THE DISTRIBUTION AND IDENTIFICATION OF ESTERASES IN THE DEVELOPING EMBRYO AND YOUNG NYMPH OF THE LARGE MILKWEED BUG, ONCOPELTUS FASCIATUS (DALL.)

Abstract

Aromatic esterase (A esterase, organophosphate-resistant esterase), aliesterase (B esterase, organophosphate-sensitive esterase), and acetylcholinesterase were localized in the developing embryo and in the young nymph of the large milkweed bug, Oncopeltus fasciatus (Dall.). The esterase complex varied qualitatively with embryonic development. Aromatic esterase occurred in the 3-day-old embryo, aromatic esterase and acetylcholine-esterase were found in the 4-day-old embryo, while all three esterases occurred in the 5-day-old embryo and in the young nymph. The distribution of each esterase remained fairly constant during embryonic development; aromatic esterase was located in many tissues and cells, aliesterase occurred in the pericardial cells, and acetylcholinesterase was found only in the neuropile of the nerve cord and brain. In the young nymph, the number of sites of aromatic esterase activity was reduced while additional sites of aliesterase occurred; acetylcholinesterase activity remained in the neuropile.