Aneuploidy during development in facultative parthenogenetic Drosophila

From concatenated chromosomes to polyploidization, large-scale genome changes are known to occur in parthenogenetic animals. Here, we report mosaic aneuploidy in larval brains of facultatively parthenogenetic Drosophila. We identified a background of aneuploidy in D. mercatorum strains and found increased levels of aneuploidy in the larval brain tissue of animals arising parthenogenetically versus those arising from sexual reproduction. There is also intra-individual variation in germline-derived aneuploidy within the same strain. To determine if this is a general feature of facultative parthenogenesis in drosophilids, we compared sexually reproduced and parthenogenetic offspring from an engineered facultative parthenogenetic strain of D. melanogaster. In addition to germline-derived aneuploidy, this revealed somatic aneuploidy that increased by up to fourfold in parthenogens compared to sexually reproduced offspring. Therefore, the genetic combination identified in D. mercatorum that causes facultative parthenogenesis in D. melanogaster results in aneuploidy, which indicates that the loss of mitotic control resulting in parthenogenesis causes subsequent genome variation within the parthenogenetic offspring. Our findings challenge the assumption that parthenogenetic offspring are near genetic replicas of their mothers.