[Some aspects of hormonal interactions between molting and vitellogenesis in Orchestia gammarellus (Pallas) (Crustacea, Amphipoda)].

The mechanisms which coordinate and regulate secondary vitellogenesis and molting in Orchestia gammarellus have been studied in natural and experimental conditions. The onset of secondary vitellogenesis, requiring a protocerebral factor and a low titer of ecdysteroids, occurs only after normal folliculogenesis. The secondary follicular tissue would secrete vitellogenin stimulating ovarian hormone (VSOH) which stimulates the subepidermal adipose tissue to produce vitellogenin. VSOH and ecdysteroids are indispensable to normal vitellogenin synthesis during secondary vitellogenesis. Moreover, the Y-organ controls vitellogenin entry into the oocytes. In secondary vitellogenesis the ovary would stimulate the secretion of molt inhibiting hormone (MIH) which would act on the epidermis, rendering this tissue unresponsive to the stimulatory action of ecdysterone. The Y-organ and the protocerebrum are involved in the control of the molting processes independently of their action on vitellogenesis.