Observations on the effect of the neuro-endocrine system of Blatta orientalis L. on the midgut protease activity of the adult female and the level of infestation with the nematode Hammerschmidtiella diesingi (Hammerschmidt, 1838)

Abstract

A possible neuroendocrine relationship between the thelastomatid parasite Hammerschmidtiella diesingi and its insect host, Blatta orientalis, has been investigated. The median neurosecretory cells (m.n.c.) of Blatta were removed by electrocautery and after 4 weeks there was a significant decrease in the total number of adult parasites. It may therefore be inferred that the nematode depends in some way upon a supply of neurosecretory material from its insect host for its existence. Two factors, which could be affected by m.n.c. cautery, were examined in the present study. First, it was shown that the midget protease activities of m.n.c. cauterized insects were not affected by the operation and second, the total food intake of the insects was unaltered by the removal of the m.n.c. Therefore, the reduced burden of adult nematodes in the cauterized insects was not an indirect effect, evoked by the removal of the m.n.c., on the midgut protease or on the feeding cycle of the insect. It was observed that removal of the m.n.c. effected a decrease in protein metabolism and this was reflected by a decrease in the fecundity of operated cockroaches. The number of oothecae produced and the over-all growth of the terminal oocytes were reduced in the cauterized insects and the number of resorption bodies per ovary was increased. The precise nature of the neuroendocrine host-parasite relationship is not known and is at present being further investigated.