Sabine Renous

Gait parameters of treadmill versus overground locomotion in mouse

Many studies of interest in motor behaviour and motor impairment in mice use equally treadmill or track as a routine test. However, the literature in mammals shows a wide difference of results between the kinematics of treadmill and overground locomotion. To study these discrepancies, we analyzed the locomotion of adult SWISS-OF1 mice over a large range of velocities using treadmill and overground track. The use of a high-speed video camera combined with cinefluoroscopic equipment allowed us to quantify in detail the various space and time parameters of limb kinematics. The results show that mice maintain the same gait pattern in both conditions. However, they also demonstrate that during treadmill exercise mice always exhibit higher stride frequency and consequently lower stride length. The relationship of the stance time and the swing time against the stride frequency are still the same in both conditions. We conclude that the conflict related to the discrepancy between the proprioceptive, vestibular, and visual inputs contribute to an increase in the stride frequency during the treadmill locomotion.

Asymmetrical gaits of juvenile Crocodylus johnstoni, galloping Australian crocodiles

Seven juvenile individuals of the Australian species Crocodylus johnstoni from the Frankfurt Zoological Park were filmed on high-speed video, at 250 fields s −1 , whilst freely moving at various speeds in a long corridor. The sequences of locomotion were analysed to determine the various space and time parameters to characterize limb kinematics. We found that the animals use diverse patterns of asymmetrical gait, revealing great flexibility in limb co-ordination. In all these gaits, the forelimb strikes the ground first, in the couple made by diagonally opposite fore- and hindlimbs. Among these gaits, rotary gallop offers probably a high level of manoeuvrability, whereas transverse gallop resulted in a higher level of stability. Speed increase is achieved by half-bound and bound, the latter being the only gait used at velocities > 2 m s −1 . Speed was increased mainly by increasing the stride length of the fore- and hindlimbs by simultaneously increasing both its components, the step and swing lengths. However, in bound, the step length of each forelimb increased more than the swing length, resulting in a stronger thrust action, whereas swing length increased more than step length for the hindlimb, causing the centre of mass to accelerate forwards during its ballistic phase. The asymmetrical gaits of crocodiles such as Crocodylus johnstoni are probably not functionally equivalent to the transitional asymmetrical gaits exhibited by lizards when building up into a bipedal run. These gaits are also not entirely equivalent to mammalian gaits, despite the use of vertical movements of the vertebral axis in these crocodiles, favouring an erect dynamic posture.

Geometric morphometrics of the shoulder girdle in extant turtles (Chelonii).

The aim of this study was to identify shape patterns of the shoulder girdle in relation to different functional and environmental behaviours in turtles. The Procrustes method was used to compare the shoulder girdles (scapula and coracoid) of 88 adult extant turtles. The results indicate that four shape patterns can be distinguished. The shoulder girdles of (1) terrestrial (Testudinidae), (2) highly aquatic freshwater (Trionychidae, Carettochelyidae) and (3) marine turtles (Cheloniidae, Dermochelyidae) correspond to three specialized morphological patterns, whereas the shoulder girdle of (4) semi‐aquatic freshwater turtles (Bataguridae, Chelidae, Chelydridae, Emydidae, Kinosternidae, Pelomedusidae, Platysternidae, Podocnemididae) is more generalized. In terrestrial turtles, the long scapular prong and the short coracoid are associated with a domed shell and a mode of locomotion in which walking is predominant. By contrast, highly aquatic freshwater turtles share traits with marine turtles. In both, the short scapular prong and the long coracoid are associated with a flat shell, and swimming locomotion. The enlarged attachment sites of the biceps, coracobrachialis magnus, and supracoracoideus also give these strong swimmers a mechanical advantage during adduction and retraction of the arm. Increasing size leads to allometrical shape changes that emphasize mechanical efficiency both in terrestrial and in aquatic turtles.

A giant Upper Jurassic turtle revealed by its trackways

Exceptional fossilization of large tetrapod swimming traces occurs in the Cerin Lagerstatte (Jura Mountains, France). These trackways are imprinted in Jurassic (Late Kimmeridgian) lagoonal fine-grained limestones and are attributed to giant turtles, which swam with a simultaneous movement of their forelimbs like the modern ones. These turtles swam in very shallow waters close to land, perhaps near a nesting area. As a major consequence, these new ichnologic data place the origin of true large marine turtles during the Jurassic period and not during the Cretaceous period as previously considered on the basis of skeletal remains.

Limb joints kinematics and their relation to increasing speed in the guinea pig Cavia porcellus (Mammalia: Rodentia)

The kinematics of each joint of the guinea pig Cavia porcellus were studied during the locomotor cycle at increasing speed by high-speed cinefluorography. The main objective was to reveal the functional specific features of these structural elements in each dynamic phase of the cycle and also which limb joints are important during the increase of animal speed. Most of the analysed angles in C. porcellus were affected as the speed increased, both in trot and gallop. However, only a few of them were correlated with speed. There were also differences with respect to symmetrical or asymmetrical gaits. Both pairs of limbs responded differently to the increase of speed; while the forelimb joints modified the duration of their action (frequency) more than the amplitude (stride length), the hindlimbs acted inversely. The movements of the joints during the stance phase changed dramatically with speed, particularly in the hindlimb. At knee level, the flexion amplitude increases to maintain the stiffness of the leg spring, a principle previously discussed as essential for the running process. In the swing phase, inertial effects are the main constraints and, as in the stance phase, the knee joint in the swing phase is correlated with speed both during trot and gallop, confirming the major importance of this joint to increasing speed.

