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 axial and 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.

[Cranial morphology of an American siphonopid, Microcaecilia unicolor (Amphibia, Gymnophiona) and its functional interpretation]. / Morphologie cranienne d'un Siphonopidé américain, Microcaecilia unicolor (Amphibien, Gymnophione) et interprétation fonctionnelle.

The skull of Microcaecilia unicolor, american Siphonopidae (Amphibia, Gymnophiona), shows 3 notable morphological characteristics: The mandibular shortening, the verticalization of the retroarticular process, and the verticalization of the quadrate. They define a peculiar morphofunctional pattern, which seems to exist in dwarf forms moving in the complex root system of trees. These morphological characters, associated with modifications of the muscle depressor mandibulae, give functional advantages: A wider gaping of the mouth and the ability of the ingestion of preys which have a great cross-section. In keeping its macrophageous habits, Microcaecilia unicolor does not compete with other dwarf vertebrates living in the same environment and feeding on microinvertebrates.

[The mechanism of digging in Arvicola terrestris and Spalax ehrenbergi: functional and evolutional studies]. / Les mécanismes du fouissage chez Arvicola terrestris et Spalax ehrenbergi: étude fonctionelle et évolutive.

The cineradiographic study of the digging modalities in Arvicola terrestris and Spalax erenbergi showed important convergences in the mechanisms used by both species. Head and incisors are the burrowing tools, acting as a "scraping-shovel" in Spalax and as a "scratching-shovel" in Arvicola. They are moved forward by a force originated by the pressure of the hind limbs against the ground, and transmitted through the vertebral axis. The myological study of these species revealed the increase of the insertional areas for the cephalic muscles. However, the adaptative answer of the cervical vertebrae to the mechanical constraints of digging are different in Arvicola and Spalax; the former developed high resistance moments and the latter increased vertebral stiffness. The characters of the post-cranial skeleton in the digging rodents tend to constitute a morphocline in which Spalax is the final stage and Arvicola an intermediate stage. Then, the adaptative divergences noted above between these animals might reflect their phyletic distance.

Patterns of correspondence between skin rings and vertebrae in gymnophiona (Amphibia).

The skin annulation seems to have a direct relation with the vertebral column segmentation. The type of rings, primary, secondary, tertiary, or quaternary set by binary division, probably results in an induction process during morphogenesis. The diverse stages of this division appear and are rubbed out from front to rear. The topographical correspondence is different for 3 distinct parts of the body: the collar, the trunk, and the posterior part. In this last region, we can find a more or less reduced true tail or a terminal appendage without vertebral element. All these new morphological data support elements of functional indications.

[Interpretation of the organization of the aortic arch in the Dibamus (Reptilia, Squamates) using findings obtained from various groups of Squamates serpentiformes]. / Interprétation de l'organisation des arcs aortiques de Dibamus (Reptiles, Squamates) à l'aide d'informations fournies par les autres groupes de Squamates serpentiformes.

The comparative study of the aortic trunks of Dibamus (subterranean limbless Squamate) and of the other Squamata shows the presence of an original vascular organization in the serpentiform animals submitted to the subterranean life constraints as Scolecophidia, Amphisbaenia, Dibamidae, Anniellidae, Feyliniidae, and some Scincidae (genus Acontias and Typhlosaurus). Nevertheless, the morphology of the systemic and carotidian trunks supplies only few informations on the phylogenetical status of Dibamus.

[The patterns of elongation of the anterior part of the body of limbless squamata]. / Réflexion sur les modalités d'élongation de la partie antérieure du corps des squamates apodes.

The interpretation of original features of the aortic trunks showed by subterranean limbless Squamata allows to propose a hypothesis about a particular pattern of elongation regarding the anterior part of these Reptiles. The comparative morphological data supplies some arguments to the idea of the breaking of the topographical link between "scapular level - heart level" and the insertion of a new "precardiac" region which produces a backward displacement of the heart.

