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1
Sheller, Mimi. "The reproduction of reproduction: theorizing reproductive (im)mobilities". Mobilities 15, n. 2 (25 febbraio 2020): 188–95. http://dx.doi.org/10.1080/17450101.2020.1730608.
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Malkandueva, A. Kh, e M. V. Kashukoev. "INFLUENCE OF REPRODUCTION ON THE YIELD AND QUALITY OF WINTER WHEAT". Scientific Life 16, n. 7 (2021): 811–19. http://dx.doi.org/10.35679/1991-9476-2021-16-7-811-819.
Testo completoAbstract (sommario):
The article presents the results of a study on the effect of seed reproduction on the yield and quality of winter wheat grain in the steppe zone of the Kabardino-Balkarian Republic. The studies were carried out in 2015-2018 on the winter common wheat variety Yuzhanka, jointly bred by the Institute of Agriculture of the KBSC RAS and the N.N. P. P. Lukyanenko in the conditions of the steppe zone of Kabardino-Balkaria. In the experiments, changes in the yield structure and grain quality were studied depending on reproduction on the crops of the breeding nursery, superelite, elite, reproductive seeds (1-4) and mass reproduction. According to the studies, the yield structure of the winter soft wheat variety Yuzhanka changed from breeding nursery to mass reproduction. Yield variation on average over the years of research on reproductions was 42.2-48.6 c/ha, with a predominance in the breeding nursery. Such indicators as the number of productive stems from 407 to 342 pcs/m2, grain weight per ear from 1.23 to 1.11 g and weight of 1000 seeds from 41.3 to 38.3 g and other indicators also decreased. The productivity and quality indicators of winter wheat tend to decrease as seeds of different reproductions are used for sowing, that is, from seeds of the breeding nursery to mass reproduction. It should be noted that in adjacent reproductions, the indicators do not differ much. The results of the research showed that as reproduction decreases, the number of grains, the weight of grain from 1 ear and the weight of 1000 seeds. The content of protein and gluten also decreased by 0.6 and 1.0%, respectively, when comparing elite seeds with mass reproduction. The vitreousness of the grain, when using seeds of mass reproductions, decreased by 2.5% compared to the elite.
3
Belk, Mark C., Peter J. Meyers e J. Curtis Creighton. "Bigger Is Better, Sometimes: The Interaction between Body Size and Carcass Size Determines Fitness, Reproductive Strategies, and Senescence in Two Species of Burying Beetles". Diversity 13, n. 12 (11 dicembre 2021): 662. http://dx.doi.org/10.3390/d13120662.
Testo completoAbstract (sommario):
The cost of reproduction hypothesis suggests that allocation to current reproduction constrains future reproduction. How organisms accrue reproductive costs and allocate energy across their lifetime may differ among species adapted to different resource types. We test this by comparing lifetime reproductive output, patterns of reproductive allocation, and senescence between two species of burying beetles, Nicrophorus marginatus and N. guttula, that differ in body size, across a range of carcass sizes. These two species of burying beetles maximized lifetime reproductive output on somewhat different–sized resources. The larger N. marginatus did better on large and medium carcasses while the smaller N. guttula did best on small and medium carcasses. For both species, reproduction is costly and reproduction on larger carcasses reduced lifespan more than reproduction on smaller carcasses. Carcass size also affected lifetime reproductive strategies. Each species’ parental investment patterns were consistent with terminal investment on carcasses on which they performed best (optimal carcass sizes). However, they exhibited reproductive restraint on carcass sizes on which they did not perform as well. Reproductive senescence occurred largely in response to carcass size. For both species, reproduction on larger carcasses resulted in more rapid senescence. These data suggest that whether organisms exhibit terminal investment or reproductive restraint may depend on type and amount of resources for reproduction.
4
Persson, Jens. "Female wolverine (Gulo gulo) reproduction: reproductive costs and winter food availability". Canadian Journal of Zoology 83, n. 11 (1 novembre 2005): 1453–59. http://dx.doi.org/10.1139/z05-143.
Testo completoAbstract (sommario):
An individual has only a given amount of resources, and therefore an increase in one demographic trait results in a trade-off that necessitates a decrease in a different demographic trait. In general, the main factor determining an individual mammal's reproductive investment is food supply. This study addresses how female wolverine (Gulo gulo (L., 1758)) reproduction is limited. I tested two complementary hypotheses: (1) current reproduction is affected by the costs of reproduction in the preceding year and (2) current reproduction is affected by food availability in the current winter. I addressed the first hypothesis by comparing reproductive rates of females in relation to their reproductive effort in the preceding year. I experimentally tested the second hypothesis by comparing reproductive rates of food-supplemented females versus non-supplemented females. Reproduction incurred costs on female wolverines that affected future reproduction, and reproductive costs appeared to be related to the duration of parental care. Reproduction was higher for food-supplemented females than for non-supplemented females, even though all food-supplemented females had reproduced the preceding year. This study suggests that reproduction is limited by winter food availability and that additional food can compensate for reproductive costs. Thus, I suggest that female wolverine reproduction is determined by their condition in winter, which is a result of the combined effect of reproductive costs and winter food availability.
5
Lanca, Margaret, e David J. Bryant. "Effect of Orientation in Haptic Reproduction of Line Length". Perceptual and Motor Skills 80, n. 3_suppl (giugno 1995): 1291–98. http://dx.doi.org/10.2466/pms.1995.80.3c.1291.
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We investigated the accuracy of haptic reproduction of line length and whether accuracy is influenced by line orientation. 13 blindfolded subjects felt along different line lengths at various orientations in the horizontal plane, then reproduced the line lengths in the same orientation as that felt. Efforts were made to equate learning and reproductive scanning movements. Reproductions of line lengths were a nonveridical power function of their true lengths, but the power function exponents did not differ across spatial orientations. It was concluded that people can encode line lengths across spatial orientations by a common power function if care is taken to equate proprioceptive information across learning and reproduction.
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Vekhnik, Victoria Alexandrovna. "Reproductive activity of male edible dormice (Glis glis L., 1766) in the peripheral population". Samara Journal of Science 5, n. 2 (1 giugno 2016): 15–19. http://dx.doi.org/10.17816/snv20162103.
