Fluctuations des nutriments au cours de la marée sur les parcs Ostreicoles de la rivière Penze (Nord-Finistère)

The design and performance of a simple, community level ecotoxicological testsystem is reported. Samples of periphyton communities, established on artificial substratum in natural streams were used to study effects on photosynthetic activity in short-term experiments. Photosynthesis was measured as light-dependent oxygen evolution or as ¹⁴CO₂-incorporation. The variability in photosynthetic activity between samples collected at the same time, expressed as coefficient of variation, was ca 20%. The variation in sensitivity of periphyton photosynthesis as dependent on sampling season was less than threefold for the two long-chained aliphatic amines and the textile industry effluent studied. Effects of the amines on periphyton from five different streams were also investigated. The ratio between maximum and minimum values of sensitivity was 5.6. It is concluded that the variation in sensitivity between different periphyton communities is similar to or less than that observed for fresh-water algal species. Some advantages with regard to ecological realism of using periphyton communities as test systems are discussed.     

La diatomée Chaetoceros simplex calcitrans Paulsen et son environnement. II. Effets de la lumière et des irradiations ultra-violettes sur la production primaire et la biosynthèse des stérols

12-day cultures of the diatom Chaetoceros simplex calcitrans Paulsen in sea water have been analysed under different conditions of light. With a $\text{12 h}\text{24 h}$ photophase the primary production is 106 % higher than under continuous light but the unsaponifiable fraction is lower (?42 %) and the sterols increase by 100 %. When ultra-violet irradiation is added to the $\text{12 h}\text{24 h}$ photophase the primary production is lowered (?56 %) but the unsaponifiable fraction increases by 191 %, and the sterols by 110 %. When ultra-violet irradiation is added to the continuous light there is an increase in primary production (+30 %) and a decrease in the unsaponifiable fraction (?16%).Modifications of the sterol composition are reported. C₂₆ sterols have never been detected in these experiments.     

Diminution de la capacité de surfusion au cours de l'embryogenèse et du développement larvaire chez un coléoptère

Potential cold resistance of non-diapause eggs and first instar larvae of Osmoderma eremita (Coleoptera, Cetoniidae, Trichiinae) during embryogenesis and post-embryonic growth was assessed by measuring individual supercooling points (SCP): sterile eggs had a mean SCP of −24.3 ± 2.0 °C; fertilized newly laid eggs a mean SCP of −23.4 ± 3.2 °C and eggs about to hatch a mean SCP of −9.2 ± 2.9 °C. Water absorption by fertilized eggs is a necessary requirement for the development of the embryo and results in an increase in weight and water content: fertilized newly laid eggs had a mean fresh weight of 10.687 ± 1.072 mg and a mean water content (expressed as a percentage of the dry weight) of 79.5 ± 10.83%; eggs about to hatch had a mean fresh weight of 19.127 ± 3.183 mg and a mean water content of 250.10 ± 74.15%. The ex-ovo larvae, hatched 30 days after oviposition, had a mean SCP of −10.1 ± 3.6 °C (no significant difference with eggs about to hatch) and had gained in weight (24.845 ± 3.911 mg) and in water content (499.72 ± 55.49%). Feeding 1st instar larvae had a decreased supercooling ability (mean SCP = −5.7 ± 0.4 °C) whereas their mean fresh weight (99.858 ± 53.091 mg) and mean water content (665.83 ± 82.74%) increased. The eggs and larvae of O. eremita are freezing intolerant. Before overwintering, all larvae switch to being freezing tolerant and can survive ice formation in their tissues and body fluids, whereas their mean SCP stays at around −5 °C. However, recent experiments in the winter of 1996 have shown that frozen larva mortality does occur at temperatures lower than about −12 °C.     

Rétablissement du cytoplasme et de la force motrice au cours de la restauration de la cyclose chezNitella après irradiation