Immunocytochemical characteristics of elbow, knee and ankle muscles of the five-toed jerboa (Allactaga elater)

Biochemical adaptations of limb myofibres to intensive bipedal hopping were investigated using the five‐toed jerboa Allactaga elater as a model in comparison with the rat. Immunofluorescence methods included immunoreactivity to anti‐fast and anti‐slow MHC and troponin I. There is no specialization of triceps caput mediale for postural function in the minute non‐locomotor forelimbs, unlike quadruped mammals. The various elbow extensor heads and the flexor muscles are alike with regard to fibre type population and cross‐sectional areas of each type of fibre. The extensor muscle in the elongated hindlimbs of the five‐toed jerboa, at both the knee and the ankle joints, differ from each other extensively. One head, made up of an extremely high percentage of type I, fatigue‐resistant fibres, is suited to postural function. Two extensor heads at each joint contain a very high percentage of type IIB fibres (having the greatest maximal velocity of contraction) and are able to produce the powerful acceleration needed to trigger the leap. The relative cross‐sectional areas of the myofibres are characteristic of hopping locomotion: predominance in number of one type of myofibre in a muscle accompanies greater cross‐sectional area, which increases muscle efficiency in either postural or accelerative function of the muscle.

Respective Role of the Axialand Appendicular Systems in Relation to the Transition to Limblessness

In lower quadrupedal vertebrates locomotor efficiency seems to result from the associate movements of the axial and appendicular systems, which are totally independent in structure and embryological origin. The curvature of the trunk, produced by a standing wave, magnifies the propulsive action of the limbs. In intermediate forms, the association of an elongate trunk with limbs reduced in size brings about functional consequences which may be noticeably diverse according to the degree of trunk elongation and limb reduction. According to environmental constraints, animals search for better locomotor efficiency, which implies the maintenance or breakage of this association of both locomotor systems. In some cases, limb action on the ground is added to the axial wave action through a perfect mutual adjustment of rhythmic activity, until mechanical inefficiency of the limbs is reached by possible loss of contact with the ground. In other cases, the limbs dragged on the ground during the stance phase act against the axial action or, on the contrary, are inhibited by the axial system. A review of available data tries to contribute to an understanding of the respective roles of both systems in the transition to limblessness.

Comments on the pelvic appendicular vestiges in an amphisbaenian: Blanus cinereus (Reptilia, squamata)

A detailed description of muscular and skeletal features of the pelvi‐cloacal region of the amphisbaenian Blanus cinereus reveals that the species has real hind limbs articulating with a real pelvic girdle. Arguments support this homology: 1) a link with the vertebral column; 2) a movable articulation, showing all the features of a diarthrosis, between the femur and the acetabulum; 3) all the long bone characteristics for the femur which distally bears a horny element. The morphological peculiarities of the amphisbaenian pelvic girdle are generally close to those of lizards, but the pubis seems to be more reduced. For the same number of precloacal vertebrae, the amphisbaenians have more appendicular elements than lizards have, and this composition recalls that of the Leptotyphlopidae, Aniliidae, and Boidae. The account provides more information concerning the aponeuro‐tendinous system associated to the skeleton of the girdle and the hindlimb, the musculature, and the interrelations between the different structures of the pelvi‐cloacal region.

Locomotion patterns in two South American gymnophthalmid lizards: Vanzosaura rubricauda and Procellosaurinus tetradactylus

We quantified gait and stride characteristics (velocity, frequency, stride length, stance and swing duration, and duty factor) in the bursts of locomotion of two small, intermittently moving, closely related South American gymnophthalmid lizards: Vanzosaura rubricauda and Procellosaurinus tetradactylus. They occur in different environments: V. rubricauda is widely distributed in open areas with various habitats and substrates, while P. tetradactylus is endemic to dunes in the semi-arid Brazilian Caatinga. Both use trot or walking trot characterised by a lateral sequence. For various substrates in a gradient of roughness (perspex, cardboard, sand, gravel), both species have low relative velocities in comparison with those reported for larger continuously moving lizards. To generate velocity, these animals increase stride frequency but decrease relative stride length. For these parameters, P. tetradactylus showed lower values than V. rubricauda. In their relative range of velocities, no significant differences in stride length and frequency were recorded for gravel. However, the slopes of a correlation between velocity and its components were lower in P. tetradactylus on cardboard, whereas on sand this was only observed for velocity and stride length. The data showed that the difference in rhythmic parameters between both species increased with the smoothness of the substrates. Moreover, P. tetradactylus shows a highly specialised locomotor strategy involving lower stride length and frequency for generating lower velocities than in V. rubricauda. This suggests the evolution of a central motor pattern generator to control slower limb movements and to produce fewer and longer pauses in intermittent locomotion.

Effects of Surface Roughness on the Locomotion of a Long-Tailed Lizard, Colobodactylus taunayi Amaral, 1933 (Gymnophthalmidae: Heterodactylini)

We analyzed the locomotor behavior of a long-tailed, forest floor, and leaf litter lizard, Colobodactylus taunayi, a species that retains the generalized Gymnophthalmidae Bauplan whilst presenting the discrete toe reduction associated with the Bachia-like pattern of limb reduction. We videotaped individuals moving on four substrates with increasing degrees of roughness: plastic, wooden board, glued sand, and glued gravel. Significantly higher speeds occurred on the last two substrates. As with most other limbed animals, increased speed was significantly correlated with simultaneous increases in both stride length and stride frequency. Independently of the kind of substrate, C. taunayi used rather slow lateral sequence walking trots. In contrast to other ectothermic tetrapods, and especially other Gymnophthalmidae, this species lacked perceptible lateral flexion of either the trunk or the tail to effectuate these slow gaits.