Turbot Psetta maxima were exposed 5 days to the dissolved fraction of fuel oil number 2, then decontaminated over 30 days in clean sea water. Biliary metabolites and ethoxyresorufin‐O‐deethylase (EROD) activity were evaluated during and after the contamination. These results were compared with chromosomal damage measured by flow cytometry (FCM). Erythrocyte nuclear abnormality, micronuclei and immaturity were also evaluated over the exposure period. Biliary metabolites and EROD analyses showed a clear and early response: biliary metabolites were detected from the first day of contamination to the 14th day of depuration, EROD activity increased during the contamination period reached a maximum 3 days after the beginning of the decontamination and decreased to the control value after 1 month of depuration. FCM showed a bimodal response: a first increase of coefficient of variation of blood cell DNA content was observed during the contamination and a second one started after 14 days of depuration and was maintained for at least 2 weeks. Erythrocyte morphology analysis showed a strong increase in nuclear abnormality during the contamination period. These results confirm previous work and show that in the context of marine accidental pollution by heavy fuel oil, the measurements of chromosomal damage by FCM allow the detection of a genotoxic response in fishes.

A habitat selection experiment was conducted to examine the behavioural response of sole Solea solea to a combination of sediment quality (exopolysaccharides, EPS-free, i.e. 0 mg l(-1) and EPS-rich, i.e. 4 mg l(-1)) and water oxygenation level (100 and 35% air saturation). The distribution of sole was influenced differently by the type of substratum depending on the water oxygenation level. In normoxia, sole settled preferentially on sand whereas under hypoxic conditions, sole settled preferentially on the muddy substratum. In order to explain these apparently counter-intuitive observations, it is proposed that, via cutaneous respiration, young sole are able to take advantage of the large quantities of oxygen produced by microphytobenthic organisms present in the upper few millimetres of muddy substratum. (c) 2008 The Authors Journal compilation (c) 2008 The Fisheries Society of the British Isles.

Evaluating the ecological impact of an oil spill is a complex issue requiring coherently articulated examination of the sequence of interactions that link the cell, where contaminants exert their effects, to the ecosystem, where interactions with human activities arise. This sequence of interactions traverses the frontiers between scientific disciplines (chemistry, toxicology, physiology, and fisheries ecology). Using the common sole (Solea solea L.) as a model species for the coastal habitats polluted by the "Erika" oil spill, our research project attempted to define indices of functional integrity that characterised the consequences of fuel exposure at the different biological levels. The coupling of field observations with experimental laboratory work revealed how functional alterations which are readily observable within individuals and their organs are progressively obscured as investigation progresses towards more complex organisational levels. Some of the approaches and indices are proposed as instruments for evaluating the impact of contamination by hydrocarbons.

Flatfishes, turbots (Scophthalmus maximus), were injected intraperitoneally with two doses of fuel oil number 2. Biliary metabolites were evaluated by fixed fluorescence to verify the efficiency of intoxication. Ethoxyresorufin-O-deethylase (EROD) activity was compared with chromosomal damage measured by flow cytometry. The analysis of biliary metabolites showed a good dose–response relation and constitutes a clear reference for the subsequent measurements. Comparing flow cytometry and EROD results, a shorter delay of response for EROD activity was obtained, but chromosomal damage was significant only after 1 week. The persistence of the EROD response was shorter, while the genotoxic signal still persisted after 1 month. The measurement of chromosomal damage allowed a good differentiation between the two tested doses. In the case of EROD activity, the results were less clear. The results suggest that within a few weeks after exposure to fuel oil number 2, the measurements of chromosomal damage by flow cytometry can be used to detect a dose-dependant genotoxic response in fish.

A comparative study of blood oxygen binding and carrying capacities of turbot Scophthalmus maximus and sea bass Dicentrarchus labrax, two fish species differing in their demand for oxygen, was carried out under three levels of chronic hypoxia (Po2 = 93, 65 and 40 mmHg) for 40 days. Blood O2 affinity in normoxia was moderately high in both species (P50 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 O2 affinity was not significantly affected by oxygen depletion whatever its level and duration. In turbot, however, P50 appeared to slightly decrease at the two more severe levels of hypoxia. In both species, blood O2 carrying capacity was not affected by hypoxia and remained twice as high in sea bass than in turbot.