Résumé En irradiant (500 kR) une fraction seulement du volume cellulaire de la cellule internodale deNitella, il est possible de distinguer au cours des phénomènes de restauration du mouvement cytoplasmique ceux qui dépendent de Pendoplasme (observation de la cyclose dans la zone protégée) et ceux qui dépendent de l'ectoplasme siège de la force motrice (observation de la cyclose dans la zone irradiée).Dans la zone protégée, la vitesse de la fraction endoplasmique irradiée se rétablit en fonction du temps suivant une équation du second ordre. L'augmentation du volume irradié diminue la rapidité du premier des deux processus de restauration et la quantité d'endoplasme qui reste altérée s'accroît.Dans la zone irradiée, le courant cytoplasmique est suspendu; il ne reprend que 4 minutes après le traitement alors que la couche chloroplastique se réorganise. Le glissement des inclusions qu'il charrie se fait un certain temps par saccades. La vitesse de la fraction endoplasmique protégée y augmente régulièrement témoignant ainsi du rétablissement de la force motrice. Le rétablissement a lieu suivant un schéma analogue à celui de Pendoplasme irradié sauf que ce phénomène y est plus rapide et que la force motrice du moins pendant les premières heures se rétablit intégralement. Ces résultats sont discutés (rôle des groupes SH, effet indirect d'empoisonnement, nature des lésions) et comparés à ceux obtenus pour des cellules irradiées in toto.

---

Cytoplasm and motive force separated recovery during the re-establishment of the gyclosis in irradiatedNitella cells

Summary In these experiments onNitella internodal cells, only a fraction of the cellular volume is irradiated (by 500 kR). The restoring of the endoplasm (by measurement of the cyclosis in the shielded zone) and the restoring of the ectoplasm where the motive force is generated (by measurement of the cyclosis in the irradiated zone) can be examinated separately during the recovery of the cytoplasmic streaming.In the shielded zone, the plot on a semi-logarithmic scale of a typical rate of streaming-time curve shows that the speed of the irradiated endoplasm. increases again according to a second order equation. With increasing irradiated cellular volume, there are a gradual slowing down of the first processus of restauration and an increase of the definitively altered fraction of the endoplasm.In the irradiated zone, the cytoplasmic streaming stopped completely. About 4 minutes after the treatment, when the chloroplasts layer is reorganising, it exhibits a tendency to flow again. The carried inclusions slide then in jerks during several minutes. The rate of the protected fraction of the endoplasm increases regularly, proving the recovery of the motive force. An analysis of this processus versus time shows that it can be exprimed by a second order equation as that of the irradiated endoplasm. But it is faster and the motive force resumes until full recovery (at least during the first hours).These results are discussed (importance of SH-groups, indirect poisoning effect, kind of lesions) and compared with those observed in completely irradiated cells.

     

Aspects toxiques du cuivre sur la biomasse et la productivité du phytoplancton de la rivière du Saguenay,Québec

In 1979 and 1980, batch culture experiments were conducted to observe the inhibitory effect of copper ion (concentrations of 10, 50, 100, 200 and 400 µg Cu · l^–1) on the standing crops and photosynthesis of phytoplankton of the Saguenay River (for 124 hours) and in Chlorella vulgaris (for 8 days). These algal assays were carried out using the surface water of the Saguenay River. In natural populatoins of phytoplankton, it was found that photosynthesis was more sensitive than growth: at the lowest concentrations, such as 10 µg Cu · 1^–1, copper seemed to increase the chlorophyll concentrations whereas the rates of primary production show a decrease of 60% with respect to the control. At higher concentrations of copper, the effect is weak in chlorophyll concentrations and more pronounced in the rates of primary production (decrease of 86 to 90%). The pennate diatoms are dominant (in all the samples) and these organisms are known as relatively resistant to copper. In Chlorella vulgaris, it was observed that with 100 µg Cu · 1^–1, chlorophyll concentrations and rates of photosynthesis respectively decrease by 63 and 99% with respect to the control. At higher concentrations of copper, a maximum decrease of 70% and 99% respectively for chlorophyll concentrations and rates of primaryproduction are observed.

     

Effets de la mise en eau du réservoir Desaulniers (Territoire de la Baie de James) sur le zooplancton d'une rivière et d'une tourbière reticulée

This paper presents the results of an investigation which lasted three years, on the effects of impounding a river on its zooplankton community. Forty zooplankton samples were collected from the Desaulniers River and from a string bog (53°35N, 77°35W) in 1976 before impoundment. Sampling was also conducted in 1977 (331 samples) and 1978 (153 samples) during and after impoundment. The population dynamics of zooplankton show different patterns in 1977 and 1978. The main impacts of impoundment on the river and the bog communities are the increase of the population density, particulary of Rotifera and Copepoda, the increase of the number of species of Rotifera and the increase of the diversity indices based on numbers and biomass. These changes are observed at each sampling station. The total biomass increases in lotic stations but decreases in the string bog because the density and the biomass of Cladocera increases in the river but drops in the bog. Results are compared to those obtained in natural lakes and bog of the same area and to those published in other studies.

