Enzymes in the Alimentary Canal of Mosquito Larvae

Abstract

An attempt has been made to determine the presence of enzymes in the digestive tract of certain species of mosquito larvae. Phillips 1 and Bertholf 2 demonstrated the presence of enzymes in the honey-bee, both larvae and adults, by feeding them on solutions of chemically pure carbohydrates and comparing the length of life in contrast to controls fed on water alone. By this method they hoped to eliminate the interference of any enzyme from the tissues surrounding the gut, a difficult matter in isolation techniques. However these workers did not exclude microorganisms from the alimentary canal and it is conceivable that organisms hydrolysed the carbohydrates which were able to maintain the insects alive for considerable periods.

The writer applied this method to culicid larvae and endeavored to exclude bacteria, etc., by sterilizing all media, either by auto-claving or filtering. Mosquito eggs disinfected in Hexyl Resorcinol (Hinman 3 ) were introduced into solutions of chemically pure compounds, dissolved in a modified Ringer's Solution and incubated at a suitable temperature. Soluble starch, sucrose, galactose, xylose, levulose, lactose, maltose, glycogen, creatinine, cystine, tyrosine, a mixture of tyrosine and glycogen, a mixture of sucrose and tyrosine, have all been used. Solutions varied in strength from 0.1% to 1.0%. The results of these experiments have been rather inconclusive owing to inconsistency when repetitions were made. Checks consisted of the sterilized Ringer's Solution as a medium. Larvae in a few cases were able to live for a significantly longer time in soluble starch, sucrose, xylose, glycogen, tyrosine, and cystine than in the checks.

Owing to these indefinite results, an attempt was made to isolate enzymes from the gut of the larvae of Aedes aegypti Linn and Culex qmnquefasciatus Say. The intestinal tracts were dissected out, placed in 50% glycerin and stored in lots of 200 each.