Meeting Abstract
Actinopterygii are named for the bony fin rays (lepidotrichia) that define the shape and function of their fins. Despite this, little is known about how these properties vary among the fins within individuals. I used three-point bending tests to measure the stiffness of the fin rays among fins of yellow perch, Perca flavescens. Yellow perch are benthopelagic; they swim in the water column, but also use their pelvic fins to rest and interact with the substrate. I tested every other fin ray from the pectoral, pelvic, soft dorsal, anal fins from multiple individuals. Each fin ray was tested at three locations, one-third (proximal), one-half (middle), and two-thirds (distal) the distance from the proximal end of each ray. Bending tests were conducted at a rate of 4mm/ minute to a maximum displacement of 0.8mm. The absolute maximum forces required to displace the rays ranged from 0.01 to 3.25 N. I calculated stiffness by dividing maximum force (N) by the displacement at which maximum force occurred (mm). All fin rays tested were most stiff proximally and least stiff distally. The paired fins exhibited the most extreme trends in stiffness; the pelvic fins were significantly more stiff than those of all other fins and the pectoral rays were much less stiff. The dorsal and anal fins were not significantly different from one another, and were intermediate in stiffness between the pelvic and pectoral fins. The rays at the edges of all fins were stiffer than those in the center. There was also a trend for rays near the leading edge to be slightly more stiff than those of the trailing edge. This contrast in stiffness between the paired and median informs our understanding of how the material properties of individual fin rays affect whole-fin function.