---

Effets de la mise en eau du réservoir Desaulniers (Territoire de la Baie de James) sur le zooplancton d'une rivière et d'une tourbière reticulée

     

L'effet de β-mercaptoéthanol et de l'urée sur la structure du phragmoplaste

Résumé Les fibrilles constitutives du phragmoplaste sont de nature protéique. L'action du-mercaptoéthanol permet de conclure que ces protéines sont liées par des ponts S-S. En présence d'urée, la structure du phragmoplaste est détruite, ce qui indique l'existence de liaisons hydrogènes.

---

Zusammenfassung Unsere Arbeit führt zu folgenden Resultaten: 1. Die im Phragmoplast befindliche Faserstruktur besitzt einen Eiweißstoffcharakter. 2. Der Effekt des-Merkaptoäthanols gestattet die Annahme, daß die Proteine mit S-S-Brücken verbunden sind. 3. Bei Anwesenheit von Harnstoff wird die Phragmoplaststruktur zerstört, was für das Vorhandensein von H-Brücken spricht.

---

---

Boursière de la Fondation Rockefeller     

Modifications pigmentaires et ultrastructurales chez la diatomée Detonula sp. cultivée en lumière rouge

Résumé La diatomée Detonula sp. lorsqu'elle est cultivée en lumière rouge (650 nm), est enrichie en holochrome chlorophyllien Ca 705 (pour la nomenclature des holochromes voir French et al., 1971). La composition pigmentaire est alors modifiée par rapport à celle de l'algue cultivée en lumière blanche. Si les mêmes composants, Chlorophylle a, Chlorophylle c, Carotène, Diadinoxanthine, Diatoxanthine, Fucoxanthine, Violaxanthine, sont tous présents, on note un abaissement du taux de Chlorophylle c (le rapport Chl c/Chl a passe de 30% à 5%) et un abaissement du taux de Fucoxanthine (le rapport Fucoxanthine/Chlorophylle a passe de 85% à 60%). Cette modification pigmentaire s'accompagne d'une modification ultrastructurale des plastes. Au lieu d'une vingtaine de thylakoïdes disposés par groupe de 4 au milieu d'un stroma abondant, on observe une disparition du stroma accompagnée d'une augmentation très importante du nombre de thylakoïdes, tous juxtaposés en un seul ensemble.La diminution importante du taux de Chlorophylle c et de la Fucoxanthine, pigments du photosystème II, liée à l'enrichissement en Chlorophylle a 705, indique une modification de l'équilibre entre les deux photosystèmes au profit du photosystème I. Cet enrichissement en photosystème I s'accompagne d'une modification ultrastructurale qui est rapprochée des modifications observées dans d'autres organismes lorsque l'équilibre des deux photosystèmes est perturbé.

---

Pigments and ultrastructure modifications in diatom Detonula sp. cultivated in red light

Summary Cultivation of the diatom Detonula sp. with red light, which causes an enrichment of the chlorophyll holochrome Ca 705 (for nomenclature of chlorophyll holochromes see French et al., 1971), also modifies the gross pigment composition of the cells. Relative to chlorophyll a, the cellular contents of chlorophyll c and fucoxanthin are considerably lower than in cells grown with white light; and this is accompanied by a change in plastid ultrastructure. The plastids of cells grown in white light contain about 20 thylakoids disposed in groups of 4, within an abundant stroma; those of cells grown in red light contain a much greater number of thylakoids (about 40), evenly distributed throughout the plastid.The diminution of chlorophyll c and fucoxanthin, pigments associated with photosystem II, coupled with the enrichment in chlorophyll a 705, points to a shift in the ratio between photosystems I and II in favor of the former. The accompanying ultrastructural modification of the plastid resembles that observed in other organisms as a result of changes in the relative amounts of the two photosystems.

---

---

Cet article recouvre en partie le travail d'une thèse de Doctorat d'Etat ès Sciences Naturelles qui sera soutenue à la Faculté des Sciences de Paris. VI.     

Influence des paramètres de fumage sur l'activité génotoxique de la phase gazeuse de fumée de cigarette,mesurée sur le lymphocyte humain et la levure

Effect of smoking-machine parameters on the genetoxic activity of cigarette gas phase, estimated on human lymphocyte and yeastCigarette smoke used in chemical research and bioassays is obtained by mechanical smoking on machines adjusted to international standards. On studying the behavior of some smokers of black tobacco, we were led to change the standard parameters: volume, duration, frequency. The gas phase obtained under those new conditions is poorer in some components. This decrease goes with a clear-cut decrease of its genotoxic activity towards cultured human lymphocytes (sister-chromatid exchange frequency) and S. cerevisiae (rate of mitotic recombinants and of respiratory deficients). This investigation emphasizes the leading part of the smoking behavior.     

