A Histochemical Study of the Digestive tract of Caspian Salmon (Salmo trutta caspius) from Hatching to Parr Stage

This research was conducted to determine the histological features as well as distribution of protein s.
carbohydrates and fatty rich tissue of alimentary canal in Caspian salmon (Salmo trutta caspius) from
hatching to parr stage. Samplings were carried out from one-day stage Gust after hatching), 10 and 2S
days, and then in 1, 2,3,4,5, and 6 month post hatching. Light microscopical observation was carried
out after preparing tissue based on conventional method tissue processing and special staining method .
(PAS & Bromo Phenol Blue). Light microscopic result s indicated that , in one -day post - hatch larvae.
yolk sac makes the greatest part of the body. The alimentary canal is a simple, undifferentiated tube
with mouth opening to some extent. Yolk sac contains mainly proteins, neutral polysaccharides, and to
a lesser extent fats. Secretion activity begins in the mouth , pharynx and esophagus epithelium with
appearance of neutral mucopolysaccharide components, covering the digestive tract's epithelium which
indicate it's protective activity. When exogenous Feeding started in 25 days post hatch larvea, secretion
of protein components began in mucose layer which was stronger in the esophagus mucosal folds. This
indicated high enzymatic activity in this region which decreased after start of exogenous feeding and
being compensated for by stomach and intestine enzyme activity.