Digestion and Digestive Enzymes in the Herring (Clupea harengus L.)

Abstract

Crustacean food is partially broken down and digested in the caecum of the stomach of the herring. It becomes more finely divided in the pyloric sac and consists of an oily chyme, intermingled with chitin, mucus and bacterial clumps in the pyloric caeca and intestine. The acidic condition of the gastric contents is probably instrumental in the reddening of chitinous food in the tract. Pepsin from the stomach and trypsin from the pyloric caeca increase in digestive power over a temperature range from 2.4 to 37.5 °C. The stomach secretes a protease (pepsin), a weak amylase, and possibly a weak lipase. The pyloric caeca secrete a strong protease (trypsin), a strong amylase, and a lipase rendered active by bile. The intestinal mucosa exhibits lipolytic and amylolytic ferments, while the bile has some amylolytic properties.