Ecdysteroid levels in haemolymph and reproductive organs of fourth and fifth nymphal instar and adult Melanoplus sanguinipes

Abstract

Levels of ecdysteroids were determined by radioimmunoassay (RIA) in the haemolymph, testes, male accessory reproductive glands (MARG) and female reproductive system of fourth and fifth (final) nymphal instars and adults of the migratory grasshopper, Melanoplus sanguinipes. In nymphs, the haemolymph ecdysteroid levels were found to peak (60.5 ng/ml [males], 40 ng/ml [females] in the fourth instar and 446 ng/ml [males], 340 ng/ml [females] in the fifth instar) a little after the middle of the stadium. The ecdysteroid level in the testes of fifth instar nymphs also peaked on the same day as that of the haemolymph. However, ecdysteroid levels in the haemolymph of adults (peak values 5.3 ng/ml [males] and 4.3 ng/ml [females]) were much lower than those of final instar nymphs. Ecdysteroids also occur in the testes, MARG and female reproductive system of adults. In mated males, the levels of ecdysteroids in the testes and MARG were greater than those in unmated males of the same age. In contrast, in females that had mated or oviposited, ecdysteroid levels in the reproductive system and haemolymph were lower than those in virgins.