Function of spiny dorsal fin erector muscles in the bluegill, Lepomis macrochirus
Abstract
Local motor control directly contributes to stability, which can be compromised by injury or multiple neuromuscular disorders. In addition, lack of sensory perception as experienced by decreased limb sensation can further deteriorate one’s quality of life. The goal of this study is to use bluegill (Lepomis macrochirus) fins as model systems to study and gain insights on local motor control and sensory perception to improve stability and locomotion in humans, especially in a rehabilitative state. We hypothesize that 1) when exposed to turbulence (T), bluegill will use the spiny dorsal fin to recover stability and muscle intensity and duration will increase in the spiny dorsal fin erector muscles; 2) we expect the removal of afferent information, by injection of lidocaine, to decrease muscle intensity and duration compared to saline (control); and 3) the removal of muscle control by injection of flaxedil, to dramatically decrease muscle intensity and duration compared to saline. Upon sedation of the bluegill, the epaxial and spine erector muscles were implanted bilaterally with double insulated electrodes via hypodermic needles, followed by injection of 0.6 mL (0.1 mL per erector muscle) with one of the three treatments: flaxedil (0.04mg/mL), lidocaine (1.25mg/mL), or buffered saline. Muscle activity was recorded with an iWire-BIO8 biopotential recorder module and two high-speed cameras for the top and side views of the tank. The findings showed that turbulence within each treatment did not affect magnitude, relative intensity, burst duration, cycle duration, or duty factor of erector or epaxial muscle bursts. However, within no turbulence conditions, lidocaine treated fish had higher muscle activity in the spiny erector muscle magnitude than the flaxedil treatment. Activity bursts of spiny erector muscle were shorter under flaxedil than control under turbulent conditions. While under no turbulence relative intensity also decreased under flaxedil conditions. We found that in lidocaine treated fish, the erector muscles were unable to correctly modulate muscle activity and that in flaxedil fish, erector muscle function was compromised. Findings on impaired motor control and blocked sensory perception may be applied to enhance human prosthetic control and thus achieve stability.