Hormonal control of oogenesis, ovulation and spawning in the annual reproductive cycle of the polychaete,Nephtys hombergiiSav. (Nephtyidae)

Publisher Website
Google Scholar
Abstract
Evidence for the existence of a gonadotrophic hormone and the possible existence of an ovulation-inhibiting hormone is presented together with further data on the timing of spawning hormone production. Decerebration of female Nephtys hombergii in the period October to December during active oogenesis results in (i) premature ovulation and dissolution of the ovaries, (ii) swelling and degeneration of the ovulated oocytes, (iii) degeneration and oosorption among oocytes remaining in the ovaries. These effects can be prevented by implanting live cerebral ganglia into the coelom of decerebrate females. Ultrastructural studies trace the effects of decerebration to the oocyte surface and dissolution of areas of close contact between oocytes and follicle cells. The morphology of the oosorptive process is described. Later in the reproductive cycle natural ovulation has begun and the immediate effects of decerebration are less severe, but decerebration still results in cytological abnormalities in developing oocytes. The spawning hormone is present in the brain only in low concentration in early April, but is present in higher concentrations in May. A hypothesis for the endocrine control of reproduction in N. hombergii is developed.