Search

Nous avons ouvert, dans le numero 437 de la revue (juillet-aout), une serie consacree a l’ocean, la mer, les littoraux et les diverses activites qui en dependent. Denis Lacroix, qui coordonne cette serie, y alertait sur les consequences du changement climatique sur le niveau de la mer. Cette fois, c’est le biologiste Gilles Boeuf qui vient confirmer la necessite de revoir au plus vite nos comportements pour eviter que ne s’aggrave la boucle infernale qui s’est mise en place entre changement climatique et pertes de biodiversite marine, modifications oceaniques…, ces pertes et modifications ayant elles-memes un impact sur le climat.Apres avoir presente le role determinant de l’ocean dans l’apparition et l’evolution de la vie sur notre planete, Gilles Boeuf souligne ici les specificites de la biodiversite marine et la richesse qu’elle abrite. Il montre aussi combien les activites humaines (surpeche, pollution, tourisme de masse…) alterent cette biodiversite, et comment les transformations qu’elles induisent dans les oceans jouent un role sur le changement climatique (la fameuse boucle). Alors que la plupart des especes marines ont developpe au fil des siecles de formidables capacites d’adaptation, de cooperation, de symbiose, l’etre humain semble avoir bascule dans l’attitude inverse, avec un risque desormais non negligeable d’autodestruction. Puisse cet article l’inciter, nous inciter, a inverser la tendance… S.D.

An ocean of living beings… This paper will expose the state of the art concerning the ocean, both a unified entity and composed of several seas Our knowledge of its connectivity, salinity and stability in space and time will be highlighted. Physical, chemical and biological aspects are also broached. The exploitation of mineral and living resources by humans is presented. Today the ocean is threatened for the destruction of coastlines, generalized contaminations, over-exploitations of all kinds of resources, the dissemination of invasive alien species and the acceleration of the climate change. Finally, there are developments on biomimicry and the value of ocean., Un océan de vivants… Nous exposons ici l’état des connaissances sur l’océan, qui est unique, et diversifié par une grande quantité de mers. Nous insistons sur sa connectivité, sa salinité et sa stabilité. Nous abordons les grands faits physiques et chimiques, puis biologiques, et présentons l’état de l’exploitation des ressources que l’humanité en tire. L’océan est aujourd’hui menacé dans son intégrité pour cause de destruction des littoraux, pollutions généralisées, surexploitation des ressources, minérales et vivantes, par la dissémination de tout partout et par l’accélération du changement climatique. Nous terminons en approchant le biomimétisme et les apports de l’océan., Un océano de seres vivos… Presentamos aquí el estado actual de los conocimientos sobre el océano, único y diversificado por una gran cantidad de mares. Nos ocupamos especialmente de las cuestiones relacionadas con la conectividad, la salinidad y estabilidad del océano, así como sus aspectos físicos, químicos y biológicos y la explotación de sus recursos. Hoy en día, la integridad del océano está amenazada por la destrucción del litoral, la contaminación generalizada, la sobreexplotación de los recursos, minerales y biológicos, por la diseminación generalizada de especies alóctonas y la aceleración del cambio climático. Para terminar, presentaremos una aproximación al biomimetismo y a las aportaciones del océano., Boeuf Gilles. Un océan de vivants…. In: Communications, 110, 2022. Vivantes interactions. pp. 181-193.

This policy brief provides recommendations for the science needed for the next decade and beyond to support the 2030 Agenda for Sustainable Development and its 17 Sustainable Development Goals (SDGs). The document outlines the societal outcomes of the UN Decade of Ocean Science for Sustainability (A Clean Ocean, A Sustainably Harvested Ocean, A Safe Ocean, A Healthy Ocean, A Predicted Ocean, A Transparent Ocean) and provides recommendations from the 'Navigating the Future V' Position Paper (2019) by the European Marine Board to address each societal outcome.

Navigating the Future V gives a birds-eye big-picture view of marine science and looks into the future (2030 and beyond) to identify key topics/themes that are set to significantly advance our understanding of the marine and broader earth and climate systems; and will be of increasing importance to societal wellbeing in decades to come.

Gilles Bœuf decrit dans cet article comment les decouvertes scientifiques sur la biodiversite et l’approfondissement des connaissances de la nature peuvent donner des perspectives et des solutions pour reparer les degâts qu’elle subit, et ouvrir des horizons pour un futur plus apaisant que celui fonde sur les technologies artificielles. Preferant le terme bio-inspiration a celui de biomimetisme, il dresse un tableau foisonnant de l’inventivite de la nature, qui peut etre « au service de l’homme » sans que celui-ci ne l’asservisse ni ne la detruise. C’est une proposition et une vision d’harmonie entre la nature et une modernite encore a inventer.

Enseignement. Biodiversite, ses croisements avec l’humanite Lecon inaugurale. Biodiversite : de l’ocean et la foret, a la cite (19 decembre 2013) Bâtie sur la chimie pre-biotique issue d’une geo-diversite anterieure, la biodiversite est nee dans l’ocean ancestral vers 3850 millions d’annees (Ma), quand les premieres cellules se sont clonees par scissiparite. La vie s’est ensuite diversifiee dans l’ocean durant des milliards et des centaines de millions d’annees et se sont alors produits des e...

Issues d’un rapport remis au ministère de l’Écologie, au début de l’année 2012,ces réflexions rassemblent une série d’interrogations fondamentales et récurrentes sur le fond et sur les aspects méthodologiques des sciences participatives : elles insistent sur l’indispensable caractère scientifique de l’objectif, la nécessaire compétence scientifique des participants et suggèrent une coordination générale et centralisée laissant une place à l’aspect spontané d’un certain nombre d’initiatives.

Les Nations Unies avaient declare l’annee 2010 « Annee internationale de la biodiversite », suite a la resolution adoptee en juin 2002 au Sommet de la Terre a Johannesburg qui avait eu la pretention de freiner, voire de stopper (!), l’erosion de la biodiversite pour 2010. Or, toutes les constatations faites en 2010, et ce des la Conference de l’Unesco tenue a Paris en janvier de la meme annee, ont montre que la situation n’avait jamais ete aussi preoccupante.

