternity biases that favour either stored or fresh sperm when they compete to fertilise eggs. Our paternity analyses revealed the almost complete dominance of freshly inseminated sperm over stored sperm, supporting previous studies reporting similar patterns following natural matings across successive brood cycles. However, our use artificial inseminations, which excluded behavioural interactions between males and females, most likely generated a far stronger pattern of fresh sperm precedence compared to those reported in previous studies, possibly implicating ‘cryptic’ forms of selection by females that may sometimes bolster the success of stored sperm
Sperm storage by males causes changes in sperm phenotype and influences the reproductive fitness of males and their sons
No full textRecent studies suggest that environmentally induced effects on sperm phenotype can influence offspring phenotype beyond the classic Mendelian inheritance mechanism. However, establishing whether such effects are conveyed purely through ejaculates, independently of maternal environmental effects, remains a significant challenge. Here, we assess whether environmentally induced effects on sperm phenotype affects male reproductive success and offspring fitness. We experimentally manipulated the duration of sperm storage by males, and thus sperm age, in the internally fertilizing fish Poecilia reticulata. We first confirm that sperm ageing influences sperm quality and consequently males reproductive success. Specifically, we show that aged sperm exhibit impaired velocity and are competitively inferior to fresh sperm when ejaculates compete to fertilize eggs. We then used homospermic (noncompetitive) artificial insemination to inseminate females with old or fresh sperm and found that male offspring arising from fertilizations by experimentally aged sperm suffered consistently impaired sperm quality when just sexually mature (four months old) and subsequently as adults (13 months old). Although we have yet to determine whether these effects have a genetic or epigenetic basis, our analyses provide evidence that environmentally induced variation in sperm phenotype constitutes an important source of variation in male reproductive fitness that has far reaching implications for offspring fitness
The role of female reproductive fluid in sperm competition
No full textThe role of non-gametic components of the ejaculate (seminal fluid) in fertility and sperm competitiveness is now well established. Surprisingly, however, we know far less about female reproductive fluid (FRF) in the context of sexual selection, and insights into male-FRF interactions in the context of sperm competition have only recently emerged. Despite this limited knowledge, evidence from taxonomically diverse species has revealed insights into the effects of FRF on sperm traits that have previously been implicated in studies of sperm competition. Specifically, through the differential effects of FRF on a range of sperm traits, including chemoattraction and alterations in sperm velocity, FRF has been shown to exert positive phenotypic effects on the sperm of males that are preferred as mating partners, or those from the most compatible or genetically diverse males. Despite these tantalizing insights into the putative sexually selected functions of FRF, we largely lack a mechanistic understanding of these processes. Taken together, the evidence presented here highlights the likely ubiquity of FRF-regulated biases in fertilization success across a diverse range of taxa, thus potentially elevating the importance of FRF to other non-gametic components that have so far been studied largely in males. This article is part of the theme issue 'Fifty years of sperm competition'
Towards a perfect QCD gravity dual
No full textMany examples of gravitational duals exist of theories that are highly supersymmetric and conformal in the UV yet have the same massless states as QCD. We discuss such theories with an explicit UV cutoff and propose that, by tuning higher dimension operators at the cutoff by hand, the effects of the extra matter states in the UV may be removed from the IR physics. We explicitly work in the AdS–Schwarzschild description of QCD4 and tune the operator TrF4 by relaxing the near horizon limit to reproduce the lattice 0++ glueball mass results. We find that to reproduce the lattice data, the IR and UV cutoffs lie close to each other and there is essentially no AdS-like period between them. The improved geometry gives a better match to the lattice data for 0?+ glueball masses
Ovarian Fluid Mediates the Temporal Decline in Sperm Viability in a Fish with Sperm Storage
No full textA loss of sperm viability and functionality during sperm transfer and storage within the female reproductive tract can have important fitness implications by disrupting fertilization and impairing offspring development and survival. Consequently, mechanisms that mitigate the temporal decline in sperm function are likely to be important targets of selection. In many species, ovarian fluid is known to regulate and maintain sperm quality. In this paper, we use the guppy Poecilia reticulata, a highly polyandrous freshwater fish exhibiting internal fertilization and sperm storage, to determine whether ovarian fluid (OF) influences the decline in sperm viability (the proportion of live sperm in the ejaculate) over time and whether any observed effects depend on male sexual ornamentation. To address these questions we used a paired experimental design in which ejaculates from individual males were tested in vitro both in presence and absence of OF. Our results revealed that the temporal decline in sperm viability was significantly reduced in the presence of OF compared to a saline control. This finding raises the intriguing possibility that OF may play a role in mediating the decline in sperm quality due to the deleterious effects of sperm ageing, although other possible explanations for this observation are discussed. Interestingly, we also show that the age-related decline in sperm viability was contingent on male sexual ornamentation; males with relatively high levels of iridescence (indicating higher sexual attractiveness) exhibited a more pronounced decline in sperm viability over time than their less ornamented counterparts. This latter finding offers possible insights into the functional basis for the previously observed trade-off between these key components of pre- and postcopulatory sexual selection
Chiral phase transitions and quantum critical points of the D3/D7(D5) system with mutually perpendicular E and B fields at finite temperature and density
No full textWe study chiral symmetry restoration with increasing temperature and density in gauge theories subject to mutually perpendicular electric and magnetic fields using holography. We determine the chiral symmetry breaking phase structure of the D3/D7 and D3/D5 systems in the temperature-density-electric field directions. A magnetic field may break the chiral symmetry and an additional electric field induces Ohm and Hall currents as well as restoring the chiral symmetry. At zero temperature the D3/D5 system displays a line of holographic BKT phase transitions in the density-electric field plane, while the D3/D7 system shows a mean-field phase transition. At intermediate temperatures, the transitions in the density-electric field plane are of first order at low density, transforming to second order at critical points as density rises. At high temperature the transition is only ever first order
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