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Letteratura scientifica selezionata sul tema "Sperrm competition"

Autore: Grafiati

Pubblicato: 5 ottobre 2024

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Articoli di riviste sul tema "Sperrm competition"

André, Gonçalo I., Renée C. Firman e Leigh W. Simmons. "Phenotypic plasticity in genitalia: baculum shape responds to sperm competition risk in house mice". Proceedings of the Royal Society B: Biological Sciences 285, n. 1882 (11 luglio 2018): 20181086. http://dx.doi.org/10.1098/rspb.2018.1086.

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Males are known to adjust their expenditure on testes growth and sperm production in response to sperm competition risk. Genital morphology can also contribute to competitive fertilization success but whether male genital morphology can respond plastically to the sperm competition environment has received little attention. Here, we exposed male house mice to two different sperm competition environments during their sexual development and quantified phenotypic plasticity in baculum morphology. The sperm competition environment generated plasticity in body growth. Males maturing under sperm competition risk were larger and heavier than males maturing under no sperm competition risk. We used a landmark-based geometric morphometric approach to measure baculum size and shape. Independent of variation in body size, males maintained under risk of sperm competition had a relatively thicker and more distally extended baculum bulb compared with males maintained under no sperm competition risk. Plasticity in baculum shape paralleled evolutionary responses to selection from sperm competition reported in previous studies of house mice. Our findings provide experimental evidence of socially mediated phenotypic plasticity in male genitalia.

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Lüke, Lena, Polly Campbell, María Varea Sánchez, Michael W. Nachman e Eduardo R. S. Roldan. "Sexual selection on protamine and transition nuclear protein expression in mouse species". Proceedings of the Royal Society B: Biological Sciences 281, n. 1783 (22 maggio 2014): 20133359. http://dx.doi.org/10.1098/rspb.2013.3359.

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Post-copulatory sexual selection in the form of sperm competition is known to influence the evolution of male reproductive proteins in mammals. The relationship between sperm competition and regulatory evolution, however, remains to be explored. Protamines and transition nuclear proteins are involved in the condensation of sperm chromatin and are expected to affect the shape of the sperm head. A hydrodynamically efficient head allows for fast swimming velocity and, therefore, more competitive sperm. Previous comparative studies in rodents have documented a significant association between the level of sperm competition (as measured by relative testes mass) and DNA sequence evolution in both the coding and promoter sequences of protamine 2. Here, we investigate the influence of sexual selection on protamine and transition nuclear protein mRNA expression in the testes of eight mouse species that differ widely in levels of sperm competition. We also examined the relationship between relative gene expression levels and sperm head shape, assessed using geometric morphometrics. We found that species with higher levels of sperm competition express less protamine 2 in relation to protamine 1 and transition nuclear proteins. Moreover, there was a significant association between relative protamine 2 expression and sperm head shape. Reduction in the relative abundance of protamine 2 may increase the competitive ability of sperm in mice, possibly by affecting sperm head shape. Changes in gene regulatory sequences thus seem to be the basis of the evolutionary response to sexual selection in these proteins.

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Champion de Crespigny, Fleur E., e Nina Wedell. "Wolbachia infection reduces sperm competitive ability in an insect". Proceedings of the Royal Society B: Biological Sciences 273, n. 1593 (21 marzo 2006): 1455–58. http://dx.doi.org/10.1098/rspb.2006.3478.

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The maternally inherited bacterium Wolbachia pipientis imposes significant fitness costs on its hosts. One such cost is decreased sperm production resulting in reduced fertility of male Drosophila simulans infected with cytoplasmic incompatibility (CI) inducing Wolbachia . We tested the hypothesis that Wolbachia infection affects sperm competitive ability and found that Wolbachia infection is indeed associated with reduced success in sperm competition in non-virgin males. In the second male role, infected males sired 71% of the offspring whereas uninfected males sired 82% of offspring. This is the first empirical evidence indicating that Wolbachia infection deleteriously affects sperm competition and raises the possibility that polyandrous females can utilize differential sperm competitive ability to bias the paternity of broods and avoid the selfish manipulations of Wolbachia . This suggests a relationship between Wolbachia infection and host reproductive strategies. These findings also have important consequences for Wolbachia population dynamics because the transmission advantage of Wolbachia is likely to be undermined by sperm competition.

