Effets du retard dans la première alimentation sur le développement de la larve planctotrophe de l'oursin Paracentrotus lividus

The growth of the skleleton and changes in biochemical constituents (proteins, carbohydrates and lipids) were observed in embryos (days 0 and 1) and larvae (2-8 days) of the sea urchin Paracentrotus lividus that were starved (C 0) or fed low (1,000 cells of Hymenomonas elongata, C 1) or high (5,000 cells, C 5). Different batches of C 1 and C 5 larvae were fed first the 2nd, 3rd, 4th or 5th day after fertilization. Initiation of feeding 24 h after hatching slowed down the rate of increase in length of the larval appendages. A differential growth of skeletic rods (somatic and postoral rods) and variations in proteins weights shows the existence of a mixotrophic phase between endotrophic and planktotrophic phases. Best development occured in larvae which were first fed at the lower food level 24 h after hatching. On the 2nd and the 3rd day the somatic/postoral rod ratio is ≥1. This higher ration can be used to estimate the age of natural populations of larvae.     

Néandertal et le feu au Paléolithique moyen ancien. Tour d’horizon des traces de son utilisation dans le Nord de la France

This article aims at drawing up balance sheet of remains of fire use by the first Neanderthals of Northern France, during the second part of the Saalian (MIS 8 to 6). This overview reminds us the rarity of fire testimonies during Early Middle Palaeolithic (300–130 ky BP) on the scale of North-Western Europe. For Northern France, only the sites of Biache-Saint-Vaast and Therdonne present remains of combustion. At Biache-Saint-Vaast, it is not less than six levels, which present clues of combustion: burnt flint and faunal remains and sometimes charcoals. At Therdonne, besides burnt numerous flint and some rare faunal remains were brought to light during the excavation of level N3 several rich zones in organic residues and micro-charcoals. All the datas collected concerning the clues of combustion at Biache-Saint-Vaast and Therdonne is compiled, analyzed and interpreted. This approach permits to establish the fire use or its absence in saalian occupations of Neanderthals of Northern France and to discuss modalities of its use, particularly at Therdonne. To conclude, fire status and its implications in first Neanderthals occupations are briefly discussed.     

Discussion sur la variabilité intraréférentiel d’accumulations osseuses de petits prédateurs

At present, the characterization of bone assemblages produced by small predators (carnivores and owls) is hampered by existence of strong intrareferential variability. A significant proportion of this variability results from methodological problems. Indeed, not taking into account the prey to predator size ratio has serious consequences on coprocoenose characteristics since this relation directly controls the predator's capacity of acquisition, transport and ingestion. Moreover, without a strict control of sampling protocols, it is impossible to minimize variations engendered by spatiotemporal changes in predator eating activities.     

Nouvelles données paléoenvironnementales dans le Sud de la France vers 30000 ans 14C BP : le cas de la grotte Marie (Hérault)

The Marie cave, discovered to the north of Montpellier, Hérault (France), has yielded a fauna of 28 vertebrates, out of which 23 are small to large mammals, notably Mammuthus primigenius. The few discovered artefacts have been attributed to the Upper Palaeolithic, which is in agreement with the two radiocarbon dates (31450 ¹⁴C yr BP for the low level, and 28680 ¹⁴C yr BP near the cave's entrance). The palynological study shows the existence (i) of a wooded steppe on the plateau, and (ii) of a riverine forest with alders in the valleys, associated with Mediterranean taxa. These data confirm the presence in Languedoc of Mediterranean species around 30000 yr BP, which qualifies the hypothesis of exclusively Spanish and Italian refuges during glacial periods.     

Les récentes découvertes à Baerya dans le district de Bijie, au nord de la province de Guizhou (Chine)

Fauna associated with stone artifacts have recently been uncovered, in the course of a survey from a cave site named Baerya, town land of Bijie, Guizhou province. The first observations suggest a human occupation. In the absence of chrono-stratigraphic data, it is not possible to assess the age of the site. Nevertheless the presence of lower Pleistocene fauna suggests a very ancient age for this human occupation. Further field research will be necessary to determinate the age and nature of the site.     

