Ultrastructure of Erythrophores and Xanthophores of the Siamese Fighting Fish, Betta splendens

The ultrastructural morphology of brightly colored pigment cells (chromatophores) of Siamese fighting fish, Betta splendens, was investigated by transmission electron microscopy. The major pigment cells in the epidermis and dermis of the red and golden strains were erythrophores and xanthophores, respectively. Specific combinations of these chromatophores formed the basis of pigmentation patterns in both strains. The ultrastructure of the erythrophores was characterized by ellipsoidal electron-lucent vesicles that had limiting membranes and inner lamellae. The latter appeared whorl-like due to a concentric arrangement of parallel membranes. The xanthophores contained small and large cytoplasmic vesicles that appeared hollow and electron-lucent, with some vesicles displaying slightly electron dense particles. Sections of some large vesicles also revealed a very thin membrane enveloping these droplet-like vesicles.