Meeting Abstract
Several species of gobiid fishes from oceanic islands have evolved the ability to climb tall waterfalls. This behavior is most common among juveniles that are returning to adult stream habitats after completing a marine larval phase, and is facilitated by the fusion of the pelvic fins (in all gobies) into a ventral sucker. Previous observations identified two distinct modes of climbing. “Powerbursting” is found in many species and is likely the ancestral mode, with climbing powered by brief bouts of axial undulation between periods of attachment to the substrate. In contrast, “inching” is known only in the genus Sicyopterus, and is executed through alternating attachment of the pelvic sucker and a novel oral sucker. Comparisons among powerbursting species from Hawai’i and the Caribbean have shown a wide range of performance within this climbing mode; however, inching performance has only been measured in one species, S. stimpsoni from Hawai’i. To evaluate whether inching species might show less diversity in performance than powerburst climbers due to the more recent evolution of inching, or the demands of oral-pelvic coordination, we filmed climbing by two additional species from the Indian Ocean island of La Réunion: the inching climber S. lagocephalus, and the powerburst climber Cotylopus acutipinnis. For inching S. lagocephalus, climbing speed and the percentage of time spent moving closely matched previous results from S. stimpsoni; however, C. acutipinnis showed reduced climbing performance that differed from that measured in other powerburst species. Thus, the novel evolution of inching may restrict gobies to a more conservative range of climbing performance than powerburst mechanics.