Etude préliminaire des effets de la mise en eau du Réservoir de LG-2 (Territoire de la Baie James,Québec) sur le seston grossier et le zooplancton des rivières et des lacs inondés

Preliminary Study of the Effects of Impoundment of LG-2 Reservoir (James Bay Territory, Quebec) on the Net Seston and the Zooplankton of Impounded Rivers and Lakes The effects of impoundment on the biomass of net seston and zooplankton in lakes and rivers of Northern Quebec were investigated from 1978 to 1980, before, during and after the completion of LG2 Reservoir on the River La Grande (53° 54′ N, 76° 78′ W). In lotic stations, a 41–77% decrease in net seston was observed due to sedimentation of mineral particles (36–80 mg/m³ in 1978 to 10–21 mg/m³ in 1979). The ratio of organic to total seston increased from an average of 0.18 before the impoundment to 0.65 after. The flooding phase brought about a trophic upsurge; the biomass of the zooplankton increased by one to two orders of magnitude at the various sites; the greatest increases occurred in the central stations near the dam, the smallest in the upper stations near the inflow. In lake stations, no significant difference between years could be detected; the mean zooplankton biomass for all three years ranged from 6.59 mg/m³ to 34.34 mg/m³. Spatial variations between lakes were however significant. Results are compared with those in other natural lakes in Canada and reservoirs in the United States. Comparative examination of phytoplankton biomass before and after impoundment of LG2 Reservoir suggests that bacterioplankton and allochthonous organic material are key elements in the pelagic food chain after impoundment.     

Régulation de la synthèse du DNA dans la glande séricigène de Bombyx mori: II. Etude de l''activité DNA-polymérasique présente dans la fraction soluble brute

In the silkglands of Bombyx mori larvae, DNA synthesis suddenly stops in the middle of the fifth larval instar, when cellular growth is over and cell activity is turned on to massive silk synthesis. Of much interest is to determine what factors are implied in the quantitative and temporal control of DNA synthesis in this tissue.Previous work on thymidine metabolism in the intact organ lead us to look for several enzymatic activities in the soluble fraction of the cells during this period.The results presented here concern the kinases of the thymidylic pathway. As measured in vitro from crude cellular extracts, thymidine-kinase is present at a lower level than thymidylate-kinase but both activities vary in connection with the pattern of in situ DNA synthesis, reaching their highest levels on the fourth day of the instar and decreasing as DNA synthesis definitively stops in the glands.     

La distribution des “coquilles d'oeufs de dinosauriens multistratifiees” dans le Maestrichtien continental du Sud de la France

The study of the numerical importance and the distribution of dinosaurian multilayered eggshells, in the various continental Maastrichtian levels of southern France, make us declare that this, type of pathological development must not be regarded, since it is very rare, as an element explaining the dinosaurian extinction at the end of the Cretaceous.     

Activité DNA-polymérase nucléaire dans les spermatozoides de souris et évolution de cette activité au cours de la spermatogenèse

The presence of a nuclear DNA polymerase activity has been demonstrated in the mouse testis by a cytochemical method. The enzyme was present in the nuclei of the various cell types of mouse spermatogenesis, including spermatozoa. The nuclear activity increased during meiotic prophase and then decreased in spermatids and spermatozoa. A peculiar attention was devoted to the properties of the nuclear DNA polymerase present in spermatozoa. All four deoxyribonucleoside-triphosphates were needed for optimal activity; the acid-insoluble radioactive product obtained by polymerization in situ was completely removed by DNase, but not by RNase nor by pronase. The reaction of polymerization was DNA-dependent, sensitive to high concentrations of KCl and not affected by NEM nor by PHMB.     

Présence des enzymes catalysant la biosynthèse d'UDP glucose dans une fraction légère de l'appareil de Golgi des hépatocytes de chat

A Golgi-rich fraction is prepared from cat hepatocytes by the means of a four-step sucrose density gradient. The material applied to this gradient is composed either of smooth microsomes prepared from healthy animals, or of total microsomes prepared from cat treated by 50 per cent ethanol (0.6 g/100 g body weight, administered by stomach tube).A light fraction (d : 1.10) is obtained by the two procedures. It does not show any glucose-6-phosphatase activity, but is enriched in sialyltransferase, known as a marker enzyme for Golgi apparatus. It also contains the three enzymes implicated in the biosynthetic pathway for UDP-glucose (glucokinase, phosphoglucomutase and UTP : glucose-1-phosphate uridylyltransferase).UDP-glucose being the ultimate substrate in membranous glucosylation reactions, these results could support the hypothesis that sugar-nucleotides necessary for the glycoprotein biosynthesis are produced in the Golgi vesicles directly.     

