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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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Subtle gardeners: inland predators enrich local topsoils and enhance plant growth

Subtle gardeners: inland predators enrich local topsoils and enhance plant growth

Authors investigated during two consecutive breeding seasons the potential enrichment of the topsoils associated with inland ground-nesting eagle owls, as well as its possible consequences in the growth of two common annual grasses in southern Spain. Owls (and probably other widespread inland predators) can exert subtle effects enhancing plant growth and primary productivity through mechanisms (i.e. nutrient enrichment) other than the well-recognized top-down control of primary consumers. The combined effect of nutrient enrichment by non-colonial birds coupled with direct and indirect seed dispersal is likely to have a strong effect on community assemblage and ecosystem functioning and represents an overlooked avenue of research that certainly deserves further investigation. informacion[at] Fedriani et al (2015) Subtle Gardeners: Inland Predators Enrich Local Topsoils and Enhance Plant Growth. PLoS ONE DOI: 10.1371/journal.pone.0138273