L'Evolution post-imaginale du tissue adipeux femelle de Locusta migratoria et son controle endocrine

Abstract

In the adult female of Locusta migratoria, during the differentiation of the periovarian fat body, there is an extensive development of rough ER and Golgi apparatus; 2 weeks after ecdysis, lipid droplets decrease in number and size, and glycogen particles are no longer detectable. At the same time, the nuclear volume is doubled and even quadrupled for a third of the adipocytes. Once this transformation is achieved, Golgi complexes cease secreting glycoprotein granules, but produce microvesicles in great number which might give rise to multivesicular bodies (mvb). These mvb are not involved in protein uptake but rather in transporting enzymes to cytolysosomes, which are conspicuous in the oldest females. These “protein granules” could contribute to elaboration of egg precursor proteins besides those normally synthesized by the rough ER. The postecdysis evolution of fat bodies does not reflect the different steps of sexual life of the female, neither the ovarian maturation nor the later ovarian cycles. Indeed, in 2-week-old ovariectomized females, the fat body maturation is realized: Moreover, there is a slight acceleration in the differentiation process of periovarian fat body cells, and peripheric cells are involved in an unusual maturation, when compared to control females. Allatectomy brings an overcharge of lipid droplets in periovarian and peripheric fat body cells. Neither proliferation of rough ER or Golgi nor an increase of nuclear volume takes place, but a certain involution of cytoplasmic organelles is observed. Implantation of corpora allata in 1-month-old allatectomized females leads to a rapid restoration of the capacity of differentiation in “female fat body.” In conclusion, the results obtained after allatectomy and after castration suggest a strict control by the juvenile hormone in determining fat body maturation. A study concerning the initial cause of hyperactivity of the corpora allata after ovariectomy is in progress.