THE ROLE OF THE CORPUS ALLATUM IN THE CONTROL OF VITELLOGENESIS AND FAT-BODY HYPERTROPHY IN PHORMIA-REGINA (MEIGEN)

Allatectomy (CA(-)) experiments revealed that the corpus allatum (CA), and thus juvenile hormone (JH), play several important roles in the c ontrol of vitellogenesis in liver-fed Phormia regina, CA(-), within 4 h of adult emergence, decreased the rate of vitellogenin (Vg) producti on, lowered the hemolymph Vg level and resulted in arrested ovarian de velopment, CA(-) at different times showed that there is a critical pe riod (i,e, about 12 h after a protein meal), prior to which the CA is required for complete vitellogenesis, When two doses of 10.0, 5.0 or 2 .5 mu g of methoprene (JH analogue) were applied, vitellogenesis was n early completely, partially or not restored in CA(-), liver-fed flies, respectively, In the absence of the CA, a liver meal resulted in fat body hypertrophy and greatly reduced hemolymph Vg levels, Methoprene t reatment restored Vg biosynthesis and prevented fat body hypertrophy o nly if the treatment was administered within 48 h after liver feeding, CA(-) greatly reduced the rate of crop emptying (thus, protein utiliz ation), but had no effect on protein ingestion, The CA is also needed to attain normal ecdysteroid levels in the hemolymph, The present resu lts support the notion that the CA (JH) can affect vitellogenesis at v arious levels in liver-fed P, regina, It appears that, within 12 h aft er a protein meal, JH primes the previtellogenic fat body to prepare f or Vg biosynthesis, and primes the ovaries to produce ecdysteroids. JH also regulates normal dietary protein utilization.