Sexual conflict reduces offspring fitness in zebra finches

Parental care is often costly; hence, in sexually reproducing species where both male and female parents rear their offspring (biparental care), sexual conflict over parental investment can arise. Such conflict occurs because each care-giver would benefit from withholding parental investment for use with another partner, leading to a reduction in the amount of care given by one parent at the expense of the other. Here we report experiments to explore the prediction from theory that parents rearing offspring alone may provide greater parental investment than when rearing offspring together with a partner. We found that when the number of offspring per parent, and hence the potential workload, were kept constant, offspring received a greater per capita parental investment from single females than from both parents working together, and that males reared by single mothers were more sexually attractive as adults than their biparentally reared siblings. This difference between single- and two-parent families is due to a reduction in care provided by females when they care together with a male, rather than laziness by males or differences in the begging behaviour of chicks, supporting the claim that sexual conflict in biparental care can reduce the quality of offspring raised.     

Pre-social benefits of extended parental care

The evolution of helping, in which some individuals forfeit their own reproduction and help others to reproduce, is a central problem in evolutionary biology. Recently proposed insurance-based mechanisms rely on a pre-existing life history with a long period of offspring dependency relative to the short life expectancies of adult carers: a lone mother's offspring are doomed if she dies young, whereas after a helper dies, other group members can finish rearing the offspring. A critical question, however, is how this life history could evolve in ancestral non-social populations, as offspring survival would then depend on a single, short-lived carer. Here, we resolve this paradox by focusing on the extended parental care inherent in prolonged dependency. We show experimentally that in non-social wasps, extended care can significantly reduce the impact of interspecific parasites. Under extended care, offspring are less vulnerable by the time they are exposed to parasites, and costs of parasitism are reduced because mothers have the option to terminate investment in failing offspring. By experimentally simulating aspects of extended care in a species where it is lacking, we demonstrate that neither benefit requires specialized behaviour. Such benefits could therefore offset the disadvantage of prolonged dependency in non-social species, thereby facilitating the evolution of helping.     

True paternal care in a multi-male primate society

Although male parental care is rare among mammals, adult males of many cercopithecine primate species provide care for infants and juveniles. This care is often in the form of grooming, carrying, support in agonistic interactions, and protection against infanticide. For these behaviours to be interpreted as true parental care, males must selectively direct care towards their own offspring and this care must result in fitness benefits. With the exception of males defending probable offspring from infanticide, male primates living in multi-male, multi-female social groups have not been shown to selectively direct care towards their own offspring. We determined paternity for 75 juveniles in a population of wild savannah baboons (Papio cynocephalus) and collected data on interventions in agonistic disputes by adult males on behalf of juveniles as a form of male care. Here we show that adult males differentiate their offspring from unrelated juveniles and selectively support their offspring in agonistic disputes. As support in agonistic disputes is likely to contribute to rank acquisition and protect juveniles from injury and stress, this can be considered true parental care.     

Sex determination. Viviparous lizard selects sex of embryos

No one suspected that temperature-dependent sex determination (TSD), whereby the sex of embryos depends on the temperature at which they develop, might occur in viviparous (live-bearing) reptiles, because thermoregulation in the mother results in relatively stable, raised gestation temperatures. But here we show that developing embryos of the actively thermoregulating viviparous skink Eulamprus tympanum are subject to TSD, offering the mother the chance to select the sex of her offspring and a mechanism to help to balance sex ratios in wild populations.     

A brood parasitic catfish of mouthbrooding cichlid fishes in Lake Tanganyika

Brood parasitism, where a brood of the parasitic species is fostered by the parents of another species, is well known among birds. In most cases, such offspring show a complete reliance upon their host parents for food, protection and warmth until their independence. In other vertebrate groups, however, such total dependence upon a host species is unknown. I report here the first example of true brood parasitic behaviour discovered among fishes. In Lake Tanganyika, an endemic mochokid catfish, Synodontis multipunctatus Boulenger, is a brood parasite of mouthbrooding fishes of the family Cichlidae. The eggs of the catfish are incubated in the mouths of any of several host species together with the host's eggs, but hatch earlier. Following absorption of their yolk sacs, the catfish fry feed upon the fry of the host while still in its mouth. Thus the early stages of development of this catfish not only depend upon their hosts for food and protection, but exploit almost their entire parental investment.     