Testo completoAbstract (sommario):
The edible dormouse is a dendrobiont hibernating rodent breeding once a year. A peculiarity of the species biology is regular reproduction failure in non-mast years. In the center of the area it occurs due to the lack of male reproductive activity. In the studied population on the eastern periphery of the dormouse area previous studies proved the decisive role of mass resorption of embryos at females in the process. The dynamics of males reproductive activity and its impact on the reproduction were not considered previously in detail. In this work the periodicity and intensity of reproductive activity of males, depending on the age and phase of population cycle, was studied. Reproductive activity of the overwhelming majority of males was annually observed, the proportion of individuals not involved in reproduction did not exceed 6,7%. The age differences in the timing of beginning of the reproduction were revealed: yearlings came the first in the activity state and after them two-year and three-year and older individuals became active. The minimal duration of the mating period was observed in yearling males, the maximal - in two-year, which were also characterized by the longest individual periods of reproductive activity. As a result of sharp fluctuations in the population age structure two-year males are the most important group in reproduction, but the three-year and older individuals in mast years are also able to ensure the reproduction of the population. The characteristic feature of reproduction was noted at yearling males: they began reproduction depending on body weight. Fluctuations in the male reproductive activity during the active period do not play a significant role in the regulation of reproduction. Shorter duration of reproductive activity of yearling animals in the years of reproduction failure is compensated by the later beginning of reproduction of three-year and older individuals. Nonsynchronous participation in breeding of males of different age groups provides the involvement in reproduction of maximal number of animals.
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Clark, Nathaniel L., Jan E. Aagaard e Willie J. Swanson. "Evolution of reproductive proteins from animals and plants". Reproduction 131, n. 1 (gennaio 2006): 11–22. http://dx.doi.org/10.1530/rep.1.00357.
Testo completoAbstract (sommario):
Sexual reproduction is a fundamental biological process common among eukaryotes. Because of the significance of reproductive proteins to fitness, the diversity and rapid divergence of proteins acting at many stages of reproduction is surprising and suggests a role of adaptive diversification in reproductive protein evolution. Here we review the evolution of reproductive proteins acting at different stages of reproduction among animals and plants, emphasizing common patterns. Although we are just beginning to understand these patterns, by making comparisons among stages of reproduction for diverse organisms we can begin to understand the selective forces driving reproductive protein diversity and the functional consequences of reproductive protein evolution.
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Méndez, M., e J. R. Obeso. "Size-dependent reproductive and vegetative allocation in Arum italicum (Araceae)". Canadian Journal of Botany 71, n. 2 (1 febbraio 1993): 309–14. http://dx.doi.org/10.1139/b93-032.
Testo completoAbstract (sommario):
The proportional allocation of plant total resources for growth, reproduction, vegetative propagation, and the balance between them were examined in Arum italicum. A minimum threshold dry mass (2.5 g) was found in this species before reproduction could occur, but above 10 g of dry mass, all individuals in a sample of 151 produced at least one inflorescence. Resource allocation for vegetative growth, sexual reproduction, and vegetative propagation significantly increased as dry mass of the plant increased. Increases in plant size resulted in increased proportional allocation to sexual reproduction, and relative decreases in both vegetative growth and vegetative propagation. Mass ratios between sexual reproductive structures and new tuber, and between sexual reproductive structures and organs of clonal growth increased with plant size. Allocation of resources to reproduction occurred at the expense of vegetative growth. In reproductive plants, the cost of reproduction, measured as relative reduction in vegetative growth was approximately 24% and was estimated by comparing growth in nonreproductive plants. Key words: Arum italicum, Araceae, cost of reproduction, reproductive allocation, vegetative growth, vegetative propagation.
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Smietana, Marcin, Charis Thompson e France Winddance Twine. "Making and breaking families – reading queer reproductions, stratified reproduction and reproductive justice together". Reproductive Biomedicine & Society Online 7 (novembre 2018): 112–30. http://dx.doi.org/10.1016/j.rbms.2018.11.001.
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Hess, B. W., S. L. Lake, E. J. Scholljegerdes, T. R. Weston, V. Nayigihugu, J. D. C. Molle e G. E. Moss. "Nutritional controls of beef cow reproduction". Journal of Animal Science 83, suppl_13 (1 giugno 2005): E90—E106. http://dx.doi.org/10.2527/2005.8313_supple90x.
Testo completoAbstract (sommario):
Abstract The livestock industry and animal scientists have long recognized the importance of proper nutrition for cattle to achieve reproductive success. Timely resumption of estrus following parturition is a major milestone that a cow must reach for optimal reproduction. Dynamic interplay among all strata of the hypothalamo-hypophyseal-ovarian axis occurs during the cow's transition from postpartum anestrus to reproductive competence. The reproductive axis integrates a milieu of nutritionally related signals that directly or indirectly affect reproduction. Directing nutritional inputs toward anabolic processes is critical to stimulating key events that promote reproductive success. Although prepartum and postpartum energy balance are the most important factors affecting duration of the postpartum interval to first estrus in beef cows, other nutritional inputs likely impinge on the hypothalamo-hypophyseal-ovarian axis to influence reproduction. For example, feeding fat to beef cows for approximately 60 d before calving may improve pregnancy rates in the upcoming breeding season. Supplementing postpartum diets with lipids high in linoleic acid can impede reproductive performance of beef cows. Precise mechanisms through which nutritional inputs mediate reproduction have not yet been fully elucidated. Scientists investigating nutritional mediators of reproduction, or how nutritional inputs affect reproduction, must be cognizant of the interactions among nutrients and nutritional cues responsible for mediating reproduction.
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Hasegawa, Shigeaki, e Hiroshi Takeda. "Functional specialization of current shoots as a reproductive strategy in Japanese alder (Alnus hirsuta var. sibirica)". Canadian Journal of Botany 79, n. 1 (1 gennaio 2001): 38–48. http://dx.doi.org/10.1139/b00-143.
Testo completoAbstract (sommario):
Current shoots, which form the crown of a tree, are specialized in various functions such as crown expansion, reproduction, and assimilation. We examined the temporal and spatial distribution of reproductive shoots in Alnus hirsuta Turcz. var. sibirica (Fischer) C.K. Schn., assessed their direct and indirect costs of reproduction, and explained their distribution in the crown as the reproductive strategy of a current shoot population. The upper and lower limits to the lengths of current shoots for reproductive growth (flower formation) were 40 and 10 cm, respectively. Reproductive 1-year-old shoots produced fewer shoots in the following year than non-reproductive 1-year-old shoots. In current shoots longer than 40 cm, the increment of reproductive output in the following year by abandonment of reproduction surpassed the decrement of reproductive output in the current year by abandonment of reproduction. This may be one reason for the upper limit of reproductive shoot length. Thus, the current shoot population of A. hirsuta var. sibirica may be divided into three functionally specialized subpopulations: reproductive, maintenance, and exploratory. This specialization is considered to be a reproductive strategy to maximize their lifetime reproductive success.Key words: current shoot population, reproductive ecology, functional specialization, cost of reproduction, Japanese alder.
