Figure 3. Micromanipulation of primary spermatocytes in Physocyclus mexicanus and Holocnemus pluchei.

A. In a Physocyclus mexicanus metaphase I spermatocyte (0 min.), a small micromanipulation needle was used to pull on the univalent chromosome near the spindle pole (2–4 min.), showing a single X chromosome (arrow). Bar = 10 µm. B. In a Holocnemus pluchei metaphase I spermatocyte (0 min.), a small micromanipulation needle was used to pull on the sex chromosomes in the middle of the spindle (0 min., arrow). Following the pulling, the chromosomes immediately return to their original position (1, 33 min.), indicating that chromosomes are connected to the spindle at both ends. X chromosome indicated by arrow, Y chromosome by arrowhead. Bar = 10 µm.