Early environment influences later performance in fishes

Conditions fish encounter during embryogenesis and early life history can leave lasting effects not only on morphology, but also on growth rate, life‐history and behavioural traits. The ecology of offspring can be affected by conditions experienced by their parents and mother in particular. This review summarizes such early impacts and their ecological influences for a variety of teleost species, but with special reference to salmonids. Growth and adult body size, sex ratio, egg size, lifespan and tendency to migrate can all be affected by early influences. Mechanisms behind such phenotypically plastic impacts are not well known, but epigenetic change appears to be one central mechanism. The thermal regime during development and incubation is particularly important, but also early food consumption and intraspecific density can all be responsible for later life‐history variation. For behavioural traits, early experiences with effects on brain, sensory development and cognition appear essential. This may also influence boldness and other social behaviours such as mate choice. At the end of the review, several issues and questions for future studies are given.     

Can spatial sorting associated with spawning migration explain evolution of body size and vertebral number in Anguilla eels?

Spatial sorting is a process that can contribute to microevolutionary change by assembling phenotypes through space, owing to nonrandom dispersal. Here we first build upon and develop the “neutral” version of the spatial sorting hypothesis by arguing that in systems that are not characterized by repeated range expansions, the evolutionary effects of variation in dispersal capacity and assortative mating might not be independent of but interact with natural selection. In addition to generating assortative mating, variation in dispersal capacity together with spatial and temporal variation in quality of spawning area is likely to influence both reproductive success and survival of spawning migrating individuals, and this will contribute to the evolution of dispersal‐enhancing traits. Next, we use a comparative approach to examine whether differences in spawning migration distance among 18 species of freshwater Anguilla eels have evolved in tandem with two dispersal‐favoring traits. In our analyses, we use information on spawning migration distance, body length, and vertebral number that was obtained from the literature, and a published whole mitochondrial DNA‐based phylogeny. Results from comparative analysis of independent contrasts showed that macroevolutionary shifts in body length throughout the phylogeny have been associated with concomitant shifts in spawning migration. Shifts in migration distance were not associated with shifts in number of vertebrae. These findings are consistent with the hypothesis that spatial sorting has contributed to the evolution of more elongated bodies in species with longer spawning migration distances, or resulted in evolution of longer migration distances in species with larger body size. This novel demonstration is important in that it expands the list of ecological settings and hierarchical levels of biological organization for which the spatial sorting hypothesis seems to have predictive power.     

Tests of associational defence provided by hairy plants for glabrous plants of Arabidopsis halleri subsp. gemmifera against insect herbivores

1. Trichome‐producing (hairy) and trichomeless (glabrous) plants of Arabidopsis halleri subsp. gemmifera were investigated to test whether plant resistance to herbivory depends on the plants' phenotypes and/or the phenotypes of neighbouring plants (associational effects). 2. A common garden experiment was conducted in which the relative frequency of hairy and glabrous plants was manipulated. Two species of leaf‐chewing insects (larvae of a white butterfly and a cabbage sawfly) were found less often on hairy plants than on glabrous plants. By contrast, the numbers of aphids and flea beetles did not differ significantly between hairy and glabrous plants. For none of these insects did abundance depend on the frequency of the two plant morphs. 3. A field survey was conducted in two natural populations of A. halleri. In the first population, a species of white butterfly was the dominant herbivore, and hairy plants incurred less leaf damage than glabrous plants across 2 years. By contrast, in the other population, where flea beetles were dominant, there were no consistent differences in leaf damage between the two types of plants. In neither of the two populations was any evidence found of associational effects. 4. This study did not provide any conclusive evidence of associational effects of anti‐herbivore resistance, but it was discovered that trichomes can confer resistance to certain herbivores. Given the results of previous work by the authors on associational effects against a flightless leaf beetle, such associational effects of the trichome dimorphism of A. halleri were herbivore‐specific.     

NMR study of the selective inhibition of water permeability of rat erythrocyte membrane

The inhibition of water diffusion across the rat erythrocyte membrane was studied by NMR using two basically different types of inhibitory agents: PCMB andin vivo irradiation. The contribution of lipid and protein to water permeability revealed the inhibitory effect of each pathway. Internal contamination with tritium (25–115 mGy) reduces water permeability due to protein modifications; for doses higher than 100 mGy the lipid mediated mechanism seems also to be impaired. The same procedure enables one to assess the extent to which the higher water permeability of rat, compared to human, erythrocyte is due to one of the two pathways.     

Molecular dynamics simulation of the graphene–water interface: comparing water models

In this work, different water models (i.e. SPC/E, TIP3P, TIP4P/2005, TIP5P, SPC/Fw, TIP4P/2005f and SWM4_DP) are implemented to simulate water on neutral, negatively charged and positively charged graphene. In all cases ambient conditions are considered. Structural and dynamical properties for water are calculated to quantify the differences among various water models. The results show that SPC/E, TIP4P/2005, SPC/Fw, TIP4P/2005f and SWM4_DP water models yield a similar structure for interfacial water on graphene, whether it is neutral, negatively charged or positively charged. TIP5P is the model whose predictions for the structure of the interface deviate the most from those of the other models. Although qualitatively the results are for the most part similar, a large quantitative variation is observed among the dynamical properties predicted when various water models are implemented. Although experimental data are not available to discriminate the most/least accurate of the model predictions, our results could be useful for comparing results for interfacial water obtained implementing different models. Such critical comparison will benefit practical applications such as the development of energy-storage and water-desalination devices (e.g. electric double-layer capacitors), among others.     

Historical demographic profiles and genetic variation of the East African Butana and Kenana indigenous dairy zebu cattle

Butana and Kenana breeds from Sudan are part of the East African zebu Bos indicus type of cattle. Unlike other indigenous zebu cattle in Africa, they are unique due to their reputation for high milk production and are regarded as dairy cattle, the only ones of their kind on the African continent. In this study, we sequenced the complete mitochondrial DNA (mtDNA) D‐loop of 70 animals to understand the maternal genetic variation, demographic profiles and history of the two breeds in relation to the history of cattle pastoralism on the African continent. Only taurine mtDNA sequences were identified. We found very high mtDNA diversity but low level of maternal genetic structure within and between the two breeds. Bayesian coalescent‐based analysis revealed different historical and demographic profiles for the two breeds, with an earlier population expansion in the Butana vis a vis the Kenana. The maternal ancestral populations of the two breeds may have diverged prior to their introduction into the African continent, with first the arrival of the ancestral Butana population. We also reveal distinct demographic history between the two breeds with the Butana showing a decline in its effective population size (N_e) in the recent past ~590 years. Our results provide new insights on the early history of cattle pastoralism in Sudan indicative of a large ancient effective population size.     

Sample Size Determination for Grouped Exponential Observations: A Cost Function Approach

Calculating the required sample size for a desired power at a given type I error level, we often assume that we know the exact time of all subject responses whenever they occur during our study period. It is very common, however, in practice that we only monitor subjects periodically and, therefore, we know only whether responses occur or not during an interval. This paper includes a quantitative discussion of the effect resulting from data grouping or interval censoring on the required sample size when we have two treatment groups. Furthermore, with the goal of exploring the optimum in the number of subjects, the number of examinations per subject for test responses, and the total length of a study time period, this paper also provides a general guideline about how to determine these to minimize the total cost of a study for a desired power at a given α-level. A specified linear cost function that incorporates the costs of obtaining subjects, periodic examinations for test responses of subjects, and the total length of a study period, is assumed, primarily for illustrative purpose.