ORCID Profile
0000-0002-5125-2983
Current Organisations
Australian National University
,
University of Tokyo
,
University of Oxford
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Publisher: Wiley
Date: 19-07-2022
DOI: 10.1111/EVO.14567
Abstract: Developmental and adult environments can interact in complex ways to influence the fitness of in iduals. Most studies investigating effects of the environment on fitness focus on environments experienced and traits expressed at a single point in an organism's life. However, environments vary with time, so the effects of the environments that organisms experience at different ages may interact to affect how traits change throughout life. Here, we test whether thermal stress experienced during development leads in iduals to cope better with thermal stress as adults. We manipulated temperature during both development and adulthood and measured a range of life-history traits, including senescence, in male and female seed beetles (Callosobruchus maculatus). We found that thermal stress during development reduced adult reproductive performance of females. In contrast, life span and age-dependent mortality were affected more by adult than developmental environments, with high adult temperatures decreasing longevity and increasing age-dependent mortality. Aside from an interaction between developmental and adult environments to affect age-dependent changes in male weight, we did not find any evidence of a beneficial acclimation response to developmental thermal stress. Overall, our results show that effects of developmental and adult environments can be both sex and trait specific, and that a full understanding of how environments interact to affect fitness and ageing requires the integrated study of conditions experienced during different stages of ontogeny.
Publisher: Springer Science and Business Media LLC
Date: 11-04-2021
Publisher: Cold Spring Harbor Laboratory
Date: 14-04-2023
DOI: 10.1101/2023.04.14.536443
Abstract: Senescence, the deterioration of organismal function with advancing age, is a puzzling biological phenomenon. While actuarial senescence ( i.e. , age-dependent increases in mortality rates) is well described across some taxa, reproductive senescence ( i.e. age- dependent declines in reproduction) is less understood, especially in males, with mixed patterns reported across studies. To examine the evidence for male reproductive senescence, we investigated how advancing male age affects ejaculate traits across non-human animals via a meta-analysis yielding 1814 effect sizes from 379 studies. We found no evidence for a general pattern of reproductive senescence. Instead, we found high heterogeneity for how reproduction changes with male age across animals. Some of this heterogeneity ( %) was associated with biological factors. For ex le, there were taxonomical differences for some ejaculate traits — sperm motility declined with male age in lab rodents and fish, whereas ejaculate size improved with male age in bulls, fish, and insects. Some methodological factors were also important in explaining this heterogeneity: studies s ling a larger proportion of a species’ lifespan were more likely to detect senescence in ejaculate traits, emphasising the need to examine the full life cycle of species to document senescence. Contrary to predictions, we reveal that the evidence for senescence in ejaculate traits is sporadic. Our findings will help generate novel hypotheses and identify more effective methodological approaches for studying male reproductive senescence.
Publisher: Cold Spring Harbor Laboratory
Date: 25-08-2020
DOI: 10.1101/2020.08.24.265736
Abstract: The environment organisms experience during development can have effects which carry over into their adult lives. These developmental environments may not only affect adult traits at a given point in time, but also how these traits change with age. Generally, stressful developmental environments can lead to sub-optimal adult fitness traits and a faster deterioration of these traits with age. But whether these environments affect how performance traits change with age or whether they affect males and females differently lacks evidence. Here, we test the sex-specific effects of crowding during development on life history traits such as lifespan, fecundity, age-dependent survival, and reproductive senescence, as well as flight performance traits, in the seed beetle- Callosobruchus maculatus . We show that although developmental crowding has no effect on flight performance of either sex, on male adult lifespan, or on female age-dependant survival, it is detrimental to female lifespan and fecundity, as well as female age-dependent reproduction. Additionally, we show that flight traits can change with age and differ between males and females, which may be reflective of sex-specific life-histories and behaviour. Our study has implications for understanding how developmental environments affect life history and behavioural strategies of both males and females.
Publisher: Cold Spring Harbor Laboratory
Date: 16-10-2021
DOI: 10.1101/2021.10.15.464502
Abstract: Early and late life environments can interact in complex ways to influence the fitness of in iduals. Most studies investigating effects of the environment on fitness focus on environments experienced and traits expressed at a single point in an organism’s life. However, environments vary with time, thus the environments organisms experience at different ages may interact to affect how traits change throughout life. Here, we test whether thermal stress experienced during development leads in iduals to cope better with thermal stress as adults. We manipulated temperature during both development and adulthood and measured a range of life-history traits, including senescence, in male and female seed beetles, Callosobruchus maculatus . We found that favourable developmental conditions increased reproductive performance of females (i.e. silver-spoon effects). In contrast, non-reproductive traits such as lifespan and survival senescence were only affected by adult environments- high adult temperatures decreased longevity and survival. Additionally, developmental and adult environments interacted to affect age-dependent changes in male weight. Overall, our results show that effects of early and late environments can be both sex- and trait- specific, and that a full understanding of how environments interact to affect fitness and ageing requires the integrated study of conditions experienced during different stages of ontogeny.
Publisher: Elsevier BV
Date: 05-2017
DOI: 10.1016/J.BRS.2016.12.001
Abstract: The potential of non-invasive brain stimulation (NIBS) for both probing human neuroplasticity and the induction of functionally relevant neuroplastic change has received significant interest. However, at present the utility of NIBS is limited due to high response variability. One reason for this response variability is that NIBS targets a diffuse cortical population and the net outcome to stimulation depends on the relative levels of excitability in each population. There is evidence that the relative excitability of complex oligosynaptic circuits (late I-wave circuits) as assessed by transcranial magnetic stimulation (TMS) is useful in predicting NIBS response. Here we examined whether an additional marker of cortical excitability, MEP litude variability, could provide additional insights into response variability following application of the continuous theta burst stimulation (cTBS) NIBS protocol. Additionally we investigated whether I-wave recruitment was associated with MEP variability. Thirty-four healthy subjects (15 male, aged 18-35 years) participated in two experiments. Experiment 1 investigated baseline MEP variability and cTBS response. Experiment 2 determined if I-wave recruitment was associated with MEP variability. Data show that both baseline MEP variability and late I-wave recruitment are associated with cTBS response, but were independent of each other together, these variables predict 31% of the variability in cTBS response. This study provides insight into the physiological mechanisms underpinning NIBS plasticity responses and may facilitate development of more reliable NIBS protocols.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Krish Sanghvi.