Process of exotrophy in fish. Effect of heavy metals—Zn and Cu

The review summarizes for the first time the information on effects of Zn and Cu on various links of the fish exotrophy process. It has been shown that essential metals, like the nonessential ones, can produce negative effects on various aspects of the food-procuring behavior, on sensor systems providing alimentary behavior, and on the digestive enzymes realizing digestion in fish of different ecological groups. A particular attention is paid to their different effects on proteinases functioning in stomach and intestine of various fish species as well as on hydrolase activities in their potential nutrition objects (fish and invertebrate animals). Several mechanisms are considered which allow decreasing the negative action of Zn and Cu on the process of fish exotrophy.     

Influence of biogenic metals (Cu,Zn) on the activity of carbohydrases in juvenile fish in vitro

It was revealed that intestine and whole-body amylolytic activity (AA) in juvenile fish serving as potential feeding items for piscivores significantly decreases in the presence of Cu and Zn ions within a wide range (0.1–25 mg/l) of concentrations in vitro. In most of the studied fish species, Cu and Zn decrease the activities of carbohydrases in the intestine mucosa stronger than in the whole-body. On the other hand, in piscivore-facultative benthivore perch, which have the least AA, the inhibiting effect of Cu and Zn ions is 1.5 to 2 times higher in the whole body than in the intestine. The study data suggest that Cu and Zn ions at concentrations found in organisms that serve as fish food may not only reduce the rate of initial stages of carbohydrates hydrolysis in the juvenile fish intestine, but also considerably decrease the potential contribution of the food objects to the digestion processes in typical and facultative piscivores.     

Physiological Adaptations (By the Example of the Exotrophy Process in Fish)

By the example of a complex process of exotrophy in fish, which includes not only search for and consumption, but also digestion of the victim, as well as transfer of products of its depolymerization into the internal organism medium, different types of physiological adaptations are described: adaptations of elementary functions, the local or subsystem adaptations, the organismal or supersystem ones, as well as the superorganism adaptations including victim-symbiotic, populational, and biocenotic ones.     

高铜、高锌猪粪对蚯蚓的急性毒性效应研究

测定了高Cu、高Zn猪粪条件下Cu、Zn单一与复合污染对蚯蚓的急性致死及亚致死效应.结果表明,Cu、Zn浓度与蚯蚓死亡率显著正相关(a=0.05,r_Cu=0.99,r_Zn=0.99),与体重增长率显著负相关(a=0.05,r_Cu=-0.99,r_Zn=-0.96).蚯蚓个体对Cu、Zn的耐受程度不同,其毒性阈值(引起蚯蚓个体死亡浓度)分别为:Cu250mg·kg^-1、Zn400mg·kg^-1.LD₅₀分别为:Cu646.68mg·kg^-1、Zn947.38mg·kg^-1.复合污染情况下,Cu浓度为250、500mg·kg^-1时,Cu、Zn复合污染表现为协同效应;Cu浓度为750mg·kg^-1时,Cu、Zn复合污染表现为拮抗效应,可见,猪粪中Cu、Zn复合污染的毒性效应与各组浓度组合密切相关.     

Metal (Fe, Zn, Cu, Pb and Cd) concentration patterns in components of a macrophyte-based coastal lagoon ecosystem

Information on the metal biological fate in macrophyte-based coastal lagoons is provided; this information can contribute to the assessment of the environmental effects of metal pollution and to the development of predictive models for rational management of coastal lagoons. Iron, Zn, Cu, Pb and Cd concentrations in the dominant invertebrate and fish species of Monolimni Lagoon, Mediterranean Sea, as well as in potential major sources for metal accumulation in these animals (water, sediments, angiosperms, seaweeds), were measured. Principal Component Analysis (PCA) was conducted using metal concentrations in invertebrates and fishes. All five metal concentrations loaded significantly on the first PCA axis; however, Zn and Cu loadings were less significant than Cd and even less than Fe and Pb ones. The samples of deposit-feeding invertebrates were separated from those of the rest of the organisms (browsing, herbivorous and carnivorous invertebrates, carnivorous gobies and muscle tissues of detritivorous mullets) along the first PCA axis. Deposit-feeding invertebrates displayed the highest Fe and Pb contents, and in general, the highest or comparatively high Cd, Zn and Cu ones. Carnivorous gobies showed comparatively high Zn contents and carnivorous shrimps the highest Cu ones, while muscle tissues of detritivorous mullets had low metal loads. In addition, there was no essential increase in metal concentrations corresponding to the increasing trophic level (autotrophs, to herbivores, to carnivores). Our findings suggest that (a) the variability in Fe, Pb and Cd contents in invertebrates and gobies depends at least to some extent on interspecific differences in feeding habits—deposit feeders accumulated the highest metal amounts probably due to high rates of uptake from sediments, (b) the variability in Zn and Cu concentrations in these organisms depends also on other interspecific differences apart from those in feeding habits, (c) metal accumulation in mullet muscle tissues does not depend markedly on feeding habits and (d) the trophic transfer of macrophyte-bound metals to the coastal lagoon food web is of relatively minor importance.     

