Meaning and titre of ecdysteroids during life span of Phormia terraenovae females

Abstract

The ecdysteroid titre in the haemolymph of Phormia terraenovae females was investigated by radioimmunoassay in relation to gonotropic cycles during the life span. Each cycle during the first 10 days after eclosion was accompanied by an ecdysteroid peak at 250–350 pmol/ml. At the end of life, peak concentrations were reduced nearly 50%. The investigations of ecdysteroids show that during ovarian stage 4a, before enzymatic hydrolysis with Helix pomatia juice 87%, and after this procedure 92% of the total immunoreactive material was detected in the migration area of ecdysone and 20-hydroxyecdysone. The highest values for deposited egg masses as well as for ecdysteroid titres of females showing the same ovarian development, peaked at day 10 and were followed by an age-related decrease. In ovaries of freshly emerged females a high content of ecdysteroid conjugates was found. Their mobilisation depends on nutrition and the total amount seems to be sufficient for the first gonotropic cycles. The necessity of nutrients containing sterols for successful reproduction becomes more important with increasing age. But the initiation of oögenesis is neither sterol nor protein dependent; it seems more likely to be due to vitamins and/or mineral salts.