Effects of food abundance, density and climate change on reproduction in the sparrowhawk Accipiter nisus

The reproductive success of predators depends on abiotic environmental conditions, food abundance and population density, and food abundance, density and their interactions may respond to changes in climatic conditions. Timing of reproduction by five of the eight numerically most common prey of the sparrowhawk Accipiter nisus advanced significantly since 1971, during a period of temperature increase. There was no evidence that mean laying date or any other reproductive parameter of sparrowhawks changed consistently during the study period 1977–1997. Laying date advanced and percentage of unsuccessful female sparrowhawks decreased with beech mast in the current year, an index of food abundance for avian prey. Mean laying date of sparrowhawks was advanced in warmer springs, and although mean clutch size was not larger in warm than in cold springs, mean brood size of successful pairs and breeding success increased in such springs, showing that sparrowhawks enjoyed a fitness gain when reproducing early. The timing of sparrowhawk reproduction with respect to the peak in abundance of fledgling prey increased, from a good match between mean timing of fledging by prey and maximum demand for food by the predator in 1977, to reproduction occurring later than the peak in fledging prey availability in 1997. The size of the breeding population of sparrowhawks was not predicted by mean spring temperature, the size of the breeding population the previous year or beech mast crop. The size of the post-breeding population was predicted by size of the breeding and post-breeding population the previous year and by the proportion of unsuccessful females the current year. These findings imply that sparrowhawks did not respond to change in climate, although climate changed the timing of reproduction by the main prey species.     

Effects of stress on reproduction in ewes

Stressors, such as poor body condition, adverse temperatures or even common management procedures (e.g., transport or shearing) suppress normal oestrus behaviour and reduce ewe fertility. All these events are co-ordinated by endocrine interactions, which are disrupted in stressful situations. This disruption is usually temporary in adult ewes, so that, when prevailing conditions improve, normal fertility would resume. Imposition of an experimental stressor (shearing, transport, isolation from other sheep, injection of endotoxin or insulin or cortisol infusion) suppresses GnRH/LH pulse frequency and amplitude. Part of the cause is at the pituitary, but effects on GnRH/LH pulse frequency and the GnRH/LH surge are mediated via the hypothalamus. It is not yet clear whether delays in the surge are caused by interruption of the oestradiol signal-reading phase, the signal transmission phase or GnRH surge release. Stressors also delay the onset of behaviour, sometimes distancing this from the onset of the pre-ovulatory LH surge. This could have deleterious consequences for fertility.     

Effects of adult-derived carbohydrates, amino acids and micronutrients on female reproduction in a fruit-feeding butterfly

It is generally believed that butterflies (and other holometabolous insects) rely primarily on reserves accumulated during the larval stage for reproduction, whereas the carbohydrate-rich adult diet is thought to mainly cover energy requirements. In at least some species though, realization of the full reproductive potential is extensively affected by post-eclosion nutrition. While the importance of carbohydrates is fairly well understood, the role of adult-derived amino acids and micronutrients is controversial and largely unknown, respectively. We here focus on the effects of different adult diets on female reproduction in the tropical, fruit-feeding butterfly Bicyclus anynana (Nymphalidae). Carbohydrates were the most important adult-derived nutrients affecting reproduction. Adding amino acids, vitamins or minerals to sucrose-based solutions did not yield a reproductive output equivalent to that of fruit-fed females, which showed the highest performance throughout. This suggests that either not yet identified compounds of fruit substantially contribute to reproduction, or that resource congruence (the use of nutrient types in a specified ratio) rather than any specific nutrient component is of key importance. Apart from adult income, realized fecundity depended on egg size and longevity, with the former dominating when dietary quality was low, but the latter when quality was high. Thus, the egg size-number trade-off seems to be affected by female nutrition.     

Effects of different temperatures and density on the survival and reproduction of Aphis gossypii on cotton plants

为探索趋近自然状态的渐变性高温胁迫对不同密度棉蚜Aphis gossypii Glover的影响,室内研究了4种不同高温模式下,不同密度(5、10、20、40)棉蚜的存活和繁殖.结果表明:随着最高温度值的升高和密度的增加,棉蚜存活率和繁殖率均呈下降趋势.当最高温度值升至40℃以上时,棉蚜存活率和繁殖率均显著下降,不同密度棉蚜存活率和繁殖率均没有差异.即随着温度的升高,密度对棉蚜的作用逐渐减弱.最高温度值为42℃时,棉蚜在3～4d内全部死亡.研究结果为提高棉蚜种群预测准确性、科学决策防治措施提供依据.     

