Astaxanthin is the major carotenoid in tissues of white storks (Ciconia ciconia) feeding on introduced crayfish (Procambarus clarkii)

We studied the carotenoid pigments in plasma, skin and body fat of white st orks (Ciconia ciconia) from a colony in Spain feeding mainly on the recentl y introduced red swamp crayfish (Procambarus clarkii). In control colonies, where crayfish was absent, plasma was collected for comparison. Our object ive was to determine whether the astaxanthin contained in the crayfish reac hed the blood, accumulated in fat, and finally was deposited in the red-col ored bill and legs. If that was true, the visual cues provided by those teg umentary areas would be altered, with potential behavioral consequences. Pl asma carotenoids were directly extracted with acetone, whereas skin and fat samples needed harsher conditions, i.e. grinding, sonication and extractio n with diethyl ether. The extracts were analyzed by thin-layer chromatograp hy (TLC) and UV/Vis spectroscopy. In crayfish-eating storks, astaxanthin wa s confirmed to be the dominant pigment in all analyzed tissues. This red pi gment was absorbed unchanged in the gut, and was responsible for the red co lor of plasma and the abnormal orange pigmentation of the feather-covered s kin. It was also present in large quantities in the exposed bill and tarsi, which are typically red-colored in the stork. Control storks with no crayf ish in the diet only presented lutein in their plasma. (C) 2000 Elsevier Sc ience Inc. All rights reserved.