The impacts of photoperiod and temperature on the swimming behaviour of hatchery-reared Atlantic salmon smolts were investigated, with a view to optimising salmon restoration strategies in the Loire-Allier basin. A novel experimental design was developed to study individual tagged fish in 9 m diameter hatchery tanks. Movements and swimming speeds were recorded over a period of eight months (January to August), repeated over four consecutive years (2005–2008). Fish switched from positive rheotactic behavior in January-February, to negative rheotactic behaviour at mid-March or April depending on the year, a period corresponding to the start of the downstream migration of wild smolts from the upper river spawning areas. Daily variation in movement and swimming speed occurred with high swimming speeds with the flow during the day and much lower speeds during the night. Swimming speeds could exceed water current velocity, showing hatchery-reared salmon can actively swim with the flow during the day. Experimental changes of photoperiod (constant light or constant darkness) allowed confirmation of the role of photoperiod in the daily variation of swimming activity. Analysis of the relationship between water temperature and swimming speeds over the four year experiments suggested a major role for water temperature in the modulation of swimming activity. Maximal swimming speed was recorded at 10.5 °C and swimming speed was reduced by 80% for temperatures under 4 or above 17 °C. Fish stopped moving above 20 °C. The data highlight the importance of temperature for the modulation of downstream movement, as well as the potential deleterious impact of the anthropogenic increase in river temperature below the spawning and juvenile habitat in the Allier tributary on the success of downstream migration. Better understanding of temperature effects on actual population-specific in-river migration patterns is required to allow managers to identify mitigation measures needed to improve migration success.

Among diversities, there is biodiversity. In Johannesburg in 2002, it was decided to curb the loss of biodiversity by 2010 and Europe chimed in 'stop 7 We shall be far from it and the UNESCO has decided to achieve the objective again for 2020. Biodiversity is much more than the only inventory of living species, it is most of all the set of the relations living beings establish between themselves and with their environment, it is the living fraction of Nature. The Millennium Ecosystem Assessment announced in its 2005 report that living species are passing away at a pace from 100 to 1000 faster than what was estimated during those last 50 million years. The human being has become the most powerful force of evolution on the planet and must imperatively change his habits if he wants to carry on living in harmony : he is tightly intertwined with that diversity and cannot do without it. So, 2020 : realistic objective or complete Utopia ?, Parmi les diversités, il y a la bio-diversité. Il avait été décidé à Johannesburg en 2002 de freiner la perte de biodiversité pour 2010 et l'Europe avait surenchéri «arrêter » ! Nous en serons loin, l'UNESCO décide donc de relancer l'objectif pour 2020. La biodiversité est bien plus que le seul inventaire des espèces vivantes, c'est surtout l'ensemble des relations établies entre les êtres vivants et avec leur environnement, c'est la fraction vivante de la Nature. Le Millennium Ecosystem Assessment annonce dans son rapport de 2005 que les espèces vivantes s'éteignent à un rythme entre 100 et 1000 fois plus fort que celui estimé sur les 50 derniers millions d'années. L'humain est devenu la plus puissante force d'évolution de la planète et il doit impérativement changer ses habitudes s'il veut continuer à vivre en harmonie : il est profondément imbriqué dans cette diversité et ne peut s'en passer. Alors, l'objectif 2020, projet réaliste ou totale utopie ?, Boeuf Gilles. Une diversité parmi les diversités : la bio-diversité. In: Les Cahiers du Musée des Confluences. Revue thématique Sciences et Sociétés du Musée des Confluences, tome 5, 2010. La Diversité. pp. 65-75.

In most species daily rhythms are synchronized by the photoperiodic cycle. They are generated by the circadian system, which is made of a pacemaker, an entrainment pathway to this clock, and one or more output signals. In vertebrates, melatonin produced by the pineal organ is one of these outputs. The production of this time-keeping hormone is high at night and low during the day. Despite the fact that this is a well-preserved pattern, the pathways through which the photoperiodic information controls the rhythm have been profoundly modified from early vertebrates to mammals. The photoperiodic control is direct in fish and frogs and indirect in mammals. In the former, full circadian systems are found in photoreceptor cells of the pineal organ, retina, and possibly brain, thus forming a network where melatonin could be a hormonal synchronizer. In the latter, the three elements of a circadian system are scattered: the photoreceptive units are in the eyes, the clocks are in the suprachiasmatic nuclei of the hypothalamus, and the melatonin-producing units are in the pineal cells. Intermediate situations are observed in sauropsids. Differences are also seen at the level of the arylalkylamine N-acetyltransferase (AANAT), the enzyme responsible for the daily variations in melatonin production. In contrast to tetrapods, teleost fish AANATs are duplicated and display tissue-specific expression; also, pineal AANAT is special--it responds to temperature in a species-specific manner, which reflects the fish ecophysiological preferences. This review summarizes anatomical, structural, and molecular aspects of the evolution of the melatonin-producing system in vertebrates.

In a preceding paper in 1980, the status of marine salmonid rearing in French coastal waters was described and the prospects analyzed. After a period of rapid increase in production (1976–1980) a plateau was reached, and in 1983 total marketed production remained below 450 metric tons. The major part of this production was composed of rainbow trout, with coho salmon and brown trout staying at a limited scale. The causes of this evolution and the possible ways of influencing further development of this activity are discussed. Among the major factors influencing production, environmental parameters (temperature, salinity), availability of juveniles, production costs of the marine phase and market acceptability are analyzed. We include a discussion about competition with marine aquaculture products of northern Europe and the emerging production of large size rainbow trout in freshwater in southern areas of France. The major inputs to be expected from research progress and their applicability to the production phase are discussed.

