Histological and morphological observations of the gill and swim bladder development of Lateolabrax maculatus

In order to elucidate the development of gill and swim bladder of Lateolabrax maculatus, in this study, histological section technique and morphological observation were used to systematically study the occurrence and development of gill and swim bladder of L. maculatus from 1 to 45 days. The results showed that the post-embryonic development of the gill of L. maculatus juvenile can be divided into four stages, including the appearance period of gills primordium (0-3 d), the differentiation period of filaments (4-14 d), the differentiation stage of lamella (15-25 d) and the completed period of gills (26-45 d). At the water temperature of 15-18 °C, the primordial filament was observed at 1 d, and the lamella structures formed from the pseudobranch were firstly observed at 15 d. After 25 d, the lamella structures were widely distributed in each juvenile gill arch. After 45 d, a well-developed gill structure of juvenile fish was clearly detected and identical with adult fish. According to the observation results, the development stages of the swim bladder organ of L. maculatus were divided into four stages: formation, expansion, aeration and degeneration. The appearance of swim bladder primordium was not observed on the newly hatched larvae, but after being hatched for 1 day. After 5 d, the swim bladder cavity of larvae became larger and longer. The inflation of the larvae swim bladder was completed at 11 d. Finally, the degeneration of swim bladder of larvae began to occur after 13 d.