Apoptose au cours de la spermatogenèse et dans le sperme éjaculé

It has become clear in recent years that programmed cell death occurs spontaneously in the cycle of the seminiferous epithelium. Induced germ cell apoptosis occurs at specific stages of the spermatogenic cycle and the existence of supracellular control of germ cell death during spermatogenesis has been documented. If apoptosis is a key phenomenon in the control of sperm production, the existence and role of apoptosis in ejaculated sperm cells remain controversial. Apoptosis — as determined by DNA fragmentation (TUNEL) and ultrastructural analysis — is abnormally frequent in the sperm cells of the ejaculate of sterile men with classical biochemical and ultrastructural pattern. In this review, we discuss the possible origins of DNA damage in ejaculated human spermatozoa and the consequences of DNA damage if the apoptotic spermatozoa is used for ICSI. Percentages of DNA fragmentation in human ejaculated sperm are correlated with fertilization rates both after FIV and ICSI. Detection of DNA fragmentation in human sperm could provide additional information about the biochemical integrity of sperm and may be used in future studies for fertilization failures not explained by conventional sperm parameters. However, the analysis of other molecular markers of apoptosis (Fas, Annexine V ...) is necessary to assess the role of apoptosis in human ejaculated sperm cells.     

Influence comparée de l'(±)-acide abscissique,de la coumarine,de l'acide p-coumarique et de certains de leurs dérivés sur la croissance de la première feuille de blé

Summary The activities of (±)-abscisic acid and a number of compounds derived from p-coumaric acid and coumarin and their interaction with gibberellic acid in the control of the elongation of the first wheat leaf are examined. (±)-Abscisic acid strongly inhibits leaf growth in the presence as well as in the absence of gibberellic acid, but the inhibition is greater in the presence of gibberellic acid (3 g/l already have an observable effect). Among other compounds, only ferulic acid and coumarin significantly reduce leaf elongation, and they are effective only at high concentrations (1.44 · 10^-4 M/l).     

Écologie / Ecology Influence de la morphométrie et du brassage vertical sur la production primaire nette du phytoplancton

In order to estimate the phytoplankton net production, a model based on the relationships between phytoplankton photosynthesis and underwater irradiance established from measurements performed in a mesotrophic reservoir (Pareloup) over 8 years has been coupled with a model of algal respiration, taking into account variations of maintenance and mitochondrial respiration among algal groups. Simulations were carried out in different hydrodynamic and meteorological conditions. The results indicated that the depth and the stability of thermocline have a great impact on the actual light energy available for phytoplankton and consequently on the net production values. Periods of light limitation coincide with the predominance of diatoms, which are best adapted to grow in low light conditions owing to high P/R ratios. Changes in light conditions related to the transient disturbances of the thermal structure may be at the origin of the replacements of species characterized by different P/R ratios. At Lake Pareloup, the mean depth is almost equal to the depth of the euphotic layer and, whatever level of water, the areal net production of the littoral zone does not significantly differ from the mean areal net production of the whole lake. The biomass produced is simultaneously eliminated from the water column by sedimentation and/or by Zooplankton grazing.     

Étude de la décomposition de la matière organique dans le sol au moyen de carbone radioactif

Conclusions Par l'emploi de substrats radioactifs, il a été possible de montrer que le glucose, le ray-grass tel quel, la fraction soluble, les hemicelluloses et la fraction cellulosique du ray-grass ne sont pas, dans les conditions expérimentales appliquées, entièrement transformés en CO₂ dans le sol après une période de deux mois.La décomposition du glucose est plus rapide que celle des hemicelluloses et celle-ci est plus rapide que celle de la fraction cellulosique. Pour le glucose et pour la fraction cellulosique, 11% et 15% respectivement ne se retrouvent pas sous forme de C¹⁴O₂ tandis que pour la fraction soluble, pour les hemicelluloses et pour le ray-grass tel quel, c'est près de 20% qui ne sont pas oxydés en CO₂.La décomposition de chacun de ces substrats radioactifs donne encore lieu à la production de produits organiques radioactifs que l'on trouve dans la fraction des substances solubles, dans la fraction groupant l'- et le -humus et dans l'humine. La radioactivité de cette dernière fraction est du même ordre de grandeur que la somme des deux autres fractions.Travail effectué sous les auspices de l'Institut pour l'Encouragement de la Recherche Scientifique dans l'Industrie et l'Agriculture (I.R.S.I.A.).     

