Patterns and processes in amphibious fish: biomechanics and neural control of fish terrestrial locomotion

Abstract

Amphibiousness in fishes spans the actinopterygian tree from the earliest to the most recently derived species. The land environment requires locomotor force production different from that in water, and a diversity of locomotor modes have evolved across the actinopterygian tree. To compare locomotor mode between species, we mapped biomechanical traits on an established amphibious fish phylogeny. Although the diversity of fish that can move over land is large, we noted several patterns, including the rarity of morphological and locomotor specialization, correlations between body shape and locomotor mode, and an overall tendency for amphibious fish to be small. We suggest two idealized empirical metrics to consider when gauging terrestrial ‘success’ in fishes and discuss patterns of terrestriality in fishes considering biomechanical scaling, physical consequences of shape, and tissue plasticity. Finally, we suggest four ways in which neural control could change in response to a novel environment, highlighting the importance and challenges of deciphering when these control mechanisms are used. We aim to provide an overview of the diversity of successful amphibious locomotion strategies and suggest several frameworks that can guide the study of amphibious fish and their locomotion.

Behaviour and muscle activity across the aquatic–terrestrial transition in Polypterus senegalus

“…While many studies have investigated how fishes move in a terrestrial environment (reviewed in Pace and Gibb, 2014 ; Lutek et al, 2022 ), less is known about how motor control and sensory information elicit terrestrial behaviour in amphibious animals ( Cabelguen et al, 2010 ; Foster et al, 2018 ; Gillis, 2000 ; Horner and Jayne, 2014 ; Perlman and Ashley-Ross, 2016 ). Studies that investigate fish muscle activation in fully aquatic or terrestrial environments often report statistically significant differences in muscle activity parameters between the two environments ( Foster et al, 2018 ; Gillis, 2000 ; Horner and Jayne, 2014 ; Perlman and Ashley-Ross, 2016 ).…”