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Hoysak, Drew J., N. Robin Liley e Eric B. Taylor. "Raffles, roles, and the outcome of sperm competition in sockeye salmon". Canadian Journal of Zoology 82, n. 7 (1 luglio 2004): 1017–26. http://dx.doi.org/10.1139/z04-073.

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In species with male alternative reproductive phenotypes, one phenotype is usually disadvantaged in mating competition. In salmonid fishes, large late-maturing males pair with nesting females and maintain close contact before and during spawning. Small early-maturing males have little contact with nesting females and, during spawning, begin to release sperm after the paired male. The effects of male phenotype and timing of ejaculation on success in sperm competition are not known. In this study, we determined paternity of offspring resulting from in vitro competitive fertilizations to examine these two aspects of sperm competition in sockeye salmon, Oncorhynchus nerka (Walbaum, 1792). When we fertilized eggs with mixtures of equal numbers of sperm from each of two male age classes, we found that success in sperm competition did not depend on male age. However, success in these competitive fertilizations did not conform to the fair raffle model of sperm competition, since paternity in most of the clutches was biased in favour of one male. When we added milt from two males sequentially to a batch of eggs, we found that sperm from the second male fertilized fewer eggs than sperm from the first male, but the difference was less than expected. In addition, a male's success when his milt was added first was not correlated with his success when his milt was added second.

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Engqvist, Leif, e Klaus Reinhold. "Sperm competition games: optimal sperm allocation in response to the size of competing ejaculates". Proceedings of the Royal Society B: Biological Sciences 274, n. 1607 (7 novembre 2006): 209–17. http://dx.doi.org/10.1098/rspb.2006.3722.

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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.

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Vuarin, Pauline, Yves Hingrat, Loïc Lesobre, Michel Saint Jalme, Frédéric Lacroix e Gabriele Sorci. "Sperm competition accentuates selection on ejaculate attributes". Biology Letters 15, n. 3 (marzo 2019): 20180889. http://dx.doi.org/10.1098/rsbl.2018.0889.

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Ejaculate attributes are important factors driving the probability of fertilizing eggs. When females mate with several males, competition between sperm to fertilize eggs should accentuate selection on ejaculate attributes. We tested this hypothesis in the North African houbara bustard ( Chlamydotis undulata undulata ) by comparing the strength of selection acting on two ejaculate attributes when sperm from single males or sperm from different males were used for insemination. In agreement with the prediction, we found that selection on ejaculate attributes was stronger when sperm of different males competed for egg fertilization. These findings provide the first direct comparison of the strength of selection acting on ejaculate attributes under competitive and non-competitive fertilizations, confirming that sperm competition is a major selective force driving the evolution of ejaculate characteristics.

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Singson, Andrew, Katherine L. Hill e Steven W. L’Hernault. "Sperm Competition in the Absence of Fertilization in Caenorhabditis elegans". Genetics 152, n. 1 (1 maggio 1999): 201–8. http://dx.doi.org/10.1093/genetics/152.1.201.

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Abstract Hermaphrodite self-fertilization is the primary mode of reproduction in the nematode Caenorhabditis elegans. However, when a hermaphrodite is crossed with a male, nearly all of the oocytes are fertilized by male-derived sperm. This sperm precedence during reproduction is due to the competitive superiority of male-derived sperm and results in a functional suppression of hermaphrodite self-fertility. In this study, mutant males that inseminate fertilization-defective sperm were used to reveal that sperm competition within a hermaphrodite does not require successful fertilization. However, sperm competition does require normal sperm motility. Additionally, sperm competition is not an absolute process because oocytes not fertilized by male-derived sperm can sometimes be fertilized by hermaphrodite-derived sperm. These results indicate that outcrossed progeny result from a wild-type cross because male-derived sperm are competitively superior and hermaphrodite-derived sperm become unavailable to oocytes. The sperm competition assays described in this study will be useful in further classifying the large number of currently identified mutations that alter sperm function and development in C. elegans.

