Sperm number trumps sperm size in mammalian ejaculate evolution

Postcopulatory sexual selection is widely accepted to underlie the extraordinary diversification of sperm morphology. However, why does it favour longer sperm in some taxa but shorter in others? Two recent hypotheses addressing this discrepancy offered contradictory explanations. Under the sperm dilution hypothesis, selection via sperm density in the female reproductive tract favours more but smaller sperm in large, but the reverse in small, species. Conversely, the metabolic constraint hypothesis maintains that ejaculates respond positively to selection in small endothermic animals with high metabolic rates, whereas low metabolic rates constrain their evolution in large species. Here, we resolve this debate by capitalizing on the substantial variation in mammalian body size and reproductive physiology. Evolutionary responses shifted from sperm length to number with increasing mammalian body size, thus supporting the sperm dilution hypothesis. Our findings demonstrate that body-size-mediated trade-offs between sperm size and number can explain the extreme diversification in sperm phenotypes.     

Genome size as a determinant of growth and life-history traits in crustaceans

Genome size varies tremendously both within and among taxa, and strong correlations between genome size and various physiological and ecological attributes suggest that genome size is a key trait of organisms, yet the causalities remains vague. In the present study, we tested how genome size is related to key physiological and ecological properties in five large orders of crustaceans: Decapoda, Cladocera, Amphipoda, Calanoida, and Cyclopoida. These span a wide range in sizes, habitats and life-history traits. To some extent, genome size reflected phylogenetic footprints but, generally, a very wide range in genome size was found within all orders. Genome size was positively correlated with body size in Amphipoda, Cladocera, and Copepoda, but not for Decapoda in general. This could indicate that the evolution of body size occurs mainly by changing cell size for the three first orders, whereas it is more attributed to cell numbers for Decapoda. Cladocera, with direct development and a high growth rate, have minute genomes compared to copepods that possess a more complex life history, whereas, within Decapoda and Amphipoda, developmental complexity is not related to genome size. The present study suggests that, within the crustaceans, selection for a wide variety of life-history strategies has led to widely different genome sizes.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 393–399.     

漆酶同工酶基因在斑玉蕈生长发育过程中的表达分析

为了探明漆酶在斑玉蕈生长发育过程中的功能,对斑玉蕈转录测序预测的13个漆酶基因序列进行分析、鉴定和构建分子系统发育树;检测了不同生长发育时期漆酶的活性和漆酶基因表达水平。研究结果显示：13个基因片段中有10个是漆酶基因。不同的漆酶同工酶之间进化关系存在明显差异,大多数漆酶与木腐菌（金针菇Flammulina filiformis和侧耳属Pleurotus）进化关系较近。对斑玉蕈不同生长发育时期的酶活检测结果显示,从斑玉蕈的菌丝恢复期到钉头期,漆酶活性逐渐升高,而在子实体形成后期酶活逐渐降低。对培养40d、60d和80d的菌丝样品以及不同生长发育时期的样品进RT-qPCR检测,结果显示在菌丝营养生长时期,大多数漆酶基因在第40-60天表达量持续增加1-3倍,而在第60-80天时表达量出现降低的情况。而在生殖生长时期,大多数漆酶基因在转色期或者原基期相对表达量达到最大值,并在子实体期出现降低,这与漆酶活性的检测具有一致性。lcc3、lcc7、lcc8和lcc9在斑玉蕈生殖生长过程中相对表达量出现了10-100倍的上调。这说明从菌丝培养到菌丝扭结形成子实体和子实体发育的过程中,不同的漆酶可能发挥着不同的作用,表达量较高的漆酶基因可能对基质降解和子实体形成起主要作用。     

整合昆虫发育生物学和果蝇遗传学来研究昆虫发育与变态

成熟动物(昆虫)个体大小主要由生长持续时间和生长速度2个因素所决定。蜕皮激素和保幼激素协同调控昆虫发育变态,并决定昆虫生长持续时间;胰岛素、营养和细胞接触抑制等生长死亡信号及其传导途径控制细胞分裂、长大、分化、死亡,并最终决定昆虫的生长速度。最近研究成果表明,蜕皮激素信号和胰岛素信号相互影响,对昆虫个体大小起决定性的作用;脂肪体和营养代谢把这2条信号传导途径整合起来。科学家将会整合昆虫发育生物学和果蝇遗传学,抓住生长持续时间和生长速率2个关键因素,并以营养代谢和脂肪体为切入点来研究昆虫的发育变态。     

