Climbing Waterfalls: How Metabolism and Behavior Impact Locomotor Performance of Tropical Climbing Gobies on Reunion Island

Abstract

The life cycle of gobies of the Sicydiinae subfamily depends on climbing waterfalls. Two sympatric sicydiines species from Reunion Island, Sicyopterus lagocephalus (SIL) and Cotylopus acutipinnis (COA), employ different climbing modes. SIL uses a steady "inching" mode interrupted by short rest periods, whereas COA exhibits short "power-burst" undulatory movements punctuated by longer rest periods. Consequently, we explored the relationship between climbing performance and metabolic activity in these two species. We demonstrated that the two climbing modes are supported by different ecophysiological profiles that promote the interspecific variability of locomotor performance. More specifically, SIL performed better than COA during a climbing experiment because of its inching climbing mode, supported by a generally greater metabolic capacity and a higher potential for oxidative metabolism. Interestingly, we did not detect any difference in metabolic fuel storage and lactate production during climbing in either species, suggesting that these species can maintain fuel reserves and limit lactate accumulation through extensive rest times. Overall, this study provides new insights into the ecophysiology of these two emblematic species and suggests that the better climbing capacity of SIL is supported by its muscular metabolic capacity.