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Lappé, Martine, Robbin Jeffries Hein e Hannah Landecker. "Environmental Politics of Reproduction". Annual Review of Anthropology 48, n. 1 (21 ottobre 2019): 133–50. http://dx.doi.org/10.1146/annurev-anthro-102218-011346.
Testo completoAbstract (sommario):
What constitutes “human reproduction” is under negotiation as its biology, social nature, and cultural valences are increasingly perceived as bound up in environmental issues. This review maps the growing overlap between formerly rather separate domains of reproductive politics and environmental politics, examining three interrelated areas. The first is the emergence of an intersectional environmental reproductive justice framework in activism and environmental health science. The second is the biomedical delineation of the environment of reproduction and development as an object of growing research and intervention, as well as the marking off of early-life environments as an “exposed biology” consequential to the entire life span. Third is researchers’ critical engagement with the reproductive subject of environmental politics and the lived experience of reproduction in environmentally dystopic times. Efforts to rethink the intersections of reproductive and environmental politics are found throughout these three areas.
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Reekie, Edward G., Sonya Budge e Jennifer L. Baltzer. "The shape of the trade-off function between reproduction and future performance in Plantago major and Plantago rugelii". Canadian Journal of Botany 80, n. 2 (1 febbraio 2002): 140–50. http://dx.doi.org/10.1139/b01-146.
Testo completoAbstract (sommario):
There is a paucity of data describing the nature of the trade-off function between reproduction and future performance. Most studies implicitly assume it is a linear function such that allocation of resources to reproduction results in a proportional decline in future survival and reproduction. We reanalyse data from a field experiment with half-sib families of Plantago major L. that suggests this relationship is in fact curvilinear. Low levels of reproductive investment had relatively little impact on future performance and higher levels of investment had a larger impact. To explain this curvilinear pattern, we conducted an experiment to examine the effect of incremental increases in reproductive investment on rates of resource uptake in P. major and Plantago rugelii Decne. Results suggest that, because of differences in the resource requirements of vegetative versus reproductive tissues, reproduction will have little effect on growth, providing that the limiting resources are required in greater quantities for vegetative as compared with reproductive tissues. These results are in accord with a curvilinear trade-off function between reproduction and future performance and provide an explanation for the maintenance of sexual reproduction in species where seed production may contribute minimally to fitness in the short term.Key words: reproductive cost, resource allocation, life-history theory, nitrogen uptake, reproductive photosynthesis, Plantago major, Plantago rugelii.
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Morton, Martin L., Maria E. Pereyra, John D. Crandall, Elizabeth A. MacDougall-Shackleton e Thomas P. Hahn. "Reproductive Effort and Return Rates in the Mountain White-Crowned Sparrow". Condor 106, n. 1 (1 febbraio 2004): 131–38. http://dx.doi.org/10.1093/condor/106.1.131.
Testo completoAbstract (sommario):
AbstractWe analyzed return rates of high-altitude-breeding Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) in relation to five components of their previous season's reproductive effort: number of fledglings produced, double brooding, number of nesting attempts (first nests plus renests), total number of eggs laid, and fledging date. No relationship of return rate to reproductive effort occurred except in the case of fledging date. Fledging dates spanned a 2-month period from mid-June to mid-August. Returns of females to the study area held steady no matter when their chicks fledged in the previous breeding season, but male return rates increased significantly when their chicks fledged after 20 July. Coincident with that time frame, they entered molt and often withdrew parental care. We hypothesized that males in this montane environment, where thermoregulatory costs are high, traded off reproductive effort (parental care) with survival (return rates). This fits well with models of life-history evolution; however, the corresponding prediction that return rates of females with late-season broods should decrease due to their assumption of greater parental care was not supported. Apparently, the cost of reproduction shifted to the young: late-season nestlings grew more slowly, fledged at a smaller mass, and exhibited a fourfold increase in brood reductions. Their recruitment as breeders in the following season was also greatly reduced. Thus, a cost of reproduction was expressed in two forms, one as changes in survival rates of breeding males, the other as changes in quality of offspring.Esfuerzo Reproductivo y Tasas de Retorno en Zonotrichia leucophrys orianthaResumen. Analizamos las tasas de retorno en las poblaciones reproductivas de alta montaña de Zonotrichia leucophrys oriantha con relación a cinco componentes de su esfuerzo reproductivo de la estación anterior: número de volantones producidos, eventos de dobles nidadas, número de intentos de nidificación (primer nido más re-nidificaciones), número total de huevos puestos y fecha de emplumamiento. No encontramos una relación entre la tasa de retorno y el esfuerzo reproductivo, excepto en el caso de la fecha de emplumamiento. Las fechas de emplumamiento se extendieron por un período de dos meses, desde mediados de junio hasta mediados de agosto. El regreso de las hembras al área de estudio se mantuvo constante, sin importar cuándo los pichones abandonaron el nido en la estación reproductiva anterior, pero las tasas de retorno de los machos incrementaron significativamente cuando sus pichones dejaron el nido luego del 20 de julio. En coincidencia con este momento, los machos comenzaron la muda y frecuentemente dejaron de cuidar a de los pichones. Hipotetizamos que los machos en este ambiente de montaña, donde los costos de termorregulación son altos, canjearon esfuerzo reproductivo (cuidado parental) por supervivencia (tasas de retorno). Esto se ajusta adecuadamente con los modelos de evolución de historias de vida. Sin embargo, la predicción correspondiente de que las tasas de retorno de las hembras con nidadas tardías deberían disminuir debido a la suposición de que brindarían mayor cuidado parental, no fue respaldada. Aparentemente, el costo reproductivo sería trasladado a las crías: los pichones de finales de la estación crecieron más despacio, dejaron el nido con menor masa corporal y exhibieron un incremento de cuatro órdenes de magnitud en la reducción de la nidada. Su reclutamiento como individuos reproductivos en la siguiente estación también se redujo enormemente. De este modo, el costo reproductivo fue expresado de dos formas, una como cambios en las tasas de supervivencia de los machos reproductivos y la otra como cambios en la calidad de la progenie.
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Franklin, Sarah, e Delphine Gardey. "40 ans de reproduction médicalement assistée : une lecture anthropologique et féministe". Travail, genre et sociétés 50, n. 2 (24 ottobre 2023): 31–41. http://dx.doi.org/10.3917/tgs.050.0031.
