Ecdysteroid levels during ovarian development and embryogenesis in the spider crab Acanthonyx lunulatus

Ecdysteroid levels (ecdysone, 20-OH-ecdysone, low and high polar products) are monitored during oogenesis and embryogenesis in the spider crab Acanthonyx lunulatus. Ecdysteroids are separated by thin-layer or high-performance liquid chromatography and quantified by radioimmunoassay. During oogenesis, ecdysone and 20-OH-ecdysone increase at the beginning of vitellogenesis and once again as oocytes reach maturity. The first rise has also been reported in some insects; the second rise is most probably involved in stimulating formation of the egg shell. In embryos, ecdysone and 20-OH-ecdysone increase at the beginning and end of embryogenesis and they also increase during metamerisation and during the secretion of the exoskeleton. These observations indicate that in Acanthonyx hormonal control of both oocyte maturation and embryo development is achieved in much the same way as in insects. The involvement of ecdysteroids in these two processes is of particular importance since oogenesis and embryogenesis are, in this species, closely synchronized in spite of the fact that embryos develop outside the female's body.