[Action of theor-gene on pigmentation inPlatynereis dumerilii (Polychaeta) : II. Pigment deposition as caused by a maternal effect or immediately byor-gene activity].

1. A maternal Effect is observed in backcross progeny derived from heterozygous (+/or) females inPlatynereis: or/or-larvae from that cross resemble wildtype larvae with respect to the color of supporting cells as well as of iridophores (Fig. 4,3). The maternal effect is due to maternalor-gene activity, a product of which is transmitted to the offspring. Activity of the inherited product of theor-gene seems to be restricted to larval development (up to an age of about 4 days). However, the juvenile eyes ofor/or-larvae affected by the maternal effect remain a dark brown. It is not before the 3-segment-larva has grown to a young worm of about 11 setigerous segments that new retinal cells are added concentrically. The new retinal tissue is an orange color as expected foror/or-genotype (Figs. 1, 2). 2. Backcross progeny were analyzed with regard to the onset of the maternal effect and of the larva's gene activity. When pigmentation depends on the larva's own gene activity the eye pigment in question is detectable as soon as supporting cells differentiate visibly (2 1/2 day-old larvae; Fig. 4,2; Table 3). When the eye pigmentation depends on the maternal effect supporting cell pigment becomes visible at the same time at the earliest (Fig. 4,3; Table 4). Hence, in wildtype larvae pigment formation in the juvenile eye is subjected to independent, simultaneous activity of both the larva'sor-gene and inherited products of maternalor-genes. Similar cases of redundancy as revealed by Mendelian genetics are discussed. 3. In transplantation experiments carried out betweenor/or- and +/+-specimens, no interaction between implant and host tissue as well as host offspring could be observed as to eye color. On the contrary, regenerating eyes as well as eyes of offspring from hosts carrying implants behaved autonomously (Fig. 5, Table 5).