Genomic and physiological footprint of the Deepwater Horizon oil spill on resident marsh fishes

The biological consequences of the Deepwater Horizon oil spill are unknown, especially for resident organisms. Here, we report results from a field study tracking the effects of contaminating oil across space and time in resident killifish during the first 4 mo of the spill event. Remote sensing and analytical chemistry identified exposures, which were linked to effects in fish characterized by genome expression and associated gill immunohistochemistry, despite very low concentrations of hydrocarbons remaining in water and tissues. Divergence in genome expression coincides with contaminating oil and is consistent with genome responses that are predictive of exposure to hydrocarbon-like chemicals and indicative of physiological and reproductive impairment. Oil-contaminated waters are also associated with aberrant protein expression in gill tissues of larval and adult fish. These data suggest that heavily weathered crude oil from the spill imparts significant biological impacts in sensitive Louisiana marshes, some of which remain for over 2 mo following initial exposures

Effects of low salinity media on growth, condition, and gill ion transporter expression in juvenile Gulf killifish, Fundulus grandis

The Gulf killifish, Fundulus grandis, is a euryhaline teleost which has important ecological roles in the brackish-water marshes of its native range as well as commercial value as live bait for saltwater anglers. Effects of osmoregulation on growth, survival, and body condition at 0.5, 5.0, 8.0 and 12.0‰ salinity were studied in F. grandis juveniles during a 12-week trial. Relative expression of genes encoding the ion transport proteins Na(+)/K(+)-ATPase (NKA), Na(+)/K(+)/2Cl(-) cotransporter(NKCC1), and cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel was analyzed. At 0.5‰, F. grandis showed depressed growth, body condition, and survival relative to higher salinities. NKA relative expression was elevated at 7 days post-transfer but decreased at later time points in fish held at 0.5‰ while other salinities produced no such increase. NKCC1, the isoform associated with expulsion of ions in saltwater, was downregulated from week 1 to week 3 at 0.5‰ while CFTR relative expression produced no significant results across time or salinity. Our results suggest that Gulf killifish have physiological difficulties with osmoregulation at a salinity of 0.5‰ and that this leads to reduced growth performance and survival while salinities in the 5.0-12.0‰ are adequate for normal function

Écophysiologie comparée de l adaptation ontogénétique à la salinité chez la daurade Sparus aurata et le loup de mer (bar) Dicentrarchus labrax

Cette étude a associé la nano-osmométrie et la biologie cellulaire et moléculaire pour explorer les mécanismes ontogénétiques d'adaptation de ces poissons à la salinité Ils acquièrent les capacités osmorégulatrices de l'adulte en plusieurs étapes, dont l'ouverture de la bouche et la métamorphose. La mise en place de l'ATPase Na+/K+ (NKA), du cotransporteur Na+/K+/2Cl- (NKCC) et du canal à chlore CFTR, a été suivie durant l'ontogenèse selon la salinité. A l'éclosion, les protéines sont localisées dans les ionocytes tégumentaires et intestinaux. Le tégument dès l'éclosion et les branchies dès leur formation, interviennent dans la sécrétion ionique en eau de mer (EM) : la NKA et le NKCC sont basolatéraux, et le CFTR apical. Au cours de l'ontogenèse, le tube digestif accroît sa fonction osmorégulatrice ; le tégument est relayé par les branchies en formation. Au niveau du rein, les protéines apparaissent plus tardivement, chez les prélarves de D. labrax et les larves de S. aurata. Chez les juvéniles, la localisation, l'expression et la quantité des 3 protéines ont été étudiées en fonction de la salinité, EM, eau douce (ED) et eau à 5 (EMD). Les branchies sont le site osmorégulateur majeur avec les plus fortes expressions protéiques. Les localisations branchiales suggèrent un basculement de la fonction de sécrétion ionique en EM à celle d'absorption ionique en EMD/ED. Le tube digestif est impliqué à la fois dans la régulation osmotique quelles que soient la salinité et l'espèce, et dans la régulation acido-basique chez D. labrax en ED et S. aurata en EM et EMD. Les ionocytes rénaux favorisent l'absorption ionique via la NKA et le NKCC (et le CFTR chez S. aurata). Les mécanismes physiologiques et cellulaires mis en évidence contribuent à comprendre les adaptations des 2 espèces à la salinité au cours du développement. Elles leur permettent d'effectuer des migrations ontogénétiques entre des milieux de salinité plus ou moins variable, en particulier entre la mer et les estuaires ou lagunes.This integrative study of the ecophysiology of the sea bass and sea bream has used nano-osmometry and cell and molecular biology to decipher the mechanisms of ontogenetic adaptation of these teleosts to their media. Adult levels of osmoregulatory capacity occur over several steps, particularly at mouth opening and after metamorphosis. The occurrence of Na+/K+ ATPase (NKA), of the Na+/K+/2Cl- (NKCC) cotransporter and of the CFTR chloride channel has been followed during the ontogeny of both species and according to salinity. At hatching, these proteins are localized in the integumentary ionocytes and in the digestive tract. The integument, from hatching, and the gills when they develop, are involved in ionic secretion in sea water (SW): NKA and NKCC are basolateral, and CFTR is apical. During ontogeny, the osmoregulatory function increases in the digestive tract; it shifts from the integument to the developing gills. In the kidney, the proteins occur later, in prelarvae of D. labrax and in larvae of S. aurata, suggesting its late involvement in ionic regulation. In juveniles, the localization, expression and quantity of the different proteins have been studied in SW, fresh water (FW) and in a 5 medium (DSW). Gills are the major site of osmoregulation, where protein expressions are highest. The gill protein locations suggest a shift from ionic secretion in SW to ionic absorption in FW and DSW. The digestive tract is involved in osmotic regulation at all salinities in both species, and also in acid-base regulation in D. labrax in FW, and in S. aurata in SW and DSW. Renal ionocytes are involved in ionic absorption via NKA and NKCC (and CFTR in S. aurata). The physiological and cellular mechanisms revealed in this study contribute to the understanding of the adaptations of both species to salinity during development. They allow ontogenetic migrations between media with different salinity regimes, particularly between the sea and estuaries or lagoonsMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Effects of potassium ion supplementation on survival and ion regulation in Gulf killifish Fundulus grandis larvae reared in ion deficient saline waters