Melatonin contributes to synchronizing behaviors and physiological functions to daily and seasonal rhythm in fish. However, no coherent vision emerges because the effects vary with the species, sex, moment of the year or sexual cycle. And, scarce information is available concerning the melatonin age, receptors, which is crucial to our understanding of the role melatonin plays. We report here the full length cloning of three different melatonin receptor subtypes in the sea bass Dicentrarchus labrax, belonging, respectively, to the MT1, MT2 and Mellc subtypes. MT1, the most abundantly expressed, was detected in the central nervous system, retina, and gills. MT2 was detected in the pituitary gland, blood cells and, to a lesser extend, in the optic tectum, diencephalon, liver and retina. Mel1c was mainly expressed in the skin; traces were found in the retina. The cellular sites of MT1 and MT2 expressions were investigated by in situ hybridization in the retina of pigmented and albino fish. The strongest signals were obtained with the MT1 riboprobes. Expression was seen in cells also known to express the enzymes of the melatonin biosynthesis, i.e., in the photoreceptor, inner nuclear and ganglion cell layers. MT1 receptor mRNAs were also abundant in the retinal pigment epithelium. The results are consistent with the idea that melatonin is an autocrine (neural retina) and paracrine (retinal pigment epithelium) regulator of retinal function. The molecular tools provided here will be of valuable interest to further investigate the targets and role of melatonin in nervous and peripheral tissues of fish. (c) 2008 Published by Elsevier Inc.

Melatonin biosynthesis from serotonin involves the sequential activation of the arylalkylamine N-acetyltransferase (AANAT) and hydroxyindole-O-methyltransferase (HIOMT). Photoperiod synchronizes a daily rhythm in pineal and retinal melatonin secretion through controlling AANAT activity. Teleost fish possess two Aanat, one expressed in the retina (AANAT1) and the other expressed in the pineal gland (AANAT2). We report here the full-length cloning of Aanat1, Aanat2, SmHiomt and Otx5 (orthodenticle homeobox homolog 5) in the turbot (Scophthalmus maximus, Sm), a flatfish belonging to an evolutionary recent group of Teleost. The temporal expression pattern of the genes investigated is consistent with the idea that OTX5 is needed for photoreceptor specification, and that the pineal gland differentiates before the retina. SmAanat2 expression remained pineal specific during the period of time investigated, whereas SmOtx5 and SmHiomt expressions were seen in both the retina and pineal gland. Our results do not support the existence of a second SmHiomt, as is the case for SmAanat. Neither SmAanat2 nor SmHiomt mRNAs displayed cyclic accumulation in the pineal organ of embryos and larvae maintained under a light-dark cycle from fertilization onward. This is in marked contrast with the situation observed with zebrafish Aanat2, indicating that the molecular mechanisms controlling the development of the pineal melatonin system have been modified during the evolution of Teleost.

Melatonin, a hormonal output signal of vertebrate circadian clocks, contributes to synchronizing behaviors and neuroendocrine regulations with the daily and annual variations of the photoperiod. Conservation and diversity characterize the melatonin system: conservation because its pattern of production and synchronizing properties are a constant among vertebrates; and diversity because regulation of both its synthesis and modes of action have been profoundly modified during vertebrate evolution. Studies of the targets and modes of action of melatonin in fish, and their parallels in mammals, are of interest to our understanding of time-related neuroendocrine regulation and its evolution from fish to mammals, as well as for aquacultural purposes.

La melatonine est l'hormone donneuse de temps chez les Vertebres. Par la dynamique de sa production nycthemerale et saisonniere, elle assure la synchronisation de fonctions physiologiques et de comportements sur des periodicites naturelles. Chez les poissons, la melatonine est synthetisee principalement par les cellules photoreceptrices de l'organe pineal et de la retine. La voie de synthese de la melatonine est egalement activee au niveau de certains types cellulaires des couches "nucleaire interne" et "ganglionnaire" de la retine. Chez une majorite d'especes, la synthese de melatonine est maximale de nuit (high-at-night ), assujettie aux variations circadiennes de l'avant-derniere enzyme de la voie de sa synthese, l'arylalkylamine N -acetyltranferase (AANAT). Chez d'autres, le profil de melatonine retinienne presente un maximum le jour (high-at-day ), ou aux interphases. Les donnees de la litterature resumees ici concernent les mecanismes moleculaires et cellulaires mis en jeu dans le controle de la production de cet important messager du systeme circadien, soulignant en particulier leur plasticite.

Melatonin is the time-keeping molecule of the organism. The production by the pineal organ is responsible for the diurnal and annual rhythms of plasma melatonin content. This contributes to synchronizing behavioural, biochemical and physiological processes to the environmental variations in photoperiod and temperature. Conservation and diversity characterize the melatonin system in vertebrates: conservation because its nocturnal pattern of production as well as its synchronizing properties are a constant; diversity because the modalities of its biosynthesis and modes of action have been profoundly modified in the course of evolution. This review summarizes our current knowledge on the targets and modes of action of melatonin in fish and comparisons are made with mammals.

On the Planet Earth, oceans and seas today correspond to the largest volume offered to Life. Roughly, 275,000 species have been described from marine environments, only representing some 15% of all the present known living. But marine biomass can be enormous. Life appeared in the ancestral ocean 3 800 million years ago and determining events occurred there: appearance of the nuclear membrane and cell nucleus, "pluricellularity", capture of bacteria transformed into organelles, then sexuality. On the 33 phyla existing today on the Earth, 12 never have left the ocean and are exclusively marine. Such biodiversity, archaism of characters, organisational and behavioural patterns make these marine organisms an excellent reservoir for identifying and extracting very interesting pharmacological and cosmetic molecules (>5 000 today) and/or to represent very pertinent "models" for basic and applied research. Relationships between ocean and public health are physical, chemical, biological and physiological. A few marine species as "models" set the base for major advances in life sciences recognized by several Nobel Prices: from the discovery of phagocytosis to anaphylactic shock, and including nervous influx transmission, memory molecular bases, cyclins discovery, eye organisation, neurotransmitter membrane receptors, bases of the specific immune system... These marine models are very useful to understand the origin and functioning of important living mechanisms in the human and sometimes to deduce applications for efficient treatments. Ocean supplies mankind with renewable living resources, much threatened today. We have to manage and protect these to maintain ecosystems, stocks and biodiversity. Only because of the greenhouse effect and anthropic emissions, temperature is globally increasing: and, what if (tomorrow?) one million species would disappear (before 2050) because of global warming?

