Morphogenesis of the frontal organ in Bufo bufo during development

Morphogenesis of the frontal organ in Bufo bufo was examined under transmission electron microscope. Many remarkable similarities to the frontal organ of other Amphibia Anura are observed. It originates from a diverticulum in the dorsal region of the neural tube. It is egg-shaped, has an eccentric lumen, and is made up of three kinds of cells: 1) photoreceptors, which protrude into the lumen; 2) supportive cells; and 3) ganglion cells, which make synaptic contact with the photoreceptors. Peculiar to Bufo bufo is the melanin-like pigments around the light-sensitive part of the photoreceptors. These pigments may prevent light dispersion. The frontal organ in Bufo bufo starts degenerating during the early premetamorphic stages.