Mealybug Chromosome Cycle as a Paradigm of Epigenetics

Figure 3

P. citri spermatogenesis. Each spermatogonial precursor cell produces a cluster of synchronously dividing spermatogonia, and after four mitotic divisions a cyst of 16 primary spermatocytes is obtained. Primary spermatocytes undergo an inverted type of meiosis, characterized by a nonindependent assortment. Meiosis produces a quadrinucleate cell with 2 elongated spermatids containing only the euchromatic chromosomes (gray staining), and 2 picnotic spermatids containing only the heterochromatic chromosomes (dark staining). Only euchromatic spermatids differentiate into 32 mature sperms.