Landing in basal frogs: evidence of saltational patterns in the evolution of anuran locomotion

Abstract

All frogs are assumed to jump in a similar manner by rapidly extending hindlimbs during the propulsive phase and rotating the limbs forward during flight in order to land forelimbs first. However, studies of jumping behavior are lacking in the most primitive living frogs of the family Leiopelmatidae. These semi-aquatic or terrestrial anurans retain a suite of plesiomorphic morphological features and are unique in using an asynchronous (trot-like) rather than synchronous "frog-kick" swimming gait of other frogs. We compared jumping behavior in leiopelmatids to more derived frogs and found that leiopelmatids maintain extended hindlimbs throughout flight and landing phases and do not land on adducted forelimbs. These "belly-flop" landings limit the ability for repeated jumps and are consistent with a riparian origin of jumping in frogs. The unique behavior of leiopelmatids shows that frogs evolved jumping before they perfected landing. Moreover, an inability to rapidly cycle the limbs may provide a functional explanation for the absence of synchronous swimming in leiopelmatids.

Reduce torques and stick the landing: limb posture during landing in toads

“…This species does not exhibit any hindlimb flexion during the aerial phase and, as result, consistently crashes into the substrate with its head or torso (Essner et al, 2010). Authors attribute such inelegant landings to the delayed flexion of the hindlimb in these species (Essner et al, 2010). In contrast, the toads used in our study flex their hindlimbs rapidly and achieve a relatively flexed posture before impact with the substrate (Fig.…”

“…The importance of hindlimb flexion is best exemplified by the relatively extreme landing behavior of the basal tailed frog (Ascaphus montanus). This species does not exhibit any hindlimb flexion during the aerial phase and, as result, consistently crashes into the substrate with its head or torso (Essner et al, 2010). Authors attribute such inelegant landings to the delayed flexion of the hindlimb in these species (Essner et al, 2010).…”

“…In contrast, the mechanics of landing tend to vary significantly among different anuran radiations. For example, species from basal radiations tend to land rather inelegantly, performing what amounts to a 'belly flop' during each landing (Essner et al, 2010). This pattern has led to the hypothesis that a finely tuned landing behavior may be a derived characteristic among certain radiations (Essner et al, 2010).…”

“…For example, species from basal radiations tend to land rather inelegantly, performing what amounts to a 'belly flop' during each landing (Essner et al, 2010). This pattern has led to the hypothesis that a finely tuned landing behavior may be a derived characteristic among certain radiations (Essner et al, 2010). Landing is also rather inconsistent in semi-aquatic species (Family: Ranidae), where the chest, torso or legs frequently contact the substrate during landing (Nauwelaerts and Aerts, 2006;Essner et al, 2010).…”

“…This pattern has led to the hypothesis that a finely tuned landing behavior may be a derived characteristic among certain radiations (Essner et al, 2010). Landing is also rather inconsistent in semi-aquatic species (Family: Ranidae), where the chest, torso or legs frequently contact the substrate during landing (Nauwelaerts and Aerts, 2006;Essner et al, 2010). However, landing behavior in toads is characterized by a controlled deceleration accomplished solely with the forelimbs (Gillis et al, 2010;Akella and Gillis, 2011).…”