Zur sexuellen Differenzierung von Ophryotrocha puerilis (Polychaeta: Eunicidae)

Intact young males of Ophryotrocha puerilis Clap. Mecz. which are about to reach the female phase are capable of producing oocytes even under conditions of fasting. Intact isolated females may change sex under fasting conditions; their oocytes are not shed but resorbed. Decerebrated males which are about to reach the female phase at the moment of decerebration are unable to develop oocytes. Decerebrated females begin earlier with the production of spermatozoa than females under fasting conditions. The oocytes of decapitated females are either resorbed (young females with oocytes ranging in diameter up to 60 μm), or shed in egg masses capable of development after fertilization (older females with oocytes of 90 μm diameter or more). The effect of decerebration on females is compensated completely by implantation of isolated prostomia from female donors. Decerebrated males with implanted isolated prostomia from female donors immediately start oocyte production; these oocytes are not shed. In the majority of cases, decerebrated females change to the male phase after implantation of prostomia isolated from male donors. The mutual influence of a pair depends on direct contact of the partners. In isolated females, anterior fragments, consisting of prostomia and some segments, may induce change of sex and shedding of oocytes. On the other hand, intact females may induce sex reversal in anterior fragments. Even isolated prostomia from female donors may induce change of sex in intact females. A possible influence of intact females upon isolated prostomia was not found. Intact females and decerebrated females with implanted prostomia from female donors exhibit no mutual influence when placed together.     

Endokrinologische und genetische Untersuchungen an einer proterandrischen Population des Polychaeten Ophryotrocha labronica

Decerebrate, sexually immature juveniles of Ophryotrocha labronica develop into males and females, although the normal ratio observed in intact worms is not attained. Even without the prostomium, primary males split into secondary females and stable males. Stable males and females do not show any reaction after decerebration as far as sexual differentiation is concerned. The females proliferate new sets of oocytes and the males continue spermatogenesis. In a great number of cases, decerebrate secondary females resume spermatogenesis. Amputation of the prostomium induces the development of the k-jaw. Even in small individuals below the size at which the k-jaw normally appears, the change to the k-jaw is induced. Heterospecific transplantations of prostomia from female O. labronica donors to decerebrate O. puerilis hosts revealed that the prostomia of female O. labronica produce and release a substance which completely compensates the lack of the host's own prostomium. Obviously, this ootropic substance is not necessary in all cases for gaining and/or maintaining female differentiation in O. labronica. Although it is produced both in stable females and secondary females, only a portion of the secondary females requires this substance for female differentiation. It is, therefore, presumed that the strength or stability of female differentiation expresses itself by hormone-dependent or independent oogenesis. In crosses with a gonochoristic population of O. labronica, protandric hermaphroditism is restricted to a few descendants. Crossing experiments within the protandric population of O. labronica seem to indicate a genetic component in the degree of protandry and in sex determination.     

Regeneration in the gonochoristic polychaete Ophryotrocha notoglandulata

Anterior and posterior regeneration in both male and female Ophryotrocha notoglandulata Pfannenstiel, 1972 was induced by amputation of parts of the prostomium or caudal segments. Regeneration capacity is identical in males and females. The prostomium is not necessary for caudal regeneration.