Open AccessNouvelles données sur 'encéphalisation des Reptiles Squamates
Author(s) -
Platel Par Roland
Publication year - 1975
Publication title -
journal of zoological systematics and evolutionary research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.769
H-Index - 50
eISSN - 1439-0469
pISSN - 0947-5745
DOI - 10.1111/j.1439-0469.1975.tb00507.x
Subject(s) - biology , squamata , intraspecific competition , encephalization , allometry , lacertidae , zoology , interspecific competition , ecology , brain size , lizard , sauria , medicine , magnetic resonance imaging , radiology
SUMMARY New datas on the level of encephalization of Squamate Reptiles This study carried out on 32 species of Lizards, 15 species of Snakes and one Amphisbaenian, the measure of the brain‐weight (Brw) and the body‐weight (Bdw) of which leads to the determination of the a and k parameters of the SNEL'S formula: Brw = k – Bdw α . In a first stage we are able to demonstrate with 9 species of Saurians and 2 species of Ophidians, each species being represented by a sample the size of which variing between 30 to 80, that the intrinsic variability of the brain gives a mean value of 6.4 % (isoponderal variability) or 7.5 % (isometric variability). The intraspecific α coefficients (allometric coefficients of growth or of size) remain between.383 and.500; the mean value of which, .43 will be considered as a characteristic of the order Squamata. The interspecific α. coefficient (filiation coefficient of BAUCHOT and PLATEL) given by the 32 species of Lizards is .669 , quite close to those previously calculated from a sample of 23 species (.686). The former values of the indices of encephalization belonging to these 23 species are meanwhile different. Six Lacertidae, selected as referrence Saurians (α= 627) lead to new indices of encephalization, the value of which will not be henceforth altered by the addition of new species to our present sample of Saurians. The various adaptative peculiarities roughly expressed by these indices of encephalization will be shortly studied in detail by the way of the volumetric analysis of the nuclear components of the brain. Amongst the 15 Snakes, the discrimination of 3 Henophidians and 12 Caenophidians leads for the last ones to an a filiation coefficient of .664; the value found for the Henophidians (.750) must be considered with suspicion because it get from only 3 species. We find with Anguis , the Amphisbaenian, some Scincidae and all the Snakes a low level of encephalization linked to the legless condition, which masks perhaps another peculiarities related to the evolutive processus which leads from Lizards to Snakes. The analyses of the K /Bdw relationship leads to results which differ from those found by BAUCHOT with the Insectivores‐Primates. Separately Saurians and Ophidians do not show any correlation between the coefficient of encephalization and the body‐weight; in compensation the Squamata in a whole show characteristics which express a negative rate of encephalization.