Abstract
Sisor rabdophorus has a very restricted distribution, being confined to a few tributaries of the main rivers af North India and Pakistan.
The fish feeds on such soft bodied animals as dipteran larvae, mainly Chironomus, a few oligochaetes and occasional algal filaments.
The alimentary canal of Sisor is small. The buccal cavity has no teeth in the adult although small premaxillary teeth are present in the young fish.
The pancreas are diffused. The gall bladder is embedded within the pancreatic tissue.
The pH in the different parts of the alimentary canal and the glands is nearer neutrality while in the stomach, it is weakly acid. The acidity of the stomach increases immediately after feeding while it decreases on starvation.
Studies on the qualitative estimation of enzymes show that most of the carbohydrases are present in the liver and pancreatic extracts. The proteases and lipase are specially very active. A few enzymes are also present in the extracts of stomach and intestine.
These investigations show that the enzymes secreted are well suited to digest the kind of food, the fish takes.
