Plasticity varies with boldness in a weakly-electric fish

The expression of animal personality is indicated by patterns of consistency in  individual behaviour. Often, the differences exhibited between individuals are consistent across situations. However, between some situations, this can be biased by variable levels of individual plasticity. The interaction between individual plasticity and animal personality can be illustrated by examining situation-sensitive personality traits such as boldness (i.e. risk-taking and exploration tendency). For the weakly electric fish Gnathonemus petersii, light condition is a major factor influencing behaviour. Adapted to navigate in low-light conditions, this species chooses to be more active in dark environments where risk from visual predators is lower. However, G. petersii also exhibit individual differences in their degree of behavioural change from light to dark. The present study, therefore, aims to  examine if an increase of motivation to explore in the safety of the dark, not only affects mean levels of boldness, but also the variation between individuals, as a result of differences  in individual plasticity.  Results: Boldness was consistent between a novel-object and a novel-environment situation in bright light. However, no consistency in boldness was noted between a bright (risky) and a  dark (safe) novel environment. Furthermore, there was a negative association between boldness and the degree of change across novel environments, with shier individuals  exhibiting greater behavioural plasticity.  Conclusions: This study highlights that individual plasticity can vary with personality. In  addition, the effect of light suggests that variation in boldness is situation specific. Finally,  there appears to be a trade-off between personality and individual plasticity with shy but  plastic individuals minimizing costs when perceiving risk and bold but stable individuals  consistently maximizing rewards, which can be maladaptive.

Effect of the processing conditions on the microstructure and properties of rotational molded polyamide 11

Rotomolded containers for solvents and hydrocarbons require the use of high-permeability resins such as polyamide (PA). The published studies with this material are very scarce. In this work, a commercial grade of PA11 was rotational-molded using different processing temperatures and characterized with a range of techniques. The study aims at investigating the influence of the processing conditions on the microstructure and properties of molded parts. The results showed that the spherulitic morphology and the mechanical properties are affected by the processing temperature, the optimum processing range being between 220°C and 240°C. Overheating causes a decrease of the impact strength and a severe increase in the formation of pinholes at the outer surface due to polymer degradation and formation of volatile products. The thermo-oxidation reactions occurring at the inner surface of the samples result in the formation of products that absorb in the UV and visible light regions and cause the microhardness and the melt viscosity of the material to increase. The extent and severity of the degradation at the inner surface may be easily assessed by fluorescence microscopy. © 2008 Wiley Periodicals, Inc.