Prey: predator ratio dependence in the functional response of a freshwater amphipod

1. First known for their shredding activity, freshwater amphipods also behave as active predators with consequences for prey population regulation and amphipod coexistence in the context of biological invasions. 2. A way to quantify predation is to determine the average consumption rate per predator, also known as its functional response (FR). 3. Although amphipods are gregarious and can display social interactions that can alter per capita consumption rates, previous studies using the FR approach to investigate amphipod predation ignored such potential mutual interference because they did not consider variations in predator density. 4. We investigated the FR of Echinogammarus berilloni feeding on dipteran larvae with joint variations in prey and predator densities. This bivariate experimental design allowed us to estimate interference and to compare the fits of the three main classes of theoretical FR models, in which the predation rate is a function of prey density alone (prey‐dependent models), of both prey and predator densities (predator‐dependent models) or of the prey‐to‐predator ratio (ratio‐dependent models). 5. The Arditi–Ginzburg ratio‐dependent FR model provided the best representation of the FR of E. berilloni, whose predation rate showed a decelerating rise to a horizontal asymptote as prey abundance increased. 6. Ratio dependence means that mutual interference between amphipods leads to prey sharing. Mutual interference is likely to vary between amphipod species, depending on their level of aggressiveness.     

Twins are more different than commonly believed,but made less different by compensating behaviors

Twin studies are popular, because twins are believed to be the same/similar in genes and environmental exposures. It is well documented, however, that the firstborns are healthier at birth. We use the entire U.S. record of twin births during 1995–2000 to show that the survival duration parameters differ between twins depending on the birth order. We also find that wiser (i.e., older or educated) or married (i.e., resource-richer) mothers take more care of the weaker, which is a “compensating” behavior reducing the twin difference, as opposed to “reinforcing (the twin difference)” behavior. The systematic survival pattern difference and the mother's intervention against nature send cautions to twin studies that regard twins homogeneous to interpret their findings accordingly. Since the survival duration in our data is 97% right-censored in one year, we devise a quantile-based ‘fixed-effect’ semiparametric estimator that can handle heavy censoring, which is our methodological contribution.     

Integrating the spatial proximity effect into the assessment of changes in ecosystem services for biodiversity conservation

The assessment of the value of ecosystem services is a valuable tool for biodiversity conservation that can facilitate better environmental policy decision-making and land management, and can help land managers develop interventions to compensate for biodiversity loss at the patch level. Previous studies have suggested that it is appropriate to assess the value of biodiversity for conservation planning by considering both the condition of the landscape and the spatial configuration of adjacent land uses that can be reflected as a proximity effect. This research examines the influence of spatial proximity on biodiversity conservation from the ecosystem service perspective based on the assumption that the variation in the proximity effect caused by land cover change has positive or negative impacts on ecological services. Three factors related to the spatial characteristics of the landscape were considered in this approach: the relative artificiality of the land cover types, the distance decay effect of patches and the impact of one land cover type on others. The proximity effect change (PE_C) parameter reflected the relationship between the spatial proximity effect and biodiversity conservation. The results of a quantitative and spatial comparative analysis of the proposed method and the conventional method in Yingkou for the periods of 2000–2005 and 2005–2010 showed that the former can account for the temporal and spatial changes in ecosystem services for biodiversity conservation that were caused by patch-level changes as well as the interaction between the altered and adjacent patches from a spatial perspective. The metric can also identify the most critical areas for biodiversity protection and inform the efficient allocation of limited land resources for nature conservation to maximize the benefit to biodiversity by guiding the process of land-use change, particularly urbanization and agriculture. Future studies should focus on the other important factors that are applicable to the assessment of the value of biodiversity conservation in socio-ecological systems, where society and nature are mutually capable of fulfilling their roles.     

The intranuclear bodies of Entamoeba

Intranuclear bodies which are spherical in shape are clearly seen by ‘Anoptral’ (negative) phase microscopy in the nucleus of Entamoeba. These bodies vary in size and numbers from cell to cell. With interference microscopy the intranuclear bodies appear as spherical granules in the nucleus of the cell. Their distribution and numbers are again very variable. With electron microscopy the bodies can be clearly seen inside the nucleus. They are always spherical in shape but vary in size from 0·1 to 1·5 μm. They may be empty or contain granular or membranous material. They display the capacity to move out of the nucleus.     

Daughters from daughterless mothers — Rescuing a female-lethal maternal effect by cytoplasmic transplantation inDrosophila embryos

Summary Daughterless is a temperature-sensitive, maternal effect mutation ofDrosophila melanogaster. Homozygousdaughterless females raised at temperatures above 22°C do not produce any female progeny. It was possible to rescue these female embryos by injecting cytoplasm from non-mutant unfertilized eggs into embryos fromdaughterless mothers. Cytoplasm from unfertilized eggs laid by homozygousdaughterless mothers was ineffective. Surprisingly, the cytoplasm from developing embryos with either wild-type ordaughterless mothers could also effect rescue. Based upon this data, we suggest that male and female embryos ofdaughterless mothers differ in their ability to initiate the synthesis of a product during the nuclear multiplication (cleavage) stage of embroniic development in the absence of a putativeda ⁺ maternally-synthesized factor, and that this is the basis for the sex-specific action of theda maternal effect.     

Mg2+ accelerates plastoquinone reduction in chloroplasts

The transient fluorescence quenching induced by the addition of a small amount of an oxidant to illuminated chloroplasts can be used to estimate the rate of electron transported by the oxidant. Using this technique, it is found that the reduction of plastoquinone by the primary acceptor of Photosystem II is sensitive to salt depletion.     

Acute and long-lasting effects of peripheral injection of caerulein and CCK-8 on the central GABAergic system in mice

Acute and long-lasting effects of peripheral injection of caerulein (CLN) and cholecystokinin octapeptide (CCK-8) on the gamma-aminobutylic acid (GABA) content and the GABA accumulation by aminooxyacetic acid (AOAA) in the discrete brain regions of mice were examined. The content and accumulation of GABA in the striatum, hypothalamus, and frontal cortex was measured with high performance liquid chromatography with electrochemical detection (HPLC-ECD). The GABA content slightly decreased in the striatum 60 min after CLN and CCK-8 were administered, whereas it slightly increased in the hypothalamus and frontal cortex. Moreover, with CLN and CCK-8, the GABA accumulation after AOAA treatment decreased in the striatum and hypothalamus 30 min after injection. Meanwhile, when administering CLN, the GABA content as well as the GABA accumulation after AOAA treatment increased in the striatum and frontal cortex 1 day after injection, and continued to increase the second and third day in the striatum. These results showed that peripheral injection of CLN and CCK-8 had effects on the central GABAergic system with local specific actions, and also the long-lasting and time-dependent biphasic effects of CLN.     

Pressure effects on the apparent viscosity of artificial dipalmitoylphosphatidylcholine and dimyristoylphosphatidylcholine membranes using intramolecular excimer probe

Emission spectroscopy of intramolecular excimer probes allows the determination of ‘equivalent viscosity’ of membranes. While increasing the pressure on artificial membrane suspensions, variations in viscosity — essentially related to an increase in the order parameter in the membranes — are observed. In the case of mixed phospholipids, the effect of pressure is amplified, probably due to the existence of holes on the molecular scale between the two lipidic layers.