Zur Determination der zeitlichen Verteilung von Fortpflanzungsprozessen in Laborkulturen des PolychaetenTyposyllis prolifera

Abstract

Factors controlling the timing of reproduction in laboratory cultures of the polychaete Trposyllis prolifera.Typosyllis prolifera (Krohn) from Poreč (Yugoslavia) has been cultured for 12 successive generations. The life cycle of the species in the laboratory is described briefly. During their life individuals reproduce several times (up to 15) by stolonization which, under constant laboratory conditions (LD 16:8, 20 °C), is cyclic and takes place about every 30 days. Based on the investigations of Durchon (1959) and Wissocq (1966), experiments on extirpation and transplantation of the proventriculus have been carried out. The results suggest that an endocrine system anatomically connected to the proventriculus is important in the control of reproduction. Most likely, the endogenous reproductive cycle of an individual is controlled by periodical changes of the activity of this system. During the period following stolonization, the endocrine system of the proventriculus, which at this time shows its maximal activity, inhibits sexual development and enables regeneration of the segments lost as stolon. A subsequent decrease of the hormonal activity induces sexual maturation and epitokous metamorphosis, thus leading to further stolonization. Exogenous factors influencing the timing of reproduction probably affect the endocrine function of the proventriculus. Short-day photoperiods (LD 10:14) and low temperatures (12 °C) given simultaneously (i.e. winter conditions) totally suppress reproduction. Under normally favourable conditions (LD 16:8, 20 °C), reproductive processes can be prevented by starving or amputation of caudal segments. In all these cases, however, stolonization can be induced by removing the proventriculus. Exogenous factors also play a decisive role in synchronizing reproductive events within the species population. Under field conditions reproduction shows a lunar periodicity. The endogenous reproductive cycles of cultured specimens can be synchronized by a periodical light regime simulating the change of the moon.