Figure 6 figure supplement 2.

(A) Carotenoid pigments are normally localized to lipid droplets, the presence of which can be revealed by Oil-red-O staining. Here, a proportion of aox5:palmEGFP+ xanthophores stained ex vivo from euthyroid fish (n = 112 cells) contained lipid (red), whereas xanthophores from hypothyroid fish (n = 48 cells) were never observed to have such lipid contents. (Incidence data in supplementary file Figure 6—figure supplement 1—source data 1.) (B) Ultrastructurally, carotenoids and lipids are detectable as electron-dense carotenoid vesicles (red circles) (Djurdjevič et al., 2015; Granneman et al., 2017; Obika, 1993), which were observed in xanthophores from euthyroid but not hypothyroid fish. N, nucleus. P, pterinosome—the pteridine-containing organelle of xanthophores (Bagnara et al., 1968; Hirata et al., 2003; Matsumoto, 1965; Obika, 1993).