| Based on the redundant and multiple signal hypotheses of animal ornamental coloration signals,one or more forms of ornamental coloration signals may provide the same or a variety of quality information.The ornamental coloration signal of bird is a conditionally dependent signal related to individual quality,whose expression is not only related to the age and gender,but also to health status,therefore,individual quality can be indicated by ornamental coloration signal.Because of the toxic effects of environmental heavy metals,they would cause a series of effects on immunity,antioxidant capacity and other aspects of birds,and these effects can be reflected by the ornamental coloration signal.At present,there are few studies on the bioindication of oxidative stress level and physical condition by ornamental coloration signal in resident birds under long-term environmental heavy metal exposure.Therefore,the present study selected the tree sparrow(Passer montanus),a widespread passerine bird of China,as the research object,and chose Silong town of Baiyin(BY)polluted mainly by heavy metals copper(Cu),zinc(Zn),lead(Pb)and cadmium(Cd)and Liujiaxia(LJX)town of Yongjing,a relatively unpolluted area,as study sampling sites.The present study detected ornamental coloration signal,oxidative stress level and physical condition of tree sparrow adults and nestlings from BY and LJX.The aim of this study is to explore the bioindication effect of ornamental coloration signal on the oxidative stress level and physical condition in tree sparrows from environmental heavy metal contaminated area.The main results are shown as follows:1.Response of tree sparrow ornamental coloration signal to environmental heavy metal pollution.In this study,the color index of head,back,flight and tail feathers of tree sparrow adults and nestlings,and the areas of black feather spot on throat and cheek of tree sparrow adults were detected.The L*(Lightness)value of tail feather of tree sparrow adults from BY was significantly lower than that from LJX.The C*(Chroma)value of flight and tail feathers of tree sparrow adults from BY was significantly lower than that from LJX.The C* value of back,tail and flight feathers of tree sparrow nestlings from BY was lower than that from LJX,and there was a significant difference in C* value of back feather between the two areas.However,there was no significant difference in the h°(Hue)value of the four kind feathers between the two areas either in adults or in nestlings.The areas of black feather spot on throat and cheek of tree sparrow adults from BY were smaller than those from LJX,although it was not significant.These results indicated that the color of flight and tail feathers of tree sparrow adults would be darker in the heavy metal polluted area,and tree sparrow nestlings could have lower color chroma in their back feather.2.Oxidative stress level of tree sparrow from BY and LJX.This study detected the oxidative stress level of the major detoxification organs in tree sparrow adults and nestlings from BY and LJX and the results showed: the superoxide dismutase(SOD)activity and glutathione(GSH)content in kidney of tree sparrow adults from BY were significantly higher than those from LJX,and the malondialdehyde(MDA)contents in liver and kidney were higher than those from LJX,but did not reach a significant level;in BY,the SOD activity in liver of tree sparrow nestlings was extremely higher than that from LJX,and GSH content in kidney was significantly lower than that from LJX,the MDA contents in liver and kidney of tree sparrow nestlings from BY were significantly higher than those from LJX,while the total antioxidant capacity(T-AOC)in liver and kidney of tree sparrow nestlings from BY were extremely higher than those from LJX;the activity of SOD in liver and kidney of tree sparrow nestlings were extremely or significantly higher than those of adults in both areas,and GSH contents in liver and kidney of nestlings were extremely higher than those of adults from both areas,the MDA contents in liver and kidney of nestlings were extremely or significantly lower than those of adults from both areas;in BY,there was an extremely negative correlation between T-AOC in kidney and Cu,Zn concentrations in flight feather of tree sparrow adults,and a significantly negative correlation between T-AOC in kidney and Cd concentration in flight feather of tree sparrow adults,with the increase of Cd concentration in tail feather,the MDA contents in liver increased significantly,the MDA contents in kidney increased extremely.These results indicated that oxidative stress level of tree sparrow adults and nestlings in heavy metal polluted area were higher,and the tree sparrow adults were subjected to more oxidative stress than nestlings.And in heavy metal polluted area,with the increase of heavy metals concentration in feathers,the level of oxidative stress in tree sparrow increased.3.Physical