982 resultados para Trios (Piano, basset horn, clarinet)


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composé par M. Henkel

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Secondary sexual traits in males of polygynous species are important determinants of reproductive success. It is, however, unknown if and how the development of continuously growing traits at different life-stages is related to reproduction in long-lived male mammals. In this study, we evaluated the relationship of early and late horn growth on social status and reproduction in long-lived male Alpine ibex (Capra ibex). For this, we analysed individual horn growth and assessed its effect on dominance and reproduction. No evidence was detected for compensatory horn growth, as late-life horn growth positively depended on early-life horn growth in males. Still, individuals with longer horn segments grown during early adulthood experienced a stronger age-dependent length decline in annual horn growth during the late development. Accordingly, a divergence between individual growth potential and realized horn growth late in life has to be assumed. Residual age-specific horn length and length of early grown horn segments both positively affected dominance and reproductive success, whereas, contrary to our expectation, no significant effect of the length of horn segments grown during the late development was detected. Suspected higher somatic costs incurred by high-quality males during their late development might at least partly be responsible for this finding. Overall, our study suggests that the total length of horns and their early development in long-lived male Alpine ibex is a reliable indicator of reproductive success and that individuals may be unable to compensate for poor early-life growth performance at a later point in life.

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von Julius David am 21. November 1875

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by Louis Freedberg

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by M. Halpern

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von J. Rosenfeld ...

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recueillis par Maurice J. Rosenspier

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composed by A. Haitmann. [Words] from Hugo Zuckermann

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Whereas the genetic background of horn growth in cattle has been studied extensively, little is known about the morphological changes in the developing fetal horn bud. In this study we histologically analyzed the development of horn buds of bovine fetuses between ~70 and ~268 days of pregnancy and compared them with biopsies taken from the frontal skin of the same fetuses. In addition we compared the samples from the wild type (horned) fetuses with samples taken from the horn bud region of age-matched genetically hornless (polled) fetuses. In summary, the horn bud with multiple layers of vacuolated keratinocytes is histologically visible early in fetal life already at around day 70 of gestation and can be easily differentiated from the much thinner epidermis of the frontal skin. However, at the gestation day (gd) 212 the epidermis above the horn bud shows a similar morphology to the epidermis of the frontal skin and the outstanding layers of vacuolated keratinocytes have disappeared. Immature hair follicles are seen in the frontal skin at gd 115 whereas hair follicles below the horn bud are not present until gd 155. Interestingly, thick nerve bundles appear in the dermis below the horn bud at gd 115. These nerve fibers grow in size over time and are prominent shortly before birth. Prominent nerve bundles are not present in the frontal skin of wild type or in polled fetuses at any time, indicating that the horn bud is a very sensitive area. The samples from the horn bud region from polled fetuses are histologically equivalent to samples taken from the frontal skin in horned species. This is the first study that presents unique histological data on bovine prenatal horn bud differentiation at different developmental stages which creates knowledge for a better understanding of recent molecular findings.