Animal behavior: male parenting of New Guinea froglets

Male parental care is exceptionally rare in nature, although one of the most fascinating aspects of New Guinea's biodiversity is the evolution of male care in the frog family Microhylidae. Here I report a new mode of parental care: transport of froglets by the male parent, which was recently discovered in two species of microhylid frogs from the mountains of Papua New Guinea. As the offspring jump off at different points, they may benefit from reduced competition for food, lower predation pressure and fewer opportunities for inbreeding between froglets, which may explain why this unusual form of parental care evolved.     

卵黄蛋白原的性质及热休克蛋白90对其合成代谢的调控

卵黄蛋白原(VTG)广泛存在于卵生脊椎动物和无脊椎动物的卵母细胞中,为卵母细胞的生长和胚胎的发育提供营养。VTG一般在卵巢、肝胰脏和(或)脂肪等组织中合成。VTGcDNA具有较强的保守性,为7 kB左右。VTG具有单体、二聚体等多种形式,其中二聚体有同源二聚体和异源二聚体两种形式。脊椎动物体内,热休克蛋白90(HSP90)通过和雌激素受体结合间接诱导VTG的合成,近年来的研究报道表明HSP90同样对无脊椎动物体内VTG合成也具有诱导作用,但其作用机制有待进一步研究。     

The genetic basis of family conflict resolution in mice

Asymmetries in the costs and benefits of parental investment for mothers, fathers and offspring result in family conflict over the production and provisioning of young. In species where females provide most resources before and after birth, the resolution of this conflict may be influenced by genes expressed in mothers and by maternally and paternally inherited genes expressed in offspring. Here we disentangle these effects by means of reciprocal mating and cross-fostering of litters between two strains of mice that differ with respect to the typical resolution of family conflict. We find that differences in litter size between these two strains are determined by paternal genotype, whereas differences in provisioning are under maternal control, showing that there is antagonistic coadaptation of maternal and paternal effects on distinct life-history traits. Maternal provisioning is also influenced by the type of foster offspring. Contradictory to theoretical expectations, however, we find no evidence for a negative correlation across strains between maternal provisioning and offspring demand. Instead, we show that there is positive coadaptation such that offspring obtain more resources from foster mothers of the same strain as their natural mother, irrespective of their father's strain.     

哺乳动物母体繁殖对策的研究

哺乳动物以雌体哺乳和雄性有限的 贡献共同哺育。雌体是整个繁殖过程的中心事件,也是最耗能量的过程。哺乳动物哺乳的行为表现可影响母体民仔未来的繁殖。哺乳期越长对后代越有利,但另一方面,母体的繁殖代价可影响其存活和繁殖力;后代质量与胎仔数间存在着权衡,作为胎仔数的函数,后代质量以种群新生个体补充概率潜在地影响亲本的适合度;与出生时不明确的格局相比较,育幼结束时的权衡通常非常明显;后代体重与生长速率的差异可影响新生个体的补充数;如果幼仔体重差异保持到成体,这些差异将超越简单的后代补充数而持续影响母体的广义适合度。雌性成体体重与胎仔数之间存在明显的相关性。     

Outbred embryos rescue inbred half-siblings in mixed-paternity broods of live-bearing females

Females commonly mate with more than one male, and polyandry has been shown to increase reproductive success in many species. Insemination by multiple males shifts the arena for sexual selection from the external environment to the female reproductive tract, where sperm competition or female choice of sperm could bias fertilization against sperm from genetically inferior or genetically incompatible males. Evidence that polyandry can be a strategy for avoiding incompatibility comes from studies showing that inbreeding cost is reduced in some egg-laying species by postcopulatory mechanisms that favour fertilization by sperm from unrelated males. In viviparous (live-bearing) species, inbreeding not only reduces offspring genetic quality but might also disrupt feto-maternal interactions that are crucial for normal embryonic development. Here we show that polyandry in viviparous pseudoscorpions reduces inbreeding cost not through paternity-biasing mechanisms favouring outbred offspring, but rather because outbred embryos exert a rescuing effect on inbred half-siblings in mixed-paternity broods. The benefits of polyandry may thus be more complex for live-bearing females than for females that lay eggs.     

