The regulation of ovary function in Cirratulus cirratus (Polychaeta)

Abstract

The ovaries of gravid female Cirratulus cirratus enter a nonproliferative phase prior to spawning; during this phase young oocytes are not released into the coelom. The role of the coelomic oocytes in the regulation of oocyte output from the ovaries has been investigated. Artificial removal of the coelomic oocytes from gravid females provokes a renewed output of oocytes into the coelom. Partial stripping experiments, in which some segments retain the full complement of oocytes while others are devoid of coelomic gametes, show that the negative feedback exerted by the coelomic oocytes acts directly upon the ovaries in the segments which contain them. In the presence of ripe coelomic oocytes the immature oocytes on the ovary are arrested at a stage prior to previtellogenic growth and yolk nucleus differentiation. The cerebral ganglia of Cirratulus cirratus are not highly differentiated. Their removal has no effect on the growth rate of the oocytes, but partially inhibits spawning. Intact cerebral ganglia appear to be necessary for the normal post-spawning or poststripping response. The mechanism of coordination of oogenesis in Cirratulus cirratus differs from those described in those other polychaetes which have been investigated.