Adhesive performance of the pelvic sucker in a waterfall-climbing gobiid, Sicyopterus japonicus

Benjamin Giustiniani

Abstract

Sicyopterus japonicus are a species of waterfall-climbing goby fish indigenous to Japan. While developing into adults from a post-larval stage, the fish migrates from the ocean to freshwater rivers and streams. During migration, the fish climbs sizable waterfalls by using a combination of the mouth and fused pelvic fins to generate suction pressure, allowing adhesion to the waterfall. This suction pressure was recorded through the setup of an artificial waterfall experiment involving multiple individuals collected from the Koza River in Wakayama, Japan. We recorded the maximal pressure produced and calculated the pressure differential (difference in pressure between the inside of the sucker and the ambient pressure) produced by the fish. In addition, the suction force was calculated by taking the area of the pelvic fins into account. S. japonicus produced suction force up to 4.3 times greater than their body weight against gravity. Some individuals showed slow reduction in suction force while staying stationary on the climbing surface, indicating the fish experiences some levels of muscle fatigue, although the absolute minimum force produced was still above the theoretical minimum force requirement. Additionally, we examined the pressure versus body size of different sized individuals.

 

Adhesive performance of the pelvic sucker in a waterfall-climbing gobiid, Sicyopterus japonicus

Sicyopterus japonicus are a species of waterfall-climbing goby fish indigenous to Japan. While developing into adults from a post-larval stage, the fish migrates from the ocean to freshwater rivers and streams. During migration, the fish climbs sizable waterfalls by using a combination of the mouth and fused pelvic fins to generate suction pressure, allowing adhesion to the waterfall. This suction pressure was recorded through the setup of an artificial waterfall experiment involving multiple individuals collected from the Koza River in Wakayama, Japan. We recorded the maximal pressure produced and calculated the pressure differential (difference in pressure between the inside of the sucker and the ambient pressure) produced by the fish. In addition, the suction force was calculated by taking the area of the pelvic fins into account. S. japonicus produced suction force up to 4.3 times greater than their body weight against gravity. Some individuals showed slow reduction in suction force while staying stationary on the climbing surface, indicating the fish experiences some levels of muscle fatigue, although the absolute minimum force produced was still above the theoretical minimum force requirement. Additionally, we examined the pressure versus body size of different sized individuals.