In the initial stage of a turn, sunfish use unilateral pectoral fin abduction to generate a laterally oriented wake flow on the same side of the body as the given stimulus (Fig.5A). Vortices observed in the raw DPIV video recording are indicated by dashed lines. The aim of future work will be to examine the locomotor roles of the spiny dorsal fin in derived teleosts as well as the soft dorsal fin in more basal clades. Change in fin morphology and position is a central component of the evolutionary transformation of functional design in ray-finned fishes (Actinopterygii). English Dictionary antonyms of Dorsal. Low-speed turns in sunfish therefore involve the generation of fluid forces that are both perpendicular and parallel to the longitudinal axis of the body and are applied sequentially by the paired and median fins. During steady swimming, for instance, the fin has been described as hydrodynamically inactive when furled (Webb and Keyes, 1981) or as a keel or body stabilizer when erected (Aleev, 1969). (D) By the end of the return stroke, a second vortex has been shed into the wake (see clockwise flow), while opposite-sign, bound vorticity develops at the fin’s trailing edge. L. macrochirus performs low-speed turns that involve minimal axial bending (Drucker and Lauder, 2001). Whether vortex interaction of the type illustrated in Fig.10 confers any hydrodynamic benefit to bluegill sunfish requires a comparison of the circulation around the tail in the presence and absence of the dorsal fin’s wake (cf. Studies of locomotor anatomy and behavior have identified a number of specialized swimming modes involving activity of the dorsal fin (summarized by Breder, 1926; Lindsey, 1978; Braun and Reif, 1985; Webb, 1993). In these fishes, the soft dorsal fin may be a less effective propulsor because of its greater compliance. The reaction force acting on the soft dorsal fin posterior to the center of mass of the body serves the dual function of slowing initial pectoral-fin-induced body rotation and helping to propel the animal forward away from the stimulus. We expect the circulation of this combined vortex, although less than the strength of a and b together, to be greater than the circulation of a or b alone. English Dictionary antonyms of Dorsum. The process illustrated in A–D is repeated on both sides of the body to yield the tail’s reverse von Kármán street wake (cf. As the tail completes its stroke, the two counterclockwise-rotating vortices coalesce, forming a single larger downstream vortex c (D). Wolfgang et al., 1999) but as surfaces with free, flexible trailing edges capable of actuation independent from that of the trunk and tail. provided by large median fins. Flow patterns within this plane were used to characterize the structure of the tail’s wake and to estimate caudal-fin swimming forces, which provided a context for interpreting calculated dorsal fin forces. In a previous study of dorsal-fin locomotor mechanics in Lepomis macrochirus, Jayne et al. Note that the vortices labeled I–IV in E–H are directly comparable with those illustrated for turning (see Fig.5F,G). Studies of man-made foils undergoing heaving and pitching motion (Triantafyllou et al., 1993; Anderson et al., 1998) show that propulsive efficiency, defined as the ratio of useful power output to total power input, is maximized when Strouhal number falls within the range 0.25