The distribution of water‐soluble phosphodiesters (WSPDEs) visible by nuclear magnetic resonance (NMR) in some intact tissues of rainbow trout (Oncorhynchus mykiss walbaum) and in perchloric extracts after partial purification was examined by 31P NMR spectroscopy. The compounds of interest were serine ethanolamine phosphate (SEP), threonine ethanolamine phosphate (TEP), glycerophosphorylcholine (GPC), and glycerophosphorylethanolamine (GPE). TEP and SEP were mostly accumulated in the heart and less accumulated in the kidney of intact trout. After the extraction procedure, two additional minor resonances were visible and identified as GPC and GPE. The liver of trout contained large amounts of GPE. Similar investigations were conducted by 31P NMR on hearts and kidneys of two elasmobranchs (Scyliorhinus canicula, Raja clavata) and four teleosts (Anguilla anguilla, Sparus auratus, Dicentrarchus labrax, Scophtlhalmus maximus); comparison with the trout data showed striking interspecies differences in the identity of WSPDEs. All teleosts, except eel and turbot, accumulated predominantly TEP. However, in elasmobranchs, first GPC and then GPE were the major compounds. Whatever the studied species, the relative abundances in the heart and kidney were similar. In the last two decades, two hypotheses were proposed to explain the occurrence of high levels of cytosoluble phosphodiesters: these compounds may constitute an index of phospholipid catabolism or a protective mechanism through which phospholipid levels are kept high. To test them and elucidate the role of these compounds in membrane phospholipid regulation in fish, we investigated the effects of two physiological stresses, that is, seawater adaptation and induced myocardial ischemia, on trout cytosolic phosphodiester levels. A 32.5‐min ischemic stress caused no effect on SEP and TEP levels. On the contrary, significant osmotic stress induced changes in the PDEs levels: 2 d after transfer from freshwater to seawater or from seawater to freshwater, both tissues displayed a transient decrease of TEP; however, a 2‐d stay in seawater after transfer from freshwater caused a rise in SEP concentration, whereas a 2‐d stay in freshwater after transfer decreased SEP level. In conclusion, our experiments suggest a relationship between the high levels of cytosoluble phosphodiesters observed in some fish tissues and resistance to stress.

Hormonal changes, substrate mobilization and energy metabolism were studied in turbot 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 CO2 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 determined in liver and white muscle tissues. Exposure to 90 or 60 mm Hg did not induce any major physiological change, as hyperventilation by itself could compensate for the decrease in water oxygen tension. At 30 mm Hg, marked increases in cortisol, adrenaline and noradrenaline concentrations, associated with a decrease in blood arterial oxygen partial pressure, were observed. During exposure to 30 nun Hg, turbot resorted to anaerobic metabolism, resulting in liver glycogen depletion and lactate production. This mechanism appeared to be efficient enough to produce energy, as no significant change in phosphorylated compounds and adenylate energy charges in muscle and liver could be observed. These results indicate an absence of metabolic depression in turbot down to 30 mm Hg and confirm the high capacity of this species to cope with low water oxygen tension.

31P nuclear magnetic resonance (NMR) was used to study the major phosphorylated compounds visible in perchloric extracts of three body regions of the vestimentiferan worm Riftia pachyptila: winged vestimentum, trunk and segmented posterior opisthosome. Two phosphagens (PGs) were present in vestimentum and opisthosome. The major resonance corresponded to those of phosphoarginine and phosphotaurocyamine, which cannot be discriminated on 31P NMR spectra. We have identified four distinct phosphodiesters (PDEs) in these tissues: glycerophosphorylethanolamine (GPE), serine ethanolamine phosphodiester (SEP), glycero-phosphorylcholine (GPC) and threonine ethanolamine phosphodiester (TEP). Three phosphonates or derivates (PAs) were observed in the three body regions. The minor one was identified as 2-aminoethyl phosphonate (2-AEP). The phosphorus profile of the trunk was appreciably different: one additional resonance in the PDE region and only one phosphagen peak were observed.

