Morphological and Biochemical Changes in Carotenoid Granules in the Ventral Skin during Growth of the Japanese Newt Cynops pyrrhogaster

Abstract The color of the ventral skin of the Japanese adult newt Cynops pyrrhogaster is red, whereas that of the small juvenile newts at metamorphosis is creamy. Xanthophores in the red skin have many ring carotenoid vesicles (rcv) and a few homogenous carotenoid granules (hcg), as reported earlier. To understand the reason for this change in coloration of the ventral skin of the newt, we carried out histological and biochemical studies to see whether the size and the number of carotenoid granules (hcg and rcv) in the xanthophores and also carotenoid content in the ventral skin change during the growth of this animal. By electron microscopic observation, only hcg were observed in the creamy skin of larvae at stage 59. The diameter of the hcg in the skin of the larvae was approximately 0.85 μm, but significantly decreased to 0.35 μm in the skin of the small juvenile newt. However, the number of the hcg/100 μm2 of a xanthophore in the ventral skin was very low in the larva at stage 59, but increased in the...