Influence of ionic strength and pH on the limitation of latex microsphere deposition sites on iron-oxide coated sand by humic acid

This study, for the first time, investigates and quantifies the influence of slight changes in solution pH and ionic strength (IS) on colloidal microsphere deposition site coverage by Suwannee River Humic Acid (SRHA) in a column matrix packed with saturated iron-oxide coated sand.Triple pulse experimental (TPE) results show adsorbed SRHA enhances microsphere mobility more at higher pH and lower IS and covers more sites than at higher IS and lower pH. Random sequential adsorption (RSA) modelling of experimental data suggests 1 μg of adsorbed SRHA occupied 9.28 ± 0.03 × 10⁹ sites at pH7.6 and IS of 1.6 mMol but covered 2.75 ± 0.2 × 10⁹ sites at pH6.3 and IS of 20 mMol. Experimental responses are suspected to arise from molecular conformation changes whereby SRHA extends more at higher pH and lower ionic strength but is more compact at lower pH and higher IS. Results suggest effects of pH and IS on regulating SRHA conformation were additive.     

The human serum paraoxonase—Polymorphism and specificity

Human serum contains EDTA‐sensitive (Ca⁺⁺‐dependent) and EDTA‐stable (albumin) paraoxonases which hydrolyse paraoxon, 0,0‐diethyl,0–4‐nitrophenyl phosphate.

In Caucasians the EDTA‐sensitive enzyme shows a genetically determined polymorphism which is governed by two alleles. In typical Mongoloid or Negro populations this polymorphism is expressed to a lesser degree, and in a few samples (e.g. Aborigines) it cannot be observed at all. The distribution of the activity of the EDTA‐stable (albumin) paraoxonase is unimodal.

Many authors supposed that paraoxonase is an arylesterase (EC 3.1.1.2) which means that it is also able to hydrolyse phenylacetate or β‐naphthylacetate. New investigations have shown that the human serum fractions splitting paraoxon can be separated from those hydrolysing phenylacetate and related substrates.

The polymorphism of the EDTA‐sensitive human serum paraoxonase can be applied to investigations concerning specificity. From this it becomes evident that this enzyme is rather specific. Already slight changes of the paraoxon molecule lead to a decrease of activity. On the other hand the enzyme seems to hydrolyse also phosphonic acid esters and 4‐nitrophenylacetate in the same way like paraoxon (polymorphism).

There is a linkage relationship of paraoxonase with cystic fibrosis and DNA markers. According to these results the (EDTA‐sensitive) paraoxonase locus is on the human chromosome 7.

A high serum paraoxonase level actually protects serum cholinesterase (EC 3.1.1.8) and has to be considered in biological monitoring of workers exposed to parathion.     

Dissecting the mechanisms underlying old male mating advantage in a butterfly

Selection is expected to maximize an individual’s own genetic reward regardless of the potential fitness consequences for its sexual partners, which may cause sexual conflict. Although performance in holometabolous insects typically diminishes with age, old male mating advantage has been documented in a few species. Whether this pattern arises from female preference for older males based on, e.g., pheromone blends (intersexual selection), or from increased eagerness to mate in older compared to younger males is currently debated. We explore the mechanistic basis of old male mating advantage, using a series of experiments including behavioral as well as manipulative approaches, in the tropical butterfly Bicyclus anynana. Consistent with the residual reproductive value hypothesis, old male mating advantage was associated with a greater eagerness to mate, evidenced by a two times higher flying and courting activity in older than in younger males. In contrast, we found only limited support for a contribution of female preference for older males based on pheromone composition, although male sex pheromones clearly do play a role in mating success. Our results suggest that male behavior may play a primary role in old male mating advantage, and that pheromones are likely of secondary importance only. Male mating success was related to higher overall pheromone titers rather than variation in a single component. A dominant importance of male behavior in determining mating success may result in sexual conflict.     