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Sloan, Nadia S., Maxine Lovegrove e Leigh W. Simmons. "Social manipulation of sperm competition intensity reduces seminal fluid gene expression". Biology Letters 14, n. 1 (gennaio 2018): 20170659. http://dx.doi.org/10.1098/rsbl.2017.0659.

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A considerable body of evidence supports the prediction that males should increase their expenditure on the ejaculate in response to sperm competition risk. The prediction that they should reduce their expenditure with increasing sperm competition intensity is less well supported. Moreover, most studies have documented plasticity in sperm numbers. Here we show that male crickets Teleogryllus oceanicus exhibit reduced seminal fluid gene expression and accessory gland mass in response to elevated sperm competition intensity. Together with previous research, our findings suggest that strategic adjustments in seminal fluid composition contribute to competitive fertilization success in this species.

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Firman, Renée C., e Leigh W. Simmons. "Sperm midpiece length predicts sperm swimming velocity in house mice". Biology Letters 6, n. 4 (10 febbraio 2010): 513–16. http://dx.doi.org/10.1098/rsbl.2009.1027.

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Evolutionary biologists have argued that there should be a positive relationship between sperm size and sperm velocity, and that these traits influence a male's sperm competitiveness. However, comparative analyses investigating the evolutionary associations between sperm competition risk and sperm morphology have reported inconsistent patterns of association, and in vitro sperm competition experiments have further confused the issue; in some species, males with longer sperm achieve more competitive fertilization, while in other species males with shorter sperm have greater sperm competitiveness. Few investigations have attempted to address this problem. Here, we investigated the relationship between sperm morphology and sperm velocity in house mice ( Mus domesticus ). We conducted in vitro sperm velocity assays on males from established selection lines, and found that sperm midpiece size was the only phenotypic predictor of sperm swimming velocity.

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Parker, Geoff A., e Jussi Lehtonen. "Gamete evolution and sperm numbers: sperm competition versus sperm limitation". Proceedings of the Royal Society B: Biological Sciences 281, n. 1791 (22 settembre 2014): 20140836. http://dx.doi.org/10.1098/rspb.2014.0836.

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Both gamete competition and gamete limitation can generate anisogamy from ancestral isogamy, and both sperm competition (SC) and sperm limitation (SL) can increase sperm numbers. Here, we compare the marginal benefits due to these two components at any given population level of sperm production using the risk and intensity models in sperm economics. We show quite generally for the intensity model (where N males compete for each set of eggs) that however severe the degree of SL, if there is at least one competitor for fertilization ( N − 1 ≥ 1), the marginal gains through SC exceed those for SL, provided that the relationship between the probability of fertilization ( F ) and increasing sperm numbers ( x ) is a concave function. In the risk model, as fertility F increases from 0 to 1.0, the threshold SC risk (the probability q that two males compete for fertilization) for SC to be the dominant force drops from 1.0 to 0. The gamete competition and gamete limitation theories for the evolution of anisogamy rely on very similar considerations: our results imply that gamete limitation could dominate only if ancestral reproduction took place in highly isolated, small spawning groups.

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Tesi sul tema "Sperrm competition"

Meunier, Léna. "Reproductive biology and senescence impact on postcopulatory sexual selection in a wild polyandrous bird, the North African Houbara Bustard (Chlamydotis undulata undulata)". Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCK028.

