Meeting Abstract
An amphidromous sicydiine goby, Sicyopterus japonicus, exhibits rock-climbing behavior during upstream migration along rivers and streams. Using the pelvic sucker, formed by fused pelvic fins, S. japonicus generates suction for adhesion on the climbing surface. By measuring performance variables that correlate to successful rock-climbing capability, we evaluated scaling relationships of suction force generated by the pelvic sucker and its fatigability during climbing in S. japonicus both with respect to body mass. During continuous climbing on the 60°-inclined surface, the pelvic sucker of S. japonicus exhibited a strong positive allometry in generating force for adhesion. In addition, during sustained adhesion, time constant as a measure of fatigue time for the pelvic sucker muscles scaled non-linearly with body mass and showed the best fit to a quadratic regression, the peak point of which predicted intermediate-sized individuals (large juveniles to small adults) to be the best in endurance performance during adhesion. Our experimental results indicate that different sizes of waterfall-climbing gobies have different performance capacities for rock climbing, relating to physiological differences in their pelvic muscles. In addition, our data from S. japonicus can indicate selection pressures on the locomotor capacities of waterfall-climbing gobiids vary during ontogeny.