Evaluation of inhibitory effects of heavy metals on anaerobic ammonium oxidation (anammox) by continuous feeding tests

To facilitate the application of anaerobic ammonium oxidation (anammox) to a nitrogen removal process, the effects of heavy metals (Ni, Cu, Co, Zn, and Mo) on anammox bacteria entrapped in gel carriers were examined by conducting continuous feeding tests for each metal. The results show that all anammox activities decreased by more than 10 % when influent concentrations of Ni, Cu, Co, Zn, and Mo were 5, 5, 5, 10, and 0.2 mg/L, respectively. It was observed that the effects of Ni, Cu, Co, and Zn on anammox activity were reversible and that of Mo on anammox activity was irreversible. Anammox activity was not affected when influent containing mixed Ni, Cu, Co, and Zn (0.5 mg/L) was fed into the reactor.     

Effects of heavy metals (Cu and Zn) on digestive glycosidases in benthivorous fish of areas of Rybinsk Reservoir differing in anthropogenic loads

The separate and combined in vitro effects of heavy metal ions (Cu and Zn) at concentrations of 0.1–25 mg/L on the activities of maltase, sucrase, and amylolytic activity in the intestines of bream and roach caught in areas of the Rybinsk Reservoir differing in anthropogenic loads have been studied. In fish from the polluted Sheksninskii Reach, membrane maltase and sucrase enzymes are less sensitive to the effects of Cu and Zn ions than in fish from the relatively clean Volzhskii Reach. On the other hand, starch-hydrolyzing enzymes were more sensitive to the effects of the metals under study in bream from a polluted area, which was especially evident in summer. The combined effect of Cu and Zn ions (1: 1) in most cases weakens the separate effects of these metals on the activities of hydrolases (except for amylolytic activity) in the studied fish.     

How metals directly affect the antioxidant status in the liver and kidney of Oreochromis niloticus? An in vitro study

BackgroundMetals can disturb the integrity of physiological and biochemical mechanisms in fish. Thus components of defense as an antioxidant system are significant biomarkers due to their vital role in coping with metal stress. The aim of the current study is to investigate the direct effects of Cd, Cu, and Zn sublethal exposures (in vitro) on the antioxidant system parameters in the liver and kidney of Nile tilapia.MethodsThe antioxidant enzyme activities and GSH levels were analyzed after in vitro sublethal metal (200 and 400 μg/L Cd, Cu, and Zn) treatments of Oreochromis niloticus liver and kidney supernatants.ResultsMetals even at lower levels caused significant changes in the levels of antioxidant system parameters due to concentration, metal, and tissue type. GSH metabolism parameters were more responsive to the metal effect. TBARS levels and GPX activity were mostly increased while CAT, SOD, rGSH, and GSH/GSSG levels decreased. The kidney was more affected than the liver in vitro conditions. Cu was more effective in the liver whereas it was Zn for the kidney. Cd caused negative correlations among the antioxidant enzymes. Significant correlations were found between enzymes and GSH levels upon Zn and Cu exposures.ConclusionsDirect metal effects may trigger different response trends due to their nature and tissue differences. The current data provide a knowledge about which antioxidant biomarkers can define better the oxidative stress caused by direct metal effect for further studies including in vivo experiments.     

