Figure 1.
Karyotypes for Physocyclus mexicanus and Holocnemus pluchei and giemsa-stained meiosis I spermatocytes.
A. Haploid karyotype for Physocyclus mexicanus taken from fixed, giemsa-stained metaphase II spermatocyte. B. Haploid karyotype for Holocnemus pluchei taken from a fixed, giemsa-stained metaphase II spermatocyte (chromosomes 1–13 and Y chromosome) and a fixed, giemsa-stained anaphase I spermatocyte (X chromosome). C. Giemsa-stained metaphase I spermatocyte of Physocyclus mexicanus. X chromosome indicated by arrow. Bar = 10 µm. D. Giemsa-stained metaphase I spermatocyte of Holocnemus pluchei. X-Y bivalent indicated by arrow. Bar = 10 µm.
Figure 2.
Metaphase I-Anaphase I in living Physocyclus mexicanus and Holocnemus pluchei spermatocytes.
A. Progression from metaphase I (0, 26, 29 min.) through anaphase I (36, 41, 47 min.) in Physocyclus mexicanus. A univalent chromosome remains near one spindle pole (arrow) through metaphase I and anaphase I. Bar = 10 µm. B. Progression from metaphase I (0, 4, 6 min.) through anaphase I (31, 37, 41 min.) in Holocnemus pluchei. X (arrow) and Y (arrowhead) chromosomes are located in the center of the spindle in metaphase (0, 4, 6 min.) and X and Y chromosomes separate from one another in anaphase (31, 37, 41 min.). Bar = 10 µm.
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.