THE EFFECT OF INVERTEBRATE HORMONES AND POTENTIAL HORMONE INHIBITORS ON THE 3RD LARVAL MOLT OF THE FILARIAL NEMATODE, DIROFILARIA-IMMITIS, IN-VITRO

The effects of the insect hormones, ecdysone and 20-hydroxyecdysone, c ertain non-steroidal ecdysteroid agonists (RH compounds) and the inhib itor, azadirachtin, on the timing of the 3rd-stage moult of Dirofilari a immitis were investigated. 20-Hydroxyecdysone and RH 5849 when used at a concentration of 10(-5) M, resulted in a premature timing of this moult. Azadiracthin, at a similar concentration, prevented moulting o f most of the larvae to the 4th stage. The results are discussed in re lation to the possibility of a hormonal role for ecdysteroids and neur opeptide-like compounds in the control of ecdysis in filarial nematode s, that maybe somewhat comparable to the system which is found in inse cts.