Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie最新文献

Humus profiles underneath the canopy of dominant tree species in two secondary semi-evergreen forest sites in Grande-Terre (Guadeloupe) were analysed with a micromorphological method. In the vertisol of a tree plantation, the humus formed was rather similar under all tree species being an eumull and essentially due to the activity of the endoanecic earthworm Polypheretima elongata. In a natural secondary forest located on a steep slope and associated with a rendzina soil (without endoanecic earthworms), the humus forms were described at lower, mid- and upper slope. In this forest, two particular humus forms were observed. At the middle slope, underneath the canopy of Pisonia subcordata L. that produces nitrogen-rich litter, a calcareous amphimull, characterised by an OH horizon made of millipede faecal pellets, was formed. In the upper slope, underneath the canopy of Bursera simaruba (L.) Sarg. that produces a litter rich in resins and aromatic compounds that are poorly consumed by soil animals, a dysmull with a thick root mat (OF_Rh horizon) developed. Other humus forms were intermediate. The formation of these humus forms is discussed.

Previous studies carried out in the bay of Brest on daily shell growth of Pecten maximus have demonstrated that temperature is a major control on daily shell growth in contrast to food supply. However, repeated events of slow growth have been observed during diatom and dinoflagellate blooms. The aim of this study was to determine how fluctuations in environmental parameters influence P. maximus food intake and daily shell growth rate. In 1995, P. maximus food intake and growth were highest when Cerataulina pelagica (diatom) blooms occurred and lowest during Gymnodinium cf. nagasakiense (dinoflagellate) blooms. During blooms of other diatom species, P. maximus food intake and growth were high when the algal concentration did not exceed a critical threshold, dependent upon the dominant species and sedimentation rate of diatoms. These results demonstrate that the morphological and physiological features of phytoplankton bloom species strongly affect benthic microphytophagy, a component of benthic–pelagic coupling.

The genus Diplozoon (Platyhelminth) exhibits one of the most striking modes of reproduction. Adults reproduce after the permanent fusion of two larval hermaphrodites, which play a symmetrical role. The Diplozoidae are also exceptional among the Monogenea Polyopisthocotylea for two other reasons. They represent the only group really diversified on continental freshwater fishes; however, this diversification is difficult to evaluate since few morphoanatomical criteria are available to distinguish species and their host specificity is atypically variable among the Monogenea. For the first time in the Diplozoidae, the problems of species definition and of host specificity are examined using molecular tools. Two ribosomal markers (ITS2 and 28S rDNA (D1)) have been sequenced in five Diplozoidae, interacting with five Cyprinidae host species: the corresponding parasite–host systems have been well characterised, revealing some contrasting situations in the relations between Diplozoidae and Cyprinidae. Some species are effectively strictly host specific, but Diplozoon scardinii initially considered as a specific species on Scardinius erythrophtalmus and D. homoion on Rutilus rutilus are proposed to be a single species on the basis of their identical ITS2 and 28S rDNA sequences. On the same basis we proposed that D. paradoxum is able to parasitize two fish species, Abramis brama and Blicca bjoerkna, despite the morphological differences observed between the two xenopopulations. Phylogenetic relationships among Diplozoidae species were estimated with ITS2 sequences while cytochrome b sequences were used for their fish hosts. Finally, the comparison between these two molecular phylogenies seems to exhibit the phenomenon of cospeciation.

In order to describe some aspects of the biology of the deep-water shrimp Aristeus antillensis (Crustacea, Decapoda, Aristeidae) in French Guiana (Western Central Atlantic), a total of 84 bottom trawls were carried out at bottom depths ranging from 200 to 900 m on the Guianan slope during four scientific surveys conducted from August 1990 through July 1991. A. antillensis is distributed in muddy grounds from 456 to 818 m with a peak abundance in the 500–600-m-depth stratum where mean catch rates are about 400 g·h^–1. In terms of biomass, catches obtained in day time and at night are similar. All samples observed show great predominance of females. The size frequency distribution indicates the existence of three age-classes for females, probably attributed to three annual cohorts. The results of a detailed study of morphometric relationships (length–weight relationships) are also presented.

