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Lorin-Nebel, C., Felten, V., Blondeau-Bidet, E., Grousset, E., Amilhat, E., Simon, G., et al. (2013). Individual and combined effects of copper and parasitism on osmoregulation in the European eel Anguilla anguilla. Aquatic toxicology, 130–131, 41–50.
Résumé: The European eel (Anguilla anguilla), a catadromous species, breeds in the sea and migrates to estuarine, lagoon or freshwater habitats for growth and development. Yellow eels, exposed to low or fluctuating salinities, are also exposed to multiple other stressors as pollution, over-fishing and parasitism, which contribute to the dramatic decrease of eel populations in several European countries. The objective of this study was to evaluate the single and combined effects of waterborne copper and experimental infestation of eels with the nematode Anguillicoloides crassus after a salinity challenge from nearly isotonic (18ppt) to hypo- (5ppt) and hypertonic (29ppt) conditions, in order to investigate the osmoregulatory capacity of eels exposed to these stressors. In a nearly isotonic condition (18ppt), blood osmolality remained constant over the 6 weeks contamination to Cu(2+) and Anguillicoloides crassus. In fish exposed to a salinity challenge of 29ppt for 2 weeks, no significant effect was recorded in blood osmolality, Na(+)/K(+)-ATPase (NKA) activity, Na(+) and Cl(-) concentrations. After 2 weeks at 5ppt however, a significant blood osmolality decrease was detected in fish exposed to Anguillicoloides crassus infestation with or without Cu(2+) addition. This decrease may originate from lower Cl(-) levels measured in eels exposed to both stressors. Blood Na(+) levels remained relatively stable in all tested animals, but gill NKA activities were lower in eels exposed to combined stress. No apparent branchial lesions were detected following the different treatments and immunolocalization of NKA revealed well-differentiated ionocytes. Thus, the 5ppt challenge in eels exposed to copper and Anguillicoloides crassus seems to clearly enhance iono/osmoregulatory disturbances. Funded by ANR CES/CIEL 2008-12.
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Rivera-Ingraham, G. A., Barri, K., Boel, M., Farcy, E., Charles, A. - L., Geny, B., et al. (2016). Osmoregulation and salinity-induced oxidative stress: is oxidative adaptation determined by gill function? J. Exp. Biol., 219(1), 80–89.
Résumé: Osmoregulating decapods such as the Mediterranean green crab Carcinus aestuarii possess two groups of spatially segregated gills: anterior gills serve mainly respiratory purposes, while posterior gills contain osmoregulatory structures. The co-existence of similar tissues serving different functions allows the study of differential adaptation, in terms of free radical metabolism, upon salinity change. Crabs were immersed for 2 weeks in seawater (SW, 37 ppt), diluted SW (dSW, 10 ppt) and concentrated SW (cSW, 45 ppt). Exposure to dSW was the most challenging condition, elevating respiration rates of whole animals and free radical formation in hemolymph (assessed fluorometrically using C-H(2)DFFDA). Further analyses considered anterior and posterior gills separately, and the results showed that posterior gills are the main tissues fueling osmoregulatory-related processes because their respiration rates in dSW were 3.2-fold higher than those of anterior gills, and this was accompanied by an increase in mitochondrial density (citrate synthase activity) and increased levels of reactive oxygen species (ROS) formation (1.4-fold greater, measured through electron paramagnetic resonance). Paradoxically, these posterior gills showed undisturbed caspase 3/7 activity, used here as a marker for apoptosis. This may only be due to the high antioxidant protection that posterior gills benefit from [superoxide dismutase (SOD) in posterior gills was over 6 times higher than in anterior gills]. In conclusion, osmoregulating posterior gills are better adapted to dSW exposure than respiratory anterior gills because they are capable of controlling the deleterious effects of the ROS production resulting from this salinity-induced stress.
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