Étude comparative des potentialités biologiques de deux trichogrammes:Trichogramma evanescens etTrichogrammatoidea lutea [Hym.: Trichogrammatidae]

Résumé La longévité, la fécondité, le nombre d'adultes émergés, le sex-ratio et le cycle de développement deTrichogramma evanescens Westwood etTrichogrammatoidea lutea Girault ont été étudiés sur un h?te de substitution (Anagasta kuehniella) ou sur un h?te naturel (Helicoverpa armigera), ainsi que le nombre d'œufs parasités par ces 2 espèces. La longévité des ♀♀ des 2 oophages est très influencée par l'alimentation. Une ♀ deT. evanescens nourrie vit 7 fois plus longtemps qu'une privée d'alimentation et celle deT. lutea 5 fois plus. La présence de l'h?te joue également un r?le non négligeable. La fécondité est plus élevée chezT. evanescens (42 œufs en moyenne) que chezT. lutea (31 œufs). Cependant le nombre moyen d'œufs deH. armigera parasités par ♀ ainsi que le nombre d'adultes émergés sont presque équivalents chez les 2 espèces parasito?des. Le sex ratio (♂♂/♀♀) est de 0,59 chezT. evanescens et de 0,71 chezT. lutea. Quant à la durée de développement, elle est plus longue chezT. evanescens que chezT. lutea aux basses températures (36 jours contre 30 jours à 15°C). Cette différence est moins marquée lors de l'augmentation de la température (4 h à 30°C). La température de 35°C s'avère néfaste pour le développement des 2 espèces oophages ce qui restreint la possibilité de leur utilisation en lutte biologique au Maroc. Des études complémentaires seront à développer pour vérifier leur aptitude dans les conditions de terrain.      

Sterol-phospholipid interactions in model membranes Effect of polar group substitutions in the cholesterol side-chain at C20 and C22

The interactions of phospholipids with four different cholesterol derivatives substituted with one OH or one keto group at position C₂₀ or C₂₂ of the side-chain were studied. The derivatives were the 22,R-hydroxy; 22,S-hydroxy; 22-keto- and 20,S-hydroxycholesterol. Two aspects of the interactions were investigated: (1) the effect of the cholesterol derivatives on the gel → liquid crystalline phase transition of dipalmitoylphosphatidylcholine (DPPC) and of dielaidoylphosphatidylethanolamine (DEPE) monitored by differential scanning calorimetry and (2) The effect on the lamellar → hexagonal H_II phase transition of DEPE monitored by DSC and by ³¹P-NMR to determine structural changes. The gel → liquid crystalline phase transition was affected by the cholesterol derivatives to a much larger extent in the case of DPPC than of DEPE. In both cases, there was a differential effect of the four derivatives, the 22,R-hydroxycholesterol being the less effective. In DPPC-sterol 1:1 systems, 22,R-hydroxycholesterol does not suppress the melting transition, the ΔH values becomes 7.1 kcal · mol^?1 as compared to 8.2 kcal · mol^?1 for the pure lipid. 22,S-OH cholesterol has a much stronger effect (ΔH = 3.1 kcal · mol^?1) and 22-ketocholesterol suppresses the transition completely. In DEPE mixtures of all these compounds, the melting transition of the phospholipid is still observable. The transition temperature was shifted to lower values (?13.5°C in the presence of 20,S-OH cholesterol). The ΔH of the transition was lowered by these compounds except in DEPE-22,R-OH cholesterol mixtures and the cooperativity of the transition (reflected by the width at half peak height) was reduced. The lamellar → hexagonal H_II phase transition was also affected by the presence of these cholesterol derivatives. The transition temperature value was depressed with all these compounds. 20,S-OH cholesterol was the most effective followed by 22,R-OH cholesterol. The ΔH of the transition was not strongly affected. The molecular interfacial properties of these derivatives were studied by the monomolecular film technique. It is most likely that 22,R-OH cholesterol due to the hydroxyl groups at the 3β- and 22,R-positions orients with the sterol nucleus lying flat at the air/water interface, since the compression isotherm of either the pure sterol or the DOPC-sterol mixture (molar ration, 1:1) monomolecular film exhibits a transition at approx. 103 Ų, corresponding to the area of revolution of the sterol nucleus. This remarkable property, due probably to the existence of a kink between the side-chain and the long axis of the steroid nucleus, might explain the smaller effect of this sterol on the melting transition of either PC or PE systems.     

