Studies on some physiological aspects of digestion in three species of elasmobranchs

Summary

The rate of digestion has been studied in three elasmobranchs and two teleosts by critical examination of food contents during fixed intervals after feeding. Among the three elasmobranchs, the rate of digestion is faster inChiloscyllium griseum than in eitherDasyatis uarnak orRhinobatus halavi. Comparing this with the teleostean species,Scatophagus argus andTherapon jarbua, it is observed that digestion is faster in elasmobranchs than in the teleosts, under similar conditions of feeding.

pH measurements were taken in the alimentary canals of the three species of elasmobranchs after starved conditions and after certain fixed intervals of feeding. The reactions in the stomachs of fasting fishes, 24, 48 and 72 hours after feeding, were acid. The acid secretion had the highest concentration after the food remained in the stomach for 24 hours. The concentration falls,i.e., pH value rises in the corpus, after 48 and 72 hours.

The reactions in the anterior region of the intestine were acid after the food remained in the stomach for 24 and 48 hours. This seems to suggest that the acid secreted from the stomach entered the intestine. The entire intestine in all the three species was alkaline within 72 hours after feeding.