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Résumé La polyandrie, lorsque les femelles s'accouplent avec plusieurs mâles, augmente les possibilités de sélection sexuelle, car outre la compétition entre les mâles pour l'accès à la femelle (sélection sexuelle pré-copulatoire), les spermatozoïdes des différents mâles sont également en compétition pour la fécondation (sélection sexuelle post-copulatoire). En conséquence, la plupart des descendants sont engendrés par le dernier mâle qui s’est accouplé avec la femelle, un phénomène appelé "last male precedence" (LMP). En plus de l'ordre d'accouplement, la quantité et la qualité des spermatozoïdes peuvent également influencer le résultat de la compétition spermatique, mais avec l'âge, ces paramètres spermatiques diminuent, ce qui réduit le succès reproducteur. Chez l'outarde Houbara d’Afrique du Nord (Chlamydotis undulata undulata), les femelles sont polyandres et les mâles souffrent de sénescence reproductive. Cette thèse vise à approfondir notre compréhension de la biologie de la reproduction de l'outarde houbara, de la sénescence reproductive et de son impact sur le succès reproductif des mâles et la sélection post-copulatoire. Dans une première partie, afin d'améliorer les connaissances sur la physiologie de la reproduction de l'espèce et de construire une base solide pour l'anatomie reproductive et la morphologie des spermatozoïdes, et les mécanismes de stockage chez la femelle, l'anatomie et l'histologie des systèmes reproducteurs femelle et mâle pendant et en dehors de la saison de reproduction ont été explorées et la morphologie des spermatozoïdes décrite. Dans une deuxième partie, les mécanismes sous-jacents la LMP et la dynamique de stockage dans l'oviducte ont été étudiés. Dans une troisième partie, la sénescence reproductive des mâles et sa relation avec la sélection post-copulatoire a été étudiée. Cette partie a été divisé en quatre sections afin d'étudier différents aspects de la sénescence reproductive. Tout d'abord, les niveaux de testostérone au cours de la saison ont été évalués ainsi qu’un éventuel effet de l'âge. Deuxièmement, un potentiel compromis entre le nombre et la qualité des spermatozoïdes en fonction de l'âge du mâle a été exploré. Troisièmement, l’effet de l'âge du mâle, l'âge des spermatozoïdes et leur éventuelle interaction sur la qualité spermatique et le succès reproducteur, ont été étudiés. Enfin, la LMP a été étudiée dans des conditions expérimentales contrôlées afin de démêler les effets de l'âge du mâle, de l'ordre d'accouplement et de la qualité du sperme sur le succès de paternité. L'anatomie et histologie reproductive ainsi qu’une classification de la morphologie des spermatozoïdes a été décrite pour la première fois chez l’outarde houbara. Le déplacement actif des spermatozoïdes est probablement le principal mécanisme de la LMP. L'âge n'a pas d'effet sur la concentration de testostérone au cours de la saison de reproduction. Les pics de testostérone ont précédé les pics de comportement sexuel et de qualité spermatique. Des covariations phénotypiques positives entre la quantité et la qualité des spermatozoïdes ont été mises en évidence et ne sont pas influencées par l’âge. Aucun signe de sénescence des spermatozoïdes au cours d'un stockage prolongé dans le tractus mâle n'a été observé. Au contraire, les spermatozoïdes collectés à des intervalles plus longs étaient de meilleure qualité, ce qui s'est traduit par un succès d'éclosion plus élevé. Conformément aux travaux antérieurs, l’âge du mâle a impacté la quantité et la qualité des spermatozoïdes, ce qui s’est reflété par un taux de croissance et de survie plus faible sur la progéniture. Enfin, l'âge n’a pas impacté la LMP, et indépendamment de l'âge, le mâle en dernière position dans la séquence d'insémination a engendré environ 60 % de la progéniture. Dans l'ensemble, ce travail de thèse a permis de mieux comprendre la biologie de la reproduction des outardes houbara et les mécanismes de sélection post-copulatoire
Polyandry, when females mate with multiple males, increases the opportunity for sexual selection to operate, because in addition to competition between males for access to the female (pre-copulatory sexual selection), sperm from different males also compete for fertilization (post-copulatory sexual selection). This often results in most offspring being sired by the last male, a phenomenon called last male precedence (LMP). In addition to mating order, sperm quantity and quality can also influence the outcome of sperm competition. As males age, sperm quality and quantity decrease, resulting in reduced reproductive success. In the North African Houbara Bustard (Chlamydotis undulata undulata), females are polyandrous, and males suffer from reproductive senescence. The thesis aims at improving our understanding of the reproductive biology of houbara bustards, reproductive senescence and its impact on male reproductive success and post-copulatory selection.In the first part, to improve the knowledge of the species’ physiology of reproduction and to construct a solid base for houbara reproductive anatomy and sperm morphology and later storage mechanism in the female tract, we explored anatomy and histology of the female and male reproductive systems during and out of the breeding season and sperm morphology was described. In the second part, we investigated the underlying mechanisms of LMP and the storage dynamics within the oviduct during competitive inseminations. In the third part, we investigated male reproductive senescence and its relationship with post-copulatory selection. This work was divided into four sections to investigate different aspects of reproductive ageing. Firstly, we examined seasonal testosterone levels and a possible age-related pattern. Second, we investigated a possible trade-off between sperm number and quality across ages. Thirdly, to test male age, sperm age, and their possible interaction on sperm quality and reproductive success, sperm ageing in the male tract was investigated by controlling the timing of collection intervals for young and old males. Finally, LMP was studied under controlled experimental conditions to disentangle the effects of male age, mating order, and sperm quality on siring success.This thesis presents the first description of houbara reproductive anatomy and histology and sperm morphology classification. Active sperm displacement is likely to be the main mechanism of LMP. There was no evidence of an age-related pattern of testosterone levels throughout the breeding season. Peak testosterone levels preceded peaks in sexual behaviour and sperm characteristics. We found a positive covariation between sperm quantity and several sperm quality traits, and male age did not influence the strength of this covariation. No evidence of sperm ageing during prolonged storage in the male tract was observed. On the contrary, sperm collected at longer intervals had higher quality, which was reflected in higher hatching success. Consistent with previous work, older males had lower sperm number, volume, motility and velocity and sired offspring with impaired growth rate. Finally, we found no evidence of an age effect on LMP. Regardless of age, sperm from the last male in the insemination sequence sired approximately 60% of the offspring. Overall, this work has provided a better understanding and new insights into the reproductive biology of houbara bustards and the mechanisms of post copulatory selection

