Is the life cycle of Derbesia (Chlorophyta) heterokaryotic? Response to the commentary of Schnetter and Eckhardt (2000)

In response to a commentary on our previous work by Schnetter & Eckhardt [P hycologia 39: 355-357 (2000)], we reinvestigated the question of whether nu clear fusion takes place immediately after plasmogamy in Derbesia. We also reexamined the first mitosis in the zygote that develops from the fusion of a male and a female gamete. As in our previous reports, we observed karyog amy to follow directly after plasmogamy and normal mitosis of the single zy gote nucleus. Our strain of D. tenuissima is therefore a diplohaplont and l acks a heterokaryotic phase in the life cycle, in contrast to what is claim ed to occur in various species and strains of Derbesia by Schnetter and co- workers.