The issue of what starts the circadian clock ticking was addressed by studying the developmental appearance of the daily rhythm in the expression of two genes in the zebrafish pineal gland that are part of the circadian clock system. One encodes the photopigment exorhodopsin and the other the melatonin synthesizing enzyme arylalkylamine N-acetyltransferase (AANAT2). Significant daily rhythms in AANAT2 mRNA abundance were detectable for several days after fertilization in animals maintained in a normal or reversed lighting cycle providing 12 h of light and 12 h of dark. In contrast, these rhythms do not develop if animals are maintained in constant lighting or constant darkness from fertilization. In contrast to exorhodopsin, rhythmicity of AANAT2 can be initiated by a pulse of light against a background of constant darkness, by a pulse of darkness against a background of constant lighting, or by single light-to-dark or dark-to-light transitions. Accordingly, these studies indicate that circadian clock function in the zebrafish pineal gland can be initiated by minimal photic cues, and that single photic transitions can be used as an experimental tool to dissect the mechanism that starts the circadian clock in the pineal gland.

Otoliths are composed of 99% CaCO3 in the aragonite form which is deposited daily onto an organic matrix. The mineralisation process takes place in an acellular medium, the endolymph, which is secreted by the inner-ear epithelium. The present review is mostly devoted to ionic and organic endolymph components (concentration and spatial distribution) in relation to otolith growth, with a special interest to the ionic supply from plasma to endolymph and to the biochemical relationships between endolymph and otolith matrix. To cite this article: P. Payan et al., C. R. Palevol 3 (2004).

This is the first study in which the effects of an external stress were analysed at different levels: plasma ho meostasis, endolymph chemistry, and otolith growth. Stress was applied to rainbow trout (Oncorhynchus mykiss) by exposure to Cl2gas. In the plasma of Cl2-stressed trout, Na+and Cl–decreased (70 mmol·L–1) and K+increased (2.0 mmol·L–1), whereas total Ca was unchanged. A slight hypercapny (+2.4 mmHg (1 mmHg = 133.322 Pa)) was observed related to a significant rise (40%) in total CO2without pH variation. In the endolymph, Na+and Cl–also decreased, whereas other parameters (K+, PO43–, Mg, and, peculiarly, total Ca) remained stable. The important effect provoked by Cl2stress in endolymph was an increase of proteins (factor of 2.6) and total CO2(factor of 3.1) concentrations at the proximal side of the endolymph. The stress induced a decrease in otolith growth rate and produced a discontinuity (check) in the microstructure pattern of the otolith characterized by a large D zone. The variations in the endolymph composition are discussed and we propose that they result not only from changes in plasma concentrations, but also from changes (organic and crystallization) in otolith deposition.

The soluble organic matrix (OM) of various biominerals (red coral skeleton, oyster shell, sea urchin test, turbot otolith, chicken eggshell) was extracted after demineralization with acetic acid. The protein content of the OM varies strongly from 0.02 to 1.6 microg/mg biomineral whereas proteoglycans present less variations (from 0.7 to 1.4 microg/mg biomineral). Electrophoresis of biominerals OM shows differences in their protein pattern although several bands are present in all matrices. OM of all biominerals shows carbonic anhydrase activity but no activity was detectable in the endolymph. OM of all biominerals also displays an anticalcifying activity. After separation of the OM extracts by chloroform-methanol, 80% of the anticalcifying activity was found in the methanol phase except in the urchin test. After OM precipitation with trichloracetic acid, 70% of the activities was found in the supernatants. Partial biochemical characterization suggests that the anticalcifying factor is a polyanionic and water-soluble molecule, which could be proteoglycans. The endolymph surrounding the otolith also displays an anticalcifying activity although its inhibitous activity was 50 times lower than that of the otolith OM. However, the anticalcifying activity of the endolymph is assumed by a proteic structure (80% activity precipitated with TCA treatment). Our results suggest that both carbonic anhydrase and anticalcifying activities are widespread and play a significant role in the regulation of biomineral formation. Results are discussed in relation to the calcification process that takes place at the fluid-mineral interface.

Turbot juveniles were exposed to four ammonia concentrations (0·17 (L), 0·34 (M), 0·73 (MH) and 0·88 (H) mg l-1 NH3-N) for different exposure durations (28 days minimum to 84 days). Their physiological status and growth performances were compared to a control group (0·004 (C) mg l-1 NH3-N). No growth was observed in the H group, and by day 57, mass increase in the MH group was only 15% of that in group C. During the first month growth in the L group was similar to that in control group while it was lower (33%) in the M group; afterwards the L and M groups had a similar growth (half that of controls). Accumulation of total ammonia nitrogen (TA-N) in plasma was dependent on ambient ammonia concentrations. Plasma urea levels in ammonia-exposed fish were lower, similar or greater than in controls (depending on ammonia concentration or exposure duration). Osmolarity, Cl- and Na+ plasma concentrations were stable in the L and M groups. The increases in Na+, Cl-, K+ and total Ca concentrations observed by the end of the experiment in the H and MH groups suggest that fish failed to adapt. There was an initial rise in plasma cortisol in all ammonia-exposed groups followed by a return to basal level (1·7-4 ng ml-1) in the L and M groups. In group MH, plasma cortisol peaked at 42 ng ml-1 by day 14, and after a decline at c. 1 month (14 ng ml-1), it rose again.

A comparative study of blood oxygen binding and carrying capacities of turbot Scopthalmus, maximus and sea bass Dicentrarchus labrax, two fish species differing in their demand for oxygen, was carried out under three levels of chronic hypoxia (Po 2 =93. 65 and 40 mmHg) for 40 days. Blood O 2 affinity in normoxia was moderately high in both species (P 50 was c. 12-13 mmHg at pH 7.7). The Bohr factor was significantly lower in turbot (-0.52) than in sea bass (-0.85). In both species, blood O 2 affinity was not significantly affected by oxygen depletion whatever its level and duration. In turbot, however, P 50 appeared to slightly decrease at the two more severe levels of hypoxia. In both species, blood O 2 carrying capacity was not affected by hypoxia and remained twice as high in sea bass than in turbot.