A fossil owl monkey from La Venta, Colombia

Knowledge of the evolutionary history of living New World anthropoids is limited by a relatively poor fossil record. The discovery in 1986 of a new fossil monkey from the middle Miocene deposits of La Venta, Colombia, 12-15 million years ago (Myr BP), is the first example of a living New World monkey genus appearing in Tertiary rocks. Including anatomical evidence of the dentition and facial skull, it provides an unambiguous link between a Neogene fossil and the owl monkey, Aotus, the only modern crepuscular-nocturnal anthropoid primate. This new form brings to three the number of La Venta fossil monkeys which preserve excellent dentitions sharing extensive similarities with modern genera. All of these species are potentially ancestral to their extant relatives. The La Ventan Aotus is additional support for the idea that the modern platyrrhine radiation includes long-lived genera or generic lineages, some of which may be traceable to the early Miocene, 20 Myr BP.     

社区老年呵护中心的创业模式探讨

目前,我国的医疗体制改革使老年人开始更加关注自己的健康,渴望有一种安全、可靠、灵活、方便、收费合理、快捷的保健服务。呵护中心投资额度低,从业人员需一定的专业知识和技能,是一种风险小、利润大、专业性较强的服务性行业。近年来,随着社会老年化趋势的进一步加强和老年保障体系的进一步完善,政府对呵护中心的建立势必会有一定的财政支持。社区老年健康呵护中心随着老年人口的日益增多,必然有一个长远的发展前景。     

Intrasexual competition and sexual selection in cooperative mammals

In most animals, the sex that invests least in its offspring competes more intensely for access to the opposite sex and shows greater development of secondary sexual characters than the sex that invests most. However, in some mammals where females are the primary care-givers, females compete more frequently or intensely with each other than males. A possible explanation is that, in these species, the resources necessary for successful female reproduction are heavily concentrated and intrasexual competition for breeding opportunities is more intense among females than among males. Intrasexual competition between females is likely to be particularly intense in cooperative breeders where a single female monopolizes reproduction in each group. Here, we use data from a twelve-year study of wild meerkats (Suricata suricatta), where females show high levels of reproductive skew, to show that females gain greater benefits from acquiring dominant status than males and traits that increase competitive ability exert a stronger influence on their breeding success. Females that acquire dominant status also develop a suite of morphological, physiological and behavioural characteristics that help them to control other group members. Our results show that sex differences in parental investment are not the only mechanism capable of generating sex differences in reproductive competition and emphasize the extent to which competition for breeding opportunities between females can affect the evolution of sex differences and the operation of sexual selection.     

Decisions about parental care in response to perceived paternity

Evolutionary ecologists are attempting to explain how parents make behavioural decisions about how much care to provide to their young. Theory predicts that when genetic relatedness to young is decreased by cuckoldry, for example, parents should reduce their care in favour of alternative broods that provide greater reproductive success. Experimental manipulation of perceived paternity has been used to test the theory, but such studies have generated mixed results. Some manipulations can fail to alter a parent's perceived paternity, whereas others may directly affect parental behaviour when, for instance, the manipulation involves capturing the parent. No study has demonstrated parental care adjustment in a manner uncomplicated by experimental design or life history correlates. Here I test the theory using the fact that nest-tending parental male bluegill sunfish (Lepomis macrochirus) can assess their paternity using both the visual presence of parasitic cuckolder males during spawning, and olfactory cues released by newly hatched eggs. By manipulating both types of cues I show that parental males dynamically adjust their parental care, favouring broods that are apparently most closely related. These results confirm the importance of genetic relatedness in parental care decision-making.     

饥饿对斜带石斑鱼卵黄囊期仔鱼摄食、存活及生长的影响

 在培育水温(25±0.5 ）℃、盐度31～32 条件下,斜带石斑鱼仔鱼孵化后第3天开口并进入摄食期,孵化后5.5 d,不能建立外源性营养的仔鱼分别进入不可逆点（PNR期）,几乎与此同时,卵黄囊和油球耗尽,仔鱼混合营养期为2~3 d,从初次摄食到进入PNR期的时间为2.5 d;仔鱼在不同饥饿阶段初次摄食发生率的变化式型是：开始较低,此后逐步上升,高峰期出现在卵黄囊接近耗尽时,此后迅速下降,记录到的最高初次摄食发生率为76.7%;饥饿仔鱼的死亡高峰出现在孵化后4~6 d,至第8天,饥饿仔鱼全部死亡;卵黄囊期仔鱼的生长可以分为3个期相：初孵时的快速生长期,卵黄囊消失前后的慢速生长期,以及在不能建立外源性摄食后的负生长期。     

