THORSEN, D/H*; CASSIDY, J/J; HALE, M/E; The University of Chicago; The University of Chicago; The University of Chicago: Development of pectoral fin morphology and locomotion in the zebrafish Danio rerio
Pectoral fins serve a variety of locomotor functions for fishes including propulsion, stabilization and maneuvering. The function of pectoral fins can change through development and in different behavioral contexts. We examined the range of pectoral fin movements of the zebrafish (Danio rerio) through the first 2 months of development using high-speed digital video (250-1000 Hz). We captured a variety of swimming and turning behaviors in still water and in a flow tank environment. In addition, we cleared and stained pectoral fins to examine the morphology of bone, cartilage and nerves. Changes in fin propulsion were correlated with changes in pectoral fin and body morphology. As adults, zebrafish primarily use pectoral fins for maneuvering and station holding (hovering) in low-speed (i.e. non-fast-start) environments. As larvae, zebrafish alternate their pectoral fins during slow swimming (10.96 � 0.87 mm/s; N=10 fish) in conjunction with axial undulations of the same frequency. During fast swimming (108.54 � 7.85 mm/s; N=5 fish), the fins are tucked against the body and propulsion occurs by axial undulation alone. The slow and fast swimming patterns are correlated with, respectively, low (43.06 � 3.41) and intermediate (427.49 � 31.07) Reynolds number conditions. We suggest that the fin-axis coordination observed in larval fish may be specialized for locomotion in low Reynolds number conditions in which resistive forces dominate. Additionally, we show that during swimming larval fishes can use the same basic limb-axis coordination pattern as walking salamanders suggesting a similarity in central pattern generator organization and coordination. We suggest that early terrestrial vertebrates may have gained the ability to coordinate limbs and lateral bending by retaining a primitive larval CPG for limb-axis coordination in the adult life history stage.
