Drift Diving by Hooded Seals (Cystophora cristata) in the Northwest Atlantic Ocean

Many pinniped species perform a specific dive type, referred to as a ‘drift dive’, where they drift passively through the water column. This dive type has been suggested to function as a resting/sleeping or food processing dive, and can be used as an indication of feeding success by calculating the daily change in vertical drift rates over time, which reflects the relative fluctuations in buoyancy of the animal as the proportion of lipids in the body change. Northwest Atlantic hooded seals perform drift dives at regular intervals throughout their annual migration across the Northwest Atlantic Ocean. We found that the daily change in drift rate varied with geographic location and the time of year and that this differed between sexes. Positive changes in buoyancy (reflecting increased lipid stores) were evident throughout their migration range and although overlapping somewhat, they were not statistically associated with high use areas as indicated by First Passage Time (FPT). Differences in the seasonal fluctuations of buoyancy between males and females suggest that they experience a difference in patterns of energy gain and loss during winter and spring, associated with breeding. The fluctuations in buoyancy around the moulting period were similar between sexes.     

Microbial Metabolism as an Evolutionary Response: The Cybernetic Approach to Modeling

ABSTRACT:?

The growth and metabolic capabilities of microorganisms depend on their interactions with the culture medium. Many media contain two or more key substrates, and an organism may have different preferences for the components. Microorganisms adjust their preferences according to the prevailing conditions so as to favor their own survival. Cybernetic modeling describes this evolutionary strategy by defining a goal that an organism tries to attain optimally at all times. The goal is often, but not always, maximization of growth, and it may require the cells to manipulate their metabolic processes in response to changing environmental conditions.

The cybernetic approach overcomes some of the limitations of metabolic control analysis (MCA), but it does not substitute MCA. Here we review the development of the cybernetic modeling of microbial metabolism, how it may be combined with MCA, and what improvements are needed to make it a viable technique for industrial fermentation processes.

IMTECH communication no.001/2001     

Evolutionary History of Lagomorphs in Response to Global Environmental Change

Although species within Lagomorpha are derived from a common ancestor, the distribution range and body size of its two extant groups, ochotonids and leporids, are quite differentiated. It is unclear what has driven their disparate evolutionary history. In this study, we compile and update all fossil records of Lagomorpha for the first time, to trace the evolutionary processes and infer their evolutionary history using mitochondrial genes, body length and distribution of extant species. We also compare the forage selection of extant species, which offers an insight into their future prospects. The earliest lagomorphs originated in Asia and later diversified in different continents. Within ochotonids, more than 20 genera occupied the period from the early Miocene to middle Miocene, whereas most of them became extinct during the transition from the Miocene to Pliocene. The peak diversity of the leporids occurred during the Miocene to Pliocene transition, while their diversity dramatically decreased in the late Quaternary. Mantel tests identified a positive correlation between body length and phylogenetic distance of lagomorphs. The body length of extant ochotonids shows a normal distribution, while the body length of extant leporids displays a non-normal pattern. We also find that the forage selection of extant pikas features a strong preference for C₃ plants, while for the diet of leporids, more than 16% of plant species are identified as C₄ (31% species are from Poaceae). The ability of several leporid species to consume C₄ plants is likely to result in their size increase and range expansion, most notably in Lepus. Expansion of C₄ plants in the late Miocene, the so-called ‘nature’s green revolution’, induced by global environmental change, is suggested to be one of the major ‘ecological opportunities’, which probably drove large-scale extinction and range contraction of ochotonids, but inversely promoted diversification and range expansion of leporids.     

Diving behaviour of white-chinned petrels and its relevance for mitigating longline bycatch

The white-chinned petrel (Procellaria aequinoctialis) is the seabird species most commonly killed by Southern Hemisphere longline fisheries. Despite the importance of diving ability for mitigating longline bycatch, little is known of this species’ diving behaviour. We obtained data from temperature–depth recorders from nine white-chinned petrels breeding on Marion Island, southwestern Indian Ocean, during the late incubation and chick-rearing period. Maximum dive depth (16 m) was slightly deeper than the previous estimate (13 m), but varied considerably among individuals (range 2–16 m). Males dived deeper than females, and birds feeding chicks dived deeper than incubating birds, but dive rate did not differ between the sexes. Time of day had no significant effect on dive depth or rate. Our findings will help to improve the design and performance of mitigation measures aimed at reducing seabird bycatch in longline fisheries, such as the calculation of minimum line sink rates and optimum aerial coverage of bird-scaring lines.     

