Figure 1

Schematic representation of the main steps of androgenetic reproduction in Corbicula spp. after fertilization. (1) The maternal chromosomes (in blue) are in metaphase I. The meiotic axis is parallel to the cell cortex. The male pronucleus is indicated in red. (2) The egg is in anaphase I and the maternal chromosomes segregate. (3) The cytoplasm around the asters is distorting and two polar bodies, containing all maternal chromosomes, are formed. (4) The male pronucleus expands. (The male gamete is considered unreduced, here diploid.) (5) Metaphase of the first cleavage (mitosis) of the zygote (with only ‘paternal’ chromosomes). (6) Anaphase of first cleavage. (7) Two-cell stage of the zygote. This schematic representation is based on cytological observations in Komaru et al. (1998).