Effects of Salinity on the Histological Structure of the Gills,Spleen,and Muscle in Lateolabrax maculatus Juveniles

To explore the histological features of Lateolabrax maculatus juveniles cultured at different salinities,the structures of the gills,spleen,and muscle were analyzed at different salinities(0,10,15,20,and 30)via histological analysis.The results showed that at salinity 0,the gill filaments of L.maculatus juveniles were closely arranged,the top of the gills expanded into a rod shape,and the gill cells were plump with more chlorine-secreting cells;the breadth of the gill filaments decreased,and the intervals of the gill lamella became larger as the salinity increased(P<0.05).At salinity 20,some gill lamellas decomposed and fell off,the number of chlorine-secreting cells on the gill filaments increased significantly.At salinity 30,the number and size of chloride cells increased as the salinity increased and some chloride cells expanded and dissolved.In freshwater,more blood cells and fewer lymphocytes were observed in the spleen,whereas in the hyposaline environment(salinity 10 and 15),the lymphocytes were enlarged and the number of melanin macrophages increased.At high salinity(30),the spleen cells and some lymphocytes showed swelling and vacuolation and were loosely arranged.At salinity 0,the muscle fibers of the juveniles were loosely arranged,polygonal or oblong,with larger major and minor diameters and smaller densities.With the increasing salinity,both the major and minor diameters of muscle fibers tended to decrease first and then increase again.At salinity 15,the short diameter of muscle fibers decreased and their densities increased,which were significantly different from that observed at salinity 0 and 10.At salinity 30,the long diameter of muscle fibers increased and their densities decreased.In summary,as the salinity increased,both the long and short diameters of muscle fibers tended to decrease first and then increase(P<0.05).The results indicated that the histological structures of the gill,spleen,and muscle of L.maculatus juveniles were affected by the environment and salinity.