Fig. 5. Tailbeat frequency, amplitude and stride length versus water velocity during steady swimming bouts for S. nigriventris: dorsal side up near the surface (0.025 m, h/d=0.6, green open circles; 0.04 m, h/d=1.2, red open circles) and deeply submerged (0.09 m, h/d=3.4, blue open circles); inverted near the surface (0.025 m, h/d=0.6, green open squares; 0.04 m, h/d=1.2, red open squares) and deeply submerged (0.09 m, h/d=3.4, blue open squares). Regressions for tailbeat frequency and stride length are represented by solid (dorsal side up) and dotted lines (inverted posture). Since ANCOVA shows no significant effects of water depth on amplitude (P>0.05), the data were pooled to generate an overall regression (black solid line). In all cases, r²>0.4, P<0.05.