Les adaptations respiratoires, acido-basiques et quelques effets circulatoires ont été étudiés chez l'esturgeon sibérien Acipenser baeri lors d'une hypoxie progressive ou d'un choc hypoxique, et du retour en normoxie. Au cours d'une hypoxie progressive, ce poisson est capable, en hyperventilant, de maintenir constante sa consommation d'oxygène jusqu'à une valeur critique de pression partielle d'oxygène dans l'eau située entre 20 et 40 mmHg. Le retour en normoxie est caractérisé par le paiement d'une dette d'oxygène, indiquant qu'un recours au métabolisme anaérobie a été nécessaire durant l'hypoxie. L'hypoxie progressive provoque initialement une alcalose ventilatoire associée ensuite à une acidose métabolique. Le choc hypoxique induit un état de stress comme en témoignent les valeurs élevées des taux plasmatiques de catécholamines. L'hyperventilation initiale est suivie d'une importante dépression ventilatoire. L'hypertension observée dans un premier temps, bien que modérée, représente un effet d'une augmentation du taux de catécholamines plasmatiques. Cet effet est ensuite atténué par une bradycardie d'origine vraisemblablement vagale, concomitante de l'hypoventilation. Les conséquences sur l'équilibre acido-basique, bien qu'amplifiées, sont comparables à celles d'une hypoxie progressive. Cependant, la libération très importante de lactate dans le sang lors du retour en normoxie n'entraîne qu'une faible diminution de pH du fait d'une augmentation concomitante du taux de sodium plasmatique. Ainsi l'esturgeon Acipenser baeri, bien que considéré comme un poisson archaïque, a développé les mêmes réponses adaptatives à l'hypoxie que les téléostéens.

Changes in circulatory, ventilatory and acid-base variables were studied in Siberian sturgeon (Acipenser baeri) exposed to acute and severe hypoxia (Pw(O2) = 10 torr), followed by a rapid return to normoxia. This treatment caused a significant stress, revealed by the high levels of plasma catecholamines and cortisol. The moderate circulatory changes firstly observed would represent the effects of increased plasma catecholamine levels together with an increased adrenergic nervous tone on the cardiovascular system. Then, these effects were masked by a possible vagal reflex resulting in bradycardia. Deep hypoxia induced a ventilatory alkalosis combined with a moderate metabolic acidosis. The latter amplified concomitantly with a massive flush of lactate into the blood stream. The initial hyperventilation was followed by a deep ventilatory depression. During return to normoxia, hyperventilation resumed consistent with the repayment of an oxygen debt. Thus, the sturgeon, although considered as an archaic fish, developped the same adaptative responses as teleosts submitted to comparable hypoxic conditions.

In order to better understand the basis for the acquisition of euryhalinity by juvenile salmon and the role of endogeneous stimuli, experiments have been carried out to examine the dynamics of ionic and acid‐base adjustments in fresh water (FW) and after direct transfer to full salinity (32 g l−1) sea water (SW) (1) on Atlantic salmon smolt during the natural period of smoltification in spring, (2) on presmolt salmon in autumn, after intraperitoneal implantation of pellets containing ovine growth hormone (oGH). During parr‐smolt transformation in FW, gill Na+/K+ ATPase activity gradually rises, the plasma osmolality (Posm) is unaffected and the total CO2 of the plasma decreases significantly while whole blood pH fluctuates slightly. Direct transfer of smolt from FW to SW provokes only a slight increase in Posm and emphasizes the acid‐base balance disruptions shown in FW. An oGHimplant in a presmolt stimulates gill Na+/K+ ATPase activity in FW, and affects the acid‐base balance. After SW transfer (12 days after implantation), oGH treatment prevents the increase of osmotic pressure and the restoration of the acid‐base, ionic equilibrium was faster for oGH‐implanted fish than for sham‐operated fish. These observations show that in FW smelting salmon develop most of the systems they need for migration and growth in SW and that oGH implants induce the development of physiological characteristics of smolts in a non‐natural period of smolting.

