Smart is the new sexy: female mountain chickadees increase reproductive investment when mated to males with better spatial cognition

Understanding the evolution of inter and intraspecific variation in cognitive abilities is one of the main goals in cognitive ecology. In scatter‐caching species, spatial memory is critical for the recovery of food caches and overwinter survival, but its effects on reproduction are less clear. Better spatial cognition may improve pre‐breeding condition allowing for earlier reproduction. Alternatively, when mated to males with better spatial memory, females may be able to invest more in reproduction which may allow increased offspring survival and hence higher fitness. Using wild food‐caching mountain chickadees, we found that when environmental conditions were favourable for breeding, females mated to males with better spatial cognition laid larger clutches and fledged larger broods than females mated to males with worse cognitive performance. Our results support the hypothesis that females may increase their reproductive investment to gain indirect, genetic benefits when mated to high‐quality males with better spatial cognitive abilities.     

Effect of age‐based and environment‐based cues on reproductive investment in Gambusia affinis

We examined the multivariate life‐history trajectories of age 0 and age 1 female Gambusia affinis to determine relative effects of age‐based and environment‐based cues on reproductive investment. Age 0 females decreased reproductive investment prior to the onset of fall and winter months, while age 1 females increased reproductive investment as the summer progressed. The reproductive restraint and terminal investment patterns exhibited by age 0 and age 1 females, respectively, were consistent with the predictions from the cost of reproduction hypothesis. Age 0 females responded to environment‐based cues, decreasing reproductive investment to increase the probability of overwinter survival and subsequent reproductive opportunities in the following summer. Age 1 females responded to age‐based cues, or the proximity of death, increasing investment to current reproduction as future reproductive opportunities decreased late in life. Thus, individuals use multiple cues to determine the level of reproductive investment, and the response to each cue is dependent on the age of an individual.     

Relationship of claw form and exoskeleton condition to reproductive system size and methyl farnesoate in the male spider crab,Libinia emarginata

Summary

Methyl farnesoate (MF) expression and reproductive system size were compared in five representative groups of male L. emarginata selected from a sample collected in November. The groups differed from each other with respect to carapace size (small, intermediate and large), relative propodus size (small and large claw forms), and condition of the exoskeleton (abraded and unabraded). Large males with large claws and abraded exoskeletons had reproductive system indices which were significantly larger than any other group. The mandibular organs of these crabs also had significantly higher rates of methyl farnesoate synthesis in vitro. Hemolymph titers of methyl farnesoate were also highest in this group, but were not significantly different from the group with small carapaces, small claws and unabraded exoskeletons. Methyl farnesoate titers were significantly lower in all other groups of unabraded animals with small or large claws. These results suggest that methyl farnesoate may play a role in morphogenesis and reproduction in male L. emarginata.     

All or nothing: Survival,reproduction and oxidative balance in Spotted Wing Drosophila (Drosophila suzukii) in response to cold

Winter severity and overwintering capacity are key ecological factors in successful invasions, especially in ectotherms. The integration of physiological approaches into the study of invasion processes is emerging and promising. Physiological information describes the mechanisms underlying observed survival and reproductive capacities, and it can be used to predict an organism’s response to environmental perturbations such as cold temperatures. We investigated the effects of various cold treatments on life history and physiological traits of an invasive pest species, Drosophila suzukii, such as survival, fertility and oxidative balance. This species, a native of temperate Asian areas, is known to survive where cold temperatures are particularly harsh and has been recently introduced into Europe and North America. We found that cold treatments had a strong impact on adult survival but no effect on female’s fertility. Although only minor changes were observed after cold treatment on studied physiological traits, a strong sex-based difference was observed in both survival and physiological markers (antioxidant defences and oxidative markers). Females exhibited higher survival, reduced oxidative defences, less damage to nucleic acids, and more damage to lipids. These results suggest that D. suzukii relies on a pathway other than oxidative balance to resist cold injury. Altogether, our results provide information concerning the mechanisms of successful invasion by D. suzukii. These findings may assist in the development of population models that predict the current and future geographic ranges of this species.     

