Phenolic content of Terminalia catappa L. leaf and toxicity evaluation on red hybrid tilapia (Oreochromis sp.)

Despite the use of Terminalia catappa (TC) leaf by traditional fish farmers around the world to improve the health status of cultured fish, there is a paucity of information on comprehensive metabolite profile and the maximum safe dose of the plant. This study aims at profiling the methanol leaf extract of T. catappa, quantifying total phenolic content (TPC) as well as the total flavonoid content (TFC) and evaluating its acute toxicity on blood, plasma biochemical parameters and histopathology of some vital organs in red hybrid tilapia (Oreochromis sp.). The experimental fish were acclimatised for 2 weeks and divided into six groups. Group (1) served as a control group and was administered 0.2 ml,g⁻¹ of phosphate buffer saline (PBS). Groups 2–6 were orally administered T. catappa leaf extracts (0.2 ml.50 g⁻¹) in the following sequence; 31.25, 62.5, 125, 250 and 500 mg.kg⁻¹ body weight. The metabolites identified in T. catappa using liquid chromatography-tandem mass electrospray ionisation spectrometry (LC-ESI-MS/MS) revealed the presence of organic acids, hydrolysable tannins, phenolic acids and flavonoids. Phenolic quantification revealed reasonable quantity of phenolic compounds (217.48 μg GAEmg⁻¹ for TPC and 91.90 μg. QCEmg⁻¹ for TFC). Furthermore, there was no significant difference in all the tested doses in terms of blood parameters and plasma biochemical analysis except for the packed cell volume (PCV) at 500 mg.kg⁻¹ when compared to the control. Significant histopathological changes were observed in groups administered with the extract at 125, 250 and 500 mg.kg⁻¹ doses. To a very large extent it is therefore safe to administer the extract at 31.25 and 62.5 mg.kg⁻¹ in tilapia.     

Metabolic and molecular responses in Nile tilapia,Oreochromis niloticus during short and prolonged hypoxia

The strictly aquatic breathing Nile tilapia, Oreochromis niloticus is an extremely hypoxia-tolerant fish. To augment our understanding of the effects of hypoxia on anaerobic glycolysis in the Nile tilapia, we studied the effect of short-term for 1 day (trial 1) and long-term for 30 days (trial 2) hypoxia on a selected glycolytic enzymes activity and mRNA expression in liver and white muscle. The hypoxic oxygen concentrations used in the two trials were 2, 1, and 0.5 mg O₂ L^?1 for comparison with a control normoxic group 8 mg O₂ L^?1. The activity of phosphofructokinase (PFK), pyruvate kinase (PK), and lactate dehydrogenase (LDH) in liver and white muscle except liver LDH decreased in trial 1 and increased in trial 2. Assessments of mRNA levels in trial 1 revealed that PFK was downregulated and LDH was upregulated in liver and white muscle, while PK fluctuated between upregulation in liver and downregulation in white muscle. Meanwhile, PK and LDH were upregulated while PFK was similar to control values in both tissues in trial 2. Comet assay results demonstrated an increase in DNA damage that was directly proportional to increasing hypoxic concentrations. This damage was more pronounced in trial 1. This suggests that the Nile tilapia cope better with long-term hypoxic conditions, possibly as an adaptive response.     

Lichenochemical Screening and Antioxidant Capacity of Four Tunisian Lichen Species

The phenolic composition and antioxidant capacity of four Tunisian lichen species, Cladonia rangiformis, Flavoparmelia caperata, Squamarina cartilaginea and Xanthoria parietina, were determined in order to provide a better understanding of their lichenochemical composition. Powdered material of F. caperata was the richest in total phenolic content (956.68 μg GAE g⁻¹ DW) and S. cartilaginea in proanthocyanidin content (77.31 μg CE g⁻¹ DW), while the acetone extract of X. parietina showed the highest flavonoid content (9.56 μg CE g⁻¹ DW). The antioxidant capacity of all lichen extracts and crude material was evaluated by DPPH^. scavenging, iron-chelating, and iron-reducing powers. Results showed that methanol extracts of S. cartilaginea had the highest DPPH^. antioxidant capacity (IC₅₀=0.9 μg mL⁻¹) and the highest iron-reducing power was attributed to the acetone extract of this species. All extracts of all species were further screened by Fourier-transform infrared spectroscopy (FT-IR) and nuclear resonance spectroscopy (NMR); results showed an abundance of phenols, aromatic compounds, and fatty acids. Overall, our results showed that the investigated species are a rich source of potentially bioactive compounds with valuable properties.     

Total Mercury in Sediments,Macrophytes, and Fish from a Shallow Steppe Lake in Eastern Austria

During summer 2011, samples of sediment, macrophytes, and fish tissues from the shallow, slightly alkaline Lake Neusiedl, Austria, were evaluated for their total Hg content. This is the first report of Hg levels from this lake. Sediments displayed Hg contents between 0.025 and 0.113 μg g^?1 dw (dry weight), significantly correlating with the proportion of organic components pointing to a small anthropogenic impact on the lake's Hg content. Hg Levels in plants and fish were unexpectedly high: both investigated submerged plant species, Potamogeton pectinatus and Myriophyllum spicatum, showed mean values of 0.245±0.152 and 0.298±0.115 μg g^?1 dw, respectively. Biomagnification was evident when comparing muscle samples of the planktivorous fish species rudd Scardinus erythrophthalmus (n=10, mean=0.084 μg g^?1 ww (wet weight)) with the piscivorous perch Perca fluviatilis (n=21, mean=0.184 μg g^?1 ww) or pike‐perch Sander lucioperca (n=9, mean=0.205 μg g^?1 ww). Significantly lower values were found in the muscle of the piscivorous pike Esox lucius (n=25, mean=0.135 μg g^?1 ww), pointing to a specific Hg metabolism of this fish, presumably under the particular physicochemical properties of the lake. Hg Concentrations in fish could pose a risk to piscivorous birds in this protected wetland system.     