不同的高温模式对不同密度棉蚜存活和繁殖的影响

为探索趋近自然状态的渐变性高温胁迫对不同密度棉蚜Aphis gossypii Glover的影响,室内研究了4种不同高温模式下,不同密度(5、10、20、40)棉蚜的存活和繁殖。结果表明:随着最高温度值的升高和密度的增加,棉蚜存活率和繁殖率均呈下降趋势。当最高温度值升至40℃以上时,棉蚜存活率和繁殖率均显著下降,不同密度棉蚜存活率和繁殖率均没有差异。即随着温度的升高,密度对棉蚜的作用逐渐减弱。最高温度值为42℃时,棉蚜在3～4 d内全部死亡。研究结果为提高棉蚜种群预测准确性、科学决策防治措施提供依据。     

Effects of heat stress on mammalian reproduction

Heat stress can have large effects on most aspects of reproductive function in mammals. These include disruptions in spermatogenesis and oocyte development, oocyte maturation, early embryonic development, foetal and placental growth and lactation. These deleterious effects of heat stress are the result of either the hyperthermia associated with heat stress or the physiological adjustments made by the heat-stressed animal to regulate body temperature. Many effects of elevated temperature on gametes and the early embryo involve increased production of reactive oxygen species. Genetic adaptation to heat stress is possible both with respect to regulation of body temperature and cellular resistance to elevated temperature.     

不同食料植物对棉古毒蛾生长发育和繁殖的影响

在恒温(28±1)℃、恒湿(80±5)%RH条件下,研究了莲雾、芒果、荔枝、龙眼、毛叶枣、木菠萝等6种食料植物对棉古毒蛾的生长发育和繁殖的影响。结果表明,棉古毒蛾能在这6种食料植物上完成其世代循环。其发育历期、雌蛹重、存活率、成虫繁殖力和寿命等,在6种寄主植物间均存在显著差异,其中莲雾和芒果是最适宜的寄主植物,荔枝和龙眼是不适宜的寄主植物。     

Effects of mechanical stress and plant density on mechanical characteristics, growth, and lifetime reproduction of tobacco plants

Plastic increases in stem elongation in dense vegetation are generally believed to be induced by canopy shading, but because plants protect each other from wind, shielding (reduced mechanical stress) could also play a role. To address this issue, tobacco Nicotiana tabacum plants were subjected to two levels of mechanical stress, 0 (control) or 40 (flexed) daily flexures, and grown solitarily, in a dense monostand (with plants of only one mechanical treatment), or in a mixed stand (flexed and control plants grown together). Flexed plants produced shorter and thicker stems with a lower Young's modulus than control plants, while dense-stand plants had relatively taller and thinner stems than solitary ones. Flexing effects on stem characteristics were independent of stand density. Growth, reproduction, and survival of solitary plants were not affected by flexing, while in the monostand growth was slightly reduced. But in the mixed stand, flexed plants were readily shaded by controls and had considerably lower growth, survival, and reproduction rates. These results suggest that wind shielding indeed plays a role in the plastic increase in stem elongation of plants in dense vegetation and that this response can have important consequences for competitive ability and lifetime seed production.     

Effects of adult nutrition on female reproduction in a fruit-feeding butterfly: the role of fruit decay and dietary lipids

