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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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Identified the main introduction routes of the red swamp crayfish Procambarus clarkii during its global-scale invasion

Identified the main introduction routes of the red swamp crayfish Procambarus clarkii during its global-scale invasion

This North American species is the most widely spread freshwater crayfish worldwide, and is one of the worst invasive species due to its severe impacts on the structure and functioning of freshwater ecosystems. The results of the study may help to prevent the further expansion of the red swamp crayfish and to avoid potential future invasions. The invasion routes followed by the red swamp crayfish during its human-driven expansion were reconstructed based on the analysis of a mitochondrial gene (COI), which was sequenced for 1,412 crayfish from 122 populations across the Northern Hemisphere. The article describes how different invasion scenarios have produced different genetic patterns among invasive populations. For example, in the US there are two main invasion routes, west- and east-wards from the native area. The invasive populations in the west are genetically more diverse, because they have received more introductions, which probably involved more individual crayfish, starting in the 1920s. The genetic results show that western US (California), itself an invaded area, was the source of the crayfish populations established in Hawaii and a probable source of the crayfish introduced to Japan, and from there to China, in the late 1920s. The low genetic diversity of all red swamp crayfish populations studied in Asia supports documentary evidence that a small group of some 20 individuals may have been the origin of the Japanese and Chinese red swamp crayfish populations which now number into the millions. The red swamp crayfish was introduced twice from Louisiana to south-western Spain, in 1973 (near the city of Badajoz) and 1974 (in the Guadalquivir River marshes). These introductions were promoted by the aristocrat Andrés Salvador de Habsburgo-Lorena. Until now, it has been assumed that these introductions were the sole origin of all red swamp crayfish populations established across Europe, but the new study finds evidence of a separate, later introduction. The large number of individuals involved in the two introduction events (around 500 in Badajoz and 6,000 in the Guadalquivir marshes) has led to the high genetic diversity levels observed in Iberian populations, although diversity values tend to be lower as populations are further away from the introduction foci. However, in this study a genetic profile in central-western Europe that is not present in the Iberian Peninsula was also unexpectedly detected, a finding that suggests that additional unrecorded introductions of the red swamp crayfish into Europe may have occurred, either from the US or from other invaded territories. información[at]ebd.csic.es: Oficialdegui et al (2019) Unravelling the global invasion routes of a worldwide invader, the red swamp crayfish (Procambarus clarkii). Freshwater Biol https://doi.org/10.1111/fwb.13312 


https://onlinelibrary.wiley.com/doi/full/10.1111/fwb.13312