A coloração corporal em Apistogramma agassizii (Cichliformes: Cichlidae) é influenciada pelos tipos de água da Amazônia?

Abstract

Natural selection improves sensory systems and render organisms better at obtaining and interpreting signals given the characteristics of the environment. Information obtained through visual cues are often used to detect predators and during social interactions. Body color is often used to convey information for visual communication, but the quality of signaling depends on the lighting within the environment. As a result, the prevailing color in the environment can affect the evolution of body color, as encapsulated by the Sensory Drive hypothesis, which has been demonstrated for several groups of organisms in different types of habitats. Amazonian upland forest streams harbor a great diversity of freshwater fish and their waters are classified into two main types according to the bias in wavelength transmission: black water, which are biased toward red and yellow, and clear water, which have no clear bias in wavelength transmission. We investigated differences in body color of two populations of the dwarf cichlid (Apistogramma agassizii) that occur in basins of different water types. The Sensory Drive hypothesis expects that individuals from black waters present a greater intensity of red color than individuals from clear waters, given the predominance of bias toward red wavelengths in black waters. We compared individuals from two populations and used morphometric measurements to control for the potential effects of morphological and color differences in four regions of the body: caudal fin, anal fin, below the dorsal and close to the operculum. The two populations differed in body color intensity in accordance with predictions of the by Sensory Drive. This result contrasts with the lack of difference in body shape, and gives further support for the hypothesis of evolution of body coloration in relation to the lighting environment, as described by the Sensory Drive hypothesis.