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.