[The use of cladistic principles in the phylogeny and biogeography of the Lacerta]. / Application des principes cladistiques à la phylogénèse et la biogéographie des Lacertiliens.

The methodology used in Phylogenetics remains one of the more interesting problems in comparative biology. Among the methods used, the cladistic is the most accurate. In the present case, among the Saurians, the characters chosen appeared early and cannot be referred to any adaptation bound to an evolutive progress. We have successively considered their distribution in the classification, their polarity and one phylogenetic hypothesis based on the Hennig's concepts. Such a work leads necessarily to systematical conclusions. For instance, we note the heterogeneity of some families. Among the Iguania, the Iguanidea are polyphyletics, the north-american forms breaking up from the other very early. Among the Scincomorpha, the Lacertilia result from two parts of different origins. This research verifies some systematic cuttings in the modern classification: among the Anguimorpha, the separation between Helodermatidea and the group, Varanidea-Lanthanotidea. The characters studied show a non-random distribution in the classification and show also some consistency with the geographical distribution of the extant Saurians. Therefore, it is important to search for the most parsimonious geographical hypothesis, which is in concern with the present data on the continental drift and generally on the history of the Earth, and which strengthens the cladograms posed from the selected characters.

[Organization of the ventral branchial and lumbar horns of the spinal cord in embryos of snake-like and tetrapod reptiles]. / Organisation des cornes ventrales de la moelle épinière, dans les régions brachiale et lombiare, chez les embryons de Reptiles serpentiformes et de Reptiles à membres bien développés.

In embryos of Snake-like Reptiles (Anguis fragilis) and of Ophidians (Tropidonotus, Python), the lay-out of motor neuroblast in the ventral horns of the spinal cord, in the brachial and the lumbar regions differs from the one observed in the same regions of embryos of tetrapod Reptiles (Lacerta viridis).

[Reverberation of the hindlimb rudimentation on its innervation in squamate reptiles]. / Retentissement de la Rudimentation du Membre Posterieur sur son Innervation Chez les Reptiles Squamates.

When the dimensional reduction of the hind limb begins, a first caudal displacement of the lombar part of the lombo-sacral plexus - which involves the loss of the first root of the sacral part -- appears with a threshold in the increase in the number of presacral vertebrae. This a first indication of the serpentiform tendancy. Others thresholds can conduct to produce the disappearance of the sacral vertebrae and sacral root. The qualitative reduction only concerns the terminal branches of the plexus and does not seem to be associated with the vertebral elongation. If a caudo-proximal reduction of the brachial plexus occurs early in the lepidosaurian line and exists in all the Squamata, even in the Iguana which have well developed limbs, it is not the same for the reduction of the lombo-sacral plexus which does not appear in these Iguana. At last, if the reduction modalities of the both plexus are often differents, their supposed displacements facilitate the extension of the intermediate vertebral region.

[Synchronization of electromyographic and cinematographic recordings. Applications to vertebrate biomechanics]. / Synchronisation d'enregistrements électromyographiques et cinématographiques. Applications á la biomécanique des vertébrés

Synchronizing each frame of the cinema of a moving animal with the corresponding EMG of some muscles permits a precise interpretation of the variations of the electric potentials in that muscle with each phase of the movement. e.g. in the rabbit, three bundles of the masseter muscle function independently during the mastication; in the pigeon, electric potentials appear in both ilio-tibialis and biceps femoris muscles some frames before the actual raising of the leg, when the animal on its perch becomes out of balance.

[Details of the muscular and nervous system in the anterior member of Sphenodon punctatus (reptiles-Rhynchocephales)]. / Particularités des systèmes musculaire et nerveux du membre antérieur de sphenodon punctatus (reptiles-rhynchocéphales)

Sphenodom is the only Lepidosaurian with an organisation of the nervous ways in the anterior member which constitute an important stage in tetrapod evoluation. Squamata are exceptions. The radial nerve is developed and possesses the most important part of the fibres for the dorsal muscles of the forearm. The flexor canal is separated into 2 voluminous trunks.