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101 results for “Reproduction: investment”

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dryad32/100

Data from: Energetic investment associated with vitellogenesis induces an oxidative cost of reproduction

1. Oxidative stress is a potential cost of reproduction, but conclusive evidence for this relationship is lacking. The goal of this study was to serially assess across a seasonal gradient the relationship between reproduction, circulating plasma energy metabolites, and oxidative state. 2. Here we examine a study animal ideally suited to test for the oxidative costs of reproduction: The Allen Cays Rock Iguana. Female rock iguanas reproduce at varying frequencies, often skipping years, allowing for a comparison between reproductive and non-reproductive females during the same narrow, annual breeding season. This feature of iguana life-history enabled us to address not just sex and seasonal differences in physiology, but also potential oxidative costs of reproduction in females. 3. Male and female iguanas were sampled during the early (vitellogenic), late (gravid), and post-reproductive seasons. Ultrasound examinations were performed on females to quantify reproductive investment, and blood samples were collected for physiology assays, which included reactive oxygen metabolites (d-ROMs), antioxidants, triglycerides, free glycerol, and glucose. 4. The early reproductive season was characterized by significant increases in reproductive female's triglycerides, free glycerol, and oxidative stress compared to late and post-reproductive periods and non-reproductive females and males during all sampling periods. Antioxidants were significantly elevated during the early reproductive season for reproductive females, non-reproductive females, and males when compared to late and post-season. Follicle number in early reproductive females was positively related to d-ROMs, triglycerides, and free glycerol, negatively related to antioxidants, and showed no relationship with glucose. Measures of oxidative stress, d-ROMs and oxidative index were positively correlated with circulating levels of the lipid metabolite free glycerol during the early reproductive period, but this relationship weakened in the late season and disappeared in the post-season. 5. Broadly, this study supports the hypothesis that the relationship between reproduction and oxidative stress is driven by energy investment, being greatest during early reproduction when vitellogenesis is occurring.

opencc-zeroDec 2017View details →

dryad32/100

Data from: Environmental conditions shape the temporal pattern of investment in reproduction and survival

The relationship between environmental stress exposure and ageing is likely to vary with stressor severity, life history stage, and the time scale over which effects are measured. Such factors could influence whether stress exposure accelerates or slows the ageing process, but their interactions have not previously been experimentally investigated. We found that experimental exposure of zebra finches to mildly challenging environmental circumstances from young to old adulthood, which increased exposure to stress hormones, reduced breeding performance during early adulthood, but had positive effects when individuals were bred in old adulthood. This difference was not due to selective mortality, since the effects were evident within individuals, and no evidence of habituation in the response to the stressor was found. The more stressful environment had no effects on survival during young or old adulthood, but substantially improved survival during middle age. Changes in the effects at different ages could be due to the duration and nature of the challenging exposure, or to variation in coping capacity or strategy with age. These results show that living under challenging environmental circumstances can influence ageing trajectories in terms of both reproductive performance and longevity. Our results provide experimental support for the emerging idea that stress exposure needs to be optimised rather than minimised to obtain the best health outcomes.

opencc-zeroDec 2016View details →

dryad32/100

Data from: Shifts in reproductive investment in response to competitors lowers male reproductive success

In many species, males exhibit phenotypic plasticity in sexually selected traits when exposed to social cues about the intensity of sexual competition. To date, however, few studies have tested how this plasticity affects male reproductive success. We initially tested whether male mosquitofish, Gambusia holbrooki (Poeciliidae), change their investment in traits under pre- and post- copulatory sexual selection depending on the social environment. Focal males were exposed, for a full spermatogenesis cycle, to visual and chemical cues of rivals that were either present (competitive treatment) or absent (control). Males from the competitive treatment had significantly slower swimming sperm, but did not differ in sperm count from control males. When two males competed for a female, competitive treatment males also made significantly fewer copulation attempts and courtship displays than control males. Further, paternity analysis of 708 offspring from 148 potential sires, testing whether these changes in reproductive traits affected male reproductive success, showed that males previously exposed to cues about the presence of rivals sired significantly fewer offspring when competing with a control male. We discuss several possible explanations for these unusual findings.

opencc-zeroMar 2020View details →

dryad32/100

Investment in adult reproductive tissues is affected by larval growth conditions but not by evolution under poor larval growth conditions in Drosophila melanogaster

