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101.
Jean-Pierre Lechaire Ghislaine Frébourg Françoise Gaill Olivier Gros 《Marine Biology》2008,154(4):693-700
In this study, Codakia orbicularis gill-tissues were cryo-fixed by using high-pressure freezing, a freeze substitution process and finally by cryo-embedding
in Lowicryl. Ultrathin sections were then used for an EFTEM microanalysis. Results show that intracellular bacterial symbionts
contain elemental sulphur in periplasmic vesicles as indicated by conventional TEM. When sulphur is temporarily depleted in
the environment, such structures may act as energy sources for bacterial metabolism. Moreover, sulphate was detected in the
cytoplasm of the bacterial symbionts, suggesting the oxidation of elemental sulphur, located in periplasmic granules, to sulphate
(the final step in sulphur oxidation) by these chemoautotrophic bacteria. To assess the effects of host starvation on the
bacterial sulphur content, adult individuals of C. orbicularis were maintained in starvation for 6 weeks in sterile artificial seawater depleted in sulphur. During starvation, both (1)
the number of bacteria inside the bacteriocytes and (2) the number of periplasmic granules per prokaryotic cell decreased.
The content of the remaining periplasmic granules had been modified to sulphate. This observation suggests that bacterial
gill-endosymbionts used the elemental sulphur in their periplasmic granules as stored substrate for oxidation in order to
produce energy in case of sulphur depletion. 相似文献
102.
Gilles Durrieu Quang-Khoai Pham Anne-Sophie Foltête Valérie Maxime Ion Grama Véronique Le Tilly Hélène Duval Jean-Marie Tricot Chiraz Ben Naceur Olivier Sire 《Environmental monitoring and assessment》2016,188(7):401
Water quality can be evaluated using biomarkers such as tissular enzymatic activities of endemic species. Measurement of molluscs bivalves activity at high frequency (e.g., valvometry) during a long time period is another way to record the animal behavior and to evaluate perturbations of the water quality in real time. As the pollution affects the activity of oysters, we consider the valves opening and closing velocities to monitor the water quality assessment. We propose to model the huge volume of velocity data collected in the framework of valvometry using a new nonparametric extreme values statistical model. The objective is to estimate the tail probabilities and the extreme quantiles of the distribution of valve closing velocity. The tail of the distribution function of valve closing velocity is modeled by a Pareto distribution with parameter ??t,τ, beyond a threshold τ according to the time t of the experiment. Our modeling approach reveals the dependence between the specific activity of two enzymatic biomarkers (Glutathione-S-transferase and acetylcholinesterase) and the continuous recording of oyster valve velocity, proving the suitability of this tool for water quality assessment. Thus, valvometry allows in real-time in situ analysis of the bivalves behavior and appears as an effective early warning tool in ecological risk assessment and marine environment monitoring. 相似文献
103.
Olivier Maire Jean-Michel Amouroux Jean-Claude Duchêne Antoine Grémare 《Marine Biology》2007,152(6):1293-1307
The filtration activity of the Mediterranean mussel, Mytilus galloprovincialis, was assessed under different concentrations and compositions of seston by using a new automated image acquisition and analysis
system. This approach allowed for frequent and simultaneous measurements of valve gape and exhalant siphon area. Filtration
rates were measured through clearance measurements whereas pumping rates were measured using hot-film probes. The average
filtration rate (17.5 l g h−1 DW−1 for a 0.36 g DW mussel) recorded during the present study was higher than those available for Mytilus edulis when standardized to flesh dry weight but almost equivalent (17.5 l h−1 g DW−1 for a 53 mm shell length mussel) to those rates when standardized to shell length. Immediately after the addition of algal
cells (Isochrysis galbana; 4.5 μm in size), valve gape, exhalant siphon area and filtration rate increased quickly as mussels reached their maximum
filtration activity. These three parameters then gradually decreased until complete closure of the shell. The algal cell concentration
inducing this transition was close to 800 cells ml−1 and 0.5 μg Chl a l−1. When algal concentration was maintained above this threshold by successive algal additions, both valve gape and exhalant
siphon area remained maximal. Temporal changes in the exhalant siphon area were continuous as opposed to those of valve gape.
