Marjan Diricx

University of Antwerp, Antwerpen, Flemish, Belgium

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Publications (12)24.68 Total impact

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    ABSTRACT: In the present study, the combined effects of hypoxia and nutritional status were examined in common carp (Cyprinus carpio), a relatively hypoxia tolerant cyprinid. Fish were either fed or fasted and were exposed to hypoxia (1.5–1.8 mg O2 L− 1) at or slightly above their critical oxygen concentration during 1, 3 or 7 days followed by a 7 day recovery period. Ventilation initially increased during hypoxia, but fasted fish had lower ventilation frequencies than fed fish. In fed fish, ventilation returned to control levels during hypoxia, while in fasted fish recovery only occurred after reoxygenation. Due to this, C. carpio managed, at least in part, to maintain aerobic metabolism during hypoxia: muscle and plasma lactate levels remained relatively stable although they tended to be higher in fed fish (despite higher ventilation rates). However, during recovery, compensatory responses differed greatly between both feeding regimes: plasma lactate in fed fish increased with a simultaneous breakdown of liver glycogen indicating increased energy use, while fasted fish seemed to economize energy and recycle decreasing plasma lactate levels into increasing liver glycogen levels. Protein was used under both feeding regimes during hypoxia and subsequent recovery: protein levels reduced mainly in liver for fed fish and in muscle for fasted fish. Overall, nutritional status had a greater impact on energy reserves than the lack of oxygen with a lower hepatosomatic index and lower glycogen stores in fasted fish. Fasted fish transiently increased Na+/K+-ATPase activity under hypoxia, but in general ionoregulatory balance proved to be only slightly disturbed, showing that sufficient energy was left for ion regulation.
    Comparative biochemistry and physiology. Part A, Molecular & integrative physiology 10/2014; DOI:10.1016/j.cbpa.2014.09.017 · 2.37 Impact Factor
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    ABSTRACT: Since hypoxia is a common event in aquatic environments, oxygen has been a major driving force in the evolution of fish. When fish are simultaneously faced with food deprivation, this poses an even greater challenge to energy metabolism and ion homeostasis. In the present study, the combined effects of hypoxia and nutritional status were examined on ventilation, energy metabolism and onoregulatory responses. Common carp (Cyprinus carpio) were exposed to hypoxia (1.5-1.8 mg O2 .L-1) during 1, 3 or 7 days followed by a 7 day recovery period, and were either fed or fasted. C.carpio managed, at least in part, to maintain aerobic metabolism during hypoxia: muscle and plasma lactate levels remained relatively stable. However, during the recovery period plasma lactate in fed fish increased while it decreased in fasting fish. Hypoxia actually increased liver glycogen in fasted fish, while the opposite trend was observed in muscle. Protein levels reduced during hypoxia and subsequent recovery, mainly in liver for fed fish and in muscle for fasting fish. The nutritional status had a greater impact on energy reserves than the lack of oxygen with a lower hepatosomatic index and lower glycogen stores in fasted fish. Furthermore, fasted fish had lower ventilation frequencies under both control and hypoxic conditions. Under both feeding regimes, ventilation initially increased in hypoxic fish, but returned to control levels after a few days. Fasting fish transiently increased Na+ /K+ -ATPase activity. Generally, ionoregulatory balance proved to be only slightly disturbed, showing that sufficient energy was left for ion regulation.