Effect of fish length and nutritional condition on the fecundity of distressed Atlantic cod Gadus morhua from the Baltic Sea

The disappearance of larger individuals and the decrease in individual body condition suffered by Atlantic cod Gadus morhua in the eastern Baltic during the past two decades can be expected to affect the stock reproductive output. To investigate this, female G. morhua were collected during the spawning and pre‐spawning period in 2015?2016. The current individual potential fecundity (F_P) of eastern Baltic G. morhua was estimated and analysed in relation to total length (L_T) and indices of nutritional status such as body condition (K) and hepato‐somatic index (I_H) using generalized linear models. In addition, the current prevalence of atresia and its potential relation to K were investigated. Moreover, a calibration curve to estimate F_P from oocyte diameter, based on the autodiametric oocyte counting method, was established for the first time for eastern Baltic G. morhua and can be used for future fecundity studies on this stock. The results showed that F_P was mainly positively related to fish length, but K and I_H also contributed significantly to the variation in F_P. The model predicted that fish with K = 1·2 have a F_P 51% higher than fish of the same L_T with K = 0·8. The prevalence of fecundity regulation by atresia was 5·8%, but it was found only in fish in the pre‐spawning maturity stage and with low K. Temporal changes in biological features such as the length composition and individual body condition of eastern Baltic G. morhua, should be accounted for when estimating stock reproductive potential.     

The Invisibility of Disability: Using Dance to Shake from Bioethics the Idea of ‘Broken Bodies’

Complex social and ethical problems are often most effectively solved by engaging them at the messy and uncomfortable intersections of disciplines and practices, a notion that grounds the InVisible Difference project, which seeks to extend thinking and alter practice around the making, status, ownership, and value of work by contemporary dance choreographers by examining choreographic work through the lenses of law, bioethics, dance scholarship, and the practice of dance by differently‐abled dancers. This article offers a critical thesis on how bioethics has come to occupy a marginal and marginalizing role in questions about the differently‐abled body. In doing so, it has rendered the disabled community largely invisible to and in bioethics. It then defends the claim that bioethics – as a social undertaking pursued collaboratively by individuals from different disciplines – must take much better notice of the body and the embodied individual if it is to better achieve its ends, which include constructing a moral and just society. Finally, this article considers how the arts, and specifically dance (and here dance by differently‐abled dancers), provides us with rich evidence about the body and our ability to respond positively to normally ‘othered’ bodies. It concludes that greater attention to empirical evidence like that being generated in InVisible Difference will help to expand the reach and significance of bioethics, and thereby its relevance to (and consciousness of) important questions about the status of bodies and bodily differences, which must be considered as central to its ambitions.     

铁皮石斛林下立体栽培比较研究

选取种植方式、树体及其部位作为研究对象,对不同林下栽培模式下铁皮石斛Dendrobium officinale存活率、增殖系数及增重系数进行比较研究。结果表明,不同种植方式的铁皮石斛存活率大小依次为：悬挂式树段(98.55%)＞树体(95.86%)＞砖石(92.67%)＞苗床(72.97%),悬挂式树段种植方式与其他三种方式均存在显著差异;而不同树的铁皮石斛存活率大小依次为：树菠萝(96.43%)＞龙眼(96.22%)＞杧果(95.37%)＞荔枝(93.54%)＞马尾松(32.93%),前三种树与其他树存在显著差异;不同部位则以树杈部存活率(86.89%)最高。比较不同种植方式的铁皮石斛增殖与增重系数,附生种植方式两指标均显著高于林下苗床种植方式,附生种植方式中又以悬挂式树段种植方式的系数值最高,其三年后增殖系数与增重系数分别为3.50和4.55,并与其他附生方式均存在显著差异。因此,在亚热带林下立体栽培模式下,铁皮石斛的种植应以悬挂式树段种植方式为主,并充分利用常绿阔叶类乔木树种及砖石类等载体进行附生种植。