Relationships between juvenile hormone levels and synthesis of major haemolymph proteins in Bombyx mori larvae

Abstract

1. 1. JH levels were determined in haemolymph of developing third, fourth and fifth instar Bombyx mori larvae. 2. 2. Total level decreased of an order of magnitude after each of these instars. 3. 3. The fourth and fifth instars were characterized by a U-shaped curve, with a minimum level respectively at the middle of the feeding period and before spinning. JH III disappeared from the third day of the fifth instar up to 3 days before larvo-pupal moult. 4. 4. Synthetic rates of Major Haemolymph Proteins (MHP) by the fat body were quantified during the same period. 5. 5. These rates were low up to the second day of the fifth instar, rised up to the onset of spinning, then declined abruptly. 6. 6. They were closely correlated with changes in JH levels. 7. 7. Hormonal treatments of the larvae confirmed that JH controls MHP synthesis. 8. 8. Characteristics of the relationship between the two processes suggest that the action of JH on MHP synthesis might be specific and indirect.