Biology subjects

Nandy, B.

Publications and source records attributed to Nandy, B..

12 recordsLinked to original sources

bioRxiv2025

ADAPTATION AGAINST LONG-TERM PROTEIN DEPRIVATION TRADES OFF WITH IMMUNOCOMPETENCE AND THE ABILITY TO SURVIVE PATHOGENIC INFECTIONS

Insufficient protein intake, leading to malnutrition, is a major global health concern that compromises the immune system and increases susceptibility to diseases. In scenarios where protein availability is constrained, organisms may experience strong selection to efficiently allocate their resources between immunity vs other energy-demanding processes, such as reproduction, resulting in evolutionary trade-offs. Additionally, in many species, protein deficiency has a more significant impact on female reproduction than on males, potentially leading to pronounced sexually dimorphic trade-offs involving immunity and infection outcomes. However, there are no experiments to test these possibilities. In this work, we demonstrate that in Drosophila melanogaster populations selected for increased early-life reproduction under protein limitations, evolved virgin females indeed suffered a greater reduction in their resistance to the pathogen Providencia rettgeri and showed lower survival following infection than males, corroborating our expectations. However, mating resulted in a loss of sexually dimorphic infection outcomes, causing both sexes to exhibit nearly identical infection costs and reduced infection tolerance compared to their ancestral, unselected populations. Moreover, several immune components, including the Toll- and IMD-mediated inducible immune pathways, were either less upregulated or more downregulated in the selected flies, which may contribute to their heightened susceptibility to pathogens. Downregulation in key metabolic pathways and genes related to phagocytosis, melanisation and ROS-mediated defence after infection in selected flies can also be associated with their increased pathogen vulnerability. Taken together, our work thus reveals the reproductive status- and sex-specific plasticity of immune investments and post-infection health in response to evolutionary constraints under chronic protein deprivation.

evolutionary biology↗

bioRxiv2025

Foam film vitrification for cryo-EM

Electron cryomicroscopy (cryo-EM) has revolutionised structural biology, enhancing applicability, size limits and speed. Despite these successes, cryo-EM sample preparation remains a major bottleneck for routinely achieving high-resolution structures through single particle analysis. Challenges such as inconsistent ice thicknesses, air-water interface interactions and preferred particle orientation persist. Here, we introduce a blot-free vitrification method that uses free-standing surfactant-stabilised foam films to address some of these issues. The method achieves uniform ice thicknesses, enables thickness control of the foam film prior to vitrification, and for some specimens enhances orientation distribution efficiency. Furthermore, it reduces particle adsorption to carbon foil on the specimen support. The method simplifies cryo-EM specimen preparation, offering improved control over ice thickness and particle orientation, to help streamline and accelerate structure determination.

biophysics↗

bioRxiv2025

Sexual conflict over mating duration and frequency in Zygogramma bicolorata

Duration and frequency of mating are the most prominent aspects of mating behaviour over which sexual conflict can occur. Parthenium beetle (Zygogramma bicolorata) exhibits an extremely high mating rate, with each mating typically lasting several hours. We investigated mating behaviour in this beetle to assess if there is sexual conflict. Theories of sexual conflict predict that such mating behaviour, while being beneficial to the males, should be detrimental to the females with regard to reproduction and/or survival. We experimentally manipulated the length and number of matings, and examined the effect on fecundity and survivorship of the females. While long mating has previously been identified as a mate-guarding strategy that benefits the males, our data reveal that it is detrimental to female fitness, supporting the sexual conflict hypothesis. Further, we checked natural variation in mating duration and its correlation with key fitness components. Our results show that female longevity is negatively correlated to reproductive rate, but positively correlated to lifetime reproduction. We argue that such a pattern is consistent with sexual conflict. While being the first clear demonstration of sexual conflict in this species, we discuss its significance, including a potential role in reducing its efficacy as a biocontrol.

animal behavior and cognition↗

bioRxiv2024

Adaptation to yeast restriction through the evolution of resource acquisition, macronutrient reserve, and ovarian function

