Luis Vargas-Chacoff

Interactive effects of environmental salinity and temperature on metabolic responses of gilthead sea bream Sparus aurata.

The gilthead sea bream Sparus aurata is a euryhaline and euritherm species with the capacity of living under different environmental conditions of salinity and temperature. The influence of acclimation to different environmental salinities (5, 38 and 55 per thousand) and temperatures (12 degrees , 19 degrees and 26 degrees C) for seven weeks was analyzed in plasma and tissues (liver, gills and kidney) of gilthead sea bream assessing levels of metabolites and enzyme activities related to energy metabolism. Changes observed in specimens acclimated to different environmental salinities agree with previous results reported for this species. The temperature alone did also affect metabolic parameters in a way similar to that previously described. A significant interaction of salinity with temperature was found in most parameters assessed in tissues suggesting that the metabolic effects of salinity are different depending on the temperature of acclimation. The interactions were different among tissues and parameters displaying different patterns of changes. In general, the acclimation to extreme temperatures (especially low) alters the metabolic responses to different salinities thus suggesting that the energy demand of increased osmoregulatory work is not so important under temperature conditions different from those commonly found in nature and in those used in culture.

Biomarker responses in Solea senegalensis exposed to sodium hypochlorite used as antifouling

The time-course stress responses (0, 1, 2, and 7 d) was assessed in plasmatic, branchial and renal parameters of juveniles Solea senegalensis exposed to different concentrations of the antifouling sodium hypochlorite (0.1, 0.2, and 0.5mgL(-1)). These stress responses were only assessed for the total length of exposure (7d) at the lowest NaClO concentration due to the high toxicity of this chemical. In addition, the xenobiotic metabolism responses were evaluated by means of enzymatic activities of ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPX), catalase (CAT), and carboxylesterase (CbE) in liver; as well as GST, GPX, CAT and acetylcholinesterase (AChE) in gill. Oxidative stress damage due to sodium hypochlorite exposure was measured by lipid peroxidation levels in liver and gill. Concentrations of 0.2 and 0.5mgL(-1) produced lethal effects after 1d and 2h of exposure, respectively. After 1d of exposure to sublethal concentration of sodium hypochlorite (0.1mgL(-1)) osmoregulatory (osmolality and chloride) and stress (cortisol, glucose and lactate) plasmatic parameters were enhanced to respect at control fish. However after 3 or 7d these parameters returned to control values. No effects were observed on plasma protein and triglyceride levels or on gill and kidney Na(+)/K(+)-ATPase activities. Diverse gill pathologies such as hypertrophy, lamellar fusion and an increase in goblet cell number and size were observed after 7d of exposure. Most biochemical parameters related to xenobiotic metabolism and oxidative stress were also significantly affected which suggests that seawater affected by sodium hypochlorite discharges from power plants, is able to alter the fish xenobiotic metabolism and generate oxidative stress.

Seasonal limnetic feeding regime of the robalo Eleginops maclovinus (Valenciennes 1830), in the Valdivia river, Chile

Eleginops maclovinus (Valenciennes, 1830) es un pez comun en el litoral, estuarios y tambien rios, preferentemente donde afectan las mareas, del sur de America del Sur, incluyendo las islas Malvinas. Se conoce su alimentacion en los dos primeros habitats, donde consume principalmente animales de ambiente marino y estuarino, donde se alimenta de fauna autoctona (mejillones, crustaceos, poliquetos, etc.). Sin embargo, se desconoce su alimentacion en ambientes limneticos, suponiendose que deberia consumir presas propias de aquellos lugares. En este estudio se analizaron 114 ejemplares de E. maclovinus, de los cuales 98 poseyeron estomagos con contenido. Se ratifico la tendencia zoofagica de la especie, pero tambien se comprobo que en ambientes limneticos consume animales propios de bajas salinidades o salinidades limneticas. El pez se presenta como una especie extraordinariamente versatil en sus capacidades troficas, con una fisiologia que le permite cubrir un amplio abanico ormorregulatorio a nivel digestivo, probablemente uno de las mas variados en el suborden Notothenioidei, de supuesto origen antartico.

