Activity of corpora allata, endocrine balance and reproduction in female Labidura riparia (Dermaptera).

The reproductive activity of Labidura riparia females involves, after a 5-day maturation stage, a regular alternation of ovarian cycles and egg-care stages averaging 10 days each. Vitellogenesis is characterized by an increase in the size of the corpora allata (CA) where structured SER bodies appear, and by a rise of juvenile hormone (JH III) content in the hemolymph which is followed by an increase in the level of ecdysteroids. During the egg-care periods, the CA are inactive; structured bodies generate autophagic vacuoles, the titer of JHs and later that of ecdysteroids in the hemolymph decreases and remains stationary. Ovariectomy causes hypertrophy and hyperactivity of the CA for about two months. Subsequently, the titer of JH decreases and old females may display parental behaviour; the level of ecdysteroids falls and remains unchanged. After cauterization of the pars intercerebralis (PI) of the protocerebrum, the ovarian activity stops, the ovary shrinks, the JHs rapidly disappear but ecdysteroids remain at the same or even higher levels than those of normal females of the same age. On the basis of these data, we postulate the existence of a center located in the PI, inhibiting the production of ecdysteroids, and of a stimulating center located outside this area. The PI also exhibits an allatotropic function.

[Hormonal control of the ovarian cycle in Labidura riparia (author's transl)]. / Les contrôles hormonaux des cycles ovariens chez la femelle d'un insecte dermaptère: Labidura riparia pallas.

The ovaries in female Labidura riparia undergo cyclical development. They require approximately 10 days to complete one vitellogenesis. During this period the Insect eats and and also mates. About 7 to 9 follicles in each ovariole are loaded progressively with vitellus and secrete a chorion. Before each oviposition degenerative phenomena appears in immature follicles. The ovaries remain at a less developed stage during the 10 days of maternal eggs cares. The follicles at the base of each ovariole degenerate. The cerebral neurosecretory centers and the corpus allatum are active during each vitellogenesis and inactive during each period when follicles degenerate and when the female cares her eggs. An experimental study shows that neurosecretory centers control the activity of the corpus allatum which itself influences the evolution of the vitellogenesis.