It was generally believed that butterflies and other holometabolous insects rely primarily on reserves accumulated during the larval stage for reproduction. Recent studies, however, highlight the often fundamental importance of adult nutrition to realize the full reproductive potential. While the importance of carbohydrates is fairly well understood, the role of most other adult-derived substances is only partially resolved. We here focus on the effects of dietary lipids (cholesterol, polyunsaturated fatty acids) and fruit decay (dietary yeast, ethanol) on female reproduction in the tropical, fruit-feeding butterfly Bicyclus anynana (Nymphalidae). We found that banana-fed control females outperformed all other groups fed on sucrose-based diets. Lipids, yeast or ethanol added to a sugar solution did not yield a similarly high reproductive output compared to fruit-fed females. Groups fed fresh or decaying banana showed no differences in reproductive performance. As we could not identify a single pivotal substance, we conclude that resource congruence (the use of nutrient types in a specified ratio) rather than any specific nutrient component is of key importance for maximum reproductive output. Further, dietary quality may affect egg hatching success in spite of no obvious effects on egg size and number. Thus, any implications about potential fitness effects of different diets need to consider egg (and hatchling) viability in addition to fecundity.     

Ant predation on different life stages of two Australian ticks

Laboratory colonies of Rhytidoponera ants were allowed to prey on the fed and unfed stages of the Australian ticks Aponomma hydrosauri and Amblyomma limbatum. The unfed tick stages had a higher survival than the fed stages. The ants took longer to handle the adult ticks than the nymphs and longer to handle the nymphs than the larvae. The ants also took longer to handle the unfed than fed nymphs, but longer to handle the fed than unfed females. As well as the differences between the tick stages, there was a species effect, with the ants taking longer to handle A. limbatum, and with that tick species having a higher survival than A. hydrosauri after ant predation. These stage and species differences may influence the tick population dynamics. This revised version was published online in November 2006 with corrections to the Cover Date.     

Effects of the juvenile hormone mimic pyriproxyfen on female reproduction and longevity in the butterfly Bicyclus anynana

Female Bicyclus anynana butterflies given pyriproxyfen, a mimic of juvenile hormone, exhibited increased egg‐laying rates and early fecundity, but reduced longevity compared with control animals. Thus, pyriproxyfen application yielded antagonistic effects on different components of fitness, possibly demonstrating a juvenile hormone‐mediated trade‐off between present and future reproduction. Lifetime fecundity and egg size, however, showed no consistent response to pyriproxyfen, with lifetime fecundity being increased or decreased and egg size being reduced in one out of four experiments only. Females were most sensitive to pyriproxyfen around the onset of oviposition, coinciding with naturally increasing juvenile hormone titers in other Lepidoptera. Amounts between 1 and 10 µg pyriproxyfen were found to be effective, with, however, pronounced differences among experiments. This is attributed to differences in assay conditions. High pyriproxyfen concentrations (100 µg) as well as repeated applications of smaller amounts did not affect reproductive traits, but tended to reduce longevity.     

幼虫密度对二点委夜蛾生长发育及繁殖的影响

【目的】在不同幼虫密度饲养条件下,研究二点委夜蛾Athetis lepigone生长发育及繁殖的情况,明确幼虫密度对该害虫的室内种群增长的影响。【方法】本实验设置5个幼虫饲养密度即1,5,10,20和30头/瓶(750 mL),分别观察5个饲养密度下该虫的各个龄期及整个幼虫发育历期及存活率、蛹重、蛹期以及成虫生殖情况。【结果】幼虫密度对该虫幼虫各龄期及整个幼虫发育历期及存活率、蛹重、蛹期以及成虫生殖情况均有显著性影响。整个幼虫发育历期随着密度的增加而缩短,10头/瓶达到最短(18.27 d),之后随着幼虫密度的增加而显著延长;幼虫至蛹的存活率随着密度增高而显著下降,30头/瓶最低(39.37%)。蛹期随着密度的增加而延长(10头/瓶除外)。蛹重和每雌产卵量均以1头/瓶最高,随着幼虫密度的增加而显著下降。雌雄蛾寿命均以10头/瓶最长,与1和5头/瓶没有显著性差异。生命表分析显示:二点委夜蛾的种群增长指数以5头/瓶最高,幼虫密度过低或者过高均不利于种群增长。【结论】幼虫密度是影响二点委夜蛾种群增长的重要因子之一。     

Effects of silicon on defense of wheat against oxidative stress under drought at different developmental stages

