1,720,973 research outputs found
Sperm accumulation induced by the female reproductive fluid: Putative evidence of chemoattraction using a new tool
Full text linkThere is considerable evidence that female reproductive fluid (FRF) interacts intimately with sperm, affecting several sperm traits, including sperm motility and longevity, and ultimately fertilization success. One of the first documented interactions between FRF and sperm is the ability of FRF to attract and guide sperm towards the eggs. However, most of the evidence of FRF’s chemoat-traction proprieties comes from a limited number of taxa, specifically mammals and invertebrate broadcasting spawners. In other species, small FRF volumes and/or short sperm longevity often im-pose methodological difficulties resulting in this gap in chemoattraction studies in non-model species. One of the outcomes of sperm chemotaxis is sperm accumulation towards high chemoattractant concentrations, which can be easily quantified by measuring sperm concentration. Here, we tested sperm accumulation towards FRF in the zebrafish, Danio rerio, using an ad hoc developed, 3D printed, device (‘sperm selection chamber’). This easy-to-use tool allows to select and collect the sperm that swim towards a chemical gradient, and accumulate in a chemoattractant-filled well thus providing putative evidence for chemoattraction. We found that sperm accumulate in FRF in zebrafish. We also found that none of the sperm quality traits we measured (sperm swimming velocity and trajectory, sperm motility, and longevity) were correlated with this response. Together with the 3D printable project, we provide a detailed protocol for using the selection chamber. The chamber is optimized for the zebrafish, but it can be easily adapted for other species. Our device lays the foundation for a standardized way to measure sperm accumulation and in general chemoattraction, stimulating future research aimed at understanding the role and the mechanisms of sperm chemoattraction by FRF
Correlati elettrofisiologici del bias attentivo nella fobia del sangue: effetto della sensibilizzazione in visione passiva
No full textReproducing in hot water: Experimental heatwaves deteriorate multiple reproductive traits in a freshwater ectotherm
Full text link1. Heatwaves are occurring at an increasing frequency and intensity under ongoing climate change. As many reproductive traits—including mating behaviour and gamete traits—are sensitive even to small temperature changes, the impact of heatwaves on reproduction and sexual selection processes is likely to be vast. Also, evaluating whether the sexes respond differently to these extreme events is crucial to understand the impact on fecundity and the consequences at the population level. Nonetheless, our knowledge of the effects of heatwaves on these key aspects of animal life is still limited.
2. Here, we expose recently mated male and female guppies Poecilia reticulata to an experimental heatwave (32°C, 6°C above the control, for 5 days) to determine its effects on several traits, including sexual behaviour, condition, ornamentation and fertility. Using this design, in contrast to alternative experimental setups, we had the possibility to attribute the effects of the heatwave to males' and females' reproductive traits independently.
3. Overall, our results indicate that heatwaves can drastically affect key reproductive traits and unravel sex-specific responses. In males, there was no effect of the heatwave on survival, but both pre- and postcopulatory reproductive traits were affected. After the heatwave, we detected a decrease in orange colouration (the most important ornament on which female choice is based) and the overall level of sexual activity, and a shift in the preferred mating tactic towards forced copulation attempts. The latter suggests implications in sexual conflict dynamics, as forced copulations override female mate choice. Also, after the heatwave, males had more sperm but of lower quality, and, in addition, an increased variance in sperm number. Overall, heatwaves may thus result in a compromised ability to secure matings and fertilizations. In females, the heatwave significantly affected survival, with increased mortality in the short term, and impaired fecundity, with many females from the heatwave treatment not reproducing at all.