Therefore, despite the significant correlation between these two parameters, valves and siphon were sometimes dissociated
due to a reduction of the area or even a closure of the exhalant siphon while the valves remained open. The velocity of exhaled
water tended to be constant irrespective of exhalant siphon area and thus pumping rates were a linear function of exhalant
siphon area. Consequently, reductions in exhalant siphon area and pumping rate were almost similar in M. galloprovincialis. Our results thus clearly support the hypothesis that exhalant siphon area constitutes a better proxy of pumping rate than
valve gape as already suggested for Mytilus edulis. Finally, the high filtration rates measured during the present study together with the high concentrations of inorganic
matter (> 40 mg DW l−1) requested to alter those rates suggest that the studied mussels were well adapted to oligotrophic waters featuring strong
hydrodynamism and frequent sediment resuspension events. 相似文献
104.
Kamran Moradkhani Laurence Cuisset Pierre Boisseau Olivier Pichon Marine Lebrun Houda Hamdi-Rozé Marie-Laure Maurin Nicolas Gruchy Marie-Christine Manca-Pellissier Perrine Malzac Frédéric Bilan Marie-Pierre Audrezet Pascale Saugier-Veber Anne-Laure Fauret-Amsellem Chantal Missirian Paul Kuentz Gregory Egea Agnès Guichet Isabelle Creveaux Caroline Janel Ines Harzallah Renaud Touraine Carole Goumy Nicole Joyé Jacques Puechberty Emmanuelle Haquet Sandra Chantot-Bastaraud Sébastien Schmitt Philippe Gosset Bénédicte Duban-Bedu Bruno Delobel Philippe Vago François Vialard Denise Molina Gomes Jean-Pierre Siffroi Jean-Paul Bonnefont Jean-Michel Dupont Philippe Jonveaux Martine Doco-Fenzy Damien Sanlaville Cédric Le Caignec 《黑龙江环境通报》2019,39(11):986-992
105.
106.
David A. Wiedenfeld Allison C. Alberts Ariadne Angulo Elizabeth L. Bennett Onnie Byers Topiltzin Contreras-MacBeath Gláucia Drummond Gustavo A. B. da Fonseca Claude Gascon Ian Harrison Nicolas Heard Axel Hochkirch William Konstant Penny F. Langhammer Olivier Langrand Frederic Launay Daniel J. Lebbin Susan Lieberman Barney Long Zhi Lu Michael Maunder Russell A. Mittermeier Sanjay Molur Razan Khalifa al Mubarak Michael J. Parr Jonah Ratsimbazafy Anders G. J. Rhodin Anthony B. Rylands Jim Sanderson Wes Sechrest Pritpal Soorae Jatna Supriatna Amy Upgren Jean-Christophe Vié Li Zhang 《Conservation biology》2021,35(5):1388-1395
Some conservation prioritization methods are based on the assumption that conservation needs overwhelm current resources and not all species can be conserved; therefore, a conservation triage scheme (i.e., when the system is overwhelmed, species should be divided into three groups based on likelihood of survival, and efforts should be focused on those species in the group with the best survival prospects and reduced or denied to those in the group with no survival prospects and to those in the group not needing special efforts for their conservation) is necessary to guide resource allocation. We argue that this decision-making strategy is not appropriate because resources are not as limited as often assumed, and it is not evident that there are species that cannot be conserved. Small population size alone, for example, does not doom a species to extinction; plants, reptiles, birds, and mammals offer examples. Although resources dedicated to conserving all threatened species are insufficient at present, the world's economic resources are vast, and greater resources could be dedicated toward species conservation. The political framework for species conservation has improved, with initiatives such as the UN Sustainable Development Goals and other international agreements, funding mechanisms such as The Global Environment Facility, and the rise of many nongovernmental organizations with nimble, rapid-response small grants programs. For a prioritization system to allow no extinctions, zero extinctions must be an explicit goal of the system. Extinction is not inevitable, and should not be acceptable. A goal of no human-induced extinctions is imperative given the irreversibility of species loss. 相似文献
107.