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Siva-Jothy, M. T. "Sperm competition in the odonata". Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370301.

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Eady, Paul E. "Sperm competition in Callosobruchus maculatus". Thesis, University of Sheffield, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263760.

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Fryer, Timothy James Osborne. "ESS models of sperm competition". Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266803.

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Gilbert, Lucy. "Sperm competition in the western gull". Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389759.

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Cook, Penelope Anne. "Sperm competition in butterflies and moths". Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307641.

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Lovell-Mansbridge, Claire. "Sperm competition in the feral pigeon Columba livia". Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364193.

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Hunter, Fiona M. "Sperm competition in the Northern fulmar (Fulmaris glacialis)". Thesis, University of Sheffield, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304668.

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Ramm, Steven Andrew. "Sperm competition and its evolutionary consequences in rodents". Thesis, University of Liverpool, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436259.

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Preston, Brian T. "Sexual selection and sperm competition in Soay sheep". Thesis, University of Stirling, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391526.

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Libri sul tema "Sperrm competition"

Watanabe, Mamoru. Sperm Competition in Butterflies. Tokyo: Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-55945-0.

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A, Bellis Mark, a cura di. Human sperm competition: Copulation, masturbation, and infidelity. London: Chapman & Hall, 1995.

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Baker, R. R. Human sperm competition: Copulation, masturbation, and infertility. London: Chapman and Hall, 1993.

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1971-, Shackelford Todd K., e Pound Nicholas 1971-, a cura di. Sperm competitions in humans: Classic and contemporary readings. New York, NY: Springer, 2006.

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Fu, Peng. Sperm competition and alternative mating tactics in bluegill sunfish. Ottawa: National Library of Canada, 2000.

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E, Johnson J. Spearfishing competitions in South Australia, 1983-1984. Adelaide, S. Aust: Dept. of Fisheries, 1985.

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Ashok, Agarwal, Borges Edson e Amanda S. Setti. Non-invasive sperm selection for in vitro fertilization: Novel concepts and methods. New York: Springer, 2015.

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Watanabe, Mamoru. Sperm Competition in Butterflies. Springer, 2018.

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Shackelford, Todd K., e Nicholas Pound, a cura di. Sperm Competition in Humans. Springer US, 2006. http://dx.doi.org/10.1007/0-387-28039-1.

