In this article, we provide a concise review of the past and current literature on the neglected influence of progesterone on male sexual behavior. Although there has been increased interest in all aspects of male sexual function, and the importance of androgens in the regulation of male copulatory behavior has long been well documented, knowledge of the role of progesterone on male sexual behavior is still patchy. Very little human data exist on this theme, and most of the literature concerns animal research, in particular reptiles and rodents. This review attempts to outline specific progesterone mechanisms involved in male sexual behavior, showing that this hormone plays a more relevant role in the control of male sexual behavior than commonly assumed. Exploring the neuroendocrine mechanisms of progesterone in the sexual behavior of males may provide insights into the regulation of sexuality in this gender. (c) 2005 Elsevier B.V. All rights reserved ...
There are two reasons why researchers are interested in the phenotypic relationship between the expression of male secondary sexual characters (SSCs) and ejaculate quality (defined as sperm/ejaculate traits that are widely assumed to increase female fertility and/or sperm competitiveness). First, if the relationship is positive then females could gain a direct benefit by choosing more attractive males for fertility assurance reasons (the phenotype-linked fertility hypothesis). Second, there is much interest in the direction of the correlation between traits favoured by pre-copulatory sexual selection (i.e. affecting mating success) and those favoured by post-copulatory sexual selection (i.e. increasing sperm competitiveness). If the relationship is negative this could lead to the two forms of selection counteracting each other. Theory predicts that the direction of the relationship could be either positive or negative depending on the underlying genetic variance and covariance in each trait, ...
A large body of literature has centred on whether female resistance evolves as a result of sexual conflict or as a form of female choice for superior mates (also known as resistance as a screen, or resistance as choice) [50,101-103]. According to this hypothesis, open-ended female resistance will ensure that a female copulates only with dominant males that are best able to overcome female resistance; male offspring will be superior competitors/coercers, and female resistance will evolve through the indirect benefits of their superior coercive male offspring [50,101-103]. This type of screening has been hypothesized to occur during pre-copulatory struggles, and during and/or after copulation via cryptic female choice mechanisms [50]. The main argument against the resistance as a screen hypothesis is that the magnitude of the direct costs imposed by coercive males may be much greater than the magnitude of any potential indirect benefit that females may gain [56], but this issue is far from ...
Male contests for access to receptive females are thought to have selected for the larger male body size and conspicuous weaponry frequently observed in mammalian species. However, when females copulate with multiple males within an oestrus, male reproductive success is a function of both pre- and post-copulatory strategies. The relative importance of these overt and covert forms of sexual competition has rarely been assessed in wild populations. The Soay sheep mating system is characterized by male contests for mating opportunities and high female promiscuity. We find that greater horn length, body size and good condition each independently influence a males ability to monopolize receptive females. For males with large horns at least, this behavioural success translates into greater siring success. Consistent with sperm-competition theory, we also find that larger testes are independently associated with both higher copulation rates and increased siring success. This advantage of larger testes ...
In this study, we show for both sexes of the dark-eyed junco that EPO have higher lifetime reproductive success than WPO. To our knowledge, this is the first case in which EPP has been shown to increase lifetime reproductive success of adult offspring in a free-living songbird. In the only similar previous study, the reproductive success of adult female F1 EPO coal tits (Parus ater) did not differ from that of female F1 WPO, and adult male F1 EPO had lower apparent (social) reproductive success than did male F1 WPO. However, extra-pair siring success of F1 males was not measured, and therefore adult genetic reproductive success could not be calculated [16-18].. In many species, there is no obvious benefit to female fitness from mating with an extra-pair male, and some have even hypothesized that extra-pair mating should carry a cost to offspring production or survival [34,35] (although not in juncos [21]; see also [36]). This lack of a cost to females, combined with the observed twofold benefit ...
The realization of polyandry is also contributing to a much more dynamic view of social conflicts. The most obvious forms of conflict relevant to polyandry are conflicts arising among members of the same sex and between males and females over reproductive decisions.. On the one hand, polyandry creates potential for conflict over some reproductive decisions such as cryptic female choice and parental care. On the other hand, it may reduce potential for sexual conflict over other reproductive decisions such as mating rates by weakening the male and increasing the female Bateman gradient. Although the notion that polyandry creates potential for intra- and inter-sexual conflict is not new, studies of sexual conflict have up until recently ignored the diversity of proximate mechanisms through which mating and sperm competition can impact female fitness. These mechanisms can have fundamental repercussions for the fitness pay-offs of sexual rivals and sexual partners. For example, the gonadotropic ...
The genome of an infant who lived in Alaska thousands of years ago represents a previously unknown group of humans called Ancient Beringians, who share a common lineage with other Native Americans. 0 Comments. ...
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and variety of mates increases a females chance to produce more viable offspring. However, multiple mates for a female means an individual male has decreased chances of producing offspring. Sperm competition is an evolutionary pressure on males, and has led to the development of adaptations to increase males chance of reproductive success. Sperm competition results in a sexual conflict of interest between males and females. Males have evolved several defensive tactics including: mate-guarding, mating plugs, and releasing toxic seminal substances to reduce female re-mating tendencies to cope with sperm competition. Offensive tactics of sperm competition involve direct interference by one male on the reproductive success of another male, for instance by ...