Effects of O-2 supersaturation on metabolism and growth were studied in juvenile turbot (Scophthalmus maximus L.). When fish were reared for 30 days in water containing O-2 at 147% or 223% air saturation, there were no significant differences in food intake, growth, food conversion or protein utilization compared to fish exposed to normoxia (100% air saturation in water outlet). Exposure to hyperoxia resulted in increased body fat deposition. Daily rates of O-2 consumption of resting fish were not affected by O-2-concentrations, and there were no significant differences in rates of nitrogenous excretion among fish exposed to the different O-2-concentrations. Turbot tolerated severe hyperoxia, 350% air saturation, for 10 days.There were changes in acid-base balance that compensated for the respiratory acidosis resulting from O-2 supersaturation. Blood pH was regulated within 24 h (it averaged 7.69 over the 30-day experiment) by significant increases in plasma CO2 content and pCO(2). Plasma CO2 was dose dependent averaging 11.3 and 18.9 mmol l(-1) under 147% and 224% O-2 saturation, respectively, compared to 6.7 mmol l(-1) under notmoxia. Over the 30-day experiment, the only change in hydromineral balance was a slight, but non-significant decrease in plasma chloride content in fish exposed to hyperoxia (137 mmol l(-1) compared to 139 under normoxia). There were no changes in haematocrit, haemoglobin and red blood cell counts (they averaged 18.3%, 3.7 g dl(-1) and 1.37 x 10(6) mm(-3). respectively) and no signs of stress (plasma cortisol averaged 3.8 ng ml(-1)) related to exposure to O-2-supersaturation for 30 days.

Hormonal changes, substrate mobilization and energy metabolism were studied inturbot Scophthalmus maximus exposed to 3 hypoxic conditions (oxygen partial pressure in water,PwO 2 = 90, 60 and 30 mm Hg) followed by recovery under normoxia. Measurements of the blood pH,total CO 2 concentration, arterial oxygen partial pressure, hematocrit, glucose, lactate, and ‘stress’hormones (cortisol, adrenaline and noradrenaline) plasmatic concentrations were performed. High-energy phosphorylated compounds, glycogen, glucose and lactate concentrations were also deter-mined in liver and white muscle tissues. Exposure to 90 or 60 mm Hg did not induce any majorphysiological change, as hyperventilation by itself could compensate for the decrease in wateroxygen tension. At 30 mm Hg, marked increases in cortisol, adrenaline and noradrenaline concen-trations, associated with a decrease in blood arterial oxygen partial pressure, were observed. Duringexposure to 30 mm Hg, turbot resorted to anaerobic metabolism, resulting in liver glycogen depletionand lactate production. This mechanism appeared to be efficient enough to produce energy, as nosignificant change in phosphorylated compounds and adenylate energy charges in muscle and livercould be observed. These results indicate an absence of metabolic depression in turbot downto 30 mm Hg and confirm the high capacity of this species to cope with low water oxygen tension.KEY WORDS: Hypoxia · Anaerobiosis · Catecholamines · Cortisol · Lactate · Turbot

Development and growth (continuous in fish) are controlled by 'internal factors' including CNS, endocrinological and neuroendocrinological systems. Among vertebrates, they also are highly dependent on environmental conditions. Among other factors, many studies have reported an influence of water salinity on fish development and growth. In most species, egg fertilization and incubation, yolk sac resorption, early embryogenesis, swimbladder inflation, larval growth are dependent on salinity. In larger fish, salinity is also a key factor in controlling growth. Do the changes in growth rate, that depend on salinity, result from an action on: (1) standard metabolic rate; (2) food intake; (3) food conversion; and/or (4) hormonal stimulation? Better growth at intermediate salinities (8-20 psu) is very often, but not systematically, correlated to a lower standard metabolic rate. Numerous studies have shown that 20 to >50% of the total fish energy budget are dedicated to osmoregulation. However, recent ones indicate that the osmotic cost is not as high (roughly 10%) as this. Data are also available in terms of food intake and stimulation of food conversion, which are both dependent on the environmental salinity. Temperature and salinity have complex interactions. Many hormones are known to be active in both osmoregulation and growth regulation, e.g. in the control of food intake. All of these factors are reviewed. As often, multiple causality is likely to be at work and the interactive effects of salinity on physiology and behaviour must also be taken into account.

This paper compares the organic compositions of the otolith and endolymph of trout and turbot. Irrespective of the method of demineralization (0.5 M EDTA or acetic acid), trout otoliths were found to be largely composed of proteins (48%), collagens (23%), and proteoglycans (29%). Collagen was only detectable in the EDTA-insoluble (0.30 microg/mg) and in the acetic acid-soluble fractions (0.53 microg/mg). The same compounds were found in the endolymph but in different proportions (proteins 85%, collagens 12%, and proteoglycans 3%). It was shown that the distribution of these compounds was not uniform within the endolymph. Proteins, collagens, and amino acids were 4, 10, and 3 times, respectively, more concentrated in the proximal (facing the macula) than the distal side whereas proteoglycans were 10 times more concentrated at the distal side. SDS PAGE analyses of proximal and distal samples of endolymph showed similar patterns suggesting that the spatial gradient of protein is quantitative and not qualitative. SDS PAGE comparison of endolymph and otolith samples showed only two proteins with similar molecular weights. We propose that collagen and protein gradients are involved in the organic matrix formation and otolith calcification process. Endolymphs from both trout and turbot display inhibitions of in vitro calcification although these inhibitions were 50 and 80 times, respectively, less than that of the otoliths. The inhibitory factor probably plays a significant role in the regulation of otolith calcification.