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Shackelford, Todd K., e Nicholas Pound, a cura di. Sperm Competition in Humans. Springer US, 2006. http://dx.doi.org/10.1007/978-0-387-28039-4.

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Capitoli di libri sul tema "Sperrm competition"

DeLecce, Tara. "Sperm Competition". In Encyclopedia of Personality and Individual Differences, 5156–58. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-319-24612-3_1269.

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McKibbin, William F. "Sperm Competition". In Encyclopedia of Evolutionary Psychological Science, 1–3. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-16999-6_73-1.

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Durrant, Kate L. "Sperm Competition". In Encyclopedia of Animal Cognition and Behavior, 6620–33. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-319-55065-7_438.

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DeLecce, Tara. "Sperm Competition". In Encyclopedia of Personality and Individual Differences, 1–3. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-28099-8_1269-1.

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Durrant, Kate L. "Sperm Competition". In Encyclopedia of Animal Cognition and Behavior, 1–14. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-47829-6_438-1.

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Cordero-Rivera, Adolfo. "Sperm Competition". In Reproductive Strategies in Insects, 205–24. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003043195-10.

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McKibbin, William F. "Sperm Competition". In Encyclopedia of Evolutionary Psychological Science, 7859–61. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-319-19650-3_73.

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Baer, Boris. "Sperm Competition". In Encyclopedia of Social Insects, 872–75. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-28102-1_114.

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Baer, Boris. "Sperm Competition". In Encyclopedia of Social Insects, 1–5. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-319-90306-4_114-1.

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Kelly, Clint D., e Michael D. Jennions. "Sperm Competition Theory". In Encyclopedia of Evolutionary Psychological Science, 1–16. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-16999-6_1941-1.

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Atti di convegni sul tema "Sperrm competition"

Khan, H., M. Alam, S. Al-Kuwari e Y. Faheem. "OFFENSIVE AI: UNIFICATION OF EMAIL GENERATION THROUGH GPT-2 MODEL WITH A GAME-THEORETIC APPROACH FOR SPEAR-PHISHING ATTACKS". In Competitive Advantage in the Digital Economy (CADE 2021). Institution of Engineering and Technology, 2021. http://dx.doi.org/10.1049/icp.2021.2422.

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Zenic, Natasa, Admir Terzic e Ivan Kvesic. "Determinants of changes in physical activity levels in late adolescence; prospective analysis in urban communities". In 12th International Conference on Kinanthropology. Brno: Masaryk University Press, 2020. http://dx.doi.org/10.5817/cz.muni.p210-9631-2020-39.

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Purpose: Physical activity levels (PA-levels) significantly decline during adolescence, and sport participation during childhood and adolescence is frequently emphasized as protec-tive factors of PA-decline. However, there is a lack of studies which specifically examined sport-related factors and its influence on changes in PA (PA-changes) in adolescence. This study aimed to prospectively observe sport factors as: (i) correlates of PA-levels and (ii) pre-dictors of PA-changes in the period between 16 and 18 years of age among urban adoles-cents from Bosnia and Herzegovina. Methods: The sample of participants comprised 324 adolescents (44% females) who were prospectively observed over two testing waves: (i) baseline, when participants were 16 years old; and (ii) follow-up, 20 months later (18 years of age). The variables were collected by previously validated questionnaires including questions on predictors (sociodemographic variables and various sport factors [current/former/ever participation in individual and team sports, experience in sports, competitive result achieved]), and criteria (PA level obtained at study baseline and follow up, measured by Physical Activity Questionnaire for Adolescents [PAQ-A], and difference between PA-levels at baseline and follow-up). The t-test was used to compare PA-levels. The associations between variables were evidenced by: (i) Spear-man’s rank order correlations (between predictors and PA-levels), and (ii) logistic regression analysis (between predictors, and PA-changes observed as binomial criterion [PA-incline vs. PA-decline] – excluding those participants who reported active sport participation at study baseline). Results: The PA-level significantly declined over the study course (t-test: 6.60, p < 0.01). Sport-related predictors were significantly associated with PA at baseline (Spearman’s R: 0.33–0.45, p < 0.01), and PAat follow-up (Spearman’s R: 0.32-0.45, p < 0.01). Meanwhile, there was no significant correlation between studied predictors and differences in PA-levels between baseline and follow-up. Also, logistic regression did not reveal any significant influ-ence of predictors obtained at study baseline and PA-changes observed as binomial criterion (PA-incline vs PA-decline). Conclusion: While studied sport-related predictors significantly influence the PA-levels in the age of 16 and 18, with the higher level of PA among those adolescents who are actively in-volved in sports, sport-participation do not predict changes in PA-levels over the observed period of life. Knowing the influence of PAon overall health status, future studies should pro-vide additional details on possible predictors of PA-changes in adolescence.