Risk-taking behavior in the lesser wax moth: disentangling within- and between-individual variation

Behaviors that appear to be plastic may well be determined by environmental influences during development. Being able to produce a wide range of variants of one kind of behavior, e.g., a very short and a very long response time to a stimulus under different environmental conditions, can be described as behavioral plasticity. How such behavioral reaction norms develop for individuals is poorly understood, but several factors are likely to play a role. We investigated what factors may affect how the risk-taking behavior of the lesser wax moth, Achroia grisella, is shaped during ontogeny. We manipulated larval density to represent the potential intensity of future competition for females in a lek of males, determined adult moths’ reaction to predator signals, and tested for plasticity in the silence response, i.e., the acoustic evasion behavior of the moths during the experiments. While we found no effect of larval density on either the probability or the duration of the silence response, 11 % of the variance in duration could be explained by differences between families, and 30 % of the variance was the result of differences between individuals. We found evidence for habituation to the predator signal, clearly indicating that the silence response is a plastic-enough trait to be adjustable to the immediate environment. These results suggest that the degree to which individuals take risks in the context of acoustic signaling depends more on the immediate context and, possibly, genetic differentiation than it is a product of adaptive developmental plasticity.     

Correlated changes in breeding status and polyunsaturated cuticular hydrocarbons: the chemical basis of nestmate recognition in the burying beetle <Emphasis Type="Italic">Nicrophorus vespilloides</Emphasis>?

Nestmate recognition in eusocial insects has received a lot of attention in the last decades. Recognition in subsocial species, in contrast, has been ignored almost completely and consequently, and little is known about proximate mechanisms of recognition in subsocial systems. We studied one subsocial species, the biparental brood caring burying beetle Nicrophorus vespilloides, an interesting model organism for studies of recognition because of its ability to discriminate between breeding partners and conspecific competitors. Recognition appears to be based on a chemical cue closely linked to the breeding status of individuals. Breeding and non-breeding beetles consistently differ in their relative proportions of polyunsaturated cuticular hydrocarbons. To investigate the function of these polyenes in the burying beetles’ recognition system, we quantified their concentration on the cuticle during the early state of a breeding attempt and tested the response of breeding beetles in corresponding behavioural experiments. We observed a rapid increase in the proportion of polyunsaturated hydrocarbons of both males and females after they were provided with a carcass suitable for reproduction. Furthermore, we found that the relative amount of polyenes on an individual’s surface was closely correlated with its chance of being accepted as breeding partner. Our results support the idea that polyunsaturated hydrocarbons are involved in breeding partner recognition in N. vespilloides, functioning as a signal that conveys information about the individual’s breeding status. Breeding females have greater amount of polyenes than breeding males, and females ingest more carrion during the first days on the carcass, which supports our hypothesis that precursors for the respective polyenes are derived from ingested carrion.     

Maintenance of variance in sperm transfer rates in a scorpionfly: food availability,genetic basis,and heritability

Variation in traits closely related to fitness is expected to be low. This is because these traits are under directional selection and the best genotype should prevail. However, there have been a number of studies demonstrating the existence of considerable variance in sexually selected traits, which is generally known as the lek paradox. Accordingly, earlier studies found substantial variation in sperm transfer rates in Panorpa vulgaris. Aiming at finding the mechanism that maintains this variation, we analyzed the condition dependence and the narrow sense heritability of sperm transfer rates. Food deprivation in the larval/adult phase caused a decrease in the males’ capability of saliva secretion resulting in shorter copulations and a reduced number of transferred sperm. There was a positive correlation between mean sperm transfer rates and mean body mass. Additionally, intermale variation in sperm transfer rates decreased with increasing food availability. Hence, we suggest that sperm transfer rates in P. vulgaris are influenced by adult feeding history. Heritability analyses of sperm transfer rates did not provide significant results, which is consistent with the general hypothesis that additive genetic variance in traits closely related to fitness is small. Since a trait’s potential to respond to selection is proportional to the amount of contained additive genetic variance, the ascertained small heritability provides a satisfying explanation for the maintenance of substantial variation in sperm transfer rates.     

Zur chemie der marsoberfläche

Analyses of 13 samples of Martian surface materials with the Viking X-ray fluorescence spectrometers show SiO₂ similar to that of terrestrial mafic rocks, whereas Fe₂O₃, Cl, and S are higher and Al₂O₃, K₂O, Rb, Sr, Y, and Zr are lower. Low totals suggest presence of CO₂, H₂O, and Na₂O. Duricrust fragments are higher in S than fines, but samples from both landing sites are surprisingly similar. We suggest that Martian surface materials are aeolian deposits of complex mixtures of weathering products of maficultramafic rocks, possibly consisting of iron-rich clays, sulfates, iron oxides, carbonates, and chlorides.