Moving in two worlds: aquatic and terrestrial locomotion in sea snakes (Laticauda colubrina, Laticaudidae)

Abstract

Yellow‐lipped sea kraits (Laticauda colubrina) are amphibious in their habits. We measured their locomotor speeds in water and on land to investigate two topics: (1) to what degree have adaptations to increase swimming speed (paddle‐like tail etc.) reduced terrestrial locomotor ability in sea kraits?; and (2) do a sea krait’s sex and body size influence its locomotor ability in these two habitats, as might be expected from the fact that different age and sex classes of sea kraits use the marine and terrestrial environments in different ways? To estimate ancestral states for locomotor performance, we measured speeds of three species of Australian terrestrial elapids that spend part of their time foraging in water. The evolutionary modifications of Laticauda for marine life have enhanced their swimming speeds by about 60%, but decreased their terrestrial locomotor speed by about 80%. Larger snakes moved faster than smaller individuals in absolute terms but were slower in terms of body lengths travelled per second, especially on land. Male sea kraits were faster than females (independent of the body‐size effect), especially on land. Prey items in the gut reduced locomotor speeds both on land and in water. Proteroglyphous snakes may offer exceptional opportunities to study phylogenetic shifts in locomotor ability, because (1) they display multiple independent evolutionary shifts from terrestrial to aquatic habits, and (2) one proteroglyph lineage (the laticaudids) displays considerable intraspecific and interspecific diversity in terms of the degree to which they use terrestrial vs. aquatic habitats.

Foraging ecology of sea kraits Laticauda spp. in the Neo-Caledonian Lagoon

“…This assumption is supported by previous reports of snake behaviour (e.g. Saint Girons 1964, Guinea 1986) and by the marked impairment of a snake's swimming ability caused by a prey item in the stomach (Shine & Shetty 2001). Sea kraits are vulnerable to predators such as sharks (Ineich & Laboute 2002) and therefore apparently return to land as soon as they have fed.…”

Locomotor behavior across an environmental transition in the ropefish,Erpetoichthys calabaricus

“…Although we attempted to select trials where fish moved at similar velocities, fish did not appear capable of moving at the same velocity across all treatments (Table1). However, other studies have also found that the very slowest gaits for aquatic locomotion are still faster than terrestrial locomotion for organisms that are primarily aquatic (Shine and Shetty, 2001;Pace and Gibb, 2009 , anterior body oscillations are minimal (Lauder and Tytell, 2006). Thus, it seems unlikely that our finding that anterior oscillations increase as the water level is lowered is because of the minimal velocity differences between our treatments (see 'Results').…”

“…Despite the tractability and simplicity of elongate fish as a model system in which to address this question, few studies have directly compared axial-only locomotion in aquatic versus terrestrial environments. In addition, most such studies have considered only undulation frequency and/or overall animal velocity (Jayne, 1986;Shine and Shetty, 2001;Shine et al, 2003), with a much smaller subset encompassing other kinematic variables (Gillis, 1998;Ellerby et al, 2001). …”

One foot out the door: limb function during swimming in terrestrial versus aquatic turtles

“…Species that specialize for particular environments often exhibit performance costs in contrasting environments [1,2]. In some cases, specializations following major habitat transitions become so extreme that a species might rarely, if ever, encounter the contrasting, ancestral habitat [3].…”