Enregistrement des fluctuations du niveau marin dans l’Holocène supérieur du lac Retba (Sénégal) par les foraminifères

A study of sea level fluctuation records based on foraminiferal assemblages was carried out for the first time in a sediment core taken at the Lac Retba edge. A total of 37 foraminifera species were collected along the core, among which most are known in the modern estuaries and lagoons of Senegal. A succession of four assemblages dominated by Ammonia parkinsoniana and A. tepida were identified; they correspond to different stages of evolution of the lake. The first association, at the base of the core, indicates a lagoon slightly opened to the sea and bordered with vegetation, under relatively humid climate. The second has the richest and most diversified microfauna with a high proportion of coastal, marine benthic and planktonic species (about 10%) that indicate a small coastal gulf bordered with mangroves. The third association is oligospecific and typical of a closed and hypersaline lagoon under a dry climate. The last association again contains coastal, marine benthic and scarce planktonic species (3%) indicating a change to a saltier and more open lagoon under dry climate. The disappearance of planktonic foraminifera at the top of the core indicates the closure of the lagoon. The biocenotic indicators are evidence for two marine intrusions that are referred to the Dakarian (3000 years B.P.) and Saint-Louisian (2140-680 years B.P.) stages of the Upper Holocene of the senegalo-mauritanian stratigraphic scale. Evidence of the Lac Retba closure since 680 years B. P. appears in the core by high reduction of foraminifers’ abundance and diversity absence of planktonic species, and salts precipitated at the bottom of the lake.     

Découverte de nouveaux rongeurs dans la formation Miocène de Bou Hanifia (Algérie occidentale)

A new rodent level has been discovered in the Bou Hanifia formation, well known for its Hipparion and Progonomys levels. The importance of this new locality lies in the presence of a new rodent, Senoussimys hanifiae nov. gen., nov. sp., Dendromuridae, the oldest representative of this group in North West Africa and of a new species of Zramys, Zramys gueltae probable descent of Zramys dubiusJaeger, from the oldest BH.II level.     

The proton-pumps at the plasmalemma of Catharanthus roseus cells

Cultured Catharanthus roseus cells exhibit transmembrane ferricyanide (FIC) reduction which is associated with a proton translocation and a decrease in the ATP content of the cells. The H+ efflux and the ATP consumption may be counteracted by vanadate, a specific inhibitor of the ATPase activity, and by Na2WO4 which prevents FIC reduction. From these data it is concluded that the redox chain could be coupled with ATP hydrolysis for electrogenic proton extrusion which may involve a redox control mechanism for the plasmamembrane ATPase.     

Étude de la capacité d'accroissement chezhyperaspis raynevali [Col.: Coccinellidae] prédateur introduit au congo pour la régulation des populations dePhenacoccus manihoti [Hom.: Pseudococcidae]

Résumé Hyperaspis raynevali Mulsant est une coccinelle prédatrice dePhenacoccus herreni Cox & Williams en Guyane. Elle a été introduite au Congo pour particier à la régulation des populations de la cochenille du maniocPhenacoccus manihoti Matile-Ferrero. Avant les lachers de plein champ, une étude a été conduite au laboratoire pour tenter de quantifier son pouvoir de multiplication et comparer ce dernier à celui des coccinelles locales précédemment étudiées. La capacité d'accroissement d'une population deP. raynevali est de 0,081 (r_c deLaughlin) dans les conditions du laboratoire avec un taux net de reproduction de 271,7 et une durée de génération de 69 jours. La durée du développement préimaginal est sensiblement allongée aux températures inférieures à 25°C et la mortalité embryonnaire reste élevée aux différentes conditions thermohygrométriques testées.      

Effects of beta-endorphin, met-enkephalin and somatostatin on the neurotensin-induced neurogenic contraction in the guinea-pig ileum

At maximally effective concentrations, the opiate peptides β-endorphin (240 nm) and Met-enkephalin (1400 nM) virtually abolished the contractions induced by a maximally effective concentration of 60 nM neurotensin (NT), either in the longitudinal smooth muscle strip or in the intact segment of guinea-pig ileum. This inhibitory effect was concentration-dependent and was totally blocked by naloxone at 100 nM. In contrast a maximally effective concentration of somatostatin (60 nM) partially inhibited (50–60%) the contraction induced by 60 nM NT in either smooth muscle preparation. Somatostatin inhibition was concentration-dependent and was not blocked by naloxone at 100 nM. Atropine at 100 nM inhibited by 50% the contractions induced by 60 nM NT in the intact segment of guinea-pig ileum. The remaining contraction was abolished by β-endorphin and Met-enkephalin and partially reduced by somatostatin. Our results confirm that NT-induced contractions in the guinea-pig ileum are neurogenic and involve a cholinergic as well as a non-cholinergic component. Furthermore, we show that the release of mediators from both components     