Antioxidant Defenses in Fish: Biotic and Abiotic Factors

Oxygen in its molecular state O₂, is essential for many metabolic processes that are vital to aerobic life. Aerobic organisms cannot exist without oxygen, which nevertheless is inherently dangerous to their lives. Like all aerobic organisms, fish are also susceptible to the effects of reactive oxygen and have inherent and effective antioxidant defenses that are well described in the literature. This review investigates the influence of different biotic and abiotic factors (age, phylogenetic position, feeding behavior, environmental factors, oxygen, temperature, presence of xenobiotics) on antioxidant defenses in fish. Studies of antioxidant activity in fish open a number of novel research lines providing greater knowledge of fish physiology, which will benefit various aspects of fish farming and artificial production.     

Experimental studies on direct and indirect interactions in a three trophic-level stream system

Summary We used a complete block design to experimentally study direct and indirect interactions in a three trophic-level freshwater system consisting of a top predator, the green sunfish, Lepomis cyanellus, an intermediate predator, small-mouthed salamander larvae, Ambystoma barbouri, and prey, hatchling isopods, Lirceus fontinalis. This system occurs naturally in small stream pools in central Kentucky; experiments were done in laboratory pools. Salamander larvae ate isopods and thus had a direct, negative effect on isopod survival. Accordingly, isopods responded to the presence of salamander larvae by increasing their tendency to bury themselves in the sand substrate. Fish ate salamanders and thus had a direct, negative effect on salamander survival. Salamanders responded to fish presence by increasing their time spent under plexiglass plates that simulate refuge rocks. The overall effect of fish on isopods depended on the presence of salamanders. In the absence of salamanders, fish predation on isopods had a direct, negative effect on isopod survival; isopods thus responded to the presence of fish by burying themselves in the sand. With salamanders present, fish had a positive overall effect on isopod survival; i.e., direct, negative effects of fish on isopods were outweighed by indirect, positive effects. Indirect positive effects of fish on isopods came through a reduction in salamander predation rates on isopods in the presence of fish. The mechanism involved both a decrease in the number of salamanders (a trophic-linkage indirect effect; cf. Miller and Kerfoot 1987) and a reduction in the feeding rate of individual salamanders on isopods (a behavioral indirect effect). The decrease in individual salamander feeding rates on isopods was due to reductions in both salamander activity and in spatial overlap between salamanders and isopods in the presence of fish. The latter effect reflected the fact that salamanders and isopods used different refuges from fish; salamanders went under refuge plates, whereas isopods primarily buried themselves in sand. Estimates of the relative importance of various direct and indirect effects of sunfish on isopods suggested that positive, behavioral indirect effects were of roughly the same magnitude as direct, negative effects, both of which were more important than were trophic-linkage indirect effects. Contrary to expectations, the presence of isopods did not affect the refuge use or survival of salamanders in the presence of fish.     

The effects of intraspecific competition on the prey capture behavior and kinematics of the bluegill sunfish, Lepomis macrochirus

Competition has broad effects on fish and specifically the effects of competition on the prey capture kinematics and behavior are important for the assessment of future prey capture studies in bony fishes. Prey capture kinematics and behavior in bony fishes have been shown to be affected by temperature and satiation. The densities at which bony fish are kept have also been shown to affect their growth, behavior, prey selection, feeding and physiology. We investigated how density induced intraspecific competition for food affects the prey capture kinematics of juvenile bluegill sunfish, Lepomis macrochirus. High speed video was utilized to film five bold individuals feeding at three different densities representing different levels of intraspecific competition. We hypothesized that: (1) the feeding kinematics will be faster at higher levels of competition compared to lower levels of competition, and (2) bluegill should shift from more suction-based feeding towards more ram-based feeding with increasing levels of competition in order to outcompete conspecifics for a prey item. We found that, with increased intraspecific competition, prey capture became faster, involving more rapid jaw opening and therefore greater inertial suction, shorter mouth closing times, and shorter gape cycles. Furthermore, the attack velocity of the fish increased with increasing competition, however a shift towards primarily ram based feeding was not confirmed. Our study demonstrates that prey capture kinematics are affected by the presence of conspecifics and future studies need to consider the effects of competition on prey capture kinematics.     