Influence de la nature et de l'abondance des proies sur l'augmentation des effectifs de deux coccinelles prédatrices de la cochenille du manioc au Congo

Résumé Les variations d'abondance des 2 cochenillesPhenacoccus manihoti Matile-Ferrero etFerrisia virgata Cockerell et des 2 prédateurs CoccinellidaeHyperaspis senegalensis hottentotta Mulsant etExochomus flaviventris Mader sont étudiées dans une parcelle de manioc. La colonisation de cette dernière parE. flaviventris est précoce, en présence de faibles niveaux numériques des 2 proies, mais avec une dominance deF. virgata; celle d'H. s. hottentotta intervient un mois plus tard en relation semble-t-il avec la présence d'une population deP. manihoti abondante et jeune. Nos observations font ressortir une dynamique des populations propre à chaque espèce de coccinelle, conditionnée par l'abondance de l'une ou l'autre des proies, la structure des colonies de chaque cochenille et les conditions climatiques (température) qui interviennent en synergie. Ainsi, la réponse numérique deH. s. hottentotta, plus forte que celle d'E. flaviventris, semble en relation plus étroite avecP. manihoti. PourE. flaviventris il appara?t difficile de séparer ce qui revient à chaque espèce de cochenille:F. virgata joue sans doute un r?le important pour son implantation dans les champs, puis sa raréfaction, mais c'est probablementP. manihoti qui permet l'augmentation de ses effectifs.      

Etude du vieillissement d’Anagallis arvensis L.: Action régulatrice de la lumière,du saccharose et de l’acide indolyl-acétique sur la capacité rhizogènique des feuilles et des rameaux axillaires

The rooting capacity of leaves isolated from a vegetative clone ofAnagallis arvensis L. exposed to 9 hours of light (75 W m⁻²) at 22 °C and 15 hours of dark at 12 °C a day is significant only in F₁ young leaves and not in adult ones. The rooting capacity of the young leaves and of the vegetative shoots is greater in longer photoperiods. The leaves make roots even under weak (14 W m⁻²) irradiance. The rooting capacity of the leaves is diminished and even suppressed by exogenous sucrose (14,60 ×10⁻³M). This inhibition may be counteracted by IAA (10⁻⁶M). When leaves and shoots are taken from clones under long (16 h) photoperiods, or in constant irradiance, they progressively lose their rooting capacity during the treatment. Rooting capaoity is regained if the clones are returned again to “short day” (9 h) condition.      

Recherches cytochimiques sur la présence de certaines hydrolases au cours de la cytocinèse chez les plantes supérieures

Résumé Les granulations qui constituent les structures les plus primitives de la plaque cellulaire contiennent des enzymes hydrolytiques caractéristiques pour les sphérosomes de la cellule végétale; la plupart de ces enzymes sont présentes dans les lysosomes de la cellule animale. Dans les granulations de la plaque cellulaire nous avons constaté l'activité des enzymes suivantes: estérases non spécifiques, lipases, phosphatases acide et alcaline, aryl-sulfatase, désoxyribonucléase acide et probablement-glucuronidase. Le caractère chimique et morphologique de ces granulations, ainsi que leur équipement enzymatique correspondent aux sphérosomes.Dans la littérature les images de la cytocinèse au microscope électronique étant divergentes, le problème de l'origine et de la nature des granulations en question ne peut pas être pour le moment totalement résolu.

---

Zusammenfassung Die Körnchen, die die ursprünglichen Strukturen der Zellplatte bilden, enthalten die hydrolytischen Enzyme, die für die Sphärosomen der pflanzlichen Zelle und meistens für die Lysosomen der tierischen Zelle charakteristisch sind. Es sind die folgenden Enzyme: Esterasen (nicht spezifisch), Lipasen, saure Phosphatase, Aryl-sulfatase, saure Desoxyribonuklease und-Glukuronidase. Außerdem enthalten diese Körnchen die alkalische Phosphatase. Der morphologische und chemische Charakter dieser Körnchen und ihr enzymatischer Inhalt entsprechen den Sphärosomen.Wegen großer Unterschiede der in der Literatur vorhandenen Beschreibungen der Zellplatte in elektronenmikroskopischen Bildern kann das Problem der Entstehung und der Natur dieser Körnchen zur Zeit nicht völlig entschieden werden.