In many insects, the larval environment is confined to the egg-laying site, which often leads to crowded larval conditions, exposing the developing larvae to poor resource availability and toxic metabolic wastes. Larval crowding imposes two opposing selection pressures. On one hand, due to poor nutritional resources during developmental stages, adults from the crowded larval environment have reduced investment in reproductive tissues. On the other hand, a crowded larval environment acts as a cue for future reproductive competition inducing increased investment in reproductive tissues. Both these selection pressures are likely affected by the level of crowding. The evolutionary consequence of adaptation to larval crowding environment on adult reproductive investment is bound to be a result of the interaction of these two opposing forces. In this study, we used experimentally evolved populations of Drosophila melanogaster adapted to larval crowding to investigate the effect of adaptation to larval crowding on investment in reproductive organs (testes and accessory glands) of males. Our results show that there is a strong effect of larval developmental environment on absolute sizes of testes and accessory glands. However, there was no effect of the developmental environment when testis size was scaled by body size. We also found that flies from crowded cultures had smaller accessory gland sizes relative to body size. Moreover, the sizes of the reproductive organs were not affected by the selection histories of the populations. This study highlights that adaptation to two extremely different developmental environments does not affect the patterns of reproductive investment. We discuss the possibility that differential investment in reproductive tissues could be influenced by the mating dynamics and/or investment in larval survival traits, rather than just the developmental environment of the populations.

opencc-zeroDec 2021View details →

dryad32/100

The developmental high-wire: Balancing resource investment in immunity and reproduction

The strategic allocation of resources into immunity poses a unique challenge for individuals, where infection at different stages of development may result in unique trade-offs with concurrent physiological processes or future fitness-enhancing traits. Here, we experimentally induced an immune challenge in female Gryllus firmus crickets to test whether illness at discrete life stages differentially impacts fitness. We injected heat-killed Serratia marcescens bacteria into antepenultimate juveniles, penultimate juveniles, sexually-immature adults, and sexually-mature adults, and then measured body growth, instar duration, mating rate, viability of stored sperm, egg production, oviposition rate, and egg viability. Immune activation significantly impacted reproductive traits, where females that were immune-challenged as adults had decreased mating success and decreased egg viability compared to healthy individuals or females that were immune-challenged as juveniles. Although there was no effect of an immune challenge on the other traits measured, the stress of handling resulted in reduced mass gain and smaller adult body size in females from the juvenile treatments, and females in the adult treatments suffered from reduced viability of sperm stored within their spermatheca. In summary, we found that an immune challenge does have negative impacts on reproduction, but also that even minor acute stressors can have significant impacts on fitness-enhancing traits. These findings highlight that the factors affecting fitness can be complex and at times unpredictable, and that the consequences of illness are specific to when during an individual's life an immune-challenge is induced.

opencc-zeroMar 2022View details →

dryad32/100

Perception of dead conspecifics increases reproductive investment in fruit flies

Adaptive plasticity in life-history traits is often critical to maximize fitness in the face of environmental heterogeneity. For example, many organisms respond to a threat to their survival (and hence residual reproductive value) by adaptively increasing their investment into current reproduction (i.e. "terminal investment"). A key to successful terminal investment is the use of adequate environmental cues to extrinsic mortality sources. In species that live at high population densities, the presence of dead conspecifics could potentially act as a reliable cue to extrinsic mortality sources (e.g. via pathogens). We experimentally tested this idea using the model organism Drosophila melanogaster, a pest species that experiences marked demographic shifts. We monitored the reproductive output of young mated females during repeated bouts of egg-laying in the presence (i.e. dead-exposed) or absence (i.e. controls) of dead conspecifics, interspersed by mating periods where dead conspecifics were always absent. Dead-exposed females produced more offspring than controls when in the presence of dead conspecifics but fewer offspring than controls when dead conspecifics were subsequently removed (i.e. during mating periods). These changes were repeatable across time, and are thus indicative of high plasticity in reproductive behaviour. Flies responded equally to starvation-induced and flash-frozen dead conspecifics, indicating that the cause of death is irrelevant to trigger the plastic response observed, and that females respond to the presence of dead conspecifics per se. Finally, we found that dead-exposed females produced heavier daughters (but not sons) than controls when in the presence of dead conspecifics, but not during mating periods (when dead conspecifics were absent). In this species body size correlates more strongly with female (than male) fitness, so higher investment in daughter weight is congruent with terminal investment. Altogether, our results show that perception of dead conspecifics leads to highly plastic life-history adjustments in the form of increased investment in both the quantity and the quality of offspring. We discuss these results in the context of terminal investment and other alternative hypotheses.

opencc-zeroMay 2022View details →

dryad32/100

Data from: Direct and indirect genetic effects on reproductive investment in a grasshopper