The seminal fluid of male Drosophila contains a cocktail of proteins that have striking effects on male and female fitness. In D. melanogaster, seminal fluid proteins affect female receptivity, ovulation, oogenesis, sperm storage, sperm competition and mating plug formation. In addition, the seminal fluid contains antibacterial peptides and protease inhibitors. Some seminal fluid-encoding genes also show high rates of evolutionary change, exhibiting both significant between-species divergence and within-species polymorphism. Seminal fluid protein genes are expressed only in males, begging the question of how and why the reproductive processes of females are influenced by males. In this review I address these issues by bringing together evidence for the function, evolution, diversification, and maintenance of variation in, seminal fluid-mediated traits.
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This study showed that two reproductive hormones from different chemical classes, PGF2α and E2, stimulate sexual displays in females of a single fish species. PGF2α, in particular, was very effective in recovering sexual behaviours after ovariectomy. The injection of this hormone 45 min before testing into females ovariectomized 7 days before, recovered the frequency of both female approaches to the males nest and courtship displays towards the nesting male to levels similar to those of intact sham females. The positive effect of this hormone on nuptial coloration was, however, less pronounced. The role of prostaglandins in the induction of sexual behaviour in females has been demonstrated in several fishes with external fertilization: paradise fish, Macropodus opercularis [32], black acara Cichlasoma bimaculatum [33] and barb Puntius gonionotus [34]. Interestingly, administration of PGF2α to non-receptive females of the anuran Bufo americanus induced female phonotaxis behaviour towards male ...
Whether females can obtain genetic benefits from mate choice is contentious, and the main problem faced by previous studies of natural populations is that many factors other than paternal genes contribute to offspring fitness. Here, we use comparisons bet. ...
DA stresses that colour vision is very important in primates, not only because colour is used in sexual displays such as advertising a females receptiveness to mating [p. 275], but also to identify ripe fruit [p.247] and to select nutritious leaves [p. 255]. This section discusses these points in more detail and explains how the visual system in primates is able to detect colour.. White light is composed of light of different wavelengths, from 300-800 nanometres (nm); 1 nm is on ...
Although I enjoyed this paper quite a bit, and it seemed perfect fodder for some clever fun in photoshop (actually by E. Lu, see above), I also felt that that the study had some methodologically weak areas. For instance, the authors failed to take advantage of a new phylogenetic logistic regression procedure by Ives & Garland [2010], which seems ideally suited to their data. (In their defense, the method is brand new.) Consequently, however, the authors found themselves of the unfortunate position of using an arbitrary scoring system to estimate size-related reproductive skew: adding 1 point for the presence of "pronounced sexual dichromatism," for example, and subtracting 1 point for "alternative reproductive tactics" (which might decrease the advantage of large male size) . With a phylogenetic multivariable logistic regression, the authors could have tested for an association between the log-odds of protogyny and each of their proxies for size-based reproductive skew (which also included ...
Hear girl complaining about how men are pigs Explain that its partly her fault, since female mate selection determines course of evolution Science Major Mouse
Sex differences in brain structure and function are widespread (Jazin and Cahill, 2010) and analysis of their functional significance has become a priority in the neurosciences (Clayton and Collins, 2014). Interestingly, these sex differences also affect rapid brain estrogen effects (Krentzel and Remage-Healey, 2015). Blocking brain estrogen action/synthesis decreases male sexual motivation within minutes without affecting sexual performance in quail (Seredynski et al., 2013). Here we confirm that blockade of brain aromatase acutely and robustly alters male sexual motivation. This effect is prevented within 15 min by a central injection of E2 or a specific agonist of ERβ, but not of ERα. Furthermore, E2 cannot restore this behavior when mGluR1a is blocked. Together with the previous demonstration that these effects are membrane initiated (Seredynski et al., 2013), the acute modulation of sexual motivation by E2 thus seems to depend on its binding to membrane ERβ, leading to the ...
(13-10-2014 03:27 PM)Forbes Wrote: (13-10-2014 03:25 PM)Nurse Wrote: To be fair, I did read the lists. Im not impressed. It was poorly written click bait. Hardly the scientific evidence that you es
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Our research group studies the quantitative and molecular genetics of sexual behaviour in the zebra finch to address fundamental questions in evolutionary biology. One of our main interests lies in the understanding of genes that contribute to sexually antagonistic evolution. For instance, we ask, what are the effects of genes that increase male promiscuity (and hence male fitness), on female promiscuity, female fecundity, but also on male and female parental qualities. These and many other questions are addressed using long term data on a very large captive population of zebra finches. Extensive observational data on extra-pair courtships in a communal aviary setting are complemented with breeding of selection lines and large-scale SNP genotyping that allows us to conduct QTL mapping and subsequent study of candidate genes involved the behaviours that lie at the core of sexual selection ...
How your Glands affect your Sexual Performance. How your Glands affect Your Sexual Performance. Dr. Wu Dhis program on Sexual Qi Gong is ...