A RT-PCR approach was used to clone and sequence the full-length growth hormone receptor (GHR) of a teleost fish, the turbot (Scophthalmus maximus). Total liver RNA was amplified by RT-PCR with degenerate primers designed in extracellular and cytoplasmic regions, and a single DNA fragment of 1100 bp was obtained. The entire coding region was obtained by 5' and 3' RACE assays, and comprises an open-reading frame of 633 amino acids. This sequence shows the characteristic motifs of the class I cytokine receptor superfamily, and its amino acid identity with mammalian, avian, reptilian and amphibian GHRs is 32-36%. The 3' RACE also revealed the occurrence of an alternate messenger encoding a membrane-anchored truncated receptor, which could facilitate the production of GH-binding protein in fish species. This report represents the first data on fish GHR sequence, and it provides evidence for the conservation of this receptor throughout vertebrate evolution.

The effects of hypoxia on growth, feed efficiency, nitrogen excretion, oxygen consumption and metabolism of juvenile turbot (120 g) were studied in a 45-day experiment carried out in sea water at 17.0 +/- 0.5 degrees C and 34.5 ppt salinity. Fish were fed to satiation at O-2-concentrations of 3.5 +/- 0.3, 5.0 +/- 0.3 mg l(-1) (hypoxia) and 7.2 +/- 0.3 mg l(-1) (normoxia). Both feed intake (FI) and growth were significantly lower under hypoxia than under normoxia, with no significant differences being observed between 3.5 and 5.0 mg O-2 l(-1). During the first 2 weeks of the experiment, FI was halved under hypoxic conditions, and there were large differences among treatments in feed conversion ratio (FCR), i.e., it was 3.2, 1.5, and 0.9 in turbot exposed to 3.5, 5.0, and 7.2 mg O-2 l(-1), respectively. Thereafter, FCR was not significantly affected by O-2-concentration. Nitrogen excretion and oxygen consumption of feeding fish were significantly higher under normoxia than under hypoxia, but following 7 days of feed deprivation oxygen consumption was similar under normoxia and hypoxia. Plasma osmolarity, ionic balance, and acid-base status were not affected by the two hypoxic conditions tested. Overall, our results indicate that turbot have some capacity to adapt to relatively low ambient O-2-concentrations.

Variations in respiratory and acid-base status were studied in turbot (Scophthalmus maximus) during progressive severe hypoxia followed by recovery under normoxic conditions. The first behavioural strategy of turbot under hypoxia was an increase in amplitude and frequency of ventilation. Consequently, standard O2 consumption remained unchanged over a broad range of O2 tensions, until a low critical level of 30 mmHg. The hyperventilation induced a moderate blood alkalosis, compensated by a lactic acidosis. The fact that blood pH did not decrease below control values could be explained by the retention in white muscle of most of the lactate produced and by a high capacity for H+ excretion. During the recovery period, the marked increase in O2 uptake corresponding to an oxygen debt repayment, was partly related to the lactate elimination. When total energy contributions of aerobic and anaerobic processes were assessed in terms of ATP, the anaerobic contribution, estimated at the deepest hypoxia level, was higher than 20% of the total energy budget and appeared to totally compensate for the decline in aerobic metabolism. Moreover, the high value of O2 tension in arterial blood in normoxia and during recovery from hypoxia showed high diffusing capacity of gills in turbot. Our results explain the high tolerance of turbot for O2 deficient waters.

The development of a recombinant turbot somatotropin (rtuGH) in Escherichia coli and an homologous antibody in rabbit has produced a sensitive and specific RIA allowing the measurement of blood levels and pituitary contents of tuGH and their responses to environmental change. Turbot IGF-1 (insulin growth factors) and IGF type 1 receptor (R) cDNA have also been cloned and sequenced. The deduced IGF-1 R primary sequence contains all the topological features characteristics of mammalian IGF-1 R and the turbot R appears highly conserved, compared to its mammalian counterpart, particularly within the catalytic domain. IGF-1 R mRNA polyadenylation status varies during development with polyadenylation occuring in oocytes and early stage larvae. It disappears in later stages and in adult somatic tissues, indicating that IGF-1 R mRNA undergoes complex post-transcriptional regulation. Thyroid hormones (TH, both T 3 and T 4 ), are also involved in growth control, but are less affected by environmental changes than GH, except in very extreme conditions. The thyroid stimulating hormone (TSH) β-subunit cDNA fragment has also been cloned and sequenced. mRNA expression levels have been quantified under conditions where blood circulating TH were modified by dietary treatments or hormone supplementation. Specific growth rate in turbot is related to food intake and is doubled with a temperature increase from 8 to 20° C. Lipid storage by contrast was higher at low temperatures. Over a long time course, growth rate in turbot can be improved in brackish water (8-20 psu) but it cannot adapt to very low salinities. Photoperiod appears to have little influence on growth when feeding is unrestricted. Under intensive farming conditions, ammonia, the major nitrogen waste product in teleosts. may increase to levels that can reduce growth. Safe ambient levels for growth are

Fish otoliths provide a record of age, growth, and environmental influences. In both trout and turbot, spatial chemical investigation of the endolymph surrounding the otolith (sagitta) showed a lack of uniformity. Proteins, [Formula: see text], and Mg2+were significantly more concentrated in the proximal (facing the macula) than distal zone, whereas the opposite was observed for K+and total CO2(totCO2). Na+concentration ([Na+]) was 20% higher in the proximal zone in trout but not in turbot. Total Ca and Cl−contents were uniformly distributed in both species. We propose that the endolymphatic gradients of protein and totCO2concentration within the endolymph are involved in the otolithic biocalcification process. Microchemical analyses of otolith sections by wavelength dispersive spectrometry showed a lack of spatial uniformity in the K/Ca and Na/Ca ratios, whereas the Sr/Ca ratio was uniform. There is a clear relationship between endolymph and otolith [K+], but the interpretation of the results for [Na+] needs further investigation. Thus the lack of uniformity in the otolith composition must be taken into account when investigating otolith microchemistry.