The effects of silicon application before sowing on the drought-induced oxidative stress and antioxidant defense in wheat (Triticum aestivum L.) were investigated. Drought stress was applied by withholding watering till sampling at booting or filling stage. Application of Si increased the water potential of drought-stressed plants at filling stage, whereas it did not at booting stage. The superoxide dismutase (SOD) activity was inhibited and peroxidase (POD) activity was enhanced by drought at booting stage, and no differences were observed due to the Si treatment. At filling stage, however, application of Si increased the SOD activity and decreased the POD activity of drought-stressed plants. The catalase (CAT) activity was slightly increased by drought only in the absence of Si and at booting stage. The activity of glutathione reductase (GR) was not greatly influenced. Application of Si did not change the contents of H₂O₂, total soluble protein and protein carbonyl of drought-stressed plants at booting stage, whereas at filling stage, it decreased the content of H₂O₂ and protein carbonyl and increased the content of total soluble protein. The content of thiobarbituric acid reactive substances (TBARS) and the activities of acid phospholipase (AP) and lipoxygenase (LOX) in drought-stressed plants were also decreased by application of Si at both stages.     

Fitness consequences of environmental conditions at different life stages in a long-lived vertebrate

The predictive adaptive response (PAR) hypothesis proposes that animals adjust their physiology and developmental trajectory during early life in anticipation of their future environments. Accordingly, when environmental conditions in early life match environmental conditions during adulthood, individual fitness should be greater. Here, we test this hypothesis in a long-lived mammal, the roe deer, using data from two contrasting populations, intensively monitored for more than 35 years. In the highly productive site, the fitness of female roe deer increased with the quality of environment during adulthood and, contrary to predictions of PAR, individuals born in good conditions always outperformed those born under poor conditions. In the resource-limited site, the fitness of female roe deer born in poor years was better than those born in good conditions in poor years when the animals were adult, but not in good years. Although consistent with predictions of PAR, we showed that this pattern is likely to be a consequence of increased viability selection during the juvenile stage for animals born in poor years. While PARs are often advanced in evolutionary medicine, our findings suggest that detailed biological processes should be investigated before drawing conclusions about the existence of this phenomenon.     

Effects of crowding and temperature on Wolbachia infection density among life cycle stages of Aedes albopictus

Species of the genus Wolbachia are a group of Rickettsia-like, maternally-inherited bacteria (gram negative), which cause various reproductive alterations in their arthropod and nematode hosts including cytoplasmic incompatibility (CI), male-killing, parthenogenesis and feminization. They can be divided into supergroups such as A and B based on phylogenetic analysis of 16S rDNA sequences. In this study, we examined the relative infection densities of Wolbachia strains among life cycle stages in the mosquito, Aedes albopictus in terms of crowding effect and temperature effect. A. albopictus is known to be superinfected with both A- and B-supergroup Wolbachia which cause CI. The relative Wolbachia densities within each individual mosquito were determined and quantified by using real-time quantitative PCR assay based on the wsp gene. We found that B-supergroup Wolbachia strain densities in this host species were consistently and significantly higher than in the A-supergroup. Larval crowding also reduced adult size of mosquitoes. Our results show clearly that the higher densities of mosquito larvae cause lower densities of Wolbachia strains. Examination of the effect of temperature on Wolbachia density in each stage of the mosquito clearly revealed a significant decrease in bacterial density following exposure to elevated temperature (37 °C) in both males and females.     

不同食料植物对美国白蛾生长发育和繁殖的影响

2010年6月至7月,在室内研究了美国白蛾Hyphantria cunea(Drury)第1代幼虫对洋白蜡、欧美107号杨、法桐和白榆的取食量及不同的食料种类对美国白蛾生长发育和繁殖的影响。结果表明,美国白蛾对受试的各树种的取食量以洋白蜡为最多,完成一代平均每头可以取食2.21 g,其次为欧美107号杨1.95 g,再次为法桐和白榆,分别为1.85 g/头和1.68 g/头。3龄后幼虫对不同的寄主呈现出一定的偏好性,特别是5龄和6龄幼虫对不同的寄主的取食量表现出显著差异。不同的食料植物对美国白蛾幼虫和蛹的发育历期、存活率、蛹重、成虫寿命、产卵量等有显著影响。取食法桐对其生长发育和繁殖表现出明显的不利性,主要表现为幼虫期延长、蛹重减轻、单雌产卵量降低。