植物响应低温胁迫的应答机制

介绍了植物响应低温胁迫的生理生化和分子机制及其信号转导途径的研究进展。并对今后这一领域研究前景作了展望和讨论。     

The Humidity Response of Stomata and its Measurement

Meidner, H. 1987. The humidity response of stomata and its measurement.—J.exp. Bot. 38:877–882. Using artificial membranes of constant conductance with vapourpressures below the membranes of 2?33 kPa (saturated) and 2?26kPa (97% saturated) it was found that an automated water vapourdiffusion porometer registered a change in conductance. In otherwords, it underestimated the conductance when the vapour pressurebelow the membranes was only 97% saturated. This is becausethe programmed computation of the conductance assumes that thespace below the membrane is at all times saturated. The implicationsfor measuring leaf conductance with these instruments is discussedin connection with the humidity response of stomata to a stepwiseincrease in the vapour pressure difference between the leafinterior and the atmosphere. This response appears to involvea lowering of the vapour pressure in the sub-stomatal spaceand, therefore, a transient opening movement which can be detectedby sensitive mass flow porometry. It is concluded that in cases in which a transient opening movementprecedes partial stomatal closure the humidity response to anincrease in vapour pressure difference cannot be due to vapourloss direct from the guard cells. Key words: Humidity, transients, stomata     

鸟类羽色多态现象:概念及其进化制假说

多态现象对了解物种的遗传、变异和进化有着重要意义,鸟类羽色多态现象的进化机制,是多态现象研究中非常重要的内容.鸟类羽色多态现象的进化机制假说主要有分化选择假说、异类选择假说和非随机性交配假说等.本文对鸟类羽色多态现象的概念和以上进化机制假说进行了综述,并针对鸟类羽色多态现象进化机制研究中存在争议的问题及研究的不足提出了自己的看法.     

Evolutionary developmental biology its roots and characteristics

The rise of evolutionary developmental biology was not the progressive isolation and characterization of developmental genes and gene networks. Many obstacles had to be overcome: the idea that all genes were more or less involved in development; the evidence that developmental processes in insects had nothing in common with those of vertebrates.Different lines of research converged toward the creation of evolutionary developmental biology, giving this field of research its present heterogeneity. This does not prevent all those working in the field from sharing the conviction that a precise characterization of evolutionary variations is required to fully understand the evolutionary process.Some evolutionary developmental biologists directly challenge the Modern Synthesis. I propose some ways to reconcile these apparently opposed visions of evolution. The turbulence seen in evolutionary developmental biology reflects the present entry of history into biology.     

鸟类羽色多态现象：概念及其进化机制假说

多态现象对了解物种的遗传、变异和进化有着重要意义,鸟类羽色多态现象的进化机制,是多态现象研究中非常重要的内容。鸟类羽色多态现象的进化机制假说主要有：分化选择假说、异类选择假说和非随机性交配假说等。本文对鸟类羽色多态现象的概念和以上进化机制假说进行了综述,并针对鸟类羽色多态现象进化机制研究中存在争议的问题及研究的不足提出了自己的看法。     

Unraveling the Entry Mechanism of Baculoviruses and Its Evolutionary Implications

The entry of baculovirus budded virus into host cells is mediated by two distinct types of envelope fusion proteins (EFPs), GP64 and F protein. Phylogenetic analysis suggested that F proteins were ancestral baculovirus EFPs, whereas GP64 was acquired by progenitor group I alphabaculovirus more recently and may have stimulated the formation of the group I lineage. This study was designed to experimentally recapitulate a possible major step in the evolution of baculoviruses. We demonstrated that the infectivity of an F-null group II alphabaculovirus (Helicoverpa armigera nucleopolyhedrovirus [HearNPV]) can be functionally rescued by coinsertion of GP64 along with the nonfusogenic F^def (furin site mutated HaF) from HearNPV. Interestingly, HearNPV enters cells by endocytosis and, less efficiently, by direct membrane fusion at low pH. However, this recombinant HearNPV coexpressing F^def and GP64 mimicked group I virus not only in its EFP composition but also in its abilities to enter host cells via low-pH-triggered direct fusion pathway. Neutralization assays indicated that the nonfusogenic F proteins contribute mainly to binding to susceptible cells, while GP64 contributes to fusion. Coinsertion of GP64 with an F-like protein (Ac23) from group I virus led to efficient rescue of an F-null group II virus. In summary, these recombinant viruses and their entry modes are considered to resemble an evolutionary event of the acquisition of GP64 by an ancestral group I virus and subsequent adaptive inactivation of the original F protein. The study described here provides the first experimental evidence to support the hypothesis of the evolution of baculovirus EFPs.     

植物表皮蜡质参与干旱胁迫的反应机制

植物表皮是植物与外部环境直接接触的部位,包括具有立体网状结构的角质和填充其间并覆盖其上的蜡质。植物在适应外界环境的过程中,表皮蜡质形成了特殊的结构和复杂的化学组成。植物表皮蜡质最重要的功能是参与阻止植物非气孔性失水,提高植物对水分的利用效率,以实现对干旱环境的适应。干旱环境会导致植物表皮蜡质代谢的变化,这种变化最终通过调控基因表达来实现。目前已经发现了多个蜡质代谢相关基因参与了植物对干旱环境的适应,部分基因已经成功克隆并且用于改良农作物的抗旱性。但这些基因参与干旱响应的分子机制及其与ABA的关系并不很清楚。就植物适应水分胁迫而发生的包括蜡质组成和含量在内的代谢变化,以及该过程中所涉及的主要基因及其分子生物学研究进行综述。探讨表皮蜡质在植物适应干旱中的重要作用及其分子机制,可为农作物的抗旱育种提供新型的分子标记和重要靶基因,最终服务于农业生产实践。