La diversité floristique de la végétation psammophile de la région de Tlemcen (nord–ouest Algérie)

This study is devoted to the analysis of the psammophyte of the coastal and semi-continental dunes in Tlemcen. Interesting results have been obtained, in particular, on the biological and ecological aspects of the psammophyte. The interpretation from Factoriel analysis of correspondences enabled us to identify the different phytosociological classes (Cakiletea maritimae, Ammophiletea, Quercetea ilicis, Therobrachypodietea and Stellarietea mediae). Some of these classes (Cakiletea maritimae and Ammophiletea) inhabit, exceedingly well, the embryonic dunes. Some species (Therobrachypodietea) colonize the quickset dunes. Lastly, some others (Quercetea ilicis) settle in the more mature and stable dunes. By using the phytosociological and phytodynamical data, we have been able to understand the vegetation and its diversity. To cite this article: H. Stambouli-Meziane et al., C. R. Biologies 332 (2009).     

La répartition spatiale des différents stades de Coccinella septempunctata dans un champ de blé: variation au cours de la saison

Résumé Au début du printemps les adultes de Coccinella septempunctata L. (Col., Coccinellidae) issus des sites d'hivernation, les larves et les nymphes qui en proviennent, fréquentent le sol et les parties basses du blé. En juin, les adultes nés dans le champ et leur descendance sont dispersés sur toute la hauteur des talles bien qu'une fraction non négligeable de leur population se rencontre à l'extrémité supérieure. La plupart des pontes sont déposées sous les mottes de terre, les pierres et les petites adventices qui constituent des sites privilégiés. Ces variations de la distribution de cette coccinelle peuvent être mises en relation avec le climat, en particulier la température, avec la thermophilie de cette espèce et avec la répartition sur les différentes parties des talles des 3 espèces de puceron qui se succèdent au cours de la saison. Ces observations sont importantes à considérer lors du choix ou de la mise au point d'une méthode d'échantillonnage.     

Etude de quelques propriétés de la phosphofructokinase érythrocytaire de l'homme normal

Human erythrocyte phosphofructokinase was purified 150 fold by DEAE cellulose adsorption and ammonium sulfate precipitation.At pH 7,5 the enzyme exhibits allosteric kinetics with respect to ATP, fructose 6 phosphate, and Mg²⁺.ATP at high concentration acted as an inhibitor and ADP, 5′AMP, 3′,5′, AMP, acted as activators. Both effectors seemed to decrease the homotropic interactions beetween the fructose 6 phosphate molecules.The activators increased the affinity of phosphofructokinase for the substrate (F6P), the inhibitor decreased it.These ligands had no effect on the maximum velocity of the reaction except in the case of ADP.Interactions between the substrates and the effector ligands on the enzyme were considered in terms of the Monod - Changeux - Wyman model for allosteric proteins.With GTP and ITP, no inhibition was observed. At saturing concentration of GTP, ATP still inhibited phosphofructokinase.Both 3′5′ AMP and fructose 6 phosphate increased the concentration of ATP required to produce an inhibition of 50 %.Citrate, like ATP, inhibited phosphofructokinase by binding most likely at the same allosteric site. Erythrocyte phosphofructokinase is inhibited by 2–3 DPG.The study of the relation log V max = f (pH) suggested, that the active center contains at least one imidazole and one sulfhydryl group.     

Patines et cortex de météorisation de grès du site rupestre d’Oum La Leg (Anti-Atlas, Maroc)

Within the framework of the European Commission's program “Patine du Desert” (DG Research; INCO-CT-FP6-2004-509100), partially concerning the preservation of Saharan engraved rock art, the approach led to the study of the sandstone patina from the rock art site of Oum La Leg (Anti-Atlas, Morocco). The rock and its Tazina school engravings are sometimes covered with a thin brown-ochre coating which only shows a dark patina, the desert patina. This film corresponds to a weathering cortex whose formation is contemporary with wet events from the Holocene period. On the surface, the patinas’ diversity is linked to the heterogeneous distribution of manganese oxides (birnessite and todorokite) due to a reorganisation which led to the incorporation of aeolian silts. Some dating suggestions are made to establish an ante quem age for the engraved lines.     

Accumulations osseuses en périphérie de terriers de petits carnivores : les stigmates de prédation et de fréquentation

Faunal remains from spoil heaps of two burrows inhabited by small carnivores (fox and badger) are analysed from a taphonomical point of view. This analysis provides characteristics for bone accumulation produced by small carnivores and will be a powerful tool for deciphering site formation about the occupational alternation of small carnivores and humans. Identified species were grouped by size classes. Faunal spectrum is composed by varied species of microfauna (70%), mesofauna (30%). Macromammal remains are under represented (less than 1%) and come from scavenged carcasses. Predators and consumed species are compared on the basis of the skeletal part representation, age classes and recording of predation marks (gnawed and digested bones). Skeletal part representation shows that all taxons exhibit a low-representation of axial skeleton and autopodial bones. Predators show a high representation of hind limb bones and a low representation of the fore limb bones whereas consumed species exhibit a reverse pattern. Mortality curve analysis provides an attritional profile for carnivores and helps for the establishment of the season of occupation of the burrow. Adults largely dominate consumed species. Moreover, predation marks are found in 1% of the carnivores’ bones and from 15% to more than 40% on prey bones. The large-sized prey bones only wear gnawed marks (20%) and anthropic marks (10–20%) whereas microfaunal remains exhibits more digested marks (40%) than gnawing stigmata (5%). Medium-sized animals bones wear both marks and with the same proportions (10–15%).