Daily rhythms of acute stress responses and antioxidant systems in the European sea bass (Dicentrarchus labrax): Effects of the time of the year

Fish reared in aquaculture face various acute stressors, including air exposure during handling. Research on the stress response in fish can provide essential insights into their physiology and help define better aquaculture practices. In this study, we investigated the daily rhythms in the stress-axis response of the European sea bass (Dicentrarchus labrax) subjected to an acute stressor consisting of air exposure (1 min), and how this response is influenced by the time of the day and the season of the year. In addition, rhythms in antioxidant systems were also assessed. The experiments were performed in late Autumn (December) and late Spring (June), with natural photoperiod (10 L:14D and 15 L:9D, respectively) and water temperature (ranging from 19.47 ± 0.17 December to 22.13 ± 0.13 ◦ ◦ C in C in June). Samples were collected throughout a 24-h cycle at Zeitgeber time (ZT) 0.5, 4, 7.5, 12, 16, 20, and 24.5 h at both seasons. At each sampling point, an untreated control (CTRL) group was sampled, while a STRESS group was exposed to air for one minute, returned to the tank, and sampled one hour later. Fish were sacrificed to collect plasma samples, hypothalamus and liver. Plasma samples were analyzed for cortisol, glucose, and lactate. In the hypothalamus, the mRNA expression levels of corticotropin-releasing hormone (crh) and crh-binding protein (crh-bp) were quantified using quantitative RT-PCR (qPCR). In the liver, genes related to antioxidant systems (catalase, superoxide dismutase 1, glutathione peroxidase,and glutathione reductase) and mitochondrial markers of stress (uncoupling protein 1, cytochrome c oxidase IV and peroxiredoxin3) were also analyzed by qPCR. The results revealed that most stress indicators (cortisol, cat, sod1, gsh-px, gsr, ucp1, coxIV) displayed daily rhythms. Furthermore, the stress response was significantly influenced by the time of day and the season in which the stressor was applied. In June, cortisol and glucose responses to stress were higher during the day than at night. The increase observed after stress in genes related to the antioxidant system was more significant in June than in December. Conversely, the response of mitochondrial markers was greater in December. Taken together, these findings highlight that the stress response of the European sea bass is time- dependent, both on a daily and a seasonal basis. This emphasizes the importance of considering cyclic environmental factors and circadian rhythms in aquaculture procedures to enhance fish welfare

Retention and diffusion of radioactive and toxic species on cementitious systems: Main outcome of the CEBAMA project

Cement-based materials are key components in radioactive waste repository barrier systems. To improve the available knowledge base, the European CEBAMA (Cement-based materials) project aimed to provide insight on general processes and phenomena that can be easily transferred to different applications. A bottom up approach was used to study radionuclide retention by cementitious materials, encompassing both individual cement mineral phases and hardened cement pastes. Solubility experiments were conducted with Be, Mo and Se under high pH conditions to provide realistic solubility limits and radionuclide speciation schemes as a prerequisite for meaningful adsorption studies. A number of retention mechanisms were addressed including adsorption, solid solution formation and precipitation of radionuclides within new solid phases formed during cement hydration and evolution. Sorption/desorption experiments were carried out on several anionic radionuclides and/or toxic elements which have received less attention to date, namely: Be, Mo, Tc, I, Se, Cl, Ra and 14C. Solid solution formation between radionuclides in a range of oxidation states (Se, I and Mo) with the main aqueous components (OH−, SO4 −2, Cl−) of cementitious systems on AFm phases were also investigated

Feeding time synchronises daily rhythms of behaviour and digestive physiology in gilthead seabream (Sparus aurata)

27 páginas, 5 figuras.Feeding cycles entrain biological rhythms, which enables animals to anticipate feeding times and so maximizes food utilization. In this article the effect of mealtime on locomotor activity, blood glucose, gastric pH and digestive enzymes was studied in two groups of seabream (Sparus aurata): one group received a single daily meal at random times either during the light or the dark (random feeding, RF), whereas the other group received the meal during the light period every day at the same time (periodic feeding, PF). PF fish showed strong synchronisation of locomotor activity to the light phase (97.9 ± 0.2% of their total daily activity during daytime). In addition, the locomotor activity rhythm of PF fish showed a statistically significant daily rhythm (p < 0.05) for a period of 24 h, whereas RF fish did not display a statistically significant rhythm. Blood glucose levels were higher in RF fish during the 8 h following feeding. Gastric pH showed a postprandial decrease in both groups, but RF fish showed a lower daily average value (4.31 ± 0.21 compared with 5.52 ± 0.20). Amylase and alkaline protease activity increased some hours before mealtime in PF fish, whereas amylase activity increased 1 h after feeding and alkaline protease showed no statistically significant differences in RF fish. Acid protease activity showed no statistically significant differences in any group. Taken together, these results demonstrate that altering the feeding time affects the physiology and behaviour of seabream, which have the capacity to prepare themselves for a forthcoming meal.The present research was funded by projects from the Spanish Ministry of Science and Innovation (MICINN) (project AGL2007-66507-C02-02), Fundación Séneca (project 05690/PI/07) and AQUAGENOMICS 28502 (Consolider-Ingenio Program) granted to F. J. Sánchez-Vázquez; and by a project from MICINN (Plan Nacional de Investigación Desarrollo e Innovación, project number AGL2007-64450-C02-01) granted to M. Yúfera.Peer reviewe

Ritmos diarios de pH gástrico y actividad enzimática digestiva en doradas (Srus aurata L., 1758) alimentadas de día, de noche y aleatoriamente

