Meeting Abstract
Highly elongate fish, from a number of distinct lineages, have traversed the water-land boundary. This movement between extreme environments is often motivated by habitat quality or lack of prey. Asian Swamp Eels (Monopterus albus) are found in rice fields and have been observed moving on mud flats to locate new bodies of water often around the breeding season. Laboratory study of Monopterus indicated that emergence from the water is often linked to starvation or increased population density. Previous study of pectoral fin-based terrestrial locomotion in fishes has shown the importance of the posterior end of the body for forward propulsion. Elongate fish tend to have highly reduced or absent paired fins, especially in the pectoral region, and thus must rely wholly on movement of the axial skeleton to move forward. Our work has shown that, similar to limbless tetrapods, elongate fishes use push-points in their environment during locomotion. In this study, we tested the role of substrate on body mechanics during undulatory locomotion; specifically we examined how compliance of a substrate affects forward movement. Individuals of M. albus were filmed moving across three different substrates: hard-packed sand, small loose pebbles, and small fixed pebbles. Fixed pebbles were secured onto the substrate and to each other with glue. We found that substrate did affect movements such as distance ratio and wave amplitude. This research, which is part of a larger comparative study on terrestrial movement in highly elongate fishes, will identify how different substrates may facilitate or constrain movement on those fishes that mostly rely on lateral undulation of the axial skeleton.
