Figure 1. F1 hybrids between a female Lepomis cyanellus and a male L. megalotis approximately six days after hatching, just before the swimming stage.

Scale bars are approximate. A. Morphologically normal larva; notice the elongate and straight spine and the comparatively reduced size of the body cavity. B. Morphologically deformed sibling of the fish in A; the spine is variously kinked and twisted, especially on the distal third, and the body cavity is notoriously enlarged. The arrow indicates the heart morphology, which appears analogous to that of the heartstrings developmental mutation observed in zebrafish (see discussion and [43], Fig. 1E). Approximately two thirds of the hybrid offspring described in this study showed morphological abnormalities of the types observed in this example (Table 2).