Comparative analysis of oocyte type frequencies in diploid and triploid catarina scallop (Argopecten ventricosus) as indicators of meiotic failure

摘要

Differences between diploid and triploid female mollusks in their gametogenic process had previously centered on comparing the general gametogenic cycle, not the oocyte types in each ploidy class, which by their presence or absence might be used as indicators of completion of specific meiotic events. In this study we compared oocyte type frequencies at three different stages of the gametogenic cycle of triploid and diploid catarina scallops. Regardless of age of sampling (81 d, 118 d, 205 d of grow out), the most abundant oocyte type in diploids was always the vitellogenic, and in triploids the previtellogenic. The frequency of occurrence of vitellogenic oocytes in triploids was only 4.7-19% of that in diploids, and that for postvitellogenic oocytes was only from 0-8% of that in diploids. This indicates that the oocyte stage in triploids at which gametogenesis was largely arrested was the previtellogenic oocyte, at meiosis I. The principal cause for the meiotic arrest might be associated with problems during zygotene at the time of synapsis between the three homologous chromosomes in triploids as previously suggested by other authors.