69.10 Jan. 7 Pelvic fin locomotion in batoids MACESIC, L.J.*; HOLMES, A.; KAJIURA, S.M.; Florida Atlantic University, Boca Raton; Florida Atlantic University, Boca Raton; Florida Atlantic University, Boca Raton email@example.com
Studies of locomotion in batoids have largely focused on pectoral fin movements. However, pelvic fin ‘punting,’ has been described as an important locomotive mechanism in skates. Other benthic batoids have been observed to perform similar punting movements despite lacking the skate’s specialized pelvic fin structure. In this study, we compared the use of pelvic fins in locomotion between two benthic batoid species with disparate pectoral and pelvic fin morphologies: Bancroft’s numbfish, Narcine bancroftii and the Atlantic stingray, Dasyatis sabina. The large, paired electric organs of N. bancroftii compromise its ability to undulate its pectoral fins and it thus swims by axial undulation. In contrast, D. sabina, although sharing a similar benthic lifestyle, swims by pectoral fin undulation. To determine structural and locomotory differences between the pelvic fins of these species, we compared the pelvic fin to pectoral fin surface area ratios, skeletal morphology, and swimming kinematics, including punting distance (body length (BL)), speed (BLsec-1), glide duration (sec), and thrust duration (sec). Narcine bancroftii punts significantly faster and covers a significantly greater distance (0.16±0.014 BLsec-1; 0.85±0.055 BL; n = 4) than D. sabina (0.06±0.005 BLsec-1; 0.34±0.041 BL; n = 4), and does so with no significant difference in duty factor. Moreover, punts by D. sabina were always accompanied by a brief undulation of the pectoral fins; N. bancroftii displayed only pelvic fin movement during punting. The relative size of the pelvic fins may indicate their importance in locomotion as the pelvic fin surface area of N. bancroftii (n = 10) is more than twice (2.202 times) that of D. sabina (n = 10). This study demonstrates that despite lacking specialized structures, benthic batoids can efficiently utilize punting in locomotion.