    Society for experimental biology, Manchester; 07/2014
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    ABSTRACT: European sea bass Dicentrarchus labrax was acutely exposed to Cd concentrations of 17.79, 142.33 and 177.92 μM and Cu concentration of 31.47, 75.54 and 80.26 μM over a 10-day period, and to chronically Cd concentration of 14.46 μM and a Cu concentration of 10.76 μM (according to 10% of 96h-LC50 obtained values at 20‰) for a short exposure period (SEP) of 10 days and long period (LEP) of 28 days, both experiments were conducted at 20‰. Survival time in relation to the tissue Cu does not show a clear relationship between tissue Cu and time to death, tissue concentrations in dead fish was in the same range as concentrations in the survivors. However for Cd, a significant difference were observed in tissue Cd, the dead individuals exhibited accumulated Cd about of 5 to 18-fold more in liver, 10-31-fold in kidney, 12-31-fold in gill and 1.5-29-fold in intestine than in surviving individuals, this seems to explain partially the cause of death. Among dead and surviving individuals, a clear difference in speed of accumulation (μmol/g dwt /day) was apparent, accumulation rates were extremely high in dead fish, such as 2.417 ± 1.774 and 10.076 ± 11.097 in kidney compared to lower values than 0.035 and 0.026 of exposed survivors to Cd and Cu respectively. All examined tissues (liver, kidney, gill and intestine) showed significantly higher Cd accumulation rates at the two highest acute exposures compared to chronic exposed fish (with the exception of kidney at 177. 92 μM), whereas for Cu, intestine and gill showed the same pattern for all acute exposures, and kidney and liver only over 80.26 and 75.54 μM exposure respectively. Among the different exposure periods, liver, gill and intestine Cd were significantly higher over the LEP, while kidney does not show variations. For Cu, liver and intestine from the LEP also exhibited significantly higher concentrations compared to those at SEP. Kidney and gill showed the opposite response but not statistically different (SEP > LEP in Cu concentrations).
    IV Congreso de Ciencias del Mar del Perú - CONCIMAR, Lima, Peru; 06/2014
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    ABSTRACT: Cadmium and copper are constituents of industrial and urban wastes that are considered a concern because its environmental levels have risen steadily worldwide (Goering et al., 1995). European sea bass, Dicentrarchus labrax, is an estuary and marine water (EMW) fish that is able to withstand gradients in many physical and chemical variables, including salinity, pH, dissolved oxygen, temperature, nutrients among others. In estuaries, the salinity is the controlling factor for the partitioning of contaminants, trace metals such as cadmium and copper change bioavailability and toxicity by complexation (Riba et al., 2003). Therefore, the effect of salinity on the bioaccumulation and toxicity of copper and cadmium in D. labrax was determined at different exposure concentrations of Cu from 0 to 5100 μg L-1 and Cd from 0 to 20000 μg L-1 over a salinity range of 1, 2.5, 5, 10, 20, 28, 35‰ in juvenile individuals during a period of 10 days. The results showed a relationship between bioaccumulation and toxicity in terms of 96h-LC50 values (the lethal concentration where 50% of the population dies), where the salinity played an important role for both elements. At 2000 μgCd L-1 of exposure, the accumulation of Cd decreased considerably at higher salinities in liver and kidney, and concurrently LC50 values increased to 16256 μg L-1 (20‰), 18326 μg L-1 (28‰) and 24383 μg L-1 (35‰). On the contrary, the highest bioaccumulation of Cu was around the iso-osmotic point (10-20‰) where the LC50 values were elevated, 2619 μg L-1 at 10‰ and 6835 μg L-1 at 20‰. Generally, liver and kidney showed the highest concentration of Cd, followed by intestine and gills. For Cu, gills contained the highest concentrations and the lowest was found in intestine, kidney and liver exhibited noticeably variations and intermediate concentrations.
    XV Congreso Latinoamericano de Ciencias del Mar – COLACMAR, Punta del Este, Uruguay; 10/2013
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    ABSTRACT: Ammonia is an environmental pollutant that is toxic to all aquatic animals. The toxic effects of ammonia can be modulated by other physiological processes such as feeding and swimming. In this study, we wanted to examine these modulating effects in common carp (Cyprinus carpio). Fish were either fed (2% body weight) or starved (unfed for seven days prior to the sampling), and swimming at a sustainable, routine swimming speed or swum to exhaustion, while being exposed chronically (up to 28 days) to high environmental ammonia (HEA, 1 mg/L ~ 58.8 µmol/L as NH4Cl at pH 7.9). Swimming performance (critical swimming speed, Ucrit) and metabolic responses such as oxygen consumption rate (MO2), ammonia excretion rate (Jamm), ammonia quotient, liver and muscle energy budget (glycogen, lipid and protein), plasma ammonia and lactate, as well as plasma ion concentrations (Na+, Cl-, K+ and Ca2+) were investigated in order to understand metabolic and iono-regulatory consequences of the experimental conditions. Cortisol plays an important role in stress and in both the regulation of energy and the ion homeostasis, therefore plasma cortisol was measured. Results show that during HEA, Jamm was elevated to a larger extent in fed fish and they were able to excrete much more efficiently than the starved fish. Consequently, the build-up of ammonia in plasma of HEA exposed fed fish was much slower. MO2 increased considerably in fed fish after exposure to HEA and was further intensified during exercise. During exposure to HEA, the level of cortisol in plasma augmented in both the feeding regimes, but the effect of HEA was more pronounced in starved fish. Energy stores dropped for both fed and the starved fish with the progression of the exposure period and further declined when swimming to exhaustion. Overall, fed fish were less affected by HEA than starved fish, and although exercise exacerbated the toxic effect in both feeding treatments, this was more pronounced in starved fish. This suggests that fish become more vulnerable to external ammonia during exercise, and feeding protects the fish against the adverse effects of high ammonia and exercise.
