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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]ebd.csic.es: Neves et al (2020) Impairment of mixed melanin-based pigmentation in parrots. J Experim Biol. DOI 10.1242/jeb.225912


https://jeb.biologists.org/content/early/2020/05/08/jeb.225912
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When GPS tracking devices do not provide reliable information

When GPS tracking devices do not provide reliable information

New technological devices used for animal tracking have evolved at a tremendous speed. The new biologgers equipped with GPS and solar panels that download data using satellites or mobile networks seem unbeatable. They provide thousands of location of marked animals with meter precision and even in real time. But, do the data we collect provide an unbiased recall of what the animals have done?, of their movements?, of their behavior? The tracking data of Bearded vultures (Gypaetus barbatus) marked in the Pyrenees and the Cantabrian mountains with solar devices have been analyzed. They show that more locations do not always provide more information. The paper concludes that recorded locations should be analyzed carefully not to get a distorted picture of the Bearded vulture behavior. Tracking devices with solar panels depend on solar radiation to recharge their batteries. When insolation is low the devices do not fully recharge and more locations are lost. If this is not taken into account during data analysis we could have the false impression that the vultures move less at this time of year. This kind of tracking devices is essential for the Bearded vulture reintroduction project success. A tracking schedule that demands too many locations can cause the devices to run-out of battery, creating gaps in the data. The problem is that data are not lost at random: more locations are lost in winter than in summer; more are lost when vultures are in rugged versus flat areas; more when they are perched versus flying. Sometimes, complex interactions arise among behavioral and environmental factors creating difficult to correct biases. The GPS looses more locations when in a dynamic versus static state. This means that when the bird is flying the GPS requires more time to obtain a fix, but when perched the GPS loose fixes because an irregular topography precludes good visibility of the GPS satellite constellation. The biases in the locations that are lost determine that devices from different manufacturers may provide very different results on the daily proportion of time bearded vultures are on the wing. The researchers remark the importance of using devices that can be reprogrammed from a distance once deployed. In this way data acquisition can be readjusted to the amount of solar energy the device is able to harvest in the real environment. informacion[at]ebd.csic.es: Silva at al (2017) Seasonal and circadian biases in bird tracking with solar GPS-tags. PLoS ONE https://doi.org/10.1371/journal.pone.0185344


http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0185344