Figure 4.

Scheme of male meiosis in pure species and interspecies hybrids of the An. gambiae complex. Unlike pure species, X and Y chromosomes in meiotic prophase I of hybrids are largely unpaired. The absence of chiasmata between the sex chromosomes and insufficient chromatin condensation reduce tension exerted across the homoeologous chromosomes, triggering premature sister chromatid segregation. As a result, instead of a reductional division, primary spermatocytes in interspecies hybrids undergo an equational mitotic division leading to diploid non-motile sperm.