    Aquatic Toxicology 08/2013; DOI:10.1016/j.aquatox.2013.08.007 · 3.51 Impact Factor
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    ABSTRACT: Feeding and swimming can influence ion balance in fish. Therefore we investigated their impact on ionoregulation and its hormonal control in goldfish and common carp. As expected due to the osmorespiratory compromise, exhaustive swimming induced increases in gill Na(+)/K(+) ATPase (NKA) activity in both species, resulting in stable levels of plasma ions. In contrast to our expectations, this only occurred in fed fish and feeding itself increased NKA activity, especially in carp. Fasting fish were able to maintain ion balance without increasing NKA activity, we propose that the increase in NKA activity is related to ammonia excretion rather than ion uptake per se. In goldfish, this increase in NKA activity coincided with a cortisol elevation while no significant change was found in carp. In goldfish, high conversion of plasma T(4) to T(3) was found in both fed and fasted fish resulting in low T(4)/T(3) ratios, which increased slightly due to exhaustive swimming. In starved carp the conversion seemed much less efficient, and high T(4)/T(3) ratios were observed. We propose that thyroid hormone regulation in carp was more related to its role in energy metabolism rather than ionoregulation. The present research showed that both species, whether fed or fasted, are able to sufficiently adapt their osmorepiratory strategy to minimise ions losses while maintaining gas exchange under exhaustive swimming.
    Comparative biochemistry and physiology. Part A, Molecular & integrative physiology 02/2013; 165(1). DOI:10.1016/j.cbpa.2013.02.009 · 2.37 Impact Factor
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    Iván Loaiza · Marjan Diricx · Gudrun De Boeck
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    ABSTRACT: Contamination by heavy metals in aquatic environments is a serious concern due to increasing human activities over the last decades. Moreover, productive areas such as estuaries have even been more affected because of the complex interaction between fluvial and marine processes, creating a stressful environment with gradients of salinity and other important parameters which can intensify negative effects of pollutants on biota such as euryhaline fish. (Oliva et al., 2012; Mieiro et al 2012). European sea bass (Dicentrarchus labrax l.) is a euryhaline species able to withstand a large variation in salinity and is considered as a bioindicador due to both economic and ecological importance (Joseph., et al 2011; Loizeau, 2001). Copper as essential micronutrient has important roles in cellular, enzymatical and protein mechanisms but is potentially toxic when its concentration increases above a certain threshold (Blanchard & Grosell, 2005; Grosell et al., 2007), and can even be more toxic than cadmium, a non-essential metal (Roméo et al., 2000) which is ubiquitous in environment and one of the most deleterious heavy metal pollutants (Nath et al., 1984 cited by Loaiza, 2011). Therefore, the effect of salinity on the acute toxicity of copper and cadmium in European sea bass D. labrax l. was examined to determine 96h-LC50 values (the lethal concentration where 50% of the population dies) at different exposure concentration of both metals (at 0 to 5100 μgCu L-1 and at 0 to 20000 μgCd L-1) over a broad salinity range (1, 2.5, 5, 10, 20, 28, 35‰) in juvenile sea bass during a period of 10 days. The results showed an important influence of the salinity in the toxicity in both elements, where for Cu mortality first decreased with increasing salinity but increased again at higher salinities and for Cd, mortality decreased continuously with increasing salinity, to a point where no reliable LC50 could be determined at the 2 highest salinities. In addition, it was observed that the individuals were affected in different ways. For instance Cu exposed fish at low salinity showed opened gills at die-off. Copper is readily taken up by the gill, where it inhibits the action of Na+/K+ adenosine triphosphatase, resulting in an osmoregulatory disturbance as Na+ is lost to the dilute external environment (Blanchard et al. 2006). In conclusion, the salinity influences the toxicity differently for Cu and Cd. This not only occurs due to the fact that salinity plays an important role in the speciation of pollutants and competition by cations in uptake processes, but as can be clearly seen in the case of Cu, also by the physiology of the fish that responds to the changes in the environment. Further research on the relationship between bio-accumulation of the metals and the mortality at different salinities is planned.