In France, city size has very little bearing on the mortality rate as a function of age and life expectancy and it is in large cities that these indicators are the most favorable. No increase in maternal or infant mortality rates or deaths due to cancers has been observed in large cities. The lower mortality rate linked to respiratory and cardiovascular diseases in large urban areas contradicts the fears concerning the impact of air pollution. Deaths linked to lifestyle are less frequent in big cities, which could be due to social structures (socio-professional level: the proportion of white-collar workers and professionals is higher in bigger cities than in the suburbs or small cities). However, although the overall mortality rate is lower, it should be emphasized that there is in large cities a greater incidence of sexually transmitted diseases, AIDS and certain infectious diseases (because of social diversity and the fact that certain individuals seeking anonymity and marginality are drawn to large cities). In terms of mental health, the breakdown of family structures, instability, unemployment, the lack of parental authority and failing schools render adolescents vulnerable and hinder their social integration. When the proportion of adolescents at risk is high in a neighborhood, individual problems are amplified and social problems result. In order to restore mental and social health to these neighborhoods, ambitious strategies are necessary which take into account family and social factors as well as environmental ones. At the present time, when physical health is constantly improving, the most pressing problems are those related to lifestyle and mental health which depend for a large part on social factors.

Molecular hydrogen reacts with the hydroxyl radical, a highly cytotoxic species produced in inflamed tissues. It has been suggested therefore to use gaseous hydrogen in a new anti-inflammatory strategy. We tested this idea, with the aid of the equipment and skills of COMEX SA in Marseille, a group who experiments with oxygen–hydrogen breathing mixtures for professional deep-sea diving. The model used was schistosomiasis-associated chronic liver inflammation. Infected animals stayed 2 weeks in an hyperbaric chamber in a normal atmosphere supplemented with 0.7 MPa hydrogen. The treatment had significant protective effects towards liver injury, namely decreased fibrosis, improvement of hemodynamics, increased NOSII activity, increased antioxidant enzyme activity, decreased lipid peroxide levels and  decreased circulating TNF-α levels. Under the same conditions, helium exerted also some protective effects, indicating that hydroxyl radical scavenging is not the only protective mechanism. These findings indicate that the proposed anti-inflammatory strategy deserves further attention.

The photoperiodic control of sexual rest in Armadillidium vulgare was investigated using various experimental protocols. When reared in conditions of a Nanda–Hamner (i.e resonance) protocol from their first parturial moult to their post experimental moult, females showed a weak resonance effect in sexual rest incidence. The transfer from a long day cycle to a symmetrical skeleton photoperiod – consisting of two equal light pulses per 24 h of continuous darkness – revealed the involvement of a circadian oscillatory system in the photoperiodic clock of this species. The data, obtained in the whole experiments, suggested that both oscillator and hourglass features are involved in the photoperiodic response controlling the sexual rest in Armadillidium vulgare. Moreover, when non-24-h light–dark cycles (with a long photophase) were applied, a mechanism responsible of arrest of reproduction also implied a photoperiodic counter which accumulated and added up the photoperiodic information within a sensitive period during post parturial intermoult.

In species with a promiscuous mating system, the functions of male–infant caretaking remain unclear in the absence of genetic paternity tests. We tested paternal investment and hypotheses concerning reproductive tactics in wild groups of Barbary macaques, including results of genetic paternity tests. Our study revealed that male–infant caretaking was not related to the probability of paternity. In principle, males could use access to females to estimate paternity. However, we found that mating success was not related to paternity, so males could invest in infants that they had not sired, and caretaking of non-offspring was actually observed. Accordingly, males might be ‘deceived’ with respect to their paternal investment. In that case, one would expect a positive relation between mating success and the subsequent rate of male caretaking of infants. Such a relation is also lacking, leading to comprehensive rejection of the paternal investment hypothesis in Barbary macaques. By contrast, there was evidence that males showing infant care achieved higher mating frequencies than other males with the mothers of the relevant infants. Thus, male Barbary macaques do not show a ‘mate-then-care’ pattern, but they do exhibit a ‘care-then-mate’ pattern.

Two new diatom species, Haslea salstonica and Haslea pseudostrearia are described in light and electron microscopy and compared with two well-known members of Haslea. Scanning electron microscope observations confirm that the new species belong to the genus Haslea. This study extends previous observations on the genus, particularly with respect to the development of a pseudostauros. The characteristic features of the genus are discussed briefly.

Partial cytochrome b sequences were used to study relationships between three Lepilemuridae species (Lepilemur dorsalis, L. septentrionalis and L. leucopus) and other Lemuridae species. L. dorsalis were subdivided into two sub-groups, according to their capture area (Nosy-Be island and Sahamalaza peninsula). Relationships deduced from phylogenetic trees as well as genetic distances lead to the classification of the Lepilemurs analysed here into separate species. These Lepilemurs form a monophyletic clade which is the sister clade of all other Lemurs used in this study. Reconstructions using randomly chosen sequences and step by step addition of sequences indicate that phylogenetic results for closely related species need to be analysed with caution, if only a small number of sequences are used to obtain them.