Meeting Abstract
Extreme body elongation has evolved multiple times within actinopterygian and sarcopterygian fishes. While this specialized body plan has been associated with living in highly structured habitats, many elongate fishes are also known to make terrestrial excursions. Here, we investigated how two elongate species, ropefish (Erpetoichthys calabaricus) and eel catfish (Gymnallabes typus), with different types of axial elongation move aquatically and terrestrially. Specifically, we examined how these species use vertical substrate in their environment by conducting aquatic and terrestrial locomotor trials where fish traveled through an array of cylindrical pegs spaced at different intervals. We predicted that ropefish, which have an elongate precaudal region, would spend more time contacting pegs than eel catfish, which have an elongated caudal region. Individuals completed both aquatic and terrestrial trials at two different peg-spacings. In general, both fish were found to move through the peg array similarly to limbless tetrapods. At the smaller spacing, individuals spent more time, on average, contacting a peg during a terrestrial trial than during an aquatic trial. Additionally, more of the body contacted the peg when the animal was moving terrestrially. Despite differences in their axial patterning, ropefish and eel catfish exhibited similar changes in locomotory patterns when traversing the terrestrial environment. However, these species did differ in speed and contact time; ropefish moved more slowly and contacted pegs for longer durations than eel catfish. This study provides further understanding of how elongate fishes can use axial undulation to move on land. In on-going studies, we are examining how these fishes move between environments.