文化反哺与道德传递

伴随着文化的技术含量急剧增加,文化生产和拥有者的年轻化和文化发展速度的加快,由子代向亲代的文化反哺成为趋势;文化反哺使道德传递丧失了传递的权威,成为纯道德传递并出现了道德逆传递的三大特征;面对文化反哺重塑亲代的道德权威,明确亲代的道德传递责任,改进道德传递方法,加强代际互动,促进有效传递等成为当务之急。     

色素细胞发育分化的分子调控机制

色素细胞是动物体内产生色素的一类特化细胞,不仅为动物提供不同的体表颜色及斑纹,还具有防止生物体免受紫外线伤害等功能.本研究概述了色素细胞的分布、发育分化以及这一过程中受到的基因调控,并概述了干细胞分化为黑色素细胞的研究进展.     

杂种马挂木的同工酶分析

<正>近年来国外在林木遗传育种研究中,对同工酶的研究日益增多,进展较快。在无性系鉴别(酒井宽一,1974),种子园的家系分析(Dag Rudin and Dag lindgren,1977),林木种内杂交及杂种后代的遗传分析(田岛正启,1977)等方面进行了广泛的研究。d.,H。I[oaoaoBA(1978)和Dag Rudin㈠976)对同工酶在林木遗传育种研究中的应用和展望作了评述。随着同工酶遗传基础研究的进一步深入,同工酶将成为林木遗传分析的一种有效手段。 两年来,我们用同工酶鉴定林木杂种,摸索同工酶与林木杂种优势的关系,试图预测林木杂种优势。现将部分试验结果报告如下。     

A stem batrachian from the Early Permian of Texas and the origin of frogs and salamanders

The origin of extant amphibians (Lissamphibia: frogs, salamanders and caecilians) is one of the most controversial questions in vertebrate evolution, owing to large morphological and temporal gaps in the fossil record. Current discussions focus on three competing hypotheses: a monophyletic origin within either Temnospondyli or Lepospondyli, or a polyphyletic origin with frogs and salamanders arising among temnospondyls and caecilians among the lepospondyls. Recent molecular analyses are also controversial, with estimations for the batrachian (frog-salamander) divergence significantly older than the palaeontological evidence supports. Here we report the discovery of an amphibamid temnospondyl from the Early Permian of Texas that bridges the gap between other Palaeozoic amphibians and the earliest known salientians and caudatans from the Mesozoic. The presence of a mosaic of salientian and caudatan characters in this small fossil makes it a key taxon close to the batrachian (frog and salamander) divergence. Phylogenetic analysis suggests that the batrachian divergence occurred in the Middle Permian, rather than the late Carboniferous as recently estimated using molecular clocks, but the divergence with caecilians corresponds to the deep split between temnospondyls and lepospondyls, which is congruent with the molecular estimates.     

Competition induces adaptive shifts in caste ratios of a polyembryonic wasp

An important transition in insect life-history evolution was the shift from a solitary existence to living in groups comprising specialized castes. Caste-forming species produce some individuals that reproduce and others with worker functions that have few or no offspring. Morphologically specialized castes are well known in eusocial species like ants and termites, but castes have also evolved in less-studied groups like thrips, aphids and polyembryonic wasps. Because selection acts at both the individual and the colony level, ratios of investment in different castes are predicted to vary with environmental factors like competition and resources. However, experimental evidence for adaptive shifts in caste ratios is limited owing to the experimental difficulty of manipulating factors thought to influence caste ratios, and because some species produce behaviourally flexible castes that switch tasks in response to colony needs. Unlike other caste-forming species, the broods of polyembryonic wasps develop clonally, so that increased production of one caste probably results in decreased production of the other. Here we show that the polyembryonic wasp Copidosoma floridanum alters caste ratios in response to interspecific competition. Our results reveal a distinct trade-off by C. floridanum between reproduction and defence, and show experimentally that caste ratios shift in an adaptive manner.