Optimization of reproduction under dietary adversity is an important aspect of diet-dependent adaptation. Yet, little is known about the mechanism of such adaptive evolution. Here, we investigated a set of experimentally evolved populations of Drosophila melanogaster where early-life fecundity evolved as an adaptation to chronic protein restriction. We tested the role of resource acquisition and macronutrient storage, and changes in ovarian function that could have allowed such reproductive adaptation. We show that higher early-life fecundity was associated with the increased larval feeding rate, aiding in accumulation of higher protein content at the time of eclosion. Further evidence also suggests increase in reproductively allocated lipid content. Evolved females were found to have larger ovaries that also had a higher number of mature, post-vitellogenic oocytes that seem to readily allow the attainment of higher fecundity. Our results further show the evolution of plasticity in ovariole count (depending on mating status) and total egg-chamber count in females. These results are important in understanding the putative role of genetic variance and covariances that aid or limit the evolution of reproductive optimization, especially under nutritional adversity.

evolutionary biology↗

bioRxiv2024

Nutrition and density dependence of spontaneous female-biased dispersal in Drosophila

Dispersal is often essential for the attainment of Darwinian fitness, especially for species living on spatially structured, heterogeneous habitats. Theoretically, sex-specific resource requirement can drive the two sexes to disperse differently, resulting in sex biased dispersal (SBD). Understanding ecological factors affecting SBD is important. Using an experimental two-patch dispersal setup we measured spontaneous dispersal in laboratory adapted populations of Drosophila melanogaster under a set of common, interlinked ecological scenarios relating to - (a) dietary ecology and (b) adult density. We found deteriorating overall nutritional quality of food affects strength of SBD, and female dispersal is particularly sensitive to availability of protein. Adult density had sex specific effect on dispersal. Female dispersal was found to be density independent but males showed increased dispersal at higher density. Female tend to disperse more from male biased patch likely to avoid male harassment whereas absence of female drives male dispersal solidifying mate-finding dispersal hypothesis. These evidences of dispersal suggest that variation in dietary ecology and intraspecific competition can affect the degree and strength of existing SBD and thereby male-female interactions in a patch potentially affecting fitness components and population dynamics.

evolutionary biology↗

bioRxiv2024

Long mounting with repeated copulations in Zygogramma bicolorata: A test of adaptive significance of a curious mating behaviour

Long matings are abundant in insects despite the range of the costs involved. The causes and consequences of the evolution of long matings remain an interesting problem for behavioural ecologists. We studied the Parthenium beetle (Zygogramma bicolorata), which is known to show extraordinarily long copulations. Our detailed investigation showed, for the first time, that the long mounting in this species entails repeated copulation. Each of these copulations is preceded and succeeded by a leg-rubbing behaviour. We found the same characteristic pattern in laboratory and semi-natural conditions. We conducted a series of interrupted mounting assays to examine the fitness consequences of the duration of mounting. We tested multiple hypotheses regarding the transfer of sperm and non-sperm components, and the function of leg rubbing in modulating the female copulatory behaviour. Sperm transfer and fertility did not exhibit a linear increase with the number of copulations. There was also no evidence of nutrient transfer by the males. In contrast, our experiments reveal significant cost of long mounting in these beetles. We showed female remating behaviour can be modulated by the long previous mounting. Our data also suggest that leg rubbing may reduce female resistance to mating. While the long mating possibly serves as copulatory mate guarding, the males may increase their competitive ability through modulating female remating. We also propose leg rubbing to be a copulatory courtship behaviour. Our study provides preliminary insights into the evolution of long mating in such systems and necessitates further research on sexual selection.

animal behavior and cognition↗

bioRxiv2022

Evolution of mate harm resistance in females from Drosophila melanogaster populations selection for faster development and early reproduction

