Comparative light and electron microscopic studies of dorsal skin melanophores of Indian toad, Bufo melanostictus

Indian toad, Bufo melanostictus is an amphibian, which is able to change the body color to adapt to its ambient need. This ability is due to specialized skin pigment cells known as melanophores which are excellent animal-cell models to study most of the physiological phenomenon related to color changes. In the present investigation morpho-anatomic details of dorsal skin melanophores of B. melanostictus were studied by means of light and electron microscope to establish their phylogenetic relevance with other vertebrates. Light microscopic observations revealed that toad skin contains dominantly present black pigment cells, the melanophores in its sub epidermis while dermal melanophores are rare. The ultrastructure of the melanophore is characterized by oval nucleus and numerous pigment granules, the melanosomes which remain scattered in the cytoplasm. Other sub-cellular organelles like mitochondria, well-developed tubular endoplasmic reticulum and Golgi vesicles were also found to be present in the remaining cytoplasmic area. Toad melanophore contains four distinct stages of melanosomes which are similar in development pattern to the mammalian melanocytes. These findings indicate that toad melanophores contain phylogenetically significant information of anatomical similarity with lower as well as higher vertebrates which can help to better understand the inter relationships between vertebrate pigment cells and their role in skin dysfunctions.