Search

After the suggestion of the genus Bitis Gray, 1842 snakes, we studied in details three species, among the largest and most widespread ones: Bitis arietans, Bitis gabonica and Bitis nasicornis. The main morphological characteristics and some of the zoological data presented may be very useful, as well as the clinical signs, for physicians to identify, the snake that bits a patient. Thus, an adapted treatment can be undertaken. The biochemical composition of the venoms and their experimental toxicity are also presented for a better understanding of the clinical symptoms.

The volumetric measure of the main subdivisions of the telencephalon has been carried on 24 species of Lizards and 2 species of Snakes. The studied structures are termed as follows: main and accessory olfactory bulbs, medial cortex (M 1 and M 2), dorsal cortex (D 1, D 2 and D 3), lateral cortex (L), Septum, Tuberculum olfactorium, dorsal and ventral striatum, amygdala and nucleus sphaericus. The analysis of the datas makes use of the SNEL L's formula which relates the volume of the various telencephalic subdivisions (V) to the somatic weight (S): V = k x S alpha. Each alpha value is compared to the value of the coefficient of allometry (A) of the whole brain. The evolutive (phylogenetic) growth of a structure is said fast (or slow) when its corresponding alpha value is higher (or lower) than the encephalic A value. At the cortical level such analysis shows the progressive nature of the dorsal cortex. A partition of the sample into Lacertomorpha (14 species) and Dracomorpha (10 species) (in agreement with the NORTHCUTT'S definition of his Type I and Type II Lizards) corroborates this cortical detail, more distinctly with the second group as well (especially for the D 2 portion). Moreover the high number of progressive structures among the Dracomorpha leads to consider this group as phylogenetically the most advanced in the Order of Lizards. The somatic indices are calculated according the allometric characteristics of the Reference Lizards. The judicious choice of some species allows to show how the development of a biological function may be expressed by the values of the indices of the related structures. For examples: dorsal cortex, dorsal striatum and mode of locomotion; olfactory bulbs, lateral cortex, part M 1 of the medial cortex and olfactory system; D 3 subdivision of the dorsal cortex and visual performances. The duality between Lacertomorpha and Dracomorpha is therefore corroborated by significant differences found for the various indices of a great number of telencephalic subdivisions. It leads moreover to find, grosso modo, two functional types of Lizards: moving-on-the-ground and wellsmelling (mainly Lacertomorpha) on the one hand, arboreal and with a fine vision (mainly Dracomorpha) on the other hand. The isoponderal percentages take an useful illustration of these results; it allows to establish the telencephalic pattern of a standard Lizard in which the pallium keeps the larger part (42%); in the pallium itself, the M 1 subdivision of the medial cortex has the most important percentage, a little more than the D 2 part of the dorsal cortex. A comparative study carried on 2 Snakes gives for Boa constrictor the lowest values of the indices, for almost all the structures. In return Natrix natrix stays, for a great number of structures, close to the level of the legless Lizards; this last result confirms distinctly the two levels of telencephalization already found in Snakes (PLATEL, 1976 a).

The present paper using classical and transmission electron microscopy brings the first data on the pulp of the fangs of Viperidae (poisonous serpents with terrestrial or semi-aquatic habits). The pulp of the fangs of Viperidae shows a poor collagen and fibroblast content and a high developed vascular system. The odontoblasts are polarized, with a high organelle content. The interconnections are constituted of lateral "gap junction" systems. At a late secretion stage, the odontoblastic processes show a poor cytoplasm, mainly constituted of microfilaments.

A case of a double-headed Viperine Snake Natrix maura (Linné, 1758) hatching is reported. Its two heads are side by side, about equally and perfectly developed and the neck is dual for the 8 first vertebras. Two post-pharyngeal fistulas and dissymetries in the cephalic markings and scales are noted. The origin of such an anterior dichtomy is discussed.

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 present study, using classical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, infrared spectroscopy, has shown the dental hard tissues of the fangs of Viperidae (poisonous serpents with terrestrial or semi-aquatic habits) to be constituted of: a calcified outer layer, 0.4 microns thick, made of very small needle-like crystals, randomly distributed. The calcified outer layer contains organic invaginations inducing pores at the surface and many collagen fibres incompletely mineralized, which may suggest enameloid. a calcified inner layer, in the wall of the poison canal. The calcified inner layer, 0.6 microns thick, is constituted of very small crystals, which are parallel to each other and perpendicular to the calcified outer layer. It might be the inner layer of enameloid, an orthodentine, whose tubules present a special lateral branching system resembling a fish bone. The TEM data, which show the dentine to be constituted of very small ill-defined crystals and incompletely mineralized collagen fibres are corroborated by chemical analyses which reveal a poorly mineralized apatite with high carbonate content.

Morphological, morphometrical and histochemical studies of the cell types in the salivary glands of Philodryas patagoniensis have been performed. It is concluded: 1) the acini of supra, infralabial and premaxillary glands are formed by mucous and mucoserous cells; the Duvernoy's gland by seromucous cells; 2) mucous cells show neutral and sulphated mucosubstances and sialic acid; mucoserous cells show neutral mucosubstance, sialic acid and protein radicals; seromucous cells of Duvernoy's gland show neutral mucosubstance and protein radicals. The acinar area, height of tubule and duct cells, and nuclear volume of acinar, tubule and duct cells were evaluated morphometrically.

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.

It is stated that there are sufficient different morphological characteristics in order to distinguish the sexes with a certain practice, but that each of these characteristics by itself does not alone represent a completely valid criterium. These observations have shown in the periods of reproduction a chifting of six months after six years of captivity. Then the various phases of sexual behaviour are related: the male-fight, the courtship, the conquest of the partner by sexual display and finally the copulation. It is established moreover that the period between the copulation and parturition does not necessarily constitute the duration of gestation, which seems in fact shorter because of retarded fertilizations. However, there is quite a constant average of a period of gestation of 200 days. There follows a complete inventory of the 29 copulations and 67 layings that were observed.

Telencephalic afferents and efferents of the dorsal cerebral cortex of the Viper were examined using neurohistological techniques of orthograde degeneration (Fink-Heimer) and intra-axonal transport of HRP. Feed-back loops between the dorsal and medial cortex as well as between the dorsal cortex and septum were demonstrated.