2 páginas, 1 figura. Editores Daniel Beaz Paleo, Morris Villaroel Robinson y Salvador Cárdenas López. Congreso celebrado en Madrid el 24-26 de noviembre de 2009.[EN] The influence of scheduled vs random feeding on dayly rhythm of gastric pH and digestive enzimes was investigated in Gilthead seabream. Fish of an initial body weight of 80g were feed at 15 h, 3 h and randomly during 2 weeks by a diet constituted on 5% of protein, 30% of carbohidrates and 20% of lipids, using gelatin and casein (1:5) as protein source, dextrin for carbohidrate and soybean oil and cod liver oil (1:3) for lipids. After this period fish were anesthetized and stomach and intestine were sampled and gastic pH in stomach measured every 4 hours (n=6). Stomach and intestine samples were inmediately frozen at -80ºC and stored until digestive enzimes analysis (amilase and proteases). Daily rhithm of gastric pH showed for the three treatements a downfall in the next hours to mealtime and fish feed randomly showed a similar curve (sampling day were feed at 15 h) to feeds at 15 h buth with lower pH values. In conclusion, this is the first study that shows the effect of random feeding on dayly rhythm of gastric pH, and suggest this parameter as a new welfare indicator.[ES] Si un organismo es capaz de anticipar una comida, la ingesta de alimento y la utilización de nutrientes puede ser mejorada, permitiendo al animla preparar y optimizar los procesos digestivos y metabólicos, proporcionando una ventaja adaptativa (Strubbe y Van Dijk, 2002). Varios trabajos describen variaciones diarias del pH gastrointestinal en peces teleósteos (Yúfera et al., 2004, Yúfera y Darias, 2007) señalando una caída del pH durante la digestión gástrica, aunque el efecto del horario de alimentación y de la alimentación aleatoria sobre el ritmo de pH gástrico aún no se ha estudiado. Por ello, el objetivo de este trabjo fue investigar las variaciones diarias de pH gástrico y enzimas digestivas en doradas alimentadas de día, de noche y aleatoriamente.Peer reviewe

Monthly day/night changes and seasonal daily rhythms of sexual steroids in Senegal sole (Solea senegalensis) under natural fluctuating or controlled environmental conditions

20 p., 4 figuras y bibliografíaIn this paper we attempted to investigate the existence of daily fluctuations on plasma sexual steroids (17beta-estradiol, E2 and testosterone, T) in Senegal sole (Solea senegalensis) females. We described the monthly day/night concentrations and seasonal daily rhythms in animals reared under natural photo- and thermo-period. In addition, the influence of the natural annual fluctuation of the water temperature on the plasma concentration of these steroids was investigated, using one group of Senegal sole under a natural photoperiod, but with an attenuated thermal cycle (around 17-20 °C) for one year. Although no significant day/night differences were detected in monthly samplings, the existence of an annual rhythm of E2 and T (p < 0.01) with an acrophase in February was revealed by COSINOR analysis. Maximum values were reached in March for both steroids (6.1 ± 1.7 ng mL- 1 at mid-dark, MD and 4.0 ± 0.6 ng mL- 1 at mid-light, ML for E2 and 1.4 ± 0.4 ng mL- 1 at MD and 0.8 ± 0.1 ng mL- 1 at ML for T) in anticipation of the spawning season (May-June). As regards seasonal daily rhythms, the presence of daily oscillations was revealed. At the spring solstice (21st March) a daily rhythm was observed for both steroids (COSINOR, p < 0.01), with an acrophase at 20:00 h (E2) and at 21:08 h (T). In summer, autumn and winter no daily rhythms were observed due to the low steroid levels at those seasons. When Senegal sole females were submitted to an attenuated annual thermal cycle, the steroid rhythm disappeared (there was no surge in spring, as in the control group) and these fish did not spawn, despite being subjected to natural photoperiod conditions. This result underlined the importance of the natural annual fluctuation of water temperature and photoperiod on the synchronization of the spawning season and on the onset of steroidogenesis.This research was funded by the MEC (Spanish Ministry of Education and Science) project Reprosolea (AGL 2004-07984-C02-01) to FJSV and by the MAPA (Ministry of Agriculture, Fisheries and Food) project JACUMAR 2006 (II National plan for the cultivation of sole) to EM. CO received a FPI Fellowship from the MEC

The Light Wavelength Affects the Ontogeny of Clock Gene Expression and Activity Rhythms in Zebrafish Larvae.

Light plays a key role in synchronizing rhythms and setting the phase of early development. However, to date, little is known about the impact of light wavelengths during the ontogeny of the molecular clock and the behavioural rhythmicity. The aim of this research was to determine the effect of light of different wavelengths (white, blue and red) on the onset of locomotor activity and clock gene (per1b, per2, clock1, bmal1 and dbp) expression rhythms. For this purpose, 4 groups of zebrafish embryo/larvae were raised from 0 to 7 days post-fertilization (dpf) under the following lighting conditions: three groups maintained under light:dark (LD) cycles with white (full visible spectrum, LDW), blue (LDB), or red light (LDR), and one group raised under constant darkness (DD). The results showed that lighting conditions influenced activity rhythms. Larvae were arrhythmic under DD, while under LD cycles they developed wavelength-dependent daily activity rhythms which appeared earlier under LDB (4 dpf) than under LDW or LDR (5 dpf). The results also revealed that development and lighting conditions influenced clock gene expression. While clock1 rhythmic expression appeared in all lighting conditions at 7 dpf, per1b, per2 and dbp showed daily variations already at 3 dpf. Curiously, bmal1 showed consistent rhythmic expression from embryonic stage (0 dpf). Summarizing, the data revealed that daily rhythms appeared earlier in the larvae reared under LDB than in those reared under LDW and LDR. These results emphasize the importance of lighting conditions and wavelengths during early development for the ontogeny of daily rhythms of gene expression and how these rhythms are reflected on the behavioural rhythmicity of zebrafish larvae