Optimization of reproductive effort and foraging time in mammals: The influence of resource level and predation risk

Summary The trade-off between fitness benefits from foraging and associated costs in terms of predation risk is analysed by a simple model which takes into account the differential predation risk for reproducing and non-reproducing individuals. The currency that animals are assumed to maximize is their expected absolute fitness (probability of survival plus half of the expected litter size) after a potential reproductive period. Depending on resource levels and predation risk, this maximization can be achieved by (1) opting for individual survival and behaving as a strict time minimizer, (2) by reproducing at the maximal rate and behaving as a strict energy maximizer or (3) by submaximal reproductive effort and a behaviour intermediate between time minimization and energy maximization. Small changes in the availability of food or cover or in the density of predators can shift the optimum from one strategy to another. The shift is particularly abrupt, if predation pressure increases and the availability of resources remains high. This could explain the spatial and temporal variation in the reproductive effort and body weight observed in boreal small mammals with sustained, multiannual population fluctuations.     

Pigment-based skin colour in the blue-footed booby: an honest signal of current condition used by females to adjust reproductive investment

In monogamous species, the value of present reproduction is affected by the current condition of the mate, and females may use male ornaments to evaluate his condition and adjust their level of investment according. Many animals display colour in fleshy structures which may be accurate indicators of quality due to their potentially rapid response to changes in condition. Here we show that in the blue-footed booby, Sula nebouxii, male foot colour is structurally (collagen arrays) and pigment based. In 48 h foot colour became duller when males were food deprived and brighter when they were re-fed with fresh fish. Variation of dietary carotenoids induced comparable changes in cell-mediated immune function and foot colour, suggesting that carotenoid-pigmentation reveals the immunological state of individuals. These results suggest that pigment-based foot colour is a rapid honest signal of current condition. In a second experiment, we found that rapid variation in male foot colour caused parallel variation in female reproductive investment. One day after the first egg was laid we captured the males and modified the foot colour of experimental males with a non-toxic and water resistant duller blue intensive make-up, mimicking males in low condition. Females decreased the size of their second eggs, relative to the second egg of control females, when the feet of their mates were experimentally duller. Since brood reduction in this species is related to size differences between brood mates at hatching, by laying lighter second eggs females are facilitating brood reduction. Our data indicate that blue-footed booby females are continuously evaluating their mates and can perform rapid adjustments of reproductive investment by using dynamic sexual traits. We suggest that this fine-tuned adjustment may be widespread in socially monogamous animals.     

Ejaculate expenditures of male crickets in response to varying risk and intensity of sperm competition: not all species play games

Costs incurred in the manufacture of ejaculates may constrainthe number of sperm that males can produce, so males shouldshow some economy in their allocation of sperm across multiplematings. In species in which females mate with multiple malesand are capable of storing sperm for extended periods, spermallocation of males should be tailored to the risk of spermcompetition. Recent game theory predicts that males shouldtransfer the least sperm when there are no other rivals, andthe most sperm when only one other rival is likely to inseminatethe female. However, as the numbers of competitors increasesbeyond two, the models predict a corresponding decrease in ejaculate expenditure. We tested these predictions in three cricket species, Gryllodes sigillatus, Gryllus veletis, and Gryllus texensis, assessing the sperm allocation of males held under three levelsof apparent interrival competition: no rivals, one rival andsix rivals. Sperm allocation of G. veletis varied accordingto theory: males increased their sperm allocation with an increasedrisk of sperm competition (no rivals vs. one), but decreasedtheir allocation with an increased intensity of sperm competition(one rival vs. six). Sperm allocation of male G. texensis showedno significant response to the density of rivals, and spermallocation in G. sigillatus was influenced by an unexpectedinteraction between treatment density and the order in whichmales experienced the three treatments. The observed interspecificvariation in facultative sperm allocation may be due to interspecificdifferences in population density, rearing environment, orfemale mating behavior.     

Long‐term after‐effects of cold exposure in adult Alphitobius diaperinus (Tenebrionidae): the need to link survival ability with subsequent reproductive success

