Identification of WZ bivalents in orcein-stained preparations of pachytene oocytes of three tortricid species.

<p><b>a</b> – pachytene complement of <i>Grapholita molesta</i>; the WZ bivalent is indistinguishable. <b>b</b> – incomplete pachytene nucleus of <i>Lobesia botrana</i>; note a WZ bivalent (arrow) identified according to W-chromosome heterochromatin. <b>c</b> – a WZ bivalent of <i>L. botrana</i>; note the deeply stained W-chromosome thread while the Z-chromosome thread shows a chromomere pattern (see arrowheads pointing to deeply stained chromatin beads). <b>d</b> – a part of pachytene nucleus of <i>Eupoecilia ambiguella</i> with a WZ bivalent (arrow) anchored by one end in the nucleolus (N); note that most of the W chromosome is formed by a continuous thread except the end opposite to the nucleolar end, which shows a chromomere pattern similar to the Z chromosome (arrowheads). <b>e</b> – a part of zygotene/early pachytene nucleus of <i>E. ambiguella</i> with not yet paired sex chromosomes; note W and Z univalents (arrows) anchored by one end in the nucleolus (N); also note a deeply stained Z-end (arrowhead) inbuilt in the nucleolus. Bar = 10 µm; <b>b–e</b> have the same scale.