Histological and Biochemical Features of the Digestive System in the Cage-Reared Gilthead Sea Bream (Sparus aurata)

Abstract

Five adult cage-reared gilthead sea bream Sparus aurata specimens were sampled to study the histological and biochemical features of its digestive system. Staining using Hematoxylin-eosin, Alcian blue and Orcein were used to elucidate the histological and biochemical features of the digestive organs in cage-reared gilthead sea bream. The digestive system is a hollow tube made of esophagus, stomach and intestines. The esophagus consists of four layers: mucosa, sub-mucosa, muscular layer and the outer layer. The esophageal epithelium contains abundant goblet cells with alkaline or neutral mucopolysaccharides (MPS) inside them. The wall of the fundic and pyloric region of the stomach is also four-layered and goblet cells of the stomach mucosa contain acid MPS. Four pyloric caeca were found between stomach and the intestines. According to its morphology the intestines of gilthead sea bream could be distinguished in three parts: anterior, middle and posterior intestines. In spite the difference in their diameter all three parts of the intestines has shown certain similarity regarding histological features. Goblet cells containing acid MPS were found in all three parts of the intestines although they are more numerous in the upper intestines. The liver in gilthead sea bream consists of two lobes. The structure of the hepatocytes is damaged due to large amounts of fat inside the cells. Pancreatic tissue is scattered down the length of the intestines as well as throughout the liver parenchyma. It contains zymogene cells arranged in serous acing. It can be concluded that the histological and biochemical of the digestive system in cage-reared gilthead sea bream is mostly like in other carnivorous fishes and congruent to its feeding habits.