A fundamental part of the quantitative genetic theory deals with the partitioning of the phenotypic variance into additive genetic and environmental components. During interaction with conspecifics, the interaction partner becomes a part of the environment from the perspective of the focal individual. If the interaction effects have a genetic basis, they are called indirect genetic effects (IGEs) and can evolve along with direct genetic effects. Sexual reproduction is a classic context where potential conflict between males and females can arise from trade-offs between current and future investments. We studied five female fecundity traits, egg length and number, egg pod length and number and latency to first egg pod, and estimated the direct and IGEs using a half-sib breeding design in the grasshopper Chorthippus biguttulus. We found that the male IGEs were an order of magnitude lower than the direct genetic effects and were not significantly different from zero. However, there was some indication that IGEs were larger shortly after mating, consistent with the idea that IGEs fade with time after interaction. Female direct heritabilities were moderate to low. Simulation shows that the variance component estimates can appear larger with less data, calling for care when interpreting variance components estimated with low power. Our results illustrate that the contribution of male IGEs is overall low on the phenotypic variance of female fecundity traits. Thus even in the relevant context of sexual conflict, the influence of male IGEs on the evolutionary trajectory of female reproductive traits is likely to be small.

opencc-zeroDec 2018View details →

dryad32/100

Reproductive effort and terminal investment in a multi-species assemblage of Amazon electric fish

The terminal investment hypothesis (TIH) predicts that individuals with favorable prospects for future reproduction (i.e., high residual reproductive value, RRV) should moderate current reproductive investment in favor of growth, survival, and future reproduction, whereas those with low RRV should 'terminally invest' by diverting somatic resources towards current reproduction at the expense of future reproduction. However, support for the TIH in wild animal populations is fragmentary, and the ecological contexts of terminal investment remain poorly known. We report a remarkable case of simultaneous terminal investment involving five sympatric species of the electric knifefish genus Brachyhypopomus, from Amazonian floodplain and terra firme stream habitats. We found that terminal investment is synchronized by seasonal breeding, in response to circannual environmental variation in mortality risk. Four species exhibit a uniseasonal iteroparous (annual) life history with complete post-reproductive mortality after a single breeding season. One species (B. beebei) exhibits a two-year multiseasonal iteroparous life history with breeding in two seasons and post-reproductive mortality after the second. In mature females and (most) males of the annual species, as well as in both mature female and male second-year (but not first-year) B. beebei, we documented an increase in two metrics of reproductive effort (size-adjusted gonad mass and electric signal amplitude) and a concomitant reduction in somatic condition (size-adjusted somatic mass) – all in response to proximity to the end of the common breeding season, when RRV approximates zero. In mature first-year B. beebei, we documented neither an increase in reproductive effort nor a decline in somatic condition, implying an alternative strategy of reproductive restraint. Our findings support Kirkwood's disposable soma theory, which posits that death by reproductive exhaustion can be delayed if terminal investment is replaced by reproductive restraint, allowing individuals to survive and breed in a subsequent season. Deferral of the terminal investment response in annual species, and the origin of a gonadal regression-regeneration sequence, may open pathways for rapid evolutionary transitions to multiseasonal iteroparity. Excepting the age (year-group) dependency of terminal investment in B. beebei, we were unable to identify intrinsic cues or extrinsic environmental cues for the terminal investment response in Brachyhypopomus.

opencc-zeroOct 2021View details →

dryad32/100

Age-specific fecundity under pathogenic threat in an insect: terminal investment versus reproductive restraint

The terminal investment hypothesis predicts that as an organism's prospects for survival decrease, through age or when exposed to a pathogenic infection, it will invest more in reproduction, which should trade-off against somatic maintenance (including immunity) and therefore future survival. Attempts to test this hypothesis have produced mixed results, which, in addition, mainly rely on the assessment of changes in reproductive effort and often overlooking its impact on somatic defences and survival. Alternatively, animals may restrain current reproduction to sustain somatic protection, increasing the chance of surviving for additional reproductive opportunities. We tested both of these hypotheses in females of the yellow mealworm beetle, Tenebrio molitor, an iteroparous insect with reproductive tactics similar to that of long-lived organisms. To achieve this, we mimicked pathogenic bacterial infections early or late in the life of breeding females by injecting them with a suspension of inactivated Bacillus cereus, a known natural pathogen of T. molitor, and measured female age-specific fecundity, survival, body mass and immunity. Inconsistent with a terminal investment, females given either an early or late-life immune challenge did not exhibit reduced survival or enhance their reproductive output. Female fecundity declined with age and was reduced by the early but not the late immune challenge. Both early and late-life fecundity correlated positively with life expectancy. Finally, young and old females exhibited similar antibacterial immune responses, suggesting that they both restrained reproduction to sustain immunity. Our results clearly demonstrate that age-specific reproduction of T. molitor females under pathogenic threat is inconsistent with a terminal investment. In contrast, our results instead suggest that females used a reproductive restraint strategy to sustain immunity and therefore subsequent reproductive opportunities. However, as infections were mimicked only, the fitness benefit of this reproductive restraint could not be shown.

opencc-zeroOct 2021View details →

zenodo32/100

Female investment in terminal reproduction or somatic maintenance depends on infection dose - data

This is the data used in an experiment investigating the effects of infection dose on fecundity compensation in the red flour beetle.

opencc-by-4.0May 2023View details →

dryad32/100