Fig. 8

Comparison of opercle shapes of (A) zebrafish, Danio rerio, (B) sucker, Castostomus sp., and (C) northern pike, Esox lucius.

Letters along the edges indicate hypothetically homologous locations along the bones. Shape differences along the upper (jp) edge and the j apex are discussed in the text. The arrow in (A) indicates a prominent Howship′s lacunae, a site of osteoclast-mediated bone resorption. The vp edge appears to outgrow differentially in all three species, as indicated by the incremental bands being wider in region c. The region between c and p shows the narrowest banding for both zebrafish and sucker, resulting in the concavity here shared by these two species but not by the pike. Zebrafish and the sucker are placed in separate families within the order Cypriniformes, the pike is in the order Esociformes and therefore is an outgroup to the other two species. Scale bars: 0.5 mm (A), 10 mm (B,C).