1. The effects of cold acclimation and cold exposure on the survival and reproductive capabilities of Alphitobius diaperinus (Tenebrionidae) adult beetles are examined. 2. First, the impact of temperature on survival duration was assessed by placing beetles in a range of cool temperature treatments. Second, the importance of acclimation duration was assessed. Third, the impact of thermal stress on subsequent reproductive ability was examined for beetles that had no previous cold exposure, and for beetles that had been subjected to previous cold exposure (i.e. acclimated) at various conditions, including fluctuating temperatures. 3. In all groups, the number of recorded survivors was strongly impacted by recovery period duration (i.e. 2 vs. 10 days). Survival of non‐acclimated and 3‐day acclimated beetles, expressed as lethal time for 50% of the samples, was reduced significantly when the insects were re‐assessed for survival at 10 days after being returned to optimal growth conditions (7.9 ± 0.4 vs. 5.1 ± 0.6 days and 8.8 ± 0.5 vs. 6.8 ± 0.6 days, respectively). 4. Insects that had been subject to cold acclimation expressed better subsequent reproduction success than non‐acclimated beetles. This beneficial impact increased when the acclimation period was prolonged, but some longer acclimation periods had no significant impact on survival. 5. Our results indicate that cold exposure has the capacity to irreversibly damage the reproductive system and that insect survival depends on the duration of the recovery period. Both the survival ability and subsequent reproductive output have to be examined to objectively determine insect cold resistance.     

Dopamine and glutamate in individuals at high risk for psychosis: a meta‐analysis of in vivo imaging findings and their variability compared to controls

Dopaminergic and glutamatergic dysfunction is believed to play a central role in the pathophysiology of schizophrenia. However, it is unclear if abnormalities predate the onset of schizophrenia in individuals at high clinical or genetic risk for the disorder. We systematically reviewed and meta‐analyzed studies that have used neuroimaging to investigate dopamine and glutamate function in individuals at increased clinical or genetic risk for psychosis. EMBASE, PsycINFO and Medline were searched form January 1, 1960 to November 26, 2020. Inclusion criteria were molecular imaging measures of striatal presynaptic dopaminergic function, striatal dopamine receptor availability, or glutamate function. Separate meta‐analyses were conducted for genetic high‐risk and clinical high‐risk individuals. We calculated standardized mean differences between high‐risk individuals and controls, and investigated whether the variability of these measures differed between the two groups. Forty‐eight eligible studies were identified, including 1,288 high‐risk individuals and 1,187 controls. Genetic high‐risk individuals showed evidence of increased thalamic glutamate + glutamine (Glx) concentrations (Hedges’ g=0.36, 95% CI: 0.12‐0.61, p=0.003). There were no significant differences between high‐risk individuals and controls in striatal presynaptic dopaminergic function, striatal D2/D3 receptor availability, prefrontal cortex glutamate or Glx, hippocampal glutamate or Glx, or basal ganglia Glx. In the meta‐analysis of variability, genetic high‐risk individuals showed reduced variability of striatal D2/D3 receptor availability compared to controls (log coefficient of variation ratio, CVR=–0.24, 95% CI: –0.46 to –0.02, p=0.03). Meta‐regressions of publication year against effect size demonstrated that the magnitude of differences between clinical high‐risk individuals and controls in presynaptic dopaminergic function has decreased over time (estimate=–0.06, 95% CI: –0.11 to –0.007, p=0.025). Thus, other than thalamic glutamate concentrations, no neurochemical measures were significantly different between individuals at risk for psychosis and controls. There was also no evidence of increased variability of dopamine or glutamate measures in high‐risk individuals compared to controls. Significant heterogeneity, however, exists between studies, which does not allow to rule out the existence of clinically meaningful differences.     

短时高温暴露下东亚飞蝗雌虫血淋巴蛋白表达分析及质谱鉴定

为研究短时高温对东亚飞蝗Locusta migratoria manilensis Meyen血淋巴蛋白的影响,采用Bradford法、SDSPAGE电泳和质谱等方法,对东亚飞蝗雌虫血淋巴样品进行检测。结果表明:短时高温对血淋巴蛋白含量有显著影响(P0.01),36℃-42℃范围内,随温度升高,血淋巴蛋白浓度亦升高,其中39℃、42℃处理组与对照组差异显著(P0.01);短时高温对血淋巴蛋白种类存在一定影响,对照组雌虫血淋巴中存在11种蛋白,高温处理后,4种蛋白含量逐渐增加,6种蛋白含量没有明显变化,1种蛋白消失;经质谱检测,鉴定了5种蛋白,分别为载脂蛋白前体、酚氧化酶原、2个储存蛋白和19 kDa血淋巴蛋白,另外6条蛋白未被鉴定。推测载脂蛋白前体、酚氧化酶原、储存蛋白在东亚飞蝗应对高温胁迫过程中发挥重要作用。