9813730 Ashley-Ross In vertebrates, very fast muscles are scattered among widely separated taxonomic groups. The fastest vertebrate muscles are associated with two activities: sound production and locomotion. Sound producing muscles tend to have the faster contraction times, but are thought to contract nearly isometrically, and thus to do little mechanical work. In contrast, fast locomotory muscles tend to have lower frequencies of contraction, but must produce considerable mechanical work and power as they propel their bearer about. The dorsal fin musculature of the seahorse (Hippocampus) is the primary locomotor organ of the animal, and is especially noteworthy for contracting at a high frequency against the load of the viscous medium. No systematic studies of dorsal fin work and power output or in vivo activation pattern have been made. Dr. Ashley-Ross proposes to characterize a number of properties of the dorsal fin musculature of seahorses, pipefish, grouper and perch, the latter two being non-specialized fish. The PI will record kinematics of fin movement using high-speed video, motor pattern using electromyography, in vivo muscle length-change pattern using sonomicrometry. The PI will also make a number of in vitro contractile measurements, including twitch force, twitch time course, maximum isometric force, mechanical work, and power output under conditions mimicking those of normal operation. A major aim of this proposal is to establish the limits of dorsal fin muscle performance in these species. My initial hypothesis is that the seahorse dorsal fin muscle is extremely specialized for rapid contraction in comparison to that of other more "typical" fish.
