EARLY COVER OF SQUAMATION AND THE DEVELOPMENT OF PRIMARY SCALES FOR PAMPUS ARGENTEUS

In order to study the early scale covering and primary scale development of captive Pampus argenteus, alizarin red staining and hematoxylin-eosin staining were used to observe and measure the scales of captive Pampus argenteus. The results showed that Pampus argenteus has three initial centers of scales, namely the middle region of caudal stalk, the posterior margin of gill cover and the base of pectoral fin. At water temperature of (20±1.8)℃, the scales of Pampus argenteus began to appear at (30±0.95) mm in length. The scales at the posterior edge of the gill cover and the base of the pectoral fin extend along the lateral line until they come into contact with the scales extending laterally from the center of the caudal peduncle. The scales were completely covered at the length of (45.58±0.73) mm, which spread to the head faster than to the tail, and to the back faster than to the abdomen. The whole life stage of Pampus argenteus is round scale, without the transition between round scale and comb scale. Histological results showed that the scale was formed by the aggregation of fibroblasts between the epidermis and dermis of fish, and the process included four stages: early morphogenesis, late morphogenesis, early differentiation and late differentiation. The scales of Pampus argenteus occur after metamorphosis (transition from spindle shape to adult lateral flat shape) and the fins are fully formed, which is in common with other ebony fish. These results enrich biological data of the early development of Pampus argenteus and contribute to the understanding of its systematics and functional morphology.