    VLIZ Young Marine Scientists’ Day., Brugge, Belgium; 02/2013
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    ABSTRACT: Fish need to balance their energy use between digestion and other activities, and different metabolic compromises can be pursued. We examined the effects of fasting (7days) on metabolic strategies in goldfish and common carp at different swimming levels. Fasting had no significant effect on swimming performance (U(crit)) of either species. Feeding and swimming profoundly elevated total ammonia (T(amm)) excretion in both species. In fed goldfish, this resulted in increased ammonia quotients (AQ), and additionally plasma and tissue ammonia levels increased with swimming reflecting the importance of protein contribution for aerobic metabolism. In carp, AQ did not change since oxygen consumption (MO(2)) and T(amm) excretion followed the same trend. Plasma ammonia did not increase with swimming suggesting a balance between production and excretion rate except for fasted carp at U(crit). While both species relied on anaerobic metabolism during exhaustive swimming, carp also showed increased lactate levels during routine swimming. Fasting almost completely depleted glycogen stores in carp, but not in goldfish. Both species used liver protein for basal metabolism during fasting and muscle lipid during swimming. In goldfish, feeding metabolism was sacrificed to support swimming metabolism with similar MO(2) and U(crit) between fasted and fed fish, whereas in common carp feeding increased MO(2) at U(crit) to sustain feeding and swimming independently.
    Comparative biochemistry and physiology. Part A, Molecular & integrative physiology 08/2012; 163(3-4):327-35. DOI:10.1016/j.cbpa.2012.07.012 · 2.37 Impact Factor
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    ABSTRACT: Waterborne ammonia has become a persistent pollutant of aquatic habitats. During certain periods (e.g. winter), food deprivation may occur simultaneously in natural water. Additionally, under such stressful circumstances, fish may be enforced to swim at a high speed in order to catch prey, avoid predators and so on. Consequently, fish need to cope with all these stressors by altering physiological processes which in turn are controlled by their genes. In this present study, toxicogenomic analyses using real time PCR was used to characterize expression patterns of potential biomarker genes controlling growth, ion regulation and stress responses in common carp subjected to elevated ammonia (1 mg/L; Flemish water quality guideline for surface water) following periods of feeding (2% body weight) and fasting (unfed for 7 days prior to sampling). Both feeding groups of fish were exposed to high environment ammonia (HEA) for 0 h (control), 3h, 12h, 1 day, 4 days, 10 days, 21 days and 28 days, and were sampled after performing swimming at different speeds (routine versus exhaustive). Results show that the activity and expression of Na(+)/K(+)-ATPase, an important branchial ion regulatory enzyme, was increased after 4-10 days of exposure. Effect of HEA was also evident on expression patterns of other ion-regulatory hormone and receptor genes; prolactin and cortisol receptor mRNA level(s) were down-regulated and up-regulated respectively after 4, 10 and 21 days. Starvation and exhaustive swimming, the additional challenges in present study significantly further enhanced the HEA effect on the expression of these two genes. mRNA transcript of growth regulating hormone and receptor genes such as Insulin-like growth factor I, growth hormone receptor, and the thyroid hormone receptor were reduced in response to HEA and the effect of ammonia was exacerbated in starved fish, with levels that were remarkably reduced compared to fed exposed fish. However, the expression of the growth hormone gene itself was up-regulated under the same conditions. Expression of somatolactin remained unaltered. Stress representative genes, cytochrome oxidase subunit 1 showed an up-regulation in response to HEA and starvation while the mRNA level of heat shock protein 70 was increased in response to all the three stressors. The expression kinetics of the studied genes could permit to develop a "molecular biomarker system" to identify the underlying physiological processes and impact of these stressors before effects at population level occur.
