Developmental changes in ecdysteroid biosynthesisin vitroduring adult life and embryogenesis in a cricket,Giyllus bimaculatusde Geer

Abstract

Ovaries from female adults of Gryllus bimaculatus produce considerable amounts of free and conjugated ecdysteroids in vitro. The rate of ecdysteroid synthesis after a 16 h incubation in Grace's medium, changes during vitellogenesis in a characteristic way, reaching a peak value of about 5 ng per hour, per animal, at days 415 after ecdysis, when animals start to deposit eggs. During incubation of pieces of the female abdominal integument together with the adjacent segmental fat body, a net synthesis of moulting hormones is observed, similar to that in the ovary. Ecdysteroid production by integument starts shortly after the imaginal moult and also reaches a maximum of about 3 ng per hour, per animal, around days 415 after ecdysis. Both tissues mainly synthesize and release ecdysone into the incubation medium. From tissues of male adult crickets only the abdominal integument shows a significant net synthesis of ecdysteroids. In vitro incubations of egg homogenates of various ages result in a net synthesis of free and conjugated ecdysteroids in older embryos, with a maximum one day before hatching of the larva. The imidazole compound KK-42 does not inhibit ecdysteroid synthesis in vitro in cricket embryos.

Structure and function of the prothoracic gland in honey bee (Apis melliferaL.) development

“…To date there is little cogent reason for doubting that the prothoracic glands are the prominent physiological source of ecdysteroids during preimaginal development in most insect species (Smith, 1985;Weidner et al, 1992). In the light of reports on alternative sites of ecdysteroid release (Delbecque et al, 1990) and evidence demonstrating production of considerable quantities of RIAdetectable ecdysteroids by thoracic and abdominal tissues in the mosquito, Aedes aegypti (Jenkin et al, 1992), testing tissues other than the putative prothoracic glands has become standard practice.…”

Multilocal expression of B-type allatostatins in crickets (Gryllus bimaculatus)

“…Lorenz and coworkers [4,18] demonstrated that peptides of the AST B-type could effectively inhibit the biosynthesis of ecdysteroids in the ovary (follicle cells) of adult female crickets in vitro in a dose-dependent manner. In adult females of G. bimaculatus, the synthesis of ecdysteroids in the ovary [21,22] as well as the titer of ecdysteroids in the haemolymph increase during the first 4 days after imaginal moult but decrease thereafter. Whether B-type allatostatins from the ovary are directly involved in the regulation of ecdysteroid biosynthesis in the ovary of young adult females is still speculative, but the results from injection experiments strengthened this assumption [23].…”

Secretion and Metabolism of Ecdysteroids by Oenocyte-Fat Body Complexes (OEFC) in Adult Males of Gryllus bimaculatus DEG (Insecta)

“…Experiments on elimination as serted the continuous excretion through the faeces up to the horm one maximum (Eibes and Römer, 1990). A newly published study (Weidner et al, 1992) fails to explain this dramatic increase of ecdysteroids. In the best of all cases presented within this study values of 3ng/anim alxh for the epidermis and the adjacent fat body were achieved.…”

“…This accounts for some part of each horm one peak, though not for the total amount. A part from free ecdysteroids the epidermal cells of Gryllus contained polar and apolar products, which together sometimes sur m ounted the quantities of free ecdysteroids (Weidner et al, 1992).…”

“…The interm ediate periods between these maxima are characterized by rather low titers of free ecdysteroids. Concern ing male crickets the tergites appear to be possible sources of the moulting horm ones (Bressel et al, 1990;Weidner et al, 1992). Keeping in mind the larvae of Tenebrio molitor, for which the synthesis of ecdysteroids in the oenocytes had been asserted earlier (R öm er et al, 1974), it should be tested, w hether this type of tissue could be likewise the source of horm one synthesis in Gryllus.…”