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Rapporti di organizzazioni sul tema "Sperrm competition"

Elizur, Abigail, Amir Sagi, Gideon Hulata, Clive Jones e Wayne Knibb. Improving Crustacean Aquaculture Production Efficiencies through Development of Monosex Populations Using Endocrine and Molecular Manipulations. United States Department of Agriculture, giugno 2010. http://dx.doi.org/10.32747/2010.7613890.bard.

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Background Most of Australian prawn aquaculture production is based on P. monodon. However, the Australian industry is under intense competition from lower priced overseas imports. The availability of all-female monosex populations, by virtue of their large size and associated premium prize, will offer competitive advantage to the industry which desperately needs to counteract competitors within this market. As for the redclaw production in Israel, although it is at its infancy, the growers realized that the production of males is extremely advantageous and that such management strategy will change the economic assumptions and performances of this aquaculture to attract many more growers. Original objectives (as in original proposal) Investigating the sex inheritance mechanism in the tiger prawn. Identification of genes expressed uniquely in the androgenic gland (AG) of prawns and crayfish. The above genes and/or their products will be used to localize the AG in the prawn and manipulate the AG activity in both species. Production of monosex populations through AG manipulation. In the prawn, production of all-female populations and in the crayfish, all-male populations. Achievements In the crayfish, the AG cDNA library was further screened and a third AG specific transcript, designated Cq-AG3, had been identified. Simultaneously the two AG specific genes, which were previously identified, were further characterized. Tissue specificity of one of those genes, termed Cq-AG2, was demonstrated by northern blot hybridization and RNA in-situ hybridization. Bioinformatics prediction, which suggested a 42 amino acid long signal anchor at the N-terminus of the deduced Cq-AG2, was confirmed by immunolocalization of a recombinant protein. Cq-IAG's functionality was demonstrated by dsRNA in-vivo injections to intersex crayfish. Cq-IAGsilencing induced dramatic sex-related alterations, including male feature feminization, reduced sperm production, extensive testicular apoptosis, induction of the vitellogeningene expression and accumulation of yolk proteins in the ovaries. In the prawn, the AG was identified and a cDNA library was created. The putative P. monodonAG hormone encoding gene (Pm-IAG) was identified, isolated and characterized for time of expression and histological localization. Implantation of the AG into prawn post larvae (PL) and juveniles resulted in phenotypic transformation which included the appearance of appendix masculina and enlarged petasma. The transformation however did not result in sex change or the creation of neo males thus the population genetics stage to be executed with Prof. Hulata did not materialized. Repeated AG implantation is currently being trialed. Major conclusions and Implications, both scientific and agricultural Cq-IAG's involvement in male sexual differentiation had been demonstrated and it is strongly suggested that this gene encodes an AG hormone in this crayfish. A thorough screening of the AG cDNA library shows Cq-IAG is the prominent transcript within the library. However, the identification of two additional transcripts hints that Cq-IAG is not the only gene mediating the AG effects. The successful gene silencing of Cq-IAG, if performed at earlier developmental stages, might accomplish full and functional sex reversal which will enable the production of all-male crayfish populations. Pm-IAG is likely to play a similar role in prawns. It is possible that repeated administration of the AG into prawn will lead to the desired full sex reversal, so that WZ neo males, crossed with WZ females can result in WW females, which will form the basis for monosex all-female population.

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