4.The negative effects of heatwaves on key reproductive traits unravelled by our study could have major implications for population dynamics and persistence. It highlights the need for further studies on how these extreme events affect reproduction, to improve our understanding of the impacts of climate change
Stunned by a Heatwave: Experimental Heatwaves Alter Juvenile Responsiveness to the Threat of Predation
No full textHeatwaves, increasingly prevalent in our rapidly changing climate, significantly impact animals with far-reaching ecological and evolutionary consequences. One of the first responses in animals to stress, including heat stress, is behavioural change, and this can directly influence fitness and survival. Changes in anti-predator behaviour are particularly critical, as they may compromise a prey's ability to evade predators, thus increasing predation risk and jeopardising survival. In the context of climate change, assessing anti-predator reactions under ecologically relevant heat stress is thus crucial, especially during the vulnerable life stage of development. This study investigated the effects of a heatwave on anti-predator responses in juvenile guppies (Poecilia reticulata). One-month-old guppies were subjected to a 5-day experimental heatwave (32 degrees C) or a control temperature (26 degrees C). After the treatment, all individuals were tested at a common temperature (26 degrees C) for anti-predator behavioural responses and swimming performance, the latter serving as a proxy for physical condition. While heatwave exposure did not affect swimming performance, it significantly altered anti-predator responses. Heatwave-exposed juveniles exhibited a reduced freezing response and faster resumption of normal activity compared to control fish. Our findings demonstrate that heatwaves can modify prey's anti-predator behaviours during critical developmental stages. This suggests that heatwaves may increase predation risk, potentially impacting survival rates and reshaping predator-prey interactions in the face of ongoing climate change
Color contrast and stratification of transparent figures.
No full textFigure/background organization usually entails that figures are perceived in front of the background, and in special conditions front objects appear transparent. Moreover,depth stratification is constrained by the color contrast between specific areas also when transparency is perceived. In four experiments, we showed that contrast affects surface stratification even when it is artificially produced by Cornsweet illusory contrasts, both by increasing and decreasing the color difference just at the border of the adjacent areas, and also when the colors of all areas, complementary and equiluminant included, are kept constant.The results agree with previous findings in the achromatic domain, both with opaque and transparent colors (Masin, 2000) and stress the relevance of the perceived contrast, instead of color differences, on the perception of transparency and stratification
Female reproductive fluid attracts more and better sperm: Implications for within-ejaculate cryptic female choice
Full text linkMounting evidence shows that the female reproductive fluid (FRF) can differently affect sperm performance of different males by biasing paternity share among competing males. Here, we tested for the first time the potential of 'within-ejaculate cryptic female choice' mediated by the FRF in the zebrafish (Danio rerio). Using a recently developed sperm selection chamber, we separated and collected FRF-selected from non-selected sperm to compare the two subpopulations of sperm in terms of sperm number, viability, DNA integrity and fertilizing ability. We showed that the sperm attracted by FRF are more numerous, more viable and with higher DNA integrity. In addition, FRF-selected sperm fertilized more eggs, but if this is due to fertilization ability per se or numerical advantage remains to be tested. Our results suggest that FRF can select sperm with a better phenotype, highlighting the crucial and impactful role that FRF might play in the process of fertilization and post-mating sexual selection dynamics, along with the potential implications for sperm selection in assisted reproductive techniques
Central and peripheral hemodynamics during emotional activation in essential hypotension.
No full textFemale sperm storage mediates post-copulatory costs and benefits of ejaculate anticipatory plasticity in the guppy
No full textMales of many species evolved the capability of adjusting their ejaculate phenotype in response to social cues to match the expected mating conditions. When females store sperm for a prolonged time, the expected fitness return of plastic adjustments of ejaculate phenotype may depend on the interval between mating and fertilization. Although prolonged female sperm storage (FSS) increases the opportunity for sperm competition, as a consequence of the longer temporal overlap of ejaculates from several males, it may also create variable selective forces on ejaculate phenotype, for example by exposing trade-offs between sperm velocity and sperm survival. We evaluated the relationship between the plasticity of ejaculate quality and FSS in the guppy, Poecilia reticulata, a polyandrous live-bearing fish in which females store sperm for several months and where stored sperm contribute significantly to a male's lifelong reproductive success. In this species, males respond to the perception of future mating opportunities by increasing the quantity (number) and quality (swimming velocity) of ready-to-use sperm (an anticipatory response called ‘sperm priming’). Here we investigated (a) the effect of sperm priming on in vitro sperm viability at stripping and its temporal decline (as an estimate of sperm survival), and (b) the in vivo competitive fertilization success in relation to female sperm storage using artificial insemination. As expected, sperm-primed males produced more numerous and faster sperm, but with a reduced in vitro sperm viability at stripping and after 4 hr, compared with their counterparts. Artificial insemination revealed that the small (nonsignificant) advantage of primed sperm when fertilization immediately follows insemination is reversed when eggs are fertilized by female-stored sperm, weeks after insemination. By suggesting a plastic trade-off between sperm velocity and viability, these results demonstrate that prolonged female sperm storage generates divergent selection pressures on ejaculate phenotype
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