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Waxman AR, Juni A, Kowalczyk W, Arout C, Sternberg WF, Kest B (2010). Progesterone rapidly recruits female-typical opioid-induced hyperalgesic mechanisms. Physiology and Behavior, 101(5), 759-763.. ...
New research indicates that the genetic quality of sperm worsens as men get older, increasing a mans risk of being infertile, fathering unsucces
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The first rule of thumb in any diet is balancing calories. This is just as important in a female fitness competition diet as in any other. You want to eat only as many calories as you burn in your workouts. If you still need to burn extra fat, you need to burn more calories than you eat, which is accomplished by either eating fewer calories or burning more in your workouts.. You should be eating 10 to 12 times your body weight in calories for a female fitness competition diet. If your body weight changes, your calorie intake should as well. Divide your calories using the following method:. ...
Recent studies show early exposure to BPA can change male behavior in adulthood. Male mice showed less masculine behavior (less territorial marking).
Typically this sort of thing doesnt faze me too much, as I encounter all sorts of things on a given day. In this case, its been a problem because it happens with regularity but more importantly hes a big dog -- weighing in at around 90 pounds -- and its not fun to be pummeled by that much force. In fact, the first time that it happened, I wasnt expecting it and I face-planted into the snow. Thats not something that anyone wants or needs to happen ...
Remarkably, we have actually kind of obtained a similar result in one of our previous study (Svensson et al. 2006 Evolution), where we found that strong divergent sexual selection was accompanied by a significant decrease of female response towards conspecifics from other populations. This is corroborated by another study yet from our group, that found reduced gene flow between some of these populations (Svensson et al. 2004 Heredity), like it has been found in other systems (Rice and Pfennig 2010). I had myself never really thought about it that way, and this opened my mind a lot I must say on what Erik and others of our group have done in the past. And what about learning then? Well, we know it is likely to play an important role in divergence of mate preferences in our system (Svensson et al. 2010 Evolution), and all things considered it might even facilitate this process, as mate choice may change faster and thus the constraining effects of gene flow in the early stages will then not be an ...
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In Chapter 9, "Darwin in Denial," author Tim Birkhead explains how Darwins failure to recognize avian female promiscuity resulted in a century of misconceptions about sexual selection. 0 Comments. ...
by Vetscite. It may be hard to imagine competing over who gets to kiss a frog, but when it comes to mating, a new study concludes that some frogs have moved out of the pond onto land to make it easier for the male in the pair to give sexual rivals the slip.. Biologists have long thought that some frog species evolved to mate on land - sometimes in unusual places - instead of in open water to better guard eggs and tadpoles from easily being eaten by fish and other predators. But the new research by a team of U.S. and Brazilian frog biologists suggests that mating on land in many species might in part be a strategy that male frogs use to ensure that their own DNA gets passed on, instead of the DNA of their rivals. Sexual selection may trump natural selection in the evolution of these reproductive behaviors, according to the new study, to be published online ahead of print on July 26 in The American Naturalist.. Frogs have a "dizzying array" of reproductive strategies, according to Rayna Camille ...
UPDATE: Got a temper? Get some sneaks to match your bad attitude. Find these EQTs dropping at select stockists tomorrow, June 7.. For those that remember the illustrious player days of Keyshawn Johnson, the Bad Attitude moniker attached to this newest colourway should be no surprise - and if you dont remember, its really a no brainer. Reflective of Johnsons fiery temperament, the OG hues of white and green get dropped for this more spicy black and red combination. Mostly subdued up high, the focal point is the animalistic patterning that dons the bulbous outsole. A welcome addition to an already strong sneaker lineage, those fiending these can find themselves a pair over at Oneness.. - Originally published June 2, 2014. ...
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OK, so I really should have posted this one on Valentines Day. But better late than never, right? The journal Personality and Individual Differences just published an article called Chat-up Lines as Male Sexual Displays, which analyzes the results of a questionnaire in which respondents were asked to rank pick-up lines. The article requires a subscription, but you can view the list of pickup lines at http://psy-web.psy.ed.ac.uk/people/pcaryl/pgcresearchitems/ECUS40b.txt. Some are classic, cheesy lines ("Well hey there, I may not be Fred Flintstone, but I bet I can make your Bed Rock!"), but others are mini-scenarios. Heres the bottom line, from the article abstract ...
Aepyprymnus rufescens is polyestrous, with an estrus cycle occurring approximately every 34 days. Breeding can occur at any time during the year, but there is insufficient data from both captive and wild species to indicate a particular breeding season. Females reach sexual maturity in the 11th month, males between 12 and 13 months. Males visit female nests within their territory every night to determine if the female is sexually receptive. As the female approaches ovulation, the male waits either by the female or by her nest until she is sexually receptive. Both sexes can let out low growls during investigational behavior, which usually includes sniffing of the female by the male. A receptive female allows the male to smell her cloacal and pouch areas, and eventually permits copulation (Ganslosser, 1990).. Males will try to mount the female regardless of warning signals exhibited by unreceptive females. These females try to drive away courting males by making loud growling sounds, striking at ...
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