Abstract
The fine structure of the mechanosensory organ represented by neuromasts was examined with the electron microscope. Orientation and cluster morphology of superficial neuromasts in Dhufar toad (Bufo dhufarensis) were examined in the head, trunk and tail regions, the Dhufar toad possesses superficial neuromasts which are distributed and organized into six groups supraorbital (SO), perinostril (PN), oral (AO), venrtal trunk (TR) and limb bud (LB). The morphological variation of the different components of the lateral line system (e.g. morphology of the organs, organization of neuromasts in the lines, pattern of line distribution, number of hair cells) has been explored in larval stages 40,45 and 50. Mechanosensory hair cells are arranged in a sensory epithelium, with the axis of best sensitivity perpendicular to the long axis of the neuromast. In most neuromasts there was one kinocilium, surrounded by small cilia called stereocilia but in some neuromasts there were two kinocilia, the arrangement of neuromasts found either in group or stitches. neuromasts were varied in shapes from elliptical to polygonal shape. The number of hair cells in the groups was more increasing with increasing age.. the neuromast kinocilia play an important role in catch prey or preventing microorganisms and debris from attaching to the epidermis or prey detection or perception of particles adhering on the epidermis. Loss of hair cells of ciliated cells was clearly obvious in our result, whereas in the head cilia were lost first from the periphery of each cell and later from the centre; whereas in trunk, cilia loss occurred evenly all over the cell. In the tail region, cilia resorption began at the anterior side of the cell, before progressing to the posterior. We concluded that the patterns of the lateral line neuromasts was important morphological characters in Saudi Bufonoid taxonomy. Complexity of the pattern, makes the phylogenetic interpretation of this character in systematic analysis of Bufo dhufarensis easy.