DIGESTIVE ENZYMES OF THE ECHIUROID OCHETOSTOMA ERYTHROGRAMMON

¹ Dept. of Zoology, University of Singapore, Singapore

1. The digestive enzymes of Ochetostoma erythrogrammon were investigated. They include a strong amylase, a strong protease, a moderately strong esterase and a weak maltase. No cellulase, sucrase, lactase or inulase were found.

2. The midgut fluid accumulated during starvation in the lumen of the entire midgut. It proved a richer source of digestive enzymes than extracts of the various regions of the gut. Amylase occurred along the entire gut wall except the pharynx. Protease occurred in the foregut, midgut and hindgut, esterase in the midgut and hindgut, and maltase only in the hindgut.

3. Both amylase and protease are active over a wide range of pH values, but the esterase has a more restricted range. The pH optima of these lie on the alkaline side of neutrality, with the protease having the highest pH optimum of 8.4 for the substrate gelatine.

4. The gut contents had an alkaline reaction, the pH rising from the crop to a maximum in the midgut and then dropping slightly in the hindgut. The pH of the midgut fluid in starved specimens varied between 7.0 and 8.2.

5. Digestion in O. erythrogrammon is presumably extracellular, occurring chiefly in the midgut. The ability of Ochetostoma to utilize plant detritus must be considerably reduced by its lack of carbohydrases other than amylase and a weak maltase.

6. The enzymes of O. erythrogrammon are discussed and compared with those of polychaetes.