Abstract
ABSTRACT Several organisms match their skin color to the prevalent background color, granting crypsis against predators. The rate at which body color changes occur varies among organisms as a result of physiological constraints and adaptation to variation in contrasts between objects and the environmental background. Faster darkening of body color is favored in environments that show higher amounts of contrast between common objects and the prevailing background. Soil types in Amazon forest streams (igarapés) create distinct environments with respect to the amount of contrast, a result of the amount of sand and clay, which offers different contrasts against dead leaves. Here, we investigated differences in the rates of color change among populations of the sailfin tetra (Crenuchus spilurus) that represent lineages that live in regions of different soil types. Populations inserted into blackwaters (sandy soil) showed higher rates of color darkening in response to exposure to a dark environment composed by dead leaves. We propose that natural selection stemming from predation can favor faster color change rate in environments where there is higher variability of contrasts between leaf litter and soil, which is common in most blackwater streams.
Highlights
Reversible darkening or lightening of the skin color are common to many organisms (Sugimoto, 2002; Leclercq et al, 2010)
Individuals from the two populations of the Negro lineage showed faster rate of color change when compared to individuals from populations of the Amazonas lineage
Populations of the lineage that occurs in igarapés of sandy bottom (Negro lineage) showed faster rates of body color darkening when compared to populations that live in environments with a predominance of scielo.br/ni | sbi.bio.br/ni clayey soil
Summary
Reversible darkening or lightening of the skin color are common to many organisms (Sugimoto, 2002; Leclercq et al, 2010). Many fish species adjust their body color as a response to the prevalent background (Fingerman, 1965; Healey, 1999; Hemmi et al, 2006; Zuanon et al, 2006; Stevens, Merilaita, 2009; Stevens et al, 2013, 2014) Such background matching occurs through the expansion or retraction of melanophores, which are responsible for increasing or decreasing the exposure of melanin on the surface of the skin (Fugii, 2000; Logan et al, 2006; Stuart-Fox, Moussalli, 2009). Investment in crypsis can be costly and considered a trade-off against energy resources that could be allocated to other aspects of the life cycle
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