Testo completoAbstract (sommario):
Dans cet entretien, Sarah Franklin revient sur son itinéraire, proposant des pistes pour aborder les transformations intervenues dans le champ de la reproduction médicalement assistée depuis 40 ans. Avec des enquêtes sur la médecine régénérative, le clonage ou les marchés de tissus et services reproductifs, Sarah Franklin est une figure incontournable de l’analyse des mutations médicales et sociales contemporaines dans le champ de la reproduction et de la parenté. Elle situe son parcours dans le sillage des pionnières de la critique féministe de l’anthropologie culturelle, des techniques et des sciences : Marylin Strathern, Shulamith Firestone ou Donna Haraway. Elle pointe les enjeux politiques et scientifiques de l’usage des technologies de la reproduction et les transformations intervenues dans la définition de la parenté. Soulignant l’importance des droits conquis par les personnes LGBTQ+, elle interroge les limites de ces transformations mobilisant la question de la « justice reproductive ».
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Hurley, Natasha. "Reproduction/Non-reproduction". Jeunesse: Young People, Texts, Cultures 7, n. 2 (dicembre 2015): 148–61. http://dx.doi.org/10.3138/jeunesse.7.2.148.
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Hurley, Natasha. "Reproduction/Non-reproduction". Jeunesse: Young People, Texts, Cultures 7, n. 2 (2015): 148–61. http://dx.doi.org/10.1353/jeu.2015.0024.
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Zagel, Hannah. "Reproduction policy as life course policy: normative modelling of reproductive life courses in Germany". Zeitschrift für Sozialreform 70, n. 1 (6 marzo 2024): 31–53. http://dx.doi.org/10.1515/zsr-2023-0011.
Testo completoAbstract (sommario):
Abstract This paper investigates how familialist repronormativity, pro-natalism and reproductive autonomy feature as normative models for reproductive life courses in Germany’s current landscape of reproduction policies. Life course research has largely overlooked reproduction as a life course sphere, which is subject to state intervention and strong institutionalised normative assumptions about whether, when and how people should procreate. Drawing on policy documents and a new policy database, this paper compares the current state of reproduction policies in five policy fields (sex education, contraception, abortion, medically assisted reproduction and pregnancy care) to ideal-typical normative orientations towards reproductive life courses. The result is a more systematic understanding of the multidimensionality that is inherent to “life course modelling” (Leisering 2003) of the reproductive life sphere.
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Lam, Carla. "Thinking Through Post-constructionism: Reflections on (Reproductive) Disembodiment and Misfits". Studies in Social Justice 10, n. 2 (19 dicembre 2016): 289–307. http://dx.doi.org/10.26522/ssj.v10i2.1352.
Testo completoAbstract (sommario):
In this article, I draw together feminist research on the distinct areas of assisted human reproduction (or new reproductive technology) and post-constructionist theory to examine some common methodological and epistemological issues fundamental for reproductive justice. I revisit the notion of technologically-assisted (reproductive) disembodiment (e.g., in vitro fertilization, surrogacy and egg donation) in light of theoretical developments in feminism, in particular post-constructionism. Specifically, I ask what light is shed on the paradox of reproduction (in particular disembodied reproduction) by feminist post-constructionism?
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Vasilieva, N. A., e A. V. Tchabovsky. "Timing is the only thing: reproduction in female yellow ground squirrels (Spermophilus fulvus)". Canadian Journal of Zoology 92, n. 8 (agosto 2014): 737–47. http://dx.doi.org/10.1139/cjz-2014-0084.
Testo completoAbstract (sommario):
Based on 4-year field observations of yellow ground squirrels (Spermophilus fulvus (Lichtenstein, 1823)), we determined whether female reproductive effort, annual reproductive success, and survival were dependent on age, body condition, time of emergence from hibernation, and previous reproduction. The probability of weaning a litter did not vary with female age, body condition, time of emergence, or previous reproduction. Litter size, litter mass, and offspring survival did not vary with age, whereas individual offspring mass was lower in yearlings than in older females. Body condition upon emergence had no effect on litter size, litter mass, offspring mass, and survival. Reproduction did not influence female survival, physical condition upon emergence next spring, or subsequent reproductive efforts. The only factor that affected the extent of reproductive effort and offspring survival was the date of emergence: the later a female emerged, the lower the total and mean offspring mass, and fewer offspring survived. The modulation of reproduction in female S. fulvus by only the timing of vernal emergence and independent of other individual characteristics can be explained by the high costs of missed reproductive opportunity because of short longevity combined with low costs of reproduction when resources are abundant enough to meet both somatic and reproductive needs.
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Kimmitt, Abigail A. "Females as the Gatekeepers to Seasonal Breeding: What We Can Learn by Studying Reproductive Mechanisms in Both Sexes". Integrative and Comparative Biology 60, n. 3 (3 luglio 2020): 703–11. http://dx.doi.org/10.1093/icb/icaa095.
Testo completoAbstract (sommario):
Synopsis Seasonal reproduction is a widespread adaptation in vertebrates, such that individuals time their reproductive efforts to match peak resource abundance. Individuals rely on environmental cues to regulate hormonal mechanisms governing timing of breeding. Historically, studies on physiological mechanisms of seasonal reproduction, specifically in birds, have disproportionately focused on males compared to females. For this review, I conducted a literature search of the last decade of avian research and found a persistent sex bias in the field of physiological mechanisms of seasonal reproduction. Using work conducted with the dark-eyed junco (Junco hyemalis) as a case study, I present a possible solution to combat the sex bias: natural comparisons of populations that differ in reproductive timing to investigate mechanisms of reproduction in both sexes. Populations of dark-eyed juncos that differ in migratory behavior (i.e., migrant and resident) exhibit overlapping ranges during winter and early spring; residents begin breeding in early spring prior to the departure of migrants. This system, and others like it, provides an opportunity to compare mechanisms of reproduction in populations that differ in reproductive timing despite experiencing the same environmental conditions in early spring. In juncos, migrant and resident females and males exhibit similar patterns of hypothalamic regulation of reproduction in early spring, but sex differences in gonadal sensitivity between the populations could be an important distinction that partially explains sex differences in reproductive development. Comparing mechanisms of reproduction in free-living populations and in captivity can reveal important mechanisms that determine the onset of reproductive development, as well as potential sex differences in these mechanisms. Understanding the mechanisms of reproductive phenology has important implications for understanding how species will survive and reproduce in a changing climate.
