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Impairment of mixed melanin-based pigmentation in parrots

Parrots and allies (Order Psittaciformes) have evolved an exclusive capacity to synthesize polyene pigments called psittacofulvins at feather follicles, which allows them to produce a striking diversity of pigmentation phenotypes. Melanins are polymers constituting the most abundant pigments in animals, and the sulphurated form (pheomelanin) produces colors that are similar to those produced by psittacofulvins. However, the differential contribution of these pigments to psittaciform phenotypic diversity has not been investigated. Given the color redundancy, and physiological limitations associated to pheomelanin synthesis, this study assumed that the latter would be avoided by psittaciform birds. This hypothesis was tested by using Raman spectroscopy to identify pigments in feathers exhibiting colors suspicious of being produced by pheomelanin (i.e., dull red, yellow and grey- and green-brownish) in 26 species from the three main lineages of Psittaciformes. The non-sulphurated melanin form (eumelanin) were detected in black, grey and brown plumage patches, and psittacofulvins in red, yellow and green patches, but no evidence of pheomelanin was found. As natural melanins are assumed to be composed of eumelanin and pheomelanin in varying ratios, these results represent the first report of impairment of mixed melanin-based pigmentation in animals. Given that psittaciforms also avoid the uptake of circulating carotenoid pigments, these birds seem to have evolved a capacity to avoid functional redundancy between pigments, likely by regulating follicular gene expression. The study provides the first vibrational characterization of different psittacofulvin-based colors and thus helps to determine the relative polyene chain length in these pigments, which is related to their antireductant protection activity. informacion[at] Neves et al (2020) Impairment of mixed melanin-based pigmentation in parrots. J Experim Biol. DOI 10.1242/jeb.225912
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Is restocking a useful tool for increasing rabbit densities?

Is restocking a useful tool for increasing rabbit densities?

The European rabbit Oryctolagus cuniculus is endemic to Mediterranean ecosystems in the Iberian Peninsula, where it is a key species. In recent years its populations have declined due to several factors including habitat transformation and viral diseases. At the same time, corrective measures including population restocking in areas with low population densities using rabbits from other geographical areas have been performed. In this study we evaluate the impact restocking has had on the population dynamics of native rabbits in the Doñana National Park. As part of the natural processes monitoring program carried out in the Doñana Biological Station (ESPN-EBD-CSIC), rabbit censuses were conducted in spring and late summer in 2005–2015?at dusk and at night along six fixed transects in habitats harbouring rabbit populations. In order to take into account restocked rabbit numbers, annual reports from the Doñana Natural Area and data provided by the Lynx team of the LIFE project were incorporated into the study. In all, 52?336 rabbits from different parts of western Andalusia were released in the Doñana Biosphere Reserve in 2005–2015. Yet, rabbit populations underwent significant declines, above all in 2013 and 2015, with decreases in some areas of up to 80%. These results show intensive rabbit restocking did not increase the native rabbit populations numbers. The impact of the release of rabbits on the population dynamics of the species in Doñana is discussed. informacion[at] Carro et al (2019) Is restocking a useful tool for increasing rabbit densities? Global Ecol Conserv