Teleost fish often live in an environment in which osmoregulatory mechanisms are critical for survival and largely unknown in larval fish. The effects of a single important marine ion (K(+)) on survival and ion regulation of larval Gulf killifish, an estuarine, euryhaline teleost, were determined. A four-week study was completed in four separate recirculating systems with newly hatched larvae. Salinity in all four systems was maintained between 9.5 and 10‰. Two systems were maintained using crystal salt (99.6% NaCl) with K(+) supplementation (1.31±0.04mmol/L and 2.06±0.04mmol/L K(+); mean±SEM), one was maintained with crystal salt and no K(+) supplementation (0.33±0.05mmol/L K(+)), the fourth system was maintained using a standard marine mix salt (2.96±0.04mmol/L K(+)), the salt mix also included standard ranges of other ions such as calcium and magnesium. Larvae were sampled throughout the experiment for dry mass, Na(+)/K(+)-ATPase (NKA) activity, whole body ion composition, relative gene expression (NKA, Na(+)/K(+)/2Cl(-) cotransporter (NKCC) and cystic fibrosis transmembrane conductance regulator (CFTR)), and immunocytochemistry staining for NKA, NKCC, and CFTR. Larvae stocked into water with no K(+) supplementation resulted in 100% mortality within 24h. Mortality and dry mass were significantly influenced by K(+) concentration (P≤0.05). No differences were observed among treatment groups for NKA activity. At 1dph NKA mRNA expression was higher in the 0.3mmol [K(+)] group than in other treatment groups and at 7dph differences in intestinal NKA and CFTR staining were observed. These data indicate that the rearing of larval Gulf killifish may be possible in ion deficient water utilizing specific ion supplementation

A novel system for embryo-larval toxicity testing of pelagic fish: Applications for impact assessment of Deepwater Horizon crude oil

Key differences in the developmental process of pelagic fish embryos, in comparison to embryos of standard test fish species, present challenges to obtaining sufficient control survival needed to successfully perform traditional toxicity testing bioassays. Many of these challenges relate to the change in buoyancy, from positive to negative, of pelagic fish embryos that occurs just prior to hatch. A novel exposure system, the pelagic embryo-larval exposure chamber (PELEC), has been developed to conduct successful bioassays on the early life stages (ELSs; embryos/larvae) of pelagic fish. Using this unique recirculating upwelling system, it was possible to significantly improve control survival in pelagic fish ELS bioassays compared to commonly used static exposure methods. Results demonstrate that control performance of mahi-mahi (Coryphaena hippurus) embryos in the PELEC system, measured as percent survival after 96-hrs, significantly outperformed agitated static exposure and static exposure systems. Similar significant improvements in 72-hr control survival were obtained with yellowfin tuna (Thunnus albacares). The PELEC system was subsequently used to test the effects of photo-induced toxicity of crude oil to mahi-mahi ELSs over the course of 96-hrs. Results indicate a greater than 9-fold increase in toxicity of Deepwater Horizon (DWH) crude oil during co-exposure to ambient sunlight compared to filtered ambient sunlight, revealing the importance of including natural sunlight in 96-hr DWH crude oil bioassays as well as the PELEC system's potential application in ecotoxicological assessments. Images and diagrams are from the corresponding author and shapes were created by the corresponding author using Microsoft PowerPoint. [Display omitted] •A novel exposure system for fish ELS toxicity testing (the PELEC) is reported.•The method improves ELS toxicity testing of high-value pelagic fish species.•Testing results indicate that mahi-mahi embryos are highly sensitive to PAHs.•The PELEC also allows for testing of photo-induced crude oil toxicity.•Natural sunlight co-exposure with DWH crude oil significantly increases toxicity