Growth Rate Of Primary Feathers Research Articles

Untangling causes of variation in mercury concentration between flight feathers.

Bird feathers are one of the most widely used animal tissue in mercury biomonitoring, owing to the ease of collection and storage. They are also the principal excretory pathway of mercury in birds. However, limitations in our understanding of the physiology of mercury deposition in feathers has placed doubt on the interpretation of feather mercury concentratoins. Throughout the literature, moult sequence and the depletion of the body mercury pool have been taken to explain patterns such as the decrease in feather mercury from the innermost (P1) to the outermost primary feather (P10) of the wing. However, it has been suggested that this pattern is rather a measurement artefact as a result of the increased feather mass to length ratio along the primaries, resulting in a dilution effect in heavier feathers. Here, we attempt to untangle the causes of variation in feather mercury concentrations by quantifying the mercury concentration as μg of mercury (i) per gram of feather, (ii) per millimetre of feather, and (iii) per day of feather growth in the primary feathers of Bulwer's Petrel Bulweria bulwerii chicks, effectively controlling for some of the axes of variation that may be acting in adults, and monitoring the growth rate of primary feathers in chicks. The mercury concentration in Bulwer's Petrel chicks' primaries increased from the innermost to the outermost primary for all three concentration measures, following the order of feather emergence. These observations confirm that the pattern of mercury concentration across primary feathers is not an artefact of the measure of concentration, but is likely an effect of the order of feather growth, whereby the earlier grown feathers are exposed to higher blood mercury concentrations than are later moulted feathers as a result of blood mercury depletion.

Characterization of microRNA and mRNA expression profiles in skin tissue between early-feathering and late-feathering chickens

BackgroundEarly feathering and late feathering in chickens are sex-linked phenotypes, which have commercial application in the poultry industry for sexing chicks at hatch and have important impacts on performance traits. However, the genetic mechanism controlling feather development and feathering patterns is unclear. Here, miRNA and mRNA expression profiles in chicken wing skin tissues were analysed through high-throughput transcriptomic sequencing, aiming to understand the biological process of follicle development and the formation of different feathering phenotypes.ResultsCompared to the N1 group with no primary feathers extending out, 2893 genes and 31 miRNAs displayed significantly different expression in the F1 group with primary feathers longer than primary-covert feathers, and 1802 genes and 11 miRNAs in the L2 group displayed primary feathers shorter than primary-covert feathers. Only 201 altered genes and 3 altered miRNAs were identified between the N1 and L2 groups (fold change > 2, q value < 0.01). Both sequencing and qPCR tests revealed that PRLR was significantly decreased in the F1 and L2 groups compared to the N1 group, whereas SPEF2 was significantly decreased in the F1 group compared to the N1 or L2 group. Functional analysis revealed that the altered genes or targets of altered miRNAs were involved in multiple biological processes and pathways related to feather growth and development, such as the Wnt signalling pathway, the TGF-beta signalling pathway, the MAPK signalling pathway, epithelial cell differentiation, and limb development. Integrated analysis of miRNA and mRNA showed that 14 pairs of miRNA-mRNA negatively interacted in the process of feather formation.ConclusionsTranscriptomic sequencing of wing skin tissues revealed large changes in F1 vs. N1 and L2 vs. N1, but few changes in F1 vs. L2 for both miRNA and mRNA expression. PRLR might only contribute to follicle development, while SPEF2 was highly related to the growth rate of primary feathers or primary-covert feathers and could be responsible for early and late feather formation. Interactions between miR-1574-5p/NR2F, miR-365-5p/JAK3 and miR-365-5p/CDK6 played important roles in hair or feather formation. In all, our results provide novel evidence to understand the molecular regulation of follicle development and feathering phenotype.

The effects of delaying the start of moult on the duration of moult, primary feather growth rates and feather mass in Common Starlings Sturnus vulgaris

In many species of birds there is a close relationship between the end of breeding and the start of moult. Late‐breeding birds therefore often start to moult late, but then moult more rapidly. This is an adaptive mechanism mediated by decreasing day lengths that allows late‐breeding birds to complete moult in time. This study asked how these birds complete moult of the primary feathers more rapidly, and the consequences of this on the mass of primary feathers. Common Starlings Sturnus vulgaris were induced to moult rapidly in one of two ways. In the first experiment, one group was exposed to artificially decreasing photoperiods from the start of moult, whereas the control group remained on a constant long photoperiod. The second experiment was a more realistic simulation. Two groups were allowed to moult in an outdoor aviary. One group started to moult at the normal time. In the other, the start of moult was delayed by 3 weeks with an implant of testosterone. The duration of moult was significantly reduced in both the group experiencing artificially decreasing photoperiods and the group in which the start of moult was delayed. The faster moult rate was achieved by moulting more feathers concurrently. The rate of increase in length of each of the primary feathers, and their final length, did not differ between groups. The rate at which total new primary feather mass was accumulated was greater in more rapidly moulting birds, but this was insufficient to compensate for the greater numbers of feathers being grown concurrently. Consequently, the rate of increase in mass of individual feathers, and the final feather mass, were less in the rapidly moulting birds. A 3‐week delay in the start of moult is not an unrealistic scenario. That this caused a measurable decrease in feather mass suggests that late‐breeding birds are indeed likely to suffer a real decrease in the quality of plumage grown during the subsequent moult.