Endocrine control of reproductive periodicity in maleTyposyllis prolifera(Polychaeta, Syllidae)

Publisher Website
Google Scholar
Abstract
Under a “summer” light-temperature regime (LD 16:8, 20°C), the polychaete Typosyllis prolifera shows a spontaneous 30-day cycle of reproduction (stolonization). Previous experiments suggested cyclic reproduction to be controlled by corresponding changes in the inhibitory endocrine activity of the proventriculus. The evidence in this paper, however, indicates that the prostomium rather than the proventriculus is the primary source of control of reproductive periodicity. The prostomium of a “summer” male undergoes a spontaneous lunar cycle of hormonal activity. Hormone secretion occurs around day 13 after previous stolon release each time. The hormone probably operates a triggering mechanism that shifts worms from the postreproductive regeneration phase to the next stolonization phase. However, the action on peripheral targets may be indirectly via the proventricular system, the inhibitory activity of which probably becomes inactivated periodically under endocrine influence of the prostomium. Considering all the information available, a model of the cooperation of environmental factors and endocrine factors (prostomial and proventricular hormone) in the timing of the reproductive cycle in male T. prolifera is presented.