The time courses of extracellular ionic and acid-base adjustments were studied in juvenile turbot (Scophthalmus maximus) following a decrease of water salinity, either abruptly from 32 to 10%. or after a first step (4 weeks) in 19%. salinity followed by a direct transfer to 10%. brackish water (BW). Net exchanges of acid-base equivalents with the external water were also determined after transfer from 32%. SW to 10%. BW. Direct transfer from seawater (SW) to 10%. BW induced a transient decrease in plasma osmolarity, plasma sodium and chloride concentrations, associated with a marked and transient metabolic alkalosis in the blood. A significant net outflux of acidic equivalents was also measured only during the first day in BW. Four weeks preadaptation in 19%. BW reduced the intensity of the osmotic disturbances elicited by a subsequent abrupt transfer to 10%. BW. These ionic readjustments were also coupled with minimal acid-base changes, of lesser magnitude than those described after directly from SW to 10%. BW.

Changes in respiratory and acid-base variables were studied in siberian sturgeon, Acipenser baeri, during progressive deep hypoxia followed by recovery under normoxic conditions. During hypoxia, both ventilatory frequency and amplitude increased and this sturgeon was able to maintain standard oxygen consumption down to a low critical level of ambient PO2 (PWO2 < 40 mmHg). During the posthypoxic period, an O2 debt was repaid by an elevated oxygen consumption (nearly double control value at 1 h), indicating that a shift to anaerobic metabolism had occurred during exposure to severe hypoxia. Gradually increasing ambient hypoxia initially induced a respiratory alkalosis. Below the critical PWO2 level and during normoxic recovery, a sudden flush of lactate into the blood was associated with a typical metabolic acidosis which was almost totally compensated 3.5 h after return to normoxia. Thus, as for most other fish, respiratory responses of the sturgeon to progressive hypoxia reveal a typical O2 regulatory behavior.

Subsequent to osmotic swelling, the nucleated erythrocytes of the flounder (Platichthys flesus) displayed a volume-regulatory decrease (RVD) which was similar in HEPES and HCO–3 media. This RVD was characterized by net K+, Cl– and water loss at constant Na+. During RVD, 46% of the net water flow was secondary to net inorganic ion flux in HEPES compared to about 77% in HCO-3 media, the resting might be attributed to organic osmolytes. In the presence of added bicarbonate ions at physiological concentrations and oxygen in the experimental medium, not only a K+/C1- cotransport seems to be involved during RVD, but also K+ and Cl– conductances. Moreover, transport pathways sensitive to N-phenylanthronilic acid or 4-acetamido-4'-isothyocyanate-2, 2-stilbene di-sulfonic acid play an important role in the volume-dependent ionic movements and in the volume-activated release of taurine. These results strongly suggest that the anion transporter (band 3) or another neighboring protein plays an important part in RVD in volume-activated osmolyte release after hyposmotic stress in flounder red blood cells.

In order to better understand the basis for the euryhalinity of the flounder, Platichthys flesus, which tolerates large variations in water salinity, experiments have been designed to characterize the time course of extracellular ionic and acid‐base adjustments under hypo‐ or hyperosmotic conditions. Abrupt transfer from sea water (SW) to fresh water (FW) provokes a transient decrease in the plasma osmolality (Posm) and a concomitant transient metabolic alkalosis (whole blood pH 7.78 in SW and 8.04 five days after FW transfer) associated with a marked, persistent hypercapnia. After 33 days in FW, Posm and whole blood pH are not significantly different from those in SW, but whole blood Pco2 and plasma bicarbonate concentration are always higher than SW values. Opposite transitory fluctuations, i.e. a metabolic acidosis associated with a respiratory alkalosis, occur when flounder long‐acclimated to FW are again exposed to SW. The mechanisms involved in these salinity‐dependent acid‐base disturbances are rather complex and remain to be elucidated. These observations attest to the importance of the extracellular acid‐base changes that may be (i) linked to extracellular anisosmotic regulation and/or to cellular metabolic adjustments, and (ii) compensated partially by ventilatory adjustments.