Light compares a complex of external and ecological factors, including colour spectrum, intensity and photoperiod. Light characteristics are very specific in an aquatic environment and light is extremely variable in nature. `Receptivity' of fish to light profoundly changes according to the species and the developmental status. Specific photoreceptor cells are present in both eye and pineal. If it is easy to change the light in experimentation and to observe the effects on fish growth, it is much more difficult in nature to make such determinations. In larvae, many studies have been dedicated to the influence of intensity and photoperiod on growth: generally, species need a minimal threshold intensity to be able to develop normally and grow. This is probably related to the aptitude to localize, catch and ingest prey. Light is also indispensable for body pigmentation, an important phenomenon involved in early development and growth. Too intense light can be stressful or even lethal. A few species are able to develop and grow at very low intensities or, sometimes, in the absence of light. Generally, long daylength improves larval rearing quality. The synergistic effect of `food availability-daylength' appears to be determining at this stage. In older fish, there is very little information about the influence of light `quality' but more about intensity and much more about photoperiod. Light intensity effects are not so clear and depend on the species and the experimental procedures: it is probably not an important factor for growth stimulation. Daylength appears much more important. Many species, including both marine species and salmonids, react to photoperiod treatments and long daylength stimulates growth. The most studied species is the Atlantic salmon, which is very sensitive, both during the freshwater stage, with the parr–smolt transformation very dependent on the photoperiod, and also in sea water. In this last condition, lighting also influences early maturation. An important point is to be certain that light affects fish growth through a better food conversion efficiency and not just through stimulated food intake. Also included in this review is a discussion about the endolymph–otolith system, which is very sensitive to daylight and seasonal cycles and a review of the present knowledge on the involvement of light influence on hormone levels (melatonin, somatotropin, thyroid hormones and other hormones).

Thyroid stimulating hormone (TSH) is a vertebrate pituitary heterodimeric hormone that stimulates the thyroid gland to produce the thyroid hormones, T3 and T4. We report here the cloning, by PCR on reverse-transcribed pituitary RNAs, of a 180 bp fragment of the cDNA encoding TSH β subunit in the turbot (Psetta maxima). The deduced amino acid sequence displayed 66 and 75% identity with the corresponding sequence from the European eel (Anguilla anguilla) and the rainbow trout (Oncorchyncus mykiss), respectively. This cDNA was then used as a probe for densitometric analysis of individual pituitary Northern blots. TSH β mRNA levels were quantified in turbot where circulating thyroid hormones were modified by dietary treatments or hormone supplementation. Recombinant rainbow trout growth hormone had no effect on circulating thyroid hormone levels or on pituitary TSH β mRNA level. In turbot fed heat-treated rapeseed meal, plasma T4 levels were lowered and TSH β mRNA increased more than two fold. In contrast, when turbot were fed a standard fish-meal supplemented with T3, circulating T3 levels were elevated and there was a dramatic decrease in TSH β mRNA level. It is concluded that both thyroid hormones are able to down-regulate TSH β mRNA level in vivo in the turbot. These results are discussed in the context of the evolution of the TH feed-back on TSH production.

The effect of a short period of starvation (5–6 weeks) on thechemistry of plasma and inner ear endolymph (Na+,K+, Cl-, total Ca, protein, totalCO2 concentrations and pH) was studied in trout (Oncorhynchusmykiss). In plasma, only total Ca significantly decreased, by 0.17 mM, instarved trout. A slight drop (10%) in the plasma protein content wasalso observed. Starvation induced a metabolic plasma alkalosis characterizedby a non-signifiacant increase in pH and a significant drop of 22% oftotal CO2. In endolymph, the Na+,K+, Cl- , total Ca and protein concentrationswere not significantly different in control and starved trout, but in thelatter, the pH of the endolymph was less alkaline (significant decrease of0.3 UpH) and the total CO2 concentration was significantlyreduced by 50%. Experimental starvation was selected as aphysiological situation characterized by a slowing down of both somatic andotolith growth. We propose that the reduced rate of otolith growth isdirectly related to an overall reduction in the alkalinity of theendolymph.

L'azote ammoniacal est un toxique potentiel en elevage de poissons ayant des effets plus ou moins severes selon la concentration ambiante et la duree d'exposition. Dans une premiere partie, nous rappelons que l'AAT (somme de NH 4 + et NH 3 ) est toxique essentiellement sous sa forme NH 3 . Des qu'un poisson se trouve en presence de niveaux d'AAT anormalement eleves, il y a entree d'AAT surtout sous forme de NH 3 et diffusion dans les differents compartiments du poisson (a l'equilibre, le NH 4 + est dominant). Selon les conditions d'exposition, differents etats d'equilibre se succedent entre le poisson et le milieu des lors que ses capacites d'excretion sont affectees. A partir d'un certain niveau de concentration d'AAT dans le sang et les tissus, le poisson n'arrive plus a reguler ses fonctions vitales, le seuil de toxicite est atteint. Nous faisons ensuite la synthese de l'etat des connaissances des effets de l'AAT sur la survie et la croissance du turbot (Psetta maxima) en le comparant a d'autres especes de poissons elevees en mer ou en eau douce. A court terme, la sensibilite du turbot a l'AAT est du meme ordre de grandeur que celle de la daurade et du bar, la 96-h CL50 (concentration letale pour 50 % de la population) varie dans une fourchette de 1 a 3 mg/l NH 3 . Des valeurs aussi elevees ne peuvent etre qu'accidentellement rencontrees, meme dans les elevages a haute densite. Chez toutes les especes marines eprouvees, le seuil de toxicite chronique est plus bas, 0,8-1 mg/l NH 3 pour une duree d'exposition n'excedant pas un mois. Chez le turbot, la croissance est ralentie a 0,33 mg/l NH 3 en moyenne et sensiblement aux memes valeurs chez le bar et la daurade. Chez ces memes especes selon la dure d'exposition, il y a risque de perturbation de la croissance au-dessus de 0,11 mg/l NH 3 , ce qui correspond aux pics de concentrations dans les elevages a haute densite utilisant des circuits fermes. Ces seuils de securite en termes de croissance sont sensiblement plus bas chez les salmonides (0,02-0,15 mg/l NH 3 ), surtout pendant la phase d'eau douce. En definitive, dans des conditions de croissance par ailleurs optimales (facteurs du milieu et alimentation) le turbot et les poissons marins, pris au stade juvenile, sont relativement tolerants a l'AAT. Toutefois leur sensibilite est etroitement dependante de facteurs environnementaux tels que le pH et la disponibilite en oxygene. Elle peut de meme etre modulee par les conditions d'exposition : pre-acclimatation, niveaux fluctuants d'AAT et duree d'exposition.