Interlocus sexual conflict is predicted to result in sexually antagonistic coevolution between male competitive traits, which are also female-detrimental, and mate harm resistance (MHR) in females. Little is known about connection life-history evolution and sexually antagonistic coevolution. Here, we investigated the evolution of MHR in a set of experimentally evolved populations, where mate-harming ability has been shown to have evolved in males as a correlated response to the selection for faster development and early reproduction. We measured mortality and fecundity of females of these populations and those of their matched controls, under different male exposure conditions. We observed that the evolved females were more susceptible to mate harm - suffering from significantly higher mortality under continuous exposure to control males within the twenty-day assay period. Though these evolved females are known to have shorter lifespan, such higher mortality was not observed under virgin and single-mating conditions. We used fecundity data to show that this higher mortality in evolved females is unlikely due to cost of egg production. Further analysis indicated that this decreased MHR is unlikely to be due purely to the smaller size of these females. Instead, it is more likely to be an indirect experimentally evolved response attributable to the changed breeding ecology, and/or male trait evolution. Our results underline the implications of changes in life history traits, including lifespan, to the evolution of MHR in females.

evolutionary biology↗

bioRxiv2022

Spatial structure does not reduce population level interlocus sexual conflict but imposes additional sex-specific costs

Spatial structure is a common feature of all naturally occurring populations. Theoretically, spatial structuring of a habitat could modulate the intensity of Interlocus sexual conflict (ISC) in a population, possibly by modulating intersexual encounter rate. We tested this theory using laboratory populations of Drosophila melanogaster by measuring male induced fitness decline in females in three-patch habitat systems under two alternative habitat types - structured-interconnected and unstructured. Our results on reproductive and survival costs in females suggested significant costs due to (a) male presence (i.e., ISC) and (b) living on structured habitat. However, there was only a weak evidence supporting the theory of modulation of ISC by habitat structuring only. Through a follow up experiment, we further showed that the effect of habitat on ISC is also robust to the alteration of female conditions. Therefore, it appears that spatial structuring per se is unlikely to modulate ISC, but can impose additional survival costs. We further showed such survival cost could be sex-specific possibly reflecting female biased spontaneous dispersal.

evolutionary biology↗

bioRxiv2021

Evolution of reduced mate-harming tendency of males in Drosophila melanogaster populations selected for faster life history

Detrimental effect of males on female, often termed mate harm, is a hallmark of sexual conflict. Allowed to evolve unchecked, mate harming traits are predicted to bring down average fitness of a population, unless mitigated by the evolution of resistance in females. In addition, life history may also modulate sexual conflict, but the mechanism is not clearly understood. Here we investigated the evolution of mate harm in a set of experimentally evolved laboratory populations of Drosophila melanogaster wherein a faster aging has evolved in response to >1000 generations of selection for faster development and early reproduction. We quantified mortality and fecundity of Oregon R females held with evolved (ACO) and ancestral males (CO) to show that the evolved males are significantly less detrimental to their mates. We compared our results from the ACO males with that from a phenocopied version of the ancestral regime (CCO) to show that only part of the observed difference in mate harm can be attributed to the evolved difference in body size. We further show that the reduction in mate harming ability evolved despite an increase in courtship activity, especially early in life. We discuss the causative role of an evolved reproductive schedule and altered breeding ecology. Significance statementSexually antagonistic male effects can significantly bring down female fitness. Along with female counter evolution of resistance traits, life history has been conjectured to impose constrains on the evolution of such harming ability in males. Here, we report the evolution of mate harming ability in males of a set of five replicate Drosophila melanogaster populations that evolved smaller size and faster aging as a result of >1000 generations of experimental evolution for faster development and early reproduction. We show that in spite of ample scope of sexual selection, the faster aging males have evolved reduced mate harming ability despite being more active in courting their mates. To the best of our knowledge, this is one of the first clear evidences demonstrating the causal relationship between evolution of life history and reduction in sexual antagonism in a population.

evolutionary biology↗

bioRxiv2021

Evolution of increased early-life fecundity but faster reproductive senescence in Drosophila melanogaster females through adaptation to chronic live-yeast deprivation