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Fautin, Daphne Gail. "Reproduction of Cnidaria". Canadian Journal of Zoology 80, n. 10 (1 ottobre 2002): 1735–54. http://dx.doi.org/10.1139/z02-133.
Testo completoAbstract (sommario):
Empirical and experimental data on cnidarian reproduction show it to be more variable than had been thought, and many patterns that had previously been deduced hold up poorly or not at all in light of additional data. The border between sexual and asexual reproduction appears to be faint. This may be due to analytical tools being insufficiently powerful to distinguish between the two, but it may be that a distinction between sexual and asexual reproduction is not very important biologically to cnidarians. Given the variety of modes by which it is now evident that asexual reproduction occurs, its ecological and evolutionary implications have probably been underestimated. Appropriate analytical frameworks and strategies must be developed for these morphologically simple animals, in which sexual reproduction may not be paramount, that during one lifetime may pass though two or more phases differing radically in morphology and ecology, that may hybridize, that are potentially extremely long-lived, and that may transmit through both sexual and asexual reproduction mutations arising in somatic tissue. In cnidarians, perhaps more than in any other phylum, reproductive attributes have been used to define taxa, but they do so at a variety of levels and not necessarily in the way they have conventionally been considered. At the species level, in Scleractinia, in which these features have been most studied, taxa defined on the basis of morphology, sexual reproduction, and molecular characters may not coincide; there are insufficient data to determine if this is true throughout the phylum. At the class level, transverse fission occurs in members of all three major taxa but is rare outside Scyphozoa, the group of which it is considered characteristic (pending more research, its absence in Cubozoa should be ascribed to poor knowledge). Understanding the role of transverse fission in the ecology and reproductive biology of hydrozoans and anthozoans could shed light on scyphozoan evolutionary history, and elucidating its morphogenesis in all groups is essential to determining if it is homologous across the classes. Only by comparing aspects of reproduction among cnidarians of various taxa will idiosyncratically adaptive strategies be distinguished from reproductive characters that reflect evolution and so are phylogenetically informative.
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Adams, Ibrahim, Guang Yang, Muhammad Asad e Mubashir Tariq. "An Overview of Reproduction in Insects". Asian Journal of Advances in Agricultural Research 24, n. 7 (19 luglio 2024): 133–47. http://dx.doi.org/10.9734/ajaar/2024/v24i7529.
Testo completoAbstract (sommario):
Reproduction is a fundamental process in all life forms, including insects, in which offspring are produced from the parent organisms. The offspring combines genetic information from each of its parents and is genetically unique. Insects reproduce through both sexual and asexual reproduction, ensuring rapid population increase. Sexual reproduction involves the use gametes from both male and female insects, whilst asexual reproduction permits solitary creatures to lead to genetically identical progeny. Reproductive ecology deals with the study of how physiological characteristics, behavioral, and environmental elements impact on insect reproduction. The complexity of insect reproduction is focused by important processes known as vitellogenesis, which is required for egg development and transgenerational immunity. The i5k initiative planned to sequence more than 5,000 insect genomes to increase our understanding, yet challenges remain due to genome assembly issues and budgetary limitations. Understanding the reproductive morphology and methods of insects, as well as oviposition-related genes, is critical for effective pest management and biological control measures. Insect reproductive research contributes immensely to evolutionary biology, conservation, and agricultural productivity by understanding life cycles, reproductive behaviors, and pollination roles. Insect neurobiology, microbiome and environmental entomology are three most important study fields that will come up with new insights into basic biological processes as well as anticipated pest management and conservation measures in the face of environmental changes in the coming future.
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Brischoux, François, e Marion Cheron. "Osmotic ‘cost’ of reproduction in breeding male toads". Biology Letters 15, n. 11 (novembre 2019): 20190689. http://dx.doi.org/10.1098/rsbl.2019.0689.
Testo completoAbstract (sommario):
Shifts between habitats during reproduction can induce costs that are independent of the reproductive effort and that often apply to both sexes. Such shifts can also illustrate physiological costs complementary to those involving energetic currencies. In this study, we investigated osmotic consequences of reproduction in a context where reproduction induces a shift from terrestrial habitats to freshwater environments. During reproduction, toads migrate to breeding ponds where males remain for several weeks, while females leave shortly after egg-laying. We assessed plasma osmolality of male spined toads during the whole reproductive period (approx. 30 days) in conjunction with markers of individual condition. We found that osmolality decreases during the protracted period of immersion in freshwater during reproduction, presumably through water influx as indicated by body mass changes. Hormonal markers of metabolism and sexual activity were positively correlated with osmolality. Recent research has highlighted hydric ‘costs’ of reproduction when access to water is limited. Our study adds to this growing field of investigation, yet with an opposite perspective, where water availability linked to reproduction provokes hyperhydration rather than dehydration.
25
Piotrowska, Monika. "Is ‘Assisted Reproduction’ Reproduction?" Philosophical Quarterly 68, n. 270 (19 giugno 2017): 138–57. http://dx.doi.org/10.1093/pq/pqx032.
Testo completoAbstract (sommario):
Abstract With an increasing number of ways to ‘assist’ reproduction, some bioethicists have started to wonder what it takes to become a genetic parent. It is widely agreed that sharing genes is not enough to substantiate the parent–offspring relation, but what is? Without a better understanding of the concept of reproduction (and what it means to say that an organism has reproduced), our thinking about parent–offspring relations and the ethical issues surrounding them risk being unprincipled. Here, I address that problem by offering a principled account of reproduction—the Overlap, Development and Persistence account—which I believe best captures the meaning of ‘genetic parenthood’.
26
Lambert, Yvan, e Julian J. Dodson. "Freshwater Migration as a Determinant Factor in the Somatic Cost of Reproduction of Two Anadromous Coregonines of James Bay". Canadian Journal of Fisheries and Aquatic Sciences 47, n. 2 (1 febbraio 1990): 318–34. http://dx.doi.org/10.1139/f90-033.
Testo completoAbstract (sommario):
We tested the hypothesis that the species-specific costs of migration differentially affect reproductive effort and somatic cost of reproduction in sympatric anadromous populations of cisco (Coregonus artedii) and lake whitefish (C. clupeaformis) of James Bay. Reproductive effort, which includes the energy cost of migration, is higher for cisco. Female cisco allocate more energy to reproduction than its total energy gain. The energy invested by lake whitefish in reproduction is approximately equal to its seasonal energy gain. Reproduction results in large differences in the energy content of gonads, viscera, and carcass between reproductive and nonreproductive fish of the same length. Neither cisco nor lake whitefish are able to spawn two years in succession. The somatic energy increase of reproductive female cisco is 121% lower than the somatic energy increase of nonreproductive females; similar comparisons are 89% (female) and 103% (male) for lake whitefish. The energy cost of migration is largely responsible for the higher somatic cost of reproduction observed for cisco. These different somatic costs of migration are related to resource accumulation prior to migration and to differences in the aerobic cost of swimming between the two species in combination with the difficulty of the freshwater migration.