Presence de pollens d'Hamamelis (Hamamelidaceae,Angiospermae) dans le pliocene du Sud de la France

Pollen-analysis shows the presence of the genus Hamamelis in the pliocene flora of southern France. It contributesto the knowledge of the past distribution of taxa which are now extinct in western Europe.     

Modalités du déclenchement du comportement de capture chez la larve d‘Agrion (Calopteryx auct.) splendens Harris (Odonatoptères)

Das Fangverhalten der Larven von Agrion splendens wird hauptsächlich durch Schwingungen ausgelöst, die durch den Platzwechsel der Beute entstehen. Ein künstlicher mechanischer Stimulator ermöglichte es, nacheinander den Einfluß der Amplitude, der Dauer und der Frequenz der Reize und der Form der Schwingungen zu untersuchen. Die Latenzzeit des Fangschlages verkürzt sich mit zunehmender Frequenz und Amplitude und mit abnehmender Dauer der Reize. Gleichzeitig erhöht sich die Frequenz der Fangschläge, ohne daß der Köder vorher genau untersucht wird. Ein Köder, der mit einer abklingenden oscillatorischen Bewegung vibriert, ist wirksamer als einer mit halb sinusoidaler Bewegung. Künstliche Reizung mit der Ködermethode erlaubte, die sofortige oder verzögerte Wirkung der durch die Beute erzeugten Schwingungen auf das Auslösen des Fangschlages zu prüfen: Die Fangmaske wird während oder nach den Reizserien ausgeworfen. Beide Wirkungen scheinen abhängig von den unregelmäßig verlaufenden oder sinusoidalen Schwingungen, die der Köder erzeugt, und von den Veränderungen der Amplitude während der Reizung: Das Einstellen auf den Fang scheint durch eine wellenförmige Bewegung mit geringfügigen Amplitudenschwankungen erleichtert zu werden. Wenn eine Welle am Anfang oder während der Reizung besonders groß ist, dann führt dies zu einem sofortigen oder späteren Fangschlag.     

Signification des caractères partagés entre Bennettitales et Cycadales. Implications de la découverte d''une Cycadale nouvelle du Cénomanien de l''Anjou (France)

The lagoonal Cenomanian formation (Lower Cretaceous) of clays of the region of Baugeois (north of Angers) has supplied an exceptionally well-preserved fossil flora: leaves, woody structures or/and reproductive organs of pteridophyta, gymnosperms and angiosperms. A well-preserved fossil plant found in a quarry “Le Brouillard” (8 km from Angers), has allowed a detailed morphological and structural study of this species. A comparative study with extant plants has confirmed an undoubted link between the contemporary genus Dioon (an endemic cycad from Mexico) and the fossil species. However, features observed on the lower epidermis of the leaflets, present a similarity with some Jurassic Bennettitales. This discovery, added to other common features shared by these two orders, raises questions about their relationships, thought to be different from a phylogenetic viewpoint.

Résumé

La formation lagunaire cénomanienne (Crétacé inférieur) des Argiles du Baugeois, au nord d'Angers, a fourni une flore fossile riche et exceptionnellement bien conservée: feuilles, structures ligneuses ou/et organes reproducteurs de ptéridophytes, de gymnospermes et d'angiospermes. L'excellent état de conservation d'un fragment de plante fossile, récolté dans la carrière Le Brouillard à 8 km d'Angers, a permis une étude détaillée de la morphologie et de la structure foliaire de cette plante. L'étude comparative avec des plantes actuelles a démontré l'existence d'un lien de parenté entre le genre Dioon (cycadale endémique du Mexique) et le fossile, mais des caractères originaux observés sur l'épiderme inférieur des folioles, présentent des similitudes avec certains genres de Bennettitales du Jurassique. Une telle découverte, ajoutée aux autres caractères communs préalablement décrits par d'autres auteurs, soulèvent à nouveau quelques questions sur les relations de parentés entre ces deux groupes supposés phylogénétiquement éloignés actuellement.