Single gene mutations causing exaggerated fins also cause non-genetic changes in the display behavior of male zebrafish

We show that the exaggerated changes in fin lengths of zebrafish (Danio rerio) caused by a single gene mutation also resulted in changes in the lateral display rate. However, the increase in this threat display rate only occurred when both fish had very long fins. Fish with shorter fins did not show such an increase when they met fish with longer, same size, or shorter fins. Cutting the long fins to resemble the shorter fin types reduced the display rate, demonstrating that genetic differences do not account for the differences in behavior. These results suggest that species differences in the performance of a display may reflect only the physical differences in the display structure.