The late Miocene mammals from the Konservat-Lagerstätte of Saint-Bauzile (Ardèche,France)

Diatomite deposits of Saint-Bauzile near Privas (Ardèche) in southern France have been known since more than two centuries for abundant and extremely well-preserved fossils of plants and animals. The radiometric dating brackets fossil-bearing horizons between 7.2 and 7.6 Ma, which is consistent with the biochronologic age given by fossil mammals, which are characteristics of the late MN11 zone, i.e. the second part of the late Miocene. The main interest of this site for mammals is that they are preserved almost “in the flesh”, as entire skeletons with bones in their anatomical connection, and often with skin and fur charred and forming a halo around the body. In this work, we studied the remains of a lagomorph, two rodents, an equid, a suid, a bovid and a rhino. The mode of preservation of mammals as entire bodies suggests sudden death and rapid burial of individuals.     

Density dependent selection incorporating intraspecific competition 1. A haploid model

A haploid model is introduced and analyzed in which intraspecific competition is incorporated within a density dependent framework. It is assumed that each genotype has a unique carrying capacity corresponding to the equilibrium population size when fixed for that type. Each genotypic fitness at a single multi-allelic locus is a function of a distinctive effective population size formed by adding the numbers of each genotype present, weighted by an intraspecific competition coefficient. As a result, the fitnesses depend upon the relative frequencies of the various genotypes as well as the total population size. Intergenotypic interactions can have a profound effect upon the outcome of the population. In particular, when the density effect of one individual upon another depends upon their respective genotypes, a unique stable interior equilibrium is possible in which all alleles are present. This stands in contrast to the purely density dependent haploid system in which the only possible stable state corresponds to fixation for the type with the highest carrying capacity. In the present model selective advantage is determined by a balance between carrying capacity and sensitivity to density pressures from other genotypes. Fixation for the genotype with the highest carrying capacity, for instance, will not be stable if it exerts a sufficiently weak competitive effect upon the other genotypes. In the diallelic case, maintenance of both alleles at a stable equilibrium requires that the net intragenotypic competition between individuals of like genotype be stronger than that between unlike types. As for purely density regulated systems, there may be no stable equilibria and/or regular and chaotic cycling may occur. The results may also be interpreted in terms of a discrete time model of interspecific competition with each haplotype representing a different species.     

A new Late Pleistocene non-anthropogenic vertebrate assemblage from the northern Iberian Peninsula: Artazu VII (Arrasate,Basque Country)

Late Pleistocene palaeontological sites without human intervention are limited in the Cantabrian region, and even more so those with a good state of preservation and rich biodiversity. A new vertebrate fossiliferous locality discovered at Kobate Quarry (Arrasate, northern Iberian Peninsula) is presented in this article. This site, in which remains of 40 different vertebrate taxa were accumulated, acted as a natural trap. The preliminary vertebrate faunal list includes five amphibian taxa, four reptiles, seven species of birds and 24 mammalian taxa. While small mammals are represented by 13 small mammal taxa (seven in the Order Rodentia, five in the Order Eulipotyphla, and one in the Order Chiroptera), the large mammal fauna comprises eleven species, including ungulates and carnivores. The palaeoecology inferred from this faunal assemblage suggests the existence of large forested areas with some grassland and a watercourse nearby, within a notably warm and humid climate. These palaeoenvironmental conditions, combined with AMS and AAR results carried out in macrofaunal bone samples, suggest that the deposit from Artazu VII would be located in the first half of the Late Pleistocene, in the Marine Isotope Stage (MIS) 5c.     

