Aplanogamous sexual reproduction in Carteria eugametos (Volvocales,Chlorophyta)

Morphological details of sexual reproduction in Carteria eugametos (Volvocales, Chlorophyta) were studied under controlled laboratory conditions. Protoplasts of the two pairing, flagellate cells were released from cell walls to become isogametes. Such gametes were nonmotile and soon fused to form a completely immobile zygote. The zygote then secreted a cell wall to enter the dormant period. After dark treatment, the zygote produced four, eight or 16 quadriflagellate germ cells, and a transparent vesicle enclosing all the germ cells was released from the zygote wall. This type of zygote germination and aplanogamy in C. eugametos is unique and may be related to its peculiar phylogenetic position within the Volvocales (Chlamydomonadales).