    Aquatic toxicology (Amsterdam, Netherlands) 06/2012; 122-123:93-105. DOI:10.1016/j.aquatox.2012.05.013 · 3.51 Impact Factor
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    ABSTRACT: Due to eutrophication, high environmental ammonia (HEA) has become a frequent problem in aquatic environments, especially in agricultural or densely populated areas. During certain periods, e.g. winter, feed deprivation may occur simultaneously in natural waters. Additionally, under such stressful circumstances, fish may be enforced to swim at a high speed in order to catch prey, avoid predators and so on. Consequently, fish need to cope with all these stressors by altering physiological processes which in turn are controlled by genes expression. Therefore, in the present study, ammonia toxicity was tested in function of nutrient status (fed versus starved) and swimming performance activity (routine versus exhaustive). Goldfish, a relatively tolerant cyprinid, were exposed to HEA (1 mg/L; Flemish water quality guideline for surface water) for a period of 3 h, 12 h, 1 day, 4 days, 10 days, 21 days and 28 days and were either fed (2% body weight) or starved (kept unfed for 7 days prior to sampling). Results showed that the activity of Na⁺/K⁺-ATPase in the gills was stimulated by HEA and disturbance in ion balance was obvious with increases in plasma [Na⁺], [Cl⁻] and [Ca²⁺] after prolonged exposure. Additionally, osmoregulation and metabolism controlling hormones like cortisol and thyroid hormones (T3 and T4) were investigated to understand adaptive responses. The expression kinetics of growth, stress and osmo-regulatory representative genes such as Insulin-like growth factor 1 (IGF-I), growth hormone receptor (GHR), thyroid hormone receptor β (THRβ), prolactin receptor (PRLR), cortisol receptor (CR) and Na⁺/K⁺-ATPase α(3) were examined. Overall effect of HEA was evident since Na⁺/K⁺-ATPase activity, plasma cortisol, Na⁺ and Ca²⁺ concentration, expression level of CR and Na⁺/K⁺-ATPase α₃ mRNA in fed and starved fish were increased. On the contrary, transcript level of PRLR was reduced after 4 days of HEA; additionally T3 level and expression of GHR, IGF-I and THRβ genes were decreased following 10-21 days of HEA. Starvation, the additional challenge in the present study, significantly increased plasma cortisol level and CR transcript level under HEA compared to the fed exposed and control fish. Furthermore, a remarkable reduction in T3 and mRNA levels of THRβ, IGF-I and GHR genes was observed under starvation. The toxic effects in both feeding treatments were exacerbated when imposed to exhaustive swimming with more pronounced effects in starved fish. This confirms that starvation makes fish more vulnerable to external ammonia, especially during exercise.