Siwalik synopsis: A long stratigraphic sequence for the Later Cenozoic of South Asia

The Tertiary sediments of northern Pakistan are an exceptional record of terrestrial sedimentation and represent most of Neogene time. Foremost is the Siwalik Group of the Potwar Plateau, for which multiple, superposed fossil levels span ∼18–6 Ma. Well-developed magnetostratigraphic control provides secure dating so that Siwalik fossil horizons may be interpolated into a time scale with resolution to 100,000 years. We describe the geographic setting of the Potwar, give an overview of the temporal distribution of faunas, and discuss changes in paleohabitat and paleoecology with coinciding faunal change, as seen from the Siwalik viewpoint. The long Siwalik biostratigraphy of many successive assemblages with its resolved time scale may be compared directly with other well-dated sequences. Immigrant arrival and timing of faunal change may be traced. The basins of the Iberian Peninsula show somewhat different timing of introduction of hipparionine horses, and faunal turnover in the Siwaliks clearly precedes the Vallesian crisis in Spain. In contrast to the increasingly seasonal precipitation of the late Miocene Potwar, the paleohabitat of coeval North China appears to have been moist and equable, with high diversity faunas. Continued development and comparison of resolved Neogene records allow increasing resolution of the patterns of faunal change on regional to global levels.     

Leucoencephalopathy with cerebral calcinosis in a young chimpanzee (Pan troglodytes) - a case report

CASE HISTORY: A 4-year-old chimpanzee (Pan troglodytes) had a clinical history of a 2-year progressive central nervous dysfunction including convulsions and severe paralysis. RESULTS: Gross pathology revealed cerebral atrophy, ventricular enlargement and a severe encephalomalacia with extensive calcifications. Histologically, the white matter showed diffuse demyelination as well as vascular and perivascular calcifications which also involved the basal ganglia. Blood vessels with less distinctive calcium deposits exhibited periodic acid Schiff positive hyalinosis. Large areas of necrosis, hemorrhage and intense gliosis were also present. Activation of astrocytes and macrophages was confirmed by immunohistochemical methods. CONCLUSIONS: The etiology of the leucoencepalopathy could not be ascertained by macroscopic, histological and immunohistochemical examinations. Potential differential diagnoses include the rarely occurring Fahr's disease in humans, arteriosclerosis, storage disease and the Aicardi-Goutières syndrome. Based on the results of the postmortal examinations Fahr's disease is regarded as the most likely diagnosis in the present case of the chimpanzee.     

First mammal species identified from the Upper Cretaceous of the Rusca Montană Basin (Transylvania,Romania)

Multituberculate mammals are scarce in the Late Cretaceous of Europe, being recorded exclusively from the Maastrichtian terrestrial deposits of the Ha?eg and Transylvanian basins, in Romania. Moreover, they all belong to the endemic and primitive cimolodontan family Kogaionidae. Here, we report multituberculate teeth originating from the Maastrichtian fluviatile sediments of the Rusca Montan? Basin (Occidental Carpathians, Poiana Rusc? Mountains). This is the westernmost occurrence of these Cretaceous mammals in Romania. These teeth are assigned to Barbatodon oardaensis, the smallest Cretaceous kogaionid species. This study presents the first occurrence of this species outside the Metaliferi sedimentary area (southwestern Transylvania, Romania). The distribution of Romanian Maastrichtian kogaionids is also discussed.     

Les Schackoïnes (Foraminifères planctoniques) de l’Albien supérieur du Blake Nose (marge atlantique de la Floride, Leg ODP 171B)

A study of rather rich and well-preserved material from Upper Albian levels of Site 1050 of ODP Leg 171B led us to review the criteria used in the subdivision of the schackoinids into two genera and to describe a new morphotype, Schackoina leckiei n. sp., the phylogenetic position of which is examined within the group.