Reproductive output is often constrained by availability of macronutrients, especially protein. Long term protein restriction, therefore, is expected to select for traits that maximize reproductive output in spite of such nutritional challenge. We subjected four replicate populations of Drosophila melanogaster to a complete deprivation of live-yeast supplement, thereby mimicking a protein restricted ecology. As yeast supplement is a key source of protein, such an ecology is expected to strongly limit reproductive output, especially in females. Following 24 generations of experimental evolution, compared to their matched controls, females from experimentally evolved populations showed increase in reproductive output early in life, both in presence and absence of yeast supplement. The observed increase in reproductive output was not associated with any accommodating alteration in egg size; and development time, pre-adult survivorship, and body mass at eclosion of the progeny. There was no evidence for evolution of lifespan and lifelong cumulative reproductive output in females. However, females from experiment regime were found to have a significantly faster rate of reproductive senescence, as indicated by a faster rate of age related decline in reproductive output following the attainment of the reproductive peak. Therefore, adaptation to yeast deprivation ecology in our study involved a novel reproductive strategy whereby females attained higher reproductive output early in life followed by faster reproductive aging. To the best of our knowledge, this set of results is one of the most clear demonstration of optimization of fitness by fine tuning of reproductive schedule during adaptation to a prolonged nutritional deprivation. Supplementary informationA separate file that includes three figures and six tables.

evolutionary biology↗

bioRxiv2021

Extremely rapid development and early reproduction reduces sexual selection in D. melanogaster populations.

The role of sexual selection in mediating levels of sexual conflict has been demonstrated in many experimental evolution studies on Drosophila spp. where competition among males for mating was the target of selection. Sexual selection has also been shown to affect the evolution of life-histories. However, the influence of divergent life-histories on reproductive strategies and, therefore, sexual selection and possibly sexual conflict, has been less well studied. We examined D. melanogaster populations selected for a short development time and early age at reproduction for changes in reproductive behaviour and traits that are proxies of sexual selection. We report a large reduction in reproductive competition experienced by the males of these populations, compared to ancestral populations that are not consciously selected for rapid development or early reproduction, potentially leading to reduced sexual selection. We show that rapidly developing and early reproducing populations have very low levels of mating in their lifetime (females are more or less monandrous), low courtship levels, shorter copulation duration, and longer time from eclosion to first mating, compared to the controls. These results are discussed in the context of the previously demonstrated reduction of inter-locus sexual conflict in these populations. We show that life-history strategies might have a large and significant impact on sexual selection, with each influencing the other and contributing to the complexities of adaptation. Significance statementSexual conflict, often manifested as an arms-race between males and females trying to enhance their own reproductive success at some cost to the other, is of great evolutionary interest because it can maintain genetic variation in populations, prevent the independent optimization of male and female traits, and also promote speciation. Sexual selection, or variation in mating success, is well known to affect levels of sexual conflict. However, it is not so clear whether, and how, the regular evolution of life-histories also affects sexual selection. Here, we show that life-history evolution in fruit fly populations selected for traits not directly related to sexual conflict might, nevertheless, mediate the possible evolution of altered sexual conflict levels through effects on sexual selection. Populations that evolved to develop to adulthood fast, and reproduce relatively early in life, are shown to potentially experience less sexual selection, which can explain the low sexual conflict levels earlier observed in them.

evolutionary biology↗

bioRxiv2018

Transgenerational effect of adult density through paternal effect in Drosophila melanogaster

O_LINotwithstanding recent evidences, paternal environment is thought to be a potential but unlikely source of fitness variation that can affect trait evolution. Here we studied intergenerational effects of males exposure to varying adult density in Drosophila melanogaster laboratory populations.\nC_LIO_LIWe held sires at normal (N), medium (M) and high (H) adult densities for two days before allowing them to mate with virgin females. This treatment did not introduce selection through differential mortality. Further, we randomly paired males and females and allowed a single round of mating between the sires and the dams. We then collected eggs from the dams and measured the egg size. Finally, we investigated the effect of the paternal treatment on juvenile and adult (male) fitness components.\nC_LIO_LIWe found a significant treatment effect on juvenile competitive ability where the progeny sired by the H-males had higher competitive ability. Since we did not find the treatment to affect egg size, this effect is unlikely to be mediated through variation in female provisioning.\nC_LIO_LIMale fitness components were also found to have a significant treatment effect: M-sons had lower dry weight at eclosion, higher mating latency and lower competitive mating success.\nC_LIO_LIWhile being the first study to show both adaptive and non-adaptive effect of the paternal density in Drosophila, our results highlight the importance of considering paternal environment as important source of fitness variation.\nC_LI

evolutionary biology↗