Stress-induced effects on feeding behavior and growth performance of the sea bass (<Emphasis Type="Italic">Dicentrarchus labrax</Emphasis>): a self-feeding approach

Repetitive aquaculture-related protocols may act as cyclic stressors that induce chronic stress in cultured fish. The sea bass is particularly sensitive to stressful conditions and the mere presence of humans will disturb feeding behavior. In this paper, we study whether chronic stress induced by repetition of acute stress protocols affects long-term feeding behavior and growth performance in sea bass and whether exogenous cortisol may induce stress-like changes in these parameters. We demonstrate that both chronic stress and dietary cortisol decrease food intake and have a negative effect on feed conversion efficiency, severely impairing sea bass performance. Both experimental approaches induced changes in the daily feeding activity by lengthening the active feeding periods. Fish subjected to a cyclic stressor modify their daily feeding pattern in an attempt to avoid interference with the time of the stressor. The delay in feeding when fish are acutely and repeatedly stressed could be of substantial adaptive importance.     

Copper,zinc, and selenium in whole blood and thyroid tissue of people with various thyroid diseases

We investigated the possible differences among the concentrations of copper, zinc, and selenium, and their mutual relations in the whole blood and thyroid tissue of patients with various thyroid disorders. Trace elements were determined by total-reflection X-ray fluorescence. The mean levels of these metals in blood as well as the mean Cu/Zn, Cu/Se, and Zn/Se ratios in the patients with thyroid cancer were significantly higher that in other patients and the control groups. However, the mean Zn and Se concentrations in the thyroid cancer tissue were significantly lower than in the thyroid tissue of other patients. In addition, the mean Cu/Zn and Cu/Se ratios in the thyroid cancer tissue were significantly higher than in the patients with other thyroid diseases. We confirm that the highest levels of copper and zinc as well as the Cu/Zn, Cu/Se, and Zn/Se ratios in the whole blood of the patients with thyroid cancer may suggest the progression of the proliferation process in the thyroid gland. We suggest that the low concentrations of zinc and selenium in the thyroid tissue confirm their participation in the carcinogenic process.     

Effect of copper- and zinc-methionine supplementation on bioavailability,mineral status and tissue concentrations of copper and zinc in ewes

The effect of feeding Cu- and Zn-methionine to ewes was studied in a 240d feeding trial. The plasma and tissue Cu and Zn concentrations and Cu/Zn-superoxide dismutase (Cu/Zn-SOD) activity were employed to assess the relative bioavailability from Cu- and Zn-methionine. The macro and micronutrient intake, utilization, plasma mineral status, tissue accumulation of Cu and Zn as well as wool concentration of Cu and Zn were studied in ewes (n=12) fed a corn-soybean meal based basal diet with 50% more Cu and Zn supplementation over the basal diet either from Cu- and Zn-sulfate (Cu-Sulf+Zn-Sulf group) or Cu- and Zn-methionine (Cu-Meth+Zn-Meth group). The average daily feed intake and body weight gain of ewes did not differ due to dietary supplementation of Cu- and Zn-methionine. However, dry matter intake was comparatively lower and thus resulted in better feed: gain in Cu- and Zn-methionine group as compared to ewes fed Cu- and Zn-sulfate. Supplementation of Cu and Zn over the basal diet either from methionine-chelated or sulfate sources resulted in increased plasma Cu and Zn as well as Cu/Zn-SOD activity on d-30, which indicated a positive correlation between plasma Cu and Zn and Cu/Zn-SOD activity. The gut absorption, liver concentrations of Cu and Zn, and liver Cu/Zn-SOD activity were significantly (P<0.01) higher in ewes supplemented with Cu- and Zn-methionine compared to Cu- and Zn-sulfate. Periodical analysis of wool samples indicated no significant difference in Cu and Zn content between Cu-and Zn-methionine and Cu- and Zn-sulfate groups. Feeding of Cu and Zn from methionine-chelated source resulted in reduced (P<0.01) excretion of Cu and Zn in feces indicating their better utilization, and this will have positive implication on environment. The gut absorption values, plasma and liver tissue concentrations of Cu and Zn supported the hypothesis that Cu- and Zn-methionine supplements have better bioavailability compared to Cu- and Zn-sulfate and Cu- and Zn-dependent enzyme (Cu/Zn-SOD) could be used to determine the bioavailability of Cu and Zn.     

