Apport des odonates à l’endocrinologie des insectes: rétrospective historique
Advances in odonatology , Volume 4 - Issue 1 p. 95- 122
THE ROLE OF ODONATA IN INSECT ENDOCRINOLOGY: A HISTORICAL RETROSPECTIVE VIEW. – The groundwork of insect endocrinology was laid in 1934 by V. B. WIGGLESWORTH ( Q. Jl microsc. Sci. 77: 191-222) following his studies on the development and growth of a blood-sucking bug. Later works confirmed the role of endocrine glands in hormonal mechanisms that preside over the growth and metamorphosis of the silkworm. Eventually, such research was extended to most of the insect orders. Among these, Odonata gave rise to a preliminary experimental work which remained without any follow-up although many anatomohistological studies on the endocrine glands of these insects have provided reliable foundations for such work. 1957 saw the beginning of a study on the hormonal control over the postembryonic development of Aeshna cyanea, concerning: — (1) ventral glands (VG), equivalent to prothoracic glands of other insects, responsible for moulting and metamorphosis; — (2) the corpora allata (CA) whose secretory activity ensures the maintaining of the larval character of moulting; — (3) the pars intercerebralis (PI), a group of neurosecretory brain cells whose hormonal factor stimulates the activity of VG. These three main axes were the starting point of a series of work on Aeshna cyanea performed by an enlarged research team which got together from 1962 onwards. In this context a number of works should be quoted, research focusing on: – (1) ecdysone, the hormone produced by VG (hormonal level in the blood, metabolism, biosynthesis and biological activity of ecdysone); — (2) the juvenile hormone produced by CA, which acts as an inhibiting factor of metamorphosis; — (3) works on the brain, in which PI is situated, and other sites of secretory cells (cytology, in vitro culture, control of diapause and moulting by the brain neurohormone). In addition, each member of the research team paid particular attention to a special field: cellular activity of regeneration nidi in the midgut, ocular growth and development of the optic lobes, morphogenesis of the male copulatory apparatus, PI-VG interrelation during larval moulting and metamorphosis. Since 1962, this research has given rise to 90 publications whose main part is specially devoted to endocrinology. Finally, attention should be drawn to works performed in India concerning neurosecretory phenomena in an Anisopteron, Orthetrum chrysis (about ten publications since 1974).
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