27
Jasienska, Grazyna. "Costs of reproduction and ageing in the human female". Philosophical Transactions of the Royal Society B: Biological Sciences 375, n. 1811 (21 settembre 2020): 20190615. http://dx.doi.org/10.1098/rstb.2019.0615.
Testo completoAbstract (sommario):
Evolutionary theories of ageing point to reproduction as a significant factor to consider when asking why ageing occurs and why there is inter-individual variation in its progression. Reproduction in human females is costly, in terms of energy, nutrients and metabolic adjustments. Thus, it is expected that women who experienced high reproductive effort resulting from multiple reproductive events will age faster. However, the evidence for long-term negative effects of reproduction is not conclusive. The lack of understanding of whether there are trade-offs between reproduction and ageing in women is partly due to methodological challenges. The costs of reproduction are often calculated based only on parity, while other elements contributing to these costs (e.g. breastfeeding, timing of reproduction) are neglected, which may significantly underestimate the total costs and obscure the all-important inter-individual variation in such costs. Costs must be evaluated in relation to individual characteristics, including developmental conditions, nutritional status and social support that a mother receives during reproduction. Furthermore, ageing and health must be assessed based on comprehensive markers rather than arbitrarily assembled variables. Finally, longitudinal rather than cross-sectional studies and new statistical approaches are needed to reveal how much of a decline in health and progressing ageing can actually be attributed to past reproductive processes. This article is part of the theme issue ‘Evolution of the primate ageing process'.
28
Weibel, Chelsea J., Jenny Tung, Susan C. Alberts e Elizabeth A. Archie. "Accelerated reproduction is not an adaptive response to early-life adversity in wild baboons". Proceedings of the National Academy of Sciences 117, n. 40 (21 settembre 2020): 24909–19. http://dx.doi.org/10.1073/pnas.2004018117.
Testo completoAbstract (sommario):
In humans and other long-lived species, harsh conditions in early life often lead to profound differences in adult life expectancy. In response, natural selection is expected to accelerate the timing and pace of reproduction in individuals who experience some forms of early-life adversity. However, the adaptive benefits of reproductive acceleration following early adversity remain untested. Here, we test a recent version of this theory, the internal predictive adaptive response (iPAR) model, by assessing whether accelerating reproduction following early-life adversity leads to higher lifetime reproductive success. We do so by leveraging 48 y of continuous, individual-based data from wild female baboons in the Amboseli ecosystem in Kenya, including prospective, longitudinal data on multiple sources of nutritional and psychosocial adversity in early life; reproductive pace; and lifetime reproductive success. We find that while early-life adversity led to dramatically shorter lifespans, individuals who experienced early adversity did not accelerate their reproduction compared with those who did not experience early adversity. Further, while accelerated reproduction predicted increased lifetime reproductive success overall, these benefits were not specific to females who experienced early-life adversity. Instead, females only benefited from reproductive acceleration if they also led long lives. Our results call into question the theory that accelerated reproduction is an adaptive response to both nutritional and psychosocial sources of early-life adversity in baboons and other long-lived species.
29
Muir, Angela M. "The cost of reproduction to the clonal herb Asarum canadense (wild ginger)". Canadian Journal of Botany 73, n. 10 (1 ottobre 1995): 1683–86. http://dx.doi.org/10.1139/b95-182.
Testo completoAbstract (sommario):
The cost of reproduction to the clonal understorey herb Asarum canadense (wild ginger) was examined by measuring subsequent growth and storage. All connected vegetative rhizome was controlled and fully measured. Three important aspects of reproductive effort were addressed: (i) the effect of sexual reproduction on subsequent storage and growth of fragments, (ii) the effect of asexual reproduction on subsequent storage and growth of fragments, and (iii) a comparison to determine the least costly method of reproduction. It was found that sexual reproduction in wild ginger has an energy cost that diverts energy from storage and growth. Asexual reproduction represents neither a net energy cost nor gain to the fragment and is the least costly mode of reproduction to wild ginger. Key words: Asarum canadense, reproduction, rhizome, clonal.
30
Mirando, M. A., e F. Stormshak. "REPRODUCTION SYMPOSIUM: External influences on reproductive neuroendocrinology1". Journal of Animal Science 92, n. 8 (1 agosto 2014): 3183–84. http://dx.doi.org/10.2527/jas.2014-8219.
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31
Usacheva, E. "Reproductive choice in natural and assisted reproduction". Russian Juridical Journal, n. 3 (2021): 139–49. http://dx.doi.org/10.34076/20713797_2021_139.
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32
Tkachenko, L. V., I. A. Gritsenko, K. Yu Tikhaeva, N. I. Sviridova, I. S. Gavrilova, V. A. Dolgova, A. S. Romanchenko e E. A. Savostova. "Abortion: reproductive choice or loss of reproduction?" Medical alphabet, n. 8 (11 giugno 2021): 44–48. http://dx.doi.org/10.33667/2078-5631-2021-8-44-48.
Testo completoAbstract (sommario):
This literature review of articles devoted to the problem of abortion and pre-abortion counseling has been carried out. The legal features of the development of the right to abortion at the request of a woman are outlined. The main stages in the development of the concept of perinatal psychology and pre-abortion counseling are described. The procedure for conducting pre-abortion counseling in the Russian Federation has been studied. The effectiveness of the existing algorithm was assessed and the prospects for further research aimed at studying and improving the effectiveness of pre-abortion counseling were outlined.
33
Renfree, Marilyn B. "WOMEN IN REPRODUCTIVE SCIENCE: Reproduction down under". Reproduction 158, n. 6 (dicembre 2019): F127—F137. http://dx.doi.org/10.1530/rep-19-0230.