Combined effects of high stocking density and Piscirickettsia salmonis treatment on the immune system, metabolism and osmoregulatory responses of the Sub-Antarctic Notothenioid fish Eleginops maclovinus

The aim of this study was to evaluate immunological, metabolic and osmoregulatory secondary stress responses in Eleginops maclovinus specimens submitted to three different stocking densities: i) low (3.1 kg m(-3)), medium (15 kg m(-3)) and high (60 kg m(-3)) during 10 days, alone or in combination with a previous treatment of a protein extract of the pathogen Piscirickettsia salmonis (0.5 μg g weight body(-1)). Plasma, liver, gill and kidney samples were obtained at the end of both experiments. Plasma cortisol and amino acid levels increased, while plasma glucose, triglyceride and lactate levels decreased at higher stocking densities. However, no effects were observed on serum Immunoglobulin type M (IgM anti P. salmonis level) values. Gill Na(+), K(+)-ATPase activity enhanced under these experimental conditions, suggesting an osmotic imbalance. Energy metabolism changes, assessed by metabolite concentrations and enzyme activities, indicated a reallocation of energetic substrates at higher stocking densities. Specimens inoculated with a protein extract of P. salmonis and maintained at different stocking densities showed primary stress response, as all groups enhanced plasma cortisol concentrations. Serum IgM levels increased after treatment with P. salmonis extract but a negative influence of high stocking density on IgM production was observed when immune system was activated. Furthermore, treatment with P. salmonis protein extract evoked deep changes in the metabolite stores in all tissues tested, indicating a mobilization of energy substrates in response to infection. The results show that stocking density induced immunological, metabolic and osmoregulatory secondary stress responses in E. maclovinus specimens and that previous treatment with P. salmonis compromise these changes.

Gene and protein expression for prolactin, growth hormone and somatolactin in Sparus aurata: Seasonal variations

The seasonal variation of PRL, GH and SL gene and protein expression has been analyzed in gilthead sea bream (Sparus aurata) pituitaries using Real-Time Q-PCR and Western Blots, respectively. Animals were cultured in earthen ponds under natural photoperiod, temperature and salinity conditions. Samples were taken during winter 2005 (January), spring 2005 (April), summer 2005 (July) and autumn 2005 (October). Beta-actin, used as the housekeeping gene both for Q-RT-PCR and Western analysis, did not present significant differences among seasons. Higher expression was observed during spring and autumn for PRL, summer and winter for GH, and spring for SL. Expression of PRI, GH and SL, presented seasonal variation, suggesting that these hormones could play a role in the molecular signal transduction of environmental factors (especially of photoperiod and temperature) in eurythermal fish.

Metabolic and osmoregulatory changes and cell proliferation in gilthead sea bream (Sparus aurata) exposed to cadmium.

The impact of cadmium on metabolism and osmoregulation was assessed in gilthead sea bream (Sparus aurata). Seawater acclimated fish were injected intraperitoneally with a sublethal dose of cadmium (1.25 mg Cd/kg body wt). After 7 days, half of the injected fish were sampled. The remaining fish were transferred to hypersaline water and sampled 4 days later. Gill and kidney Na(+)/K(+)-ATPase activities, plasma levels of cortisol, several metabolites and osmolytes, as well as osmolality were measured. Hepatosomatic index and condition factor were calculated. The expression levels of Na(+)/K(+)-ATPase, heat shock proteins (HSP70, HSP90) and proliferating cell nuclear antigen was assessed by western blotting. Cadmium treatment adversely affected the Na(+)/K(+)-ATPase activity, although, there was no perturbation in ion homeostasis and the animals were not compromised following transfer to hypersaline water. Increased cell proliferation and Hsp90 expression likely contributed to the attenuation of the deleterious effects of cadmium exposure.

Sublethal responses of the common mussel (Mytilus galloprovincialis) exposed to sodium hypochlorite and Mexel®432 used as antifoulants.

The sublethal effects of two antifoulants currently used in power plant cooling systems were assessed in the common mussel Mytilus galloprovincialis. The concentrations of sodium hypochlorite (NaClO) and an alkyl amine surfactant (Mexel432) assayed, were within the range of those currently discharged by power plants into receiving waters. Enzymatic activities and oxidative stress responses were measured in digestive gland and gill of mussels after 1, 3, 7 and 14 days of exposure, as well as histopathology in gill tissue. Both antifoulants caused a pathological response in gills and the activities of the enzymes glutathione S-transferase, catalase, acetylcholinesterase and the lipid peroxidation levels were also affected. Exposure to NaClO caused a greater toxicological response than Mexel432. In both treatments, gills appeared to be the most affected tissue, although Mexel432 also significantly affected digestive gland parameters.

