Abstract: In order to know whether there are impacts of the digestive system during over-wintering stage in Larimichthys crocea, some anatomical, histological, microscopic and submicroscopic technologies were used to study the changes of morphological structure of digestive tract and liver for the cultured large yellow croaker in Xiangshan Bay. The results show that liver weight is significantly decreased (P<0.05) and liver index (HSI) is also extremely decreased (P<0.01) after over-wintering. By microscopic observation, the thickness of wall becomes higher (P<0.05) and submucosa becomes thinner extremely (P<0.01) in esophagus after over-wintering. The thickness of submucosa of stomach is increased extremely (P<0.01) and muscle is reduced significantly (P<0.05) after over-wintering. Furthermore, gastric gland cells is shrinked and the cells' gaps become bigger after over-wintering. Before over-wintering, the gaps of villus in foregut are short, but it become larger after over-wintering. The height of epithelial cell of foregut is reduced extremely (P<0.01) and the long diameters of goblet become smaller extremely (P<0.01) after over-wintering. The height of wall and the diameters of lumen in the midgut are reduced significantly (P<0.05) after over-wintering. The width of wall in the midgut is reduced extremely (P<0.01) but the thickness of serous is increased significantly (P<0.01) after over-wintering. The long and short diameters of goblet cells in the hindgut become extremely smaller (P<0.01). While the thickness of serous in the hindgut is increased significantly (P<0.05). Before over-wintering, the gaps of the liver lobule boundary are not obvious and there are lots of fat droplets in the liver cells. However, after over-wintering, the liver lobule boundary becomes obvious and the fat droplets are decreased. Transmission electron microscope show that the fat droplets are small but abundant in the liver cells and the rough endoplasmic reticulum are developed around the nuclear before over-wintering. While after over-wintering, the fat droplets become bigger and the number of droplets are reduced in the liver cells. Moreover, the rough endoplasmic reticulum is reduced too. This research shows that histological structures of digestive tract and liver of large yellow croaker juveniles have been changed after over-wintering. The lipid of liver has been consumed and the synthesis of protein of liver cells has been weakened. It is proposed that the staff should strengthen the management of feeding lager yellow croaker for restoring the structure and functions of digestive tract and liver.

Key words: Larimichthys crocea, over-wintering, digestive tract, liver