The Histochemistry of Esterases in Eggs of Diabrotica undecimpunctata howardi1,2

Abstract

The esterases that hydrolyse naphthol esters were located histochemically in eggs and newly hatched larvae of the southern corn rootworm, Diabrotica undecimpunctata howardi Barber. Extra-embryonic structures that bore detectable esterase levels were the proteinaceous yolk globules, periplasm, cleavage nuclei, fat droplets, and scrosa. Embryonic tissues were generally devoid of esterase activity until that time when structures differentiated which have postembryonic functional roles; then cholinesterase was present in the neuropile and esterases of unspecified function were present in the midgut, body hairs, malpighian tubules, and epidermal cells. Paraoxon inhibited the esterases of the neuropile, some regions of the midgut epithelium, malpighian tubules, serosa, periplasm, cleavage nuclei, and body hairs. Eserine inhibited enzyme activity in the neuropile. A lipase known to be present in these eggs, and which can hydrolyse naphthol esters, could not be definitively located; some evidence related to the possible location of this enzyme was obtained.