Histochemistry of the development of the digestive system of Siberian sturgeon during early ontogeny

At hatching, the yolk-sac matrix of Siberian sturgeon Acipenser baeri conta ined neutral glycoconjugates, glycogen, proteins rich in arginine, lysine, tyrosine, cysteine and cystine, glycoproteins containing mannose (Man) and/ or glucose (Glc), N-acetyl-D-galactosamine (GalNAc), L-fucose (Fuc), sialic acid and/or N-acetyl-D-glucosamine (GlcNAc) residues, as well as neutral a nd acidic lipids. Buccopharyngeal and anterior oesophageal goblet cells pro duced a combination of neutral and acid sialoglycoproteins, while those fro m the posterior oesophagus secreted only neutral glycoproteins; both types of secretions contained tryptophan and -S-S- groups and were unreactive to lectin techniques. Most intestinal goblet cells secreted mainly carboxylate d and sulphated sialoglycoproteins with some rests of neutral glycoconjugat es, while few of them produced only acid or neutral glycoproteins. Intestin al glycoproteins were rich in GalNAc, GlcNAc and sialic acid residues. Clos e relationships between digestive enzymes and morphological development of digestive organs were observed. Histochemistry of enzymes revealed that jus t after hatching, alkaline and acid phosphatase, ATP-ase and non-specific e sterase activities were detected in the yolk sac. From the onset of exogeno us feeding to the juvenile stage (30 days post-hatch), an enhancement of en zymatic activities was observed, as alkaline and acid phosphatase, ATP-ase, aminopeptidase M and nonspecific esterase sharply increased. However, lipa se activity decreased in the liver and brush border of enterocytes by 13-14 days post-hatch. Two types of lipase were detected in the alimentary canal , a non-pancreatic lipase that was secreted in the cardiac stomach by gastr ic glands, and a pancreatic lipase, which activity was mainly detected in t he brush border of the intestinal epithelium. (C) 1999 The Fisheries Societ y of the British Isles.