Mosaic metabolic ageing:Basal and standard metabolic rates age in opposite directions and independent of environmental quality, sex and life span in a passerine

1. Crucial to our understanding of the ageing process is identifying how traits change with age, which variables alter their ageing process and how these traits associate with fitness. 2. Here we investigated metabolic ageing in outdoor-living captive zebra finches experiencing foraging costs. We longitudinally monitored 407 individuals over 6 years and collected 3,213 measurements of two independent mass-adjusted metabolic traits: basal metabolic rate (BMRm) at thermoneutral temperatures and standard metabolic rate (SMRm), measured as BMRm but at ambient temperatures below thermoneutrality. 3. We define mosaic or asynchronous ageing as the difference in standardized absolute ageing rates between traits, and we estimate the degree of asynchrony using the within-individual correlation of change in trait values with age. 4. BMRm decreased linearly with age, consistent with earlier reports. In contrast, SMRm increased linearly with age. The absolute standardized change with age was significantly faster for BMRm compared to SMRm, and the within-individual correlation of age related change was negligible. To the best of our knowledge, this is the first quantification of SMRm ageing, and the finding that SMRm and BMRm age in opposite directions. 5. Neither metabolic rate nor metabolic ageing rate were associated with variation in life span between individuals. Moreover, experimental manipulations of environmental quality that decreased BMRm and SMRm and shortened life span by 6 months (12%) did not affect the ageing of either metabolic trait. Females lived 2 months (4%) shorter than males, but none of the metabolic traits showed sex-specific differences at any age. 6. Our findings indicate, in contrast to the current view, that baseline energy requirements increase with age, because animals do not generally live in thermoneutral conditions, and illustrate the importance of studying the ageing phenotype in an ecologically realistic setting

Stabilising survival selection on pre-senescent expression of a sexual ornament followed by a terminal decline

Senescence is a decrease in functional capacity, increasing mortality rate with age. Sexual signals indicate functional capacity, because costs of ornamentation ensure signal honesty, and are therefore expected to senesce, tracking physiological deterioration and mortality. For sexual traits, mixed associations with age and positive associations with life expectancy have been reported. However, whether these associations are caused by selective disappearance and/or within-individual senescence of sexual signals, respectively, is not known. We previously reported that zebra finches with redder bills had greater life expectancy, based on a single bill colour measurement per individual. We here extend this analysis using longitudinal data and show that this finding is attributable to terminal declines in bill redness in the year before death, with no detectable change in presenescent redness. Additionally, there was a quadratic relationship between presenescent bill colouration and survival: individuals with intermediate bill redness have maximum survival prospects. This may reflect that redder individuals overinvest in colouration and/or associated physiological changes, while below-average bill redness probably reflects poorer phenotypic quality. Together, this pattern suggests that bill colouration is defended against physiological deterioration, because of mate attraction benefits, or that physiological deterioration is not a gradual process, but accelerates sharply prior to death. We discuss these possibilities in the context of the reliability theory of ageing and sexual selection

Ennayer

Ennayer est le nom du premier mois du calendrier julien et dérive manifestement du latin İanuarius (janvier). C’est aussi le nom que porte une fête célébrée dans toute l’Afrique du nord en relation avec le solstice d’hiver bien que généralement celui-ci soit assimilé à la fête de Mouloud Aïsa du 24 djambir (décembre) julien, correspondant au Noël chrétien. D’après E. Destaing, le Mouloud Aïsa qui était fêté huit jours avant Ennayer était connu dans l’Aurès sous le nom de Bou Ini, cette appell..

Burnous

Le port du burnous a été général en Afrique du Nord, chez les citadins et surtout dans les campagnes, aussi bien chez les berbérophones que les arabophones mais Ibn Khaldoun, parlant des Maghrébins de son époque, dit qu’il est le vêtement porté par les Berbères. C’est une cape très ample descendant jusqu’aux pieds et munie d’un capuchon ; elle est fermée sur la poitrine par une couture (sader) longue environ d’une main. Ce mode de fermeture partielle permet de porter cette cape sans avoir à l..