Sublethal effects of the organic antifoulant Mexel® 432 on osmoregulation and xenobiotic detoxification in the flatfish Solea senegalensis

Mexel(R)432 is an anionic surfactant used as biocide in the cooling water system of power plants for biofouling reduction. Refrigeration waters from power plants do not usually follow, prior to their discharge to sea, any treatment aimed to eliminate biocides and this can have negative consequences on the aquatic fauna nearby. The effects of different concentrations of the antifoulant Mexel(R)432 (0.5, 1 and 2mgL(-1)) on osmoregulation (osmolality and Na(+)/K(+)-ATPase activity) and stress parameters (cortisol, glucose, and lactate) were assessed in juveniles of the flatfish Solea senegalensis. Gill histopathology and alterations due to oxidative stress (increased lipid peroxidation, LPO, levels) at branchial and hepatic levels were also considered. Other parameters tested were the antioxidant enzymes (catalase, CAT; glutathione peroxidase, GPX; and glutathione reductase, GR), xenobiotic metabolism defenses involved in detoxification (carboxylesterase, CbE; 7-ethoxyresorufin O-deethylase, EROD; and glutathione S-transferase, GST) and the neurotransmitter acetylcholinesterase (AChE) activity. Significant variations in osmoregulatory parameters, histological lesions and decreased branchial Na(+)/K(+)-ATPase activity were observed in exposed fish. Other gill biomarkers presented little or no significant variations in relation to controls. In contrast, hepatic parameters, such as CAT activity, were inhibited while EROD activity was initially elevated but after longer exposures it recovered basal values. These results suggested that under our experimental protocol exists toxic associated to Mexel(R)432 exposures.

Stocking density affects growth and metabolic parameters in the brill ( Scophthalmus rhombus )

In this work, the effects of the stocking density on the physiological stress and biometric features of the brill were studied. No differences for survival rate, feeding efficiency, Conversion Index and feeding intake were not detected among the treatments. The growth rate showed an inverse lineal relationship with stocking density, and there were no significant differences between specimens cultured at medium and high density. Plasma cortisol and osmolality were directly related to stocking density, though the former was not significantly different among the treatments. Plasma glucose and lactate significantly increased, while stocking density rose. Triglycerides enhanced significantly in MSD and HSD with respect to LSD cultured specimens. Differences among treatments were not registered for hepatic glucose, triglycerides and amino acids. However, glycogen showed an inverse lineal relationship with respect to stocking density with significant differences between low and high stocking density. Several lipid classes were different among the treatments, with the high-density specimens presenting the highest values. Liver total lipid was not significantly different among the treatments, but total polar lipid was higher in high density. Muscle metabolites did not vary significantly among the treatments. Concluding, the brill showed a clear secondary response to crowding stress through the mobilization of energy substrates to tissues, evoking a reduction in the growth and other biometric parameters.

STUDY OF THE COPPER, CHROMIUM AND LEAD CONTENT IN MUGIL CEPHALUS AND ELEGINOPS MACLOVINUS OBTAINED IN THE MOUTHS OF THE MAULE AND MATAQUITO RTVERS (MAULE REGION, CHILE)

The Cu, Cr and Pb concentrations were determined in Mugil cephalus and Eleginops maclovinus, fish species inhabiting the mouths of the Maule and Mataquito Rivers (Maule Region, Chile) which are consumed by the coastal population in large quantities. Measurements were taken by flame atomic absorption spectroscopy to analyse representative muscle tissue of the two species. The method was validated using certified reference material (DOLT-1). The concentration ranges of Cu, Cr and Pb (mg . kg -1 , dry weight) in Mugil cephalus from the Maule river were: Cu 0.5-36.2; Cr 0.3-6.3; Pb 0.4-11.2 and from the Mataquito river varied between: Cu 0.6-23.2; Cr 0.3-6.0 and Pb 0.4-11.1. For the species Eleginops maclovinus from the Maule river the concentration ranges were: Cu 0.8-13.2; Cr 0.2-5.6; Pb 0.2-9.6 and from the Mataquito river: Cu 0.5-18.4; Cr 0.2-3.2 and Pb 0.3-4.0. The concentration ranges of Cu and Cr recorded in the two species of fish are within the levels permitted by FAO and EPA, however the concentrations of Pb in Mugil cephalus originating from both estuaries exceeds the levels permitted by current legislation. The statistical analysis done with one way ANOVA (p < 0.05) indicated that for each metal there are no significant differences between the species and the two sampling sites; however with two way ANOVA between the species and the two sampling sites a significant difference was found for Cu and Cr, but not for Pb.