Testo completoAbstract (sommario):
Australia is home to a unique assembly of mammals – the marsupials and monotremes. Despite this uniqueness, they have been largely ignored by the biomedical scientific community, and yet study of marsupials has contributed to modern research on reproduction, development, evolution, conservation, molecular and comparative genomics. My lifetime passion for these long-neglected Australian fauna has led to unexpected discoveries and insights that challenged assumptions and opened up new areas of international research. I used a range of disciplinary expertise to pursue the study of these unique mammals. My main experimental species has been the tammar wallaby that I have used as a model species to investigate and understand not only biomedical problems but also to provide knowledge that is critical for the continued conservation and management of Australia’s dwindling native mammals. This model provided more than a few surprises for me and my wonderful team of students, post-docs and collaborators about how hormones, genes and signalling molecules control reproductive biology and development in a wider context as well as how the interactions of the environment with mother and conceptus, with mother and fetus and mother and young ultimately control most aspects of successful reproduction in mammals.
34
Guderley, Helga. "Reproduction & DevelopmentVertebrate Reproduction.E. W. Jameson, Jr." Quarterly Review of Biology 65, n. 1 (marzo 1990): 81. http://dx.doi.org/10.1086/416627.
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35
Ferguson, P. R. "Book Review: Artificial Reproduction and Reproductive Rights". Medical Law International 1, n. 1 (marzo 1993): 123–24. http://dx.doi.org/10.1177/096853329300100109.
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36
Day, B. N. "Reproductive biotechnologies: current status in porcine reproduction". Animal Reproduction Science 60-61 (luglio 2000): 161–72. http://dx.doi.org/10.1016/s0378-4320(00)00079-8.
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Condit, Deirdre M. "Writing reproduction: Reproductive technologies and motherhood examined". Policy Sciences 27, n. 2-3 (1994): 287–94. http://dx.doi.org/10.1007/bf00999894.
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38
Halliday, Tim. "Reproduction in mammals: Book 4. Reproductive fitness". Animal Behaviour 34 (febbraio 1986): 310–11. http://dx.doi.org/10.1016/0003-3472(86)90053-9.
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39
Forslund, Helena, e Lena Kautsky. "Reproduction and reproductive isolation inFucus radicans(Phaeophyceae)". Marine Biology Research 9, n. 3 (aprile 2013): 321–26. http://dx.doi.org/10.1080/17451000.2012.731694.
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40
Bahadur, G. "Ethical challenges in reproductive medicine: posthumous reproduction". International Congress Series 1266 (aprile 2004): 295–302. http://dx.doi.org/10.1016/j.ics.2004.01.105.
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41
Pijnenborg, R. "Reproduction in mammals. Book 4. Reproductive fitness". European Journal of Obstetrics & Gynecology and Reproductive Biology 22, n. 5-6 (settembre 1986): 383. http://dx.doi.org/10.1016/0028-2243(86)90130-9.
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42
Søvik, Guldborg, e Hans Petter Leinaas. "Adult survival and reproduction in an arctic mite, Ameronothrus lineatus (Acari, Oribatida): effects of temperature and winter cold". Canadian Journal of Zoology 81, n. 9 (1 settembre 2003): 1579–88. http://dx.doi.org/10.1139/z03-113.
Testo completoAbstract (sommario):
Survival and reproduction of an arctic population of Ameronothrus lineatus were studied at four constant temperatures (5, 10, 15, and 21 °C). By simulating winters in the laboratory, an adult population was followed through 3 "years". Increasing temperatures reduced adult longevity. Females survived longer than males. A temperature of 15 °C was the most favourable for reproduction, with highest larviposition rate and reproductive output. Lifetime reproductive output was also high at 10 °C, while lower numbers of larvae at 21 °C indicated the beginning of heat stress. Comparison with field data showed that the reproductive performance at 15 °C corresponded to reproduction in a natural population experiencing a mean temperature of 89 °C, suggesting a positive effect of daily temperature fluctuations. A simulated winter with freezing temperatures increased male survival and positively affected all aspects of reproduction the following laboratory summer.
43
Whitekettle, Richard. "Biblical Lessons on Third-Party Reproduction". Ethics & Medics 45, n. 4 (2020): 3–4. http://dx.doi.org/10.5840/em202045413.
Testo completoAbstract (sommario):
Third-party reproduction uses ovum donors, sperm donors, embryo donors, and gestational surrogates in various combinations to create a child for heterosexual couples, same-sex couples, and individuals to raise. Its use is increasing in the United States and around the world, and it is increasingly the subject of legislation. But third-party reproduction tells the individuals who provide the ovum, sperm, and gestation required to create a child that they are reproductive mechanisms, not reproductive persons. By contrast, multiple stories in the Bible involving third-party reproduction recognize the motherhood and fatherhood, and thus the reproductive personhood, of those whose sexual union brings forth a new child. This is an important point for people of faith and the public to be mindful of.
44
Barve, Sahas, Christina Riehl, Eric L. Walters, Joseph Haydock, Hannah L. Dugdale e Walter D. Koenig. "Lifetime reproductive benefits of cooperative polygamy vary for males and females in the acorn woodpecker ( Melanerpes formicivorus )". Proceedings of the Royal Society B: Biological Sciences 288, n. 1957 (18 agosto 2021): 20210579. http://dx.doi.org/10.1098/rspb.2021.0579.
Testo completoAbstract (sommario):
Cooperative breeding strategies lead to short-term direct fitness losses when individuals forfeit or share reproduction. The direct fitness benefits of cooperative strategies are often delayed and difficult to quantify, requiring data on lifetime reproduction. Here, we use a longitudinal dataset to examine the lifetime reproductive success of cooperative polygamy in acorn woodpeckers ( Melanerpes formicivorus ), which nest as lone pairs or share reproduction with same-sex cobreeders. We found that males and females produced fewer young per successful nesting attempt when sharing reproduction. However, males nesting in duos and trios had longer reproductive lifespans, more lifetime nesting attempts and higher lifetime reproductive success than those breeding alone. For females, cobreeding in duos increased reproductive lifespan so the lifetime reproductive success of females nesting in duos was comparable to those nesting alone and higher than those nesting in trios. These results suggest that for male duos and trios, reproductive success alone may provide sufficient fitness benefits to explain the presence of cooperative polygamy, and the benefits of cobreeding as a duo in females are higher than previously assumed. Lifetime individual fitness data are crucial to reveal the full costs and benefits of cooperative polygamy.
45
Kim, Byeongseok, e Youngsok Choi. "The Development, Differentiation, and Toxicity in Reproduction". International Journal of Molecular Sciences 23, n. 13 (28 giugno 2022): 7183. http://dx.doi.org/10.3390/ijms23137183.
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46
Jonsen, Albert R. "Reproduction and Rationality". Cambridge Quarterly of Healthcare Ethics 4, n. 3 (1995): 263–67. http://dx.doi.org/10.1017/s0963180100006009.