condition of tree sparrow from BY and LJX.This study detected the physical condition of tree sparrow adults and nestlings from BY and LJX and the results showed: there was no significant difference in body condition of tree sparrow adults between BY and LJX,but the body condition of nestlings from BY was significantly lower than that from LJX;the fluctuating asymmetry level of tree sparrow adults and nestlings from BY were significantly higher than those from LJX.The results indicated that heavy metal pollution would lead to decrease in body condition of tree sparrow nestlings,and increase in fluctuating asymmetry level of adults and nestlings.4.Relationship between ornamental coloration signal and oxidative stress level of tree sparrow.In tree sparrow adults from BY,there was no correlation between the L* value of head,back,flight and tail feathers and the oxidative stress index,however,there was a significantly negative correlation between the C* value of head feather and SOD activity in kidney,a significantly negative correlation between the C* value of head feather and T-AOC in liver,a significantly negative correlation between the C* value of back feather and SOD activity in liver,an extremely positive correlation between C* value of flight feather and MDA contents in liver and kidney;there was a significant positive correlation between h° value of head feather and SOD activity in kidney,and an extremely positive correlation between h° value of head feather and TAOC in liver.In tree sparrow adults from LJX,there was a significantly positive correlation between L* value of tail feather and SOD activity in kidney,an extremely negative correlation between L* value of tail feather and MDA contents in liver and kidney;there was an extremely positive correlation between C* value of tail feather and SOD activity in liver and kidney,an extremely negative correlation between C* value of tail feather and MDA contents in liver and kidney,and a significantly positive correlation between C* value of tail feather and T-AOC in kidney;however,there was no correlation between the h° value of tail feather and oxidative stress index.Between tree sparrow adults from BY and LJX,there was a significantly or extremely negative correlation between the area of black feather spot on throat and GSH content in kidney,a negative correlation between the area of black feather spot on throat and SOD activity in liver and kidney,and the correlation was significant in LJX;there was a positive correlation between the area of black feather spot on throat and MDA contents in liver and kidney,and the correlation was extremely significant in LJX.The results showed that in the heavy metal polluted area,tree sparrow adults with higher C* value of feather and larger area of black feather spot on throat have the higher oxidative stress level;meanwhile,in the unpolluted area,tree sparrow adults with the brighter tail feather,the higher color chroma and smaller area of black feather spot on throat have the lower level of oxidative stress.5.The relationship between ornamental coloration signal and physical condition of tree sparrow.In tree sparrow adults from BY,there was an extremely negative correlation between PC1(Principal component 1)of C* value of feathers and body condition;in tree sparrow adults from LJX,there was a significantly negative correlation between L* value of head feather and body condition,a significantly positive correlation and extremely positive correlation between h° value of back and flight feathers and body condition;however,there was no correlation between the ornamental coloration signal and fluctuating asymmetry level in both areas.These results indicated that in the heavy metal polluted area,tree sparrow adults with the higher color chroma of feathers may have the worse body condition;meanwhile,at the unpolluted area,tree sparrow adults with the lower brightness of head feather and the higher hue of back and flight feathers may have the better body condition.It has not been found that the ornamental coloration signal is directly related to the level of fluctuating asymmetry in tree sparrow.In conclusion,this study found that the environmental heavy metal pollution would lead to: the increase of SOD activity and GSH content in tree sparrow adults,and the enhance of lipid peroxidation level and antioxidant capacity in tree sparrow nestlings;the increases of fluctuating asymmetry level in tree sparrow adults and nestlings,and the decrease of body condition of nestlings;the darker trend of ornamental coloration,and the values of L*,C* and h° of feathers and the area of black feather spot on throat in tree sparrows were correlated with oxidative stress level and body condition to some extent.All these results indicated that the ornamental coloration signal of tree sparrows could reflect their oxidative stress level and individual quality. |
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