The invertebrate microtubule-associated protein PTL-1 functions in mechanosensation and development in <Emphasis Type="Italic">Caenorhabditis elegans</Emphasis>

PTL-1, a microtubule-associated protein of the structural MAP2/tau family, is the sole member of this gene family in Caenorhabditis elegans. Sequence analysis of available invertebrate genomes revealed a number of single, putative tau-like genes with high similarity to ptl-1. The ptl-1 gene is expressed in a number of cells, most notably mechanosensory neurons. We examined the role of ptl-1 in C. elegans in adult neurons as well as during development. A ptl-1 knockout strain of worms exhibited an egg-hatching defect, as well as a reduced sensitivity to touch stimuli. In addition, the knockout allele ptl-1(ok621) acts as a dominant enhancer of several temperature-sensitive alleles of mec-7 and mec-12, which code the isoforms of β-tubulin and α-tubulin that together form the unusual 15 protofilament microtubules involved in touch sensation. These results demonstrate for the first time a functional role for this microtubule-associated protein in nematodes and suggest that PTL-1 is involved in mechanosensation as well as some aspect of embryogenesis.     

Sex differences in heritability of BMI: a comparative study of results from twin studies in eight countries.

Body mass index (BMI), a simple anthropometric measure, is the most frequently used measure of adiposity and has been instrumental in documenting the worldwide increase in the prevalence of obesity witnessed during the last decades. Although this increase in overweight and obesity is thought to be mainly due to environmental changes, i.e., sedentary lifestyles and high caloric diets, consistent evidence from twin studies demonstrates high heritability and the importance of genetic differences for normal variation in BMI. We analysed self-reported data on BMI from approximately 37,000 complete twin pairs (including opposite sex pairs) aged 20-29 and 30-39 from eight different twin registries participating in the GenomEUtwin project. Quantitative genetic analyses were conducted and sex differences were explored. Variation in BMI was greater for women than for men, and in both sexes was primarily explained by additive genetic variance in all countries. Sex differences in the variance components were consistently significant. Results from analyses of opposite sex pairs also showed evidence of sex-specific genetic effects suggesting there may be some differences between men and women in the genetic factors that influence variation in BMI. These results encourage the continued search for genes of importance to the body composition and the development of obesity. Furthermore, they suggest that strategies to identify predisposing genes may benefit from taking into account potential sex specific effects.     

Assessment Strategies and the Effects of Fighting Experience on Future Contest Performance in the Green Anole (Anolis carolinensis)

Social experiences can be useful sources of information for animals charged with making fitness‐related decisions. Fighting experience can alter an animal's perception of its fighting ability possibly leading to changes in future contest decisions, which may increase/decrease their probability of winning future contests. Winner and loser effects have been revealed in a wide array of animals, but studies using reptilian models are rare. This study investigated the impact of fighting experience on future contest performance and outcome in the green anole lizard and investigated the assessment strategies used by anoles during contests of different intensities. To determine whether the green anole expresses winner or loser effects, focal animals engaged in a primary contest with a smaller (larger) opponent to gain a winning (losing) experience; opponent size asymmetries were a significant predictor of contest outcome. Focal individuals were isolated for 2 d before being given a secondary contest with a size‐matched, naïve opponent. We found no evidence of winner or loser effects 2 d following a previous contest. Although previous contest outcome did not dictate future contest success, dynamics of the previous contest did. Highly aggressive primary contest losers won a significant proportion of the secondary contests, while less aggressive losers were more apt to lose the secondary contest. Secondary contest success of prior winners was not influenced by earlier contest performance. Further analyses of contest dynamics reveal that individuals may use different assessment strategies depending on the intensity of the contest. Our results demonstrate that future contest success may be driven more by individual performance in a prior contest and less by prior contest outcome.     

The influence of nest attendance and provisioning on nestling stress physiology in the Florida scrub-jay

Stressful conditions during development may have lasting consequences for an animal's lifetime fitness. We investigated the degree to which parental provisioning and nest attendance influenced baseline levels of the stress hormone corticosterone in nestling Florida scrub-jays. Provisioning rates of male and female breeders and nest attendance of female breeders were recorded during focal watches conducted between days 3 and 5 post-hatch. A small blood sample was taken from each nestling on day 11 post-hatch and used to quantify levels of baseline corticosterone. The proportion of time spent by female breeders at a considerable distance from the nest was positively related to nestling corticosterone levels. Nestling corticosterone was also negatively related to parental provisioning rate, although this effect seemed to be secondary to the effect of the female's time away from the nest. These results indicate that parental behavior contributes to nestling stress physiology, which may in turn direct the formation of the adult phenotype and influence an individual's chances of survival.