Des turbots d'un poids moyen initial de 32 g ont ete exposes pendant 60 jours a 4 photoperiodes constantes (8L:160, 12L:12O, 16L:8O, 24L:0O) et a 2 photophases variables : l'une croissante (de 12 a 16 h) et l'autre decroissante (de 12 a 8 h). Les autres parametres du milieu ont ete maintenus constants pendant les 2 mois de l'experimentation (temperature : 17 ± 0,5 °C, salinite : 34,5 ppm, intensite lumineuse : 2 W.m -2 , concentration en oxygene superieure a 6 mg.l -1 ). La survie, la croissance ponderale et differents indicateurs alimentaires (taux de conversion apparent, coefficients d'utilisation et d'efficacite proteiques) ont ete determines. L'excretion azotee (niveaux journaliers et profils horaires de l'excretion d'Azote Ammoniacal Total, AAT, et d'azote ureique) et certains parametres plasmatiques (osmolarite, natremie, kaliemie, chloremie, niveaux circulants des hormones thyroidiennes) ont ete mesures. Au cours de l'experience, aucune mortalite n'est apparue. Les croissances ponderales et les taux de croissance specifique ont ete identiques pour tous les traitements (poids moyens multiplies par trois en 60 jours). De meme, la prise alimentaire (1,5-1,7 % de la biomasse par jour), le taux de conversion alimentaire (0,70-0,75) et les coefficients d'utilisation (36-39 %) et d'efficacite (2,5-2,7) proteiques ne sont pas influences par la photoperiode. La composition corporelle des animaux en proteines, lipides totaux, cendres et eau n'a pas subi de modification au cours de l'experimentation. Osmolarite et electrolytes plasmatiques sont stables et identiques pour les differentes conditions. La thyroxine est stable quelle que soit la photoperiode, les niveaux circulants sont compris entre 2 et 4 ng.ml -1 . Les concentrations plasmatiques en T 3 apparaissent significativement differentes en fin d'experience : elles sont plus basses chez les animaux en photophase decroissante et chez ceux maintenus en photophase courte (8 h). Les taux journaliers d'excretion azotee sous la forme d'AAT (200-230 mg.kg -1 .j -1 ) et d'uree (65-75 mg.kg -1 .j -1 ) sont identiques pour tous les traitements. Les profils d'excretion azotee ont presente des differences notables selon la photoperiode. Lexcretion d'AAT est caracterisee par un pic post-prandial chez les animaux soumis a une alternance jour/nuit. Par contre, en eclairage continu, les taux horaires d'excretion d'AAT restent stables tout au long du nycthemere. Curee presente un pic nocturne dont l'amplitude, l'etalement et l'heure d'apparition dependent de la photoperiode. En eclairage continu, cette augmentation de l'excretion d'uree est observee a un moment durant lequel les autres poissons sont en phase nocturne. A l'instar d'autres especes de poissons plats, le turbot est peu sensible a la photoperiode du moins lorsque les conditions d'alimentation sont ajustees a la duree de la phase eclairee.

The IGFs, their receptors and their binding proteins constitute a family of cellular modulators that play essential functions in the regulation of growth and development. In our study, we have carried out the molecular characterization of the IGF-I and its receptor (IGF-1R) from the turbot (Psetta maxima), a teleost flatfish. By RT-PCR, we have cloned an IGF-I cDNA. The deduced peptide shows 70-96 % identity with the other vertebrate IGF-I sequences previously described. We have also cloned a cDNA encoding the IGF type 1 receptor precursor from an embryos cDNA library. The deduced IGF-1R primary sequence contains all the topological features characteristic of the IGF-1R. Indeed, the turbot receptor is highly conserved compared to its mammalian counterparts, particularly within the catalytic domain. Some differences were nevertheless observed in the primary sequence that may affect the function of the receptor. Finally, by using an RT-PCR approach, we have shown that IGF-1R mRNA polyadenylation status varies according to the developmental stage., Les IGF, leurs récepteurs et leurs protéines de liaison constituent une famille moléculaire qui joue un rôle essentiel dans la régulation de la croissance et du développement. Nous nous sommes intéressés à la caractérisation moléculaire de l'IGF-l et de son récepteur (IGF-1R) chez le turbot (Psetta maxima), un poisson plat téléostéen. Par RT-PCR, nous avons clone un ADNc codant pour les quatre domaines de l'IGF-l mature. La protéine présente 70 à 96 % d'identité avec les autres IGF-I de vertébrés. Le clonage de la séquence codante entière du récepteur a nécessité la construction d'une banque d'ADNc d'embryons de turbots. Le récepteur est organisé en domaines dont la taille et les caractéristiques sont semblables à celles des autres récepteurs aux IGF de type 1 décrits chez les mammifères et le poulet. La région catalytique est particulièrement conservée. Dans certains domaines, notamment dans la région C-terminale du précurseur, quelques différences qui pourraient avoir une importance fonctionnelle sont cependant observées. Enfin, par RT-PCR, nous avons mis en évidence une régulation ontogénique du statut de polyadénylation des ARNm IGF-1R.

The study of marine biodiversity is timely and fundamental for a number of reasons (CBD, Global Biodiversity Outlook 3, 2010). Marine biodiversity plays a key role through ecosystem services (provisioning and regulation, amongst others). They provide economic wealth and resources that range from active ingredients for pharmaceuticals and medicine to products from fisheries and aquaculture, as well as contributing to cultural well-being and supplying relevant “biological models” for both basic and applied research. The role and dynamics of biodiversity are central themes when addressing climate change, earth and universe sciences or sustainable use of natural resources. Thus the issues of application involve policy, regulations and ways to globally manage energy and food security.