Alain Dejean Céline Leroy Bruno Corbara Régis Céréghino Olivier Roux Bruno Hérault Vivien Rossi Roberto J. Guerrero Jacques H. C. Delabie Jérôme Orivel Raphaël Boulay 《Die Naturwissenschaften》2010,97(10):925-934
Myrmecophytes offer plant-ants a nesting place in exchange for protection from their enemies, particularly defoliators. These obligate ant–plant mutualisms are common model systems for studying factors that allow horizontally transmitted mutualisms to persist since parasites of ant–myrmecophyte mutualisms exploit the rewards provided by host plants whilst providing no protection in return. In pioneer formations in French Guiana, Azteca alfari and Azteca ovaticeps are known to be mutualists of myrmecophytic Cecropia (Cecropia ants). Here, we show that Azteca andreae, whose colonies build carton nests on myrmecophytic Cecropia, is not a parasite of Azteca–Cecropia mutualisms nor is it a temporary social parasite of A. alfari; it is, however, a temporary social parasite of A. ovaticeps. Contrarily to the two mutualistic Azteca species that are only occasional predators feeding mostly on hemipteran honeydew and food bodies provided by the host trees, A. andreae workers, which also attend hemipterans, do not exploit the food bodies. Rather, they employ an effective hunting technique where the leaf margins are fringed with ambushing workers, waiting for insects to alight. As a result, the host trees’ fitness is not affected as A. andreae colonies protect their foliage better than do mutualistic Azteca species resulting in greater fruit production. Yet, contrarily to mutualistic Azteca, when host tree development does not keep pace with colony growth, A. andreae workers forage on surrounding plants; the colonies can even move to a non-Cecropia tree. 相似文献
108.
Effects of the 2008 flood on economic performance and food security in Yemen: a simulation analysis 下载免费PDF全文
Extreme weather events such as floods and droughts can have devastating consequences for individual well being and economic development, in particular in poor societies with limited availability of coping mechanisms. Combining a dynamic computable general equilibrium model of the Yemeni economy with a household‐level calorie consumption simulation model, this paper assesses the economy‐wide, agricultural and food security effects of the 2008 tropical storm and flash flood that hit the Hadramout and Al‐Mahrah governorates. The estimation results suggest that agricultural value added, farm household incomes and rural food security deteriorated long term in the flood‐affected areas. Due to economic spillover effects, significant income losses and increases in food insecurity also occurred in areas that were unaffected by flooding. This finding suggests that while most relief efforts are typically concentrated in directly affected areas, future efforts should also consider surrounding areas and indirectly affected people. 相似文献
109.
110.
The study investigated whether plasmatic parameters in fish such as Cl- content could serve as physiological indicators to evaluate water quality. The variations of plasma Cl- content in two fish species caught in a wide range of rivers representative of the hydrographic system of Lorraine (N-E France) were investigated. First, we studied autochthonous populations of chub (Leuciscus cephalus) which is a widespread species in the rivers of Lorraine. Organisms living in highly mineralised rivers (>1500 microScm(-1))--either naturally or due to salt mine contamination--showed plasma Cl- content significantly greater than organisms living in river with a lower mineralisation. Second, we investigated plasma Cl- content of brown trout (Salmo trutta fario) in poorly mineralised streams (<80 microS cm(-1)) with different degrees of acidification, both on autochthonous and transferred organisms. While indigenous trout maintained their Cl- content even in the acidic streams, transferred trout exhibited an important decrease of Cl- content after 48 h of exposure under acidic conditions. 相似文献