Serum Copper and Zinc Levels in Healthy Greek Children and Their Parents

The aim of this study was to investigate whether there is a correlation between copper (Cu) and zinc (Zn) levels in children and their parents, considering their nutritional habits. Cu and Zn concentrations were measured by flame atomic absorption spectrophotometry in the serum of 66 healthy children, aged 3–14 years, and their parents, residing in a region of Greece (Thrace). Cu levels were higher in mothers than those in fathers, but they were lower in both parents than those in children. They also tended to decrease with age in both parents and children, whereas Zn levels significantly increased with age in children. There was a positive correlation between children's and mothers' Zn levels, as well as children's and both parents' Cu levels. Children used to eat meat, fish, vegetables, and legumes as frequently as their parents, but they were consuming more eggs, milk, and fruits than the latest. Regarding parents' diet, higher Zn levels were depended on the consumption of meat and milk, whereas higher Cu levels were depended on the consumption of milk. Consequently, children’s Cu and Zn levels are related to their parents’ levels, which can be influenced by their nutritional habits.     

Effect of environmental information richness during early development of bream (<Emphasis Type="Italic">Abramis brama</Emphasis>; Cyprinidae) upon feeding and defensive behavior of its yearlings

The feeding behavior of bream (Abramis brama) yearlings kept before the experiment (four months post hatch) under different conditions has been studied. Three variants of conditions, varied in their levels of informational richness, were modeled for keeping young fish prior to the experiments: 1—minimal richness, mimicking conditions of standard commercial hatchery containers; 2—the conditions enriched by a water current; 3—the conditions enriched by modeled impact of predation and feeding by live food. In the following experiments, the conditions were similar for all three groups. It was revealed that the fish grown under the conditions of Variant 1 had a lower learning ability, higher extent of schooling behavior, and lower efficiencies of feeding and defensive behaviors. Similar traits were described in literature as being typical for the fish grown at standard fish farms. The Variant 2 fish had the shortest adaptation period and most efficient feeding behavior but were lacking the skills of defensive behavior. The fish from the 3rd variant had a medium duration of adaptation period and efficient feeding behavior and possessed well-developed skills of defensive behavior. The results have shown that the level of environmental information richness during fish early life stages plays a crucial role in further development of the most important adaptive forms of behavior. Maintaining the young fish in containers with water current facilitates swimming performance and development of feeding behavior. However, such fish, in fact, lack the skills of defensive behavior.     

Discrimination between several diterpenoid compounds in feeding by Gambusia affinis

The alcyonacean soft coral Sinularia flexibilis Quoy and Gaimard produces a number of bioactive complementary (secondary) metabolites. The ability of three of these diterpenes - flexibilide, sinulariolide and dihydroflexibilide - to elicit differential discriminatory feeding behavior in Gambusia affinis was assessed in a feeding deterrence study. Terpene-impregnated fish flakes were offered to fish trained to feed on such food, and their responses (acceptance, rejection, avoidance, or no response) were assessed as indicative of feeding deterrence. Food treated with sinulariolide (a compound previously determined to be non-bioactive) was generally accepted at a 1% concentration. It was avoided and rejected, however, at a concentration of 10%, a concentration level generally restricted to polyp-rich branchlets. This indicated negative olfactory and palatability cues, respectively. Flexibilide-treated flakes were accepted to some extent by the fish at the 1% concentration, but strongly avoided at the 10% concentration, indicating effective feeding deterrence via olfaction. Dihydroflexibilide-impregnated flakes were strongly rejected even at low concentrations (1%) after tasting, indicating a negative palatibility cue. They were strongly avoided or rejected at higher concentrations (10%), indicating a negative olfactory cue as well. This response at higher concentrations indicates that sinulariolide and flexibilide become effective at concentrations between 1% and 10%. Such concentrations may be found in the polypary (polyp-bearing portion) of the soft coral colonies. Dihydroflexibilide elicited the strongest negative palatability response from these test fish. The feeding deterrence characteristics of the compounds determined here represent the potentials of individual compounds to elicit differential feeding responses in organisms like Gambusia which are capable of discriminating between different but closely related complementary (secondary) metabolites.     