    Aquatic toxicology (Amsterdam, Netherlands) 03/2012; 114-115:153-64. DOI:10.1016/j.aquatox.2012.02.027 · 3.51 Impact Factor
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    ABSTRACT: Due to eutrophication, high environmental ammonia (HEA) has become a frequent problem in aquatic environments, especially in agricultural or densely populated areas. During certain periods, e.g. winter, feed deprivation may occur simultaneously in natural waters. Additionally, under such stressful circumstances, fish may be enforced to swim at a high speed in order to catch prey, avoid predators and so on. Consequently, fish need to cope with all these stressors by altering physiological processes which in turn are controlled by genes expression. Therefore, in the present study, ammonia toxicity was tested in function of nutrient status (fed versus starved) and swimming performance activity (routine versus exhaustive). Goldfish, a relatively tolerant cyprinid, were exposed to HEA (1 mg/L; Flemish water quality guideline for surface water) for a period of 3 h, 12 h, 1 day, 4 days, 10 days, 21 days and 28 days and were either fed (2% body weight) or starved (kept unfed for 7 days prior to sampling). Results showed that the activity of Na⁺/K⁺-ATPase in the gills was stimulated by HEA and disturbance in ion balance was obvious with increases in plasma [Na⁺], [Cl⁻] and [Ca²⁺] after prolonged exposure. Additionally, osmoregulation and metabolism controlling hormones like cortisol and thyroid hormones (T3 and T4) were investigated to understand adaptive responses. The expression kinetics of growth, stress and osmo-regulatory representative genes such as Insulin-like growth factor 1 (IGF-I), growth hormone receptor (GHR), thyroid hormone receptor β (THRβ), prolactin receptor (PRLR), cortisol receptor (CR) and Na⁺/K⁺-ATPase α(3) were examined. Overall effect of HEA was evident since Na⁺/K⁺-ATPase activity, plasma cortisol, Na⁺ and Ca²⁺ concentration, expression level of CR and Na⁺/K⁺-ATPase α₃ mRNA in fed and starved fish were increased. On the contrary, transcript level of PRLR was reduced after 4 days of HEA; additionally T3 level and expression of GHR, IGF-I and THRβ genes were decreased following 10-21 days of HEA. Starvation, the additional challenge in the present study, significantly increased plasma cortisol level and CR transcript level under HEA compared to the fed exposed and control fish. Furthermore, a remarkable reduction in T3 and mRNA levels of THRβ, IGF-I and GHR genes was observed under starvation. The toxic effects in both feeding treatments were exacerbated when imposed to exhaustive swimming with more pronounced effects in starved fish. This confirms that starvation makes fish more vulnerable to external ammonia, especially during exercise.
    Aquatic Toxicology 01/2012; · 3.51 Impact Factor
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    ABSTRACT: This study aimed to elucidate the physiological effects of high environmental ammonia (HEA) following periods of feeding (2% body weight) and starvation (unfed for 7 days prior to sampling) in gold fish (Carassius auratus). Both groups of fish were exposed to HEA (1 mg/L; Flemish water quality guideline) for 0 h (control), 3 h, 12 h, 1 day, 4 days, 10 days, 21 days and 28 days. Measurements of weight gain (%), oxygen consumption (MO2), ammonia excretion rate, ammonia quotient (AQ), critical swimming speeds (Ucrit), plasma and muscle ammonia accumulation, plasma lactate, liver and muscle glycogen, lipid and protein content were done at various time intervals during the experimental periods. Overall, ammonia excretion rates, plasma ammonia accumulation and AQ were significantly affected by food regime in ammonia free water. HEA, the additional challenge in the present study, significantly altered all the studied parameters among fed and starved groups in days-dependent manner. Results show that weight gain (%), MO2, Ucrit, protein content in liver and muscle, and glycogen content in muscle among starved fish under HEA were considerably reduced compared to control and fed fish. Additionally a remarkable increase in plasma ammonia level, muscle ammonia, lactate accumulation and AQ was seen. However in fed fish, MO2, ammonia excretion rate, AQ and lactate level augmented after exposure to HEA. These results indicate that starved fish appeared more sensitive to HEA than fed fish. Furthermore, as expected, the toxic effect of ammonia exposure in both feeding treatments was exacerbated when imposed to exhaustive swimming (swum at 3/4th Ucrit). Such effects were more pronounced in starved fish. This suggests that starvation can instigate fish more vulnerable to external ammonia during exercise. Therefore, it was evident from our study that feeding ameliorates ammonia handling and reduces its toxicity during both routine and exhaustive swimming. Moreover, recovery was observed for some physiological parameters (e.g. MO2, ammonia excretion, Ucrit, plasma ammonia) during the last exposure periods (21-28 days) while for others (e.g. growth, tissue glycogen and protein content, muscle ammonia) effects only became apparent at this time. In the future, these results need to be considered in ecological context as fish in ammonia polluted may experience different phenomenon (starvation and exercise) simultaneously.
    Aquatic toxicology (Amsterdam, Netherlands) 11/2011; 109:33-46. DOI:10.1016/j.aquatox.2011.11.002 · 3.51 Impact Factor