Figure 3.

Gonad morphology in F1 male hybrids. (A) C. nigoni EG5268, (B) F1 X^Cni, and (C) F1 X^Cbr males. Contrast of gonads enhanced in all panels. Boxes correspond to regions enlarged in insets. In panels A and C, the distal arm is outlined with a dashed line in the large insets to emphasize the tubular structure of the gonad. This tubular structure is absent in the F1 X^Cni male shown in panel C. Anterior reflex (ar), distal tip (dt), sperm (sp), and tumorous cells (tu) indicated in insets. The C. F1 X^Cni male was an ‘exceptional’ GFP^– male obtained from crosses on C. nigoni EG5268 males to C. briggsae PB192 [cbr-him-8(v188) I; stIs20120 (pmyo2::GFP) X] hermaphrodites. The F1 X^Cbr male was a GFP⁺ male obtained from the same cross.