Brightness of melanin-based plumage coloration is a cue to oxidative stress in Himalayan Black Bulbuls (Hypsipetes leucocephalus nigerrimus)

Abstract

Background: Melanin-based coloration is often found to be associated with variations in physiological and behavioral traits that are essential in avian communication. However, the function of melanin-based traits to their bearers has been investigated less than that of carotenoid-based ones. It is commonly believed that expression of melanin-based pigmentation is genetically controlled. However, whether it could be modulated by physical condition has remained controversial. In this study, we demonstrate that the level of melanin-based plumage pigmentation could be negatively correlated with an individual's oxidative stress level. Methods:In this study, we used two groups of Black Bulbuls (Hypsipetes leucocephalus nigerrimus) obtained from a pet-shop in 2010 and 2011 to examine the correlation between the melanin-based plumage coloration and the ratio of lymphocytes to heterocytes, which is an indicator of the oxidative stress experienced by an individual. Results:We found a negative correlation between oxidative stress levels and expression of melanin-based pigmentation on the breast and scapular feathers, but the correlation only appeared in the 2011 group, individuals of which had higher oxidative stress level and brighter plumage (i.e. more melanins) than those of the 2010 group. Conclusions:Our data suggest that melanin-based plumage could reflect an individual's physical condition in certain situations. Therefore, melanin-based plumage coloration could have a function in Himalayan Black Bulbuls' communication.

Conditional Handicaps in Exuberant Lizards: Bright Color in Aggressive Males Is Correlated with High Levels of Free Radicals

“…Heritable color morphs often have distinct behaviors and physiology, with associated differences in selection pressures on an otherwise common genetic background (Sinervo and Lively, 1996;Pryke and Griffith, 2006;Healey et al, 2007;Pryke et al, 2007;Olsson et al, 2009aOlsson et al, , 2007areviewed in Huxley, 1955;Wellenreuther et al, 2014). Colorful traits often fade during the breeding season, which suggests these traits may have condition-dependent expression and costly to maintain (Cotton et al, 2004;Grunst et al, 2014;Reinhart et al, 2015), which are potentially mediated by oxidative stress (von Schantz et al, 1999;Monaghan et al, 2009;Hõrak et al, 2010;Garratt and Brooks, 2012;Costantini, 2014;Hung and Li, 2015) and body condition (Slagsvold and Lifjeld, 1992;Costantini, 2008;Stephen Dobson et al, 2008). Reactive oxygen species (ROS) damage DNA, proteins and cell membranes, triggering cell death and color-fading (Dowling and Simmons, 2009;Costantini, 2010;Olsson et al, 2012).…”

Himalayan black bulbuls (Hypsipetes leucocephalus niggerimus) exhibit sexual dichromatism under ultraviolet light that is invisible to the human eye

“…Studies have shown that females may choose mates based on multiple sexual ornaments4849; multiple ornaments provide females with diverse information at different stages of mate choice50, or function as redundant signals to improve the accuracy of mate assessment5152. Our data shows that both carotenoid- and melanin-based characteristics are sexually dichromatic in Himalayan black bulbuls, and both could convey information about an individuals’ physical conditions53, [unpublished]. We here propose that in our species, individuals may use multiple cues in sexual selection.…”

“…The detailed program set-up of the polymerase chain reactions (PCRs) for molecular sex typing59 was the same as in Hung and Li53. In total, 55 male and 57 female live bulbuls were identified.…”

“…The procedure for measurement was as described in Hung and Li53. Because of the obvious fading of carotenoid-based colouration, we did not score the colouration of beaks and tarsi in the museum specimens.…”

Biological responses to environmental contamination. How can metal pollution impact signal honesty in avian species?

“…Melanin bounds many compounds and retains them for long periods of time. Therefore, melanin‐based pigmentation could be used to assess long‐term physical condition of the individual (Hung & Li, 2015). Melanin coloration results from the co‐occurrence of both eumelanin and pheomelanin pigments at different concentrations (McGraw & Parker, 2006; Zduniak et al., 2014).…”