Sur la morphologie externe et interne de Rotorboides granulosa (Heron-Allen & Earland) emendation du genre Rotorboides Sellier de Civrieux, 1977 (Foraminiferida)

Discorbis valvulata granulosa HERON-ALLEN and EARLAND, which has been found by the present authorsin the recent deposits of Watamu beach (Kenya), is the type-species of the genus RotorboidesSELLIER de CIVRIEUX, 1977. The study of this species has permitted to describe in detail its outer and inner morphology, to discuss its previous assignments (Discorbis, Rotorbinella) and to emend the genus Rotorboides.     

The Pachycrocuta and Hyaena lineages (plio-pleistocene and extant species of the Hyaenidae). Their relationships with miocene ictitheres: Palhyaena and Hyaenictitherium

The large «crocutoïd hyaenas from the Plio-Pleistocenedeposits of Eurasia do not belong to the same lineage as the extant species Hyaena hyaena and must be referred to the genus PachycrocutaKretzoi, of which an emended diagnosis is given. This revision takes into account some undescribed or ill-known specimens from Russia, China and Africa. They definitely establish that Pachycrocuta ranged over Eurasia, from West Europe to East China, as early as the early Villafranchian at least, and that it was present in North Africa too; a large sample from the Odessa Catacombs affords an estimation of the intraspecific variation in the Ruscinian species, H. pyrenaica, known until now by only a few specimens from the western part of the Mediterranean basin, and it shows H. pyrenaica to be the ancestral form of the Villafranchian Eurasian species P. perrieri, from which derived P. brevirostris, the last species of the lineage, as previously shown by other authors.It appears that the “Hyaena lineage evolved simultaneously in Africa; we knew already that the root of this lineage is H. abronia, a species from the late Miocene of South Africa whose generic attribution is discussed relative to some Ictitheres from Shan-Si, Samos, Sahabi and Klein Zee. The hypothesis of a common African origin of the two lineages is not excluded, if not demonstrated. The relationships of the Pleistocene European species H. prisca and that of the extant African species H. brunnea are discussed.     

The initial peopling of South American Plains: An overview on Late Pleistocene and Early Holocene settlers in Uruguay

This paper reviews more than 20 years of research about the Late Pleistocene and Early Holocene occupations of the Uruguayan plains. The aim of this synthesis is to provide an overview of the available information related to early human peopling of Uruguay. Here, we focus on the main issues discussed over the last two decades: early sites characterization and chronology, human response to climate change, cultural diversity, occupations patterns, mobility and technology. The systematic and continuous efforts made have provided new data and new perspectives regarding the earliest human occupations of the region. We have defined an archaeological complex landscape and ongoing research strategy is based on the three main types of site that compose it: residential camps, cave and rock shelters, and raw material sources. This has allowed us to expand and improve our understanding of the record. The new research and data provided by these sites have led us to propose a settlement model for the region and the period. A cultural diversity has been evidenced through in-depth studies of stratified archaeological sites, cultural sequence, a solid chronological database and lithic technology. Finally, we advance in the characterization of objects of social prestige among hunter-gatherers who occupied the plains during the end of the Pleistocene in Southeastern South America.     

Structures de végétation et conservation des zones humides temporaires méditerranéennes : la région des Mogods (Tunisie septentrionale)

Floristic surveys and phytoecological relevés were conducted on 36 temporary wetlands of Mogods region. Multivariate analyses (CA, AHC) performed on these data reveal the high specific and biocoenotic diversity of Mogods wetlands, which appear controlled by substrate nature and hydrology. Among the 128 hydrophytic species inventoried, 38 are presently in precarious status and 6 are presumed extinct. The Mogods region harbours, moreover, very rare habitats (peatlands and semi-permanent lakes), and a vast plain so-called Garâa Sejenane, exceptionally rich in temporary wetlands. These results underline the urgency of an adapted conservatory management, based on the development of scientific studies dealing with structure and functioning of hydrophytic communities of the region.