Male mitotic and meiotic cells of Ctenidae species stained with Giemsa. Boxes – X chromosomes without association (C, G, K, O), and with association (S). C. medius (A–D), C. ornatus (E–H), P. nigriventer (I–L), E. cyclothorax (M–P), V. andicola (Q–T). The arrowheads show sex chromosomes. Mitotic metaphases with 2n = 28 (A, E, I, M) and 2n =29 (Q). Pachytene cells (B, F, J, N, R) with positively heteropycnotic sex chromosomes. Diakinesis cells (C, G, K, O, S), note parallel association of two X chromosomes (C, G, K, O) or three X chromosomes without association (S). Metaphase II cells with n = 13 and n = 13 + X1X2(D, H, L, P) and n = 13 and n = 13 + X1X2X3(T). Bar = 10 µm.