Deposition of copper, iron, manganese and zinc in the empty body of growing lambs of the breed German Merino Landsheep

A growth experiment with 108 lambs (breed: German Merino Landsheep) was carried out to examine the effect of gender, body weight (BW) and feeding intensity on the deposition of Fe, Zn, Cu and Mn in the empty body (whole animal minus contents of the gastrointestinal tract and bladder). The lambs (50% female and 50% male animals) were fed at three feeding levels ('low', 'medium' and 'high' by varying daily amounts of concentrate and hay) and slaughtered at different final BWs (30, 45 or 55 kg). Six male and six female animals were killed at a BW of 18 kg representing the animals' BW at the beginning of the comparative slaughter experiment. There were significant main effects for the treatments growth rate and final weight on the daily rate of accretion of the trace elements examined. Feeding intensity had a marked influence on the accretion rate for Fe (P < 0.001), Zn (P < 0.001), Cu (P < 0.001) and Mn (P = 0.003). With increasing feeding intensity (low, medium, high) the daily deposition of these trace elements increased (4.4, 5.2, 6.6 mg/day for Fe; 4.9, 5.5, 6.9 mg/day for Zn; 0.20, 0.36, 0.44 mg/day for Cu; 0.14, 0.16, 0.21 mg/day for Mn). Heavier final BW led to increased daily retention of Zn (P < 0.001) and Mn (P = 0.002). Gender had a marked influence only on the accretion rate for Zn (P < 0.001). Ram lambs had a higher daily deposition of this element than female lambs. Related to 1000 g empty body gain, the following concentrations were found for the trace elements examined: Fe 26.1 mg, Zn 30.0 mg, Cu 1.41 mg and Mn 1.04 mg. A feeding influence was given for Zn (P < 0.001) and Cu (P = 0.039). Feeding level low had higher Zn and lower Cu concentrations. Male animals showed less Fe (P < 0.001) and Zn (P = 0.034) per kg empty body gain than females.     

Effect of habitat shifts on feeding behaviour and growth of 0 year-group flounder Platichthys flesus (L.) transferred between macroalgae and bare sand habitats

In this study, short-term growth and feeding behaviour were compared among juvenile European flounder Platichthys flesus reared in enclosures in either their native habitat (bare sand or vegetation) or transferred to the opposite habitat. Growth was poorest in the vegetated habitat regardless of origin of the fish. The effect of the habitat shift differed between years. In 2000, the relatively small fish used grew fastest in their native habitat. In contrast, in 2001 when larger fish were used, growth was similar between native and introduced fish in the vegetated habitat, and introduced fish grew faster than native fish in the bare sand habitat. Diet composition and feeding intensity within a habitat were also similar among native and introduced fish in 2001, suggesting that the habitat switch had a minor influence on foraging efficiency. The different results obtained from the experiments in 2000 and 2001 suggest that fish size may determine the extent to which short-term habitat shifts influence feeding and growth in juvenile flounder, and, importantly, that the negative effects of habitat fragmentation are more severe for small compared to larger juvenile flounder.     

Evaluation and Potential Health Hazard of Selected Metals in Water,Sediments, and Fish from the Gomti River

The health hazard associated with the consumption of fish from the Gomti River in India, contaminated with the heavy metals Cr, Cu, Mn, Ni, Pb, and Zn was assessed in terms of target hazard quotients (THQs). The concentrations of metals (mg kg^?1, wet weight basis) in the muscle tissues of different fish species Mastacembelus puncalus, Clupisona garua, Cyrinous carpio, Botia lochachata, Channa punctatus, Heteropneustise fossilis, Puntius sofore, and Clarious batrachus ranged as follows: Cr (2.2–21.4), Cu (0.3–14.3), Mn (2.3–5.5), Ni (0.5–10.9), Pb (1.0–3.9), and Zn (12.3–46.9). The accumulation of metals in fish muscle tissue was in the order: Zn > Cr > Ni > Mn > Cu > Pb. THQs indicated a potential health hazard to children due to the consumption of fish contaminated with Ni and Pb; their THQs were greater than 1 for almost all fish species except for Ni in C. garua (THQ, 0.07) and C. carpio (THQ, 0.90). For adults, insignificant health hazard was associated with THQs less than 1 for all metals in the different fish species, but long-term exposure to these metals and subsequent bioaccumulation in the body may require additional investigation.