The lateral line system of Chiloscyllium punctatumat the late embryonic stage

The distribution pattern and the surface structure of the lateral line system at the late embryonic stage in Chiloscyllium punctatum are examined by using Alcian blue stain,parafin section and SEM.The result reveals that morphological pattern of the lateral line system of Chiloscyllium punctatum is the same as most of the elasmobranch(Hemiscyllidae).The system consists of the mechanoreceptive canal neuromasts and pit organs,and the electroreceptive,Ampullae of Lorenzini organs.The lateral line canals are arranged in a basic seven-canal pattern.The canal neuromasts consist of mantle cells,support cells and sensory hair cells.They are surrounded by light cartilage canal wall and buried under the skin.The Pit organs are similar in compositions as,but smaller in size than,the canal neuromasts.They are standing in line on dorsal of the trunk and between the two sides of the trunk lateral line canals,each organ opens to the skin surface between two scales and through a short tube(about 40~60 μm long) with wall of irregularly arranged epidermal cells.The Ampullae of Lorenzini consists of the pore on the surface of the skin,tubules and ampulla(with sensory cells) in the derm.Most of Lorenzini tubules range from 1-50 mm with wall of regularly arranged epidermal cells;each Lorenzini ampulla is about 50 um in diameter and consists of 7 sacs.The patterns of the lateral line distribution and the structure of the receptors in Chiloscyllium punctatum are congruent with its phylogenetic relationships with others in the Chondrostei.It is also adapted to their habitat preferences.