Testo completoAbstract (sommario):
Many years ago, the esteemed patriarch of bioethics, Joseph Fletcher, spoke loud and clear in favor of rationality in reproduction. By rationality, he meant not merely limiting population growth, which he certainly favored, but bringing to bear human analytic and creative intelligence on the random and instinctive activities of sexual intercourse and procreation that we share with all mammals. In his 1974 book, The Ethics of Genetic Control: Ending Reproductive Roulette, he foresaw most of the issues that we are facing today. He reflected on artificial insemination, prenatal diagnosis, cloning, eugenics, ectogenesis, ovum transfers, and genetic engineering. He examined these innovations to the extent that he felt that each of them represents a way of exercising rational and responsible control over life and reproduction. The subtitle of his book, “Ending Reproductive Roulette,” proclaims his faith. Dr. Fletcher's dedication to rationality led him to make the astonishing statement, “Man is a maker and the more rationally contrived and deliberate anything is, the more human it is. Therefore, laboratory reproduction is radically human compared to conception by ordinary heterosexual intercourse.”
47
Tauber, Catherine A., e Maurice J. Tauber. "Inheritance of seasonal cycles in Chrysoperla (Insecta: Neuroptera)". Genetical Research 49, n. 3 (giugno 1987): 215–23. http://dx.doi.org/10.1017/s0016672300027105.
Testo completoAbstract (sommario):
SummaryTwo separate, but interacting, genetic systems underlie the variation in seasonal cycles among members of the Chrysoperla carnea species-complex. The two systems are expressed as all-or-none reproductive responses to photoperiod and prey (i.e. short-day/long-day requirement for reproduction versus long-day reproduction and prey requirement for reproduction versus reproduction without prey). In each case the alternative to reproduction is reproductive diapause. The photoperiodic responses are determined by alleles at two unlinked autosomal loci. The expression of dominance by the alleles at these loci varies among geographical populations. The genes that determine the photoperiodic responses also act as suppressors of the genes that govern responsiveness to prey. An autosomal, polygenic system, with a threshold for the expression of diapause, determines responsiveness to prey. The two genetic systems are important to seasonal diversification and speciation within the C. carnea species-complex.
48
Lafaille, Marie, Patrick Gouat e Christophe Féron. "Efficiency of delayed reproduction in Mus spicilegus". Reproduction, Fertility and Development 27, n. 3 (2015): 491. http://dx.doi.org/10.1071/rd13130.
Testo completoAbstract (sommario):
To cope with seasonally varying ecological constraints, some mammals temporally suppress breeding or delay their first reproduction. In field conditions, mound-building mice (Mus spicilegus) born in spring begin to reproduce when 2–3 months old, whereas individuals born at the end of summer delay their first reproduction for 6–8 months until the following spring. In order to test age effects on reproductive performance in M. spicilegus, sexually naïve mice were paired when 2–3 months old or at 6–8 months of age, and surveyed for reproduction. We show here that under laboratory conditions the aging of these mice does not impair their reproductive efficiency. Thus, the hypothesis of a lower reproductive potential in these relatively aged females seems to be contradicted. More surprisingly, the latency from pairing to the first reproduction was greater in the 2–3-month-old adults than in the delayed reproducers (6–8-month-old mice). Mound-building mice that are old enough to have overwintered do not suffer significant reproductive declines, but appear to reproduce as well and more quickly than younger first-time breeders.
49
Khan, Imran, Ayman Mesalam, Yun Seok Heo, Seo-Hyun Lee, Ghulam Nabi e Il-Keun Kong. "Heat Stress as a Barrier to Successful Reproduction and Potential Alleviation Strategies in Cattle". Animals 13, n. 14 (19 luglio 2023): 2359. http://dx.doi.org/10.3390/ani13142359.
Testo completoAbstract (sommario):
In recent decades, the adverse effects of global warming on all living beings have been unanimously recognized across the world. A high environmental temperature that increases the respiration and rectal temperature of cattle is called heat stress (HS), and it can affect both male and female reproductive functions. For successful reproduction and fertilization, mature and healthy oocytes are crucial; however, HS reduces the developmental competence of oocytes, which compromises reproduction. HS disturbs the hormonal balance that plays a crucial role in successful reproduction, particularly in reducing the luteinizing hormone and progesterone levels, which leads to severe problems such as poor follicle development with a poor-quality oocyte and problems related to maturity, silent estrus, abnormal or weak embryo development, and pregnancy loss, resulting in a declining reproduction rate and losses for the cattle industry. Lactating cattle are particularly susceptible to HS and, hence, their reproduction rate is substantially reduced. Additionally, bulls are also affected by HS; during summer, semen quality and sperm motility decline, leading to compromised reproduction. In summer, the conception rate is reduced by 20–30% worldwide. Although various techniques, such as the provision of water sprinklers, shade, and air conditioning, are used during summer, these methods are insufficient to recover the normal reproduction rate and, therefore, special attention is needed to improve reproductive efficiency and minimize the detrimental effect of HS on cattle during summer. The application of advanced reproductive technologies such as the production of embryos in vitro, cryopreservation during the hot season, embryo transfer, and timed artificial insemination may minimize the detrimental effects of HS on livestock reproduction and recover the losses in the cattle industry.
50
Heidinger, Britt J., Ian C. T. Nisbet e Ellen D. Ketterson. "Older parents are less responsive to a stressor in a long-lived seabird: a mechanism for increased reproductive performance with age?" Proceedings of the Royal Society B: Biological Sciences 273, n. 1598 (20 giugno 2006): 2227–31. http://dx.doi.org/10.1098/rspb.2006.3557.
Testo completoAbstract (sommario):
In many taxa, reproductive performance increases throughout the lifespan and this may occur in part because older adults invest more in reproduction. The mechanisms that facilitate an increase in reproductive performance with age, however, are poorly understood. In response to stressors, vertebrates release glucocorticoids, which enhance survival but concurrently shift investment away from reproduction. Consequently, when the value of current reproduction is high relative to the value of future reproduction and survival, as it is in older adults, life history theory predicts that the stress response should be suppressed. In this study, we tested the hypothesis that older parents would respond less strongly to a stressor in a natural, breeding population of common terns ( Sterna hirundo ). Common terns are long-lived seabirds and reproductive performance is known to increase throughout the lifespan of this species. As predicted, the maximum level of glucocorticoids released in response to handling stress decreased significantly with age. We suggest that suppression of the stress response may be an important physiological mechanism that facilitates an increase in reproductive performance with age.