Cylindrospermopsin production and release by the potentially invasive cyanobacterium Aphanizomenon ovalisporum under temperature and light gradients

The growth rates, production and release of the potent cytotoxin cylindrospermopsin (CYN) were studied in batch and semi-continuous cultures of Aphanizomenon ovalisporum (Cyanobacteria; Nostocaceae) strains UAM 289 and UAM 290 from Spain, over a gradient of temperatures (10–40 °C) and irradiances (15–340 μE m⁻² s⁻¹). This species grew in temperatures ranging from 15 °C to 35 °C as well as under all irradiances assayed. The growth rates ranged from 0.08 d⁻¹ to 0.35 d⁻¹, and the maximum growth was recorded above 30 °C and at 60 μE m⁻² s⁻¹. CYN was produced under all conditions where net growth occurred. Total CYN reached up to 6.4 μg mg⁻¹ dry weight, 2.4 μg mm⁻³ biovolume, 190.6 fg cell⁻¹ and 0.5 μg μg⁻¹ chlorophyll a. Although CYN concentrations varied only 1.9-fold within the 15–30 °C range, a drastic 25-fold decrease was observed at 35 °C. The irradiance induced up to 4-fold variations, with maximum total CYN measured at 60 μE m⁻² s⁻¹. An elevated extracellular CYN share ranging from 20% to 35% was observed during the exponential growth phase in most experiments, with extreme temperatures (15 and 35 °C) being related to the highest release (63% and 58%, respectively) and without remarkable influence of irradiance. Growth did not have a direct influence on either CYN production or release throughout the entire range of experimental conditions. Our study demonstrates a strong and stable production and release of CYN by A. ovalisporum along field-realistic gradients of temperature and light, thus becoming a predictive tool useful for the management of water bodies potentially affected by this ecologically plastic cyanobacterium.     

Distributions and Congener Patterns of PCBs in Fish from Major Aquaculture Areas in the Pearl River Delta,South China

The distribution and concentrations of polychlorinated biphenyls (PCBs) were determined in surface sediments and fish collected from freshwater fishponds in six major aquaculture areas of the Pearl River Delta. The concentrations of total PCBs ranged from 7.32 to 36.2 ng/g (dry weight) in sediments and 5.15 to 226 ng/g (lipid weight) in five species of fish, with higher concentrations in fishponds from two industrialized areas. Feeding habits of fishes played a significant role on the accumulation of PCBs and their homologue patterns in fish tissues, with higher concentrations in muscle and viscera of mandarin fish (Siniperca kneri), and tilapia (Tilapia mossambica) and lower in grass carp (Ctenopharyngodon idellus). In muscle, IUPAC No. 118, 138, 81/87, 153, 180, 52, 49, 99, and 44 congeners were the most dominant out of the 36 congeners measured in the present study. The contents of PCBs in fish cultivated in the Pearl River Delta were rather low when compared with the maximum concentration of total PCBs of 2.0 μg/g (wet weight), imposed by the U.S. Food and Drug Administration edible seafood. However, due to the bioaccumulation and biomagnification nature of PCBs through the food chain, continuous monitoring of PCBs as well as other Persistent Organic Pollutants in this rapidly developed region is encouraged.     

Activin A affects feeding by promoting the inner diameter and muscle development of the pharynx and oesophagus in zebrafish (Danio rerio) larvae

Activin A belongs to the superfamily of transforming growth factor-β and plays an important role in hormone regulation and tissue development. However, few research studies have been conducted on the effect of activin A on feeding organs in fish. In this study, the zebrafish (Danio rerio) larvae were treated with 1 ng ml^–1 activin A for 8 days continuously. The haematoxylin and eosin (H&E) staining section results revealed that the transverse inner diameter of the pharynx and oesophagus significantly increased on the third and eighth days after treatment compared with the control group (P < 0.05). On the eighth day, the cross-sectional area of the pharyngeal muscle increased by 8638 μm² compared to the control group (P < 0.05). The RNA in situ hybridization results also showed that the expression of skeletal muscle-specific genes (myog and myod) was significantly increased in pharyngeal muscle on the eighth day. Furthermore, the qRT-PCR results showed the expression of gh gene was significantly increased on the eighth day (P < 0.05). At the same time, more larvae in activin A group were able to feed larger brine shrimp (Artemia) than in the control group on the eighth day. In conclusion, activin A could affect feeding by promoting the inner diameter and muscle development of the pharynx and oesophagus in zebrafish larvae. This study is the first to report that the development of the pharynx and oesophagus can directly affect food intake in fish larvae, which provides a theoretical basis for the study of food intake of fish at an early stage.     

Revealing the polar lipidome,pigment profiles,and antioxidant activity of the giant unicellular green alga,Acetabularia acetabulum

Marine algae are one of the most important sources of high-value compounds such as polar lipids, omega-3 fatty acids, photosynthetic pigments, or secondary metabolites with interesting features for different niche markets. Acetabularia acetabulum is a macroscopic green single-celled alga, with a single nucleus hosted in the rhizoid. This alga is one of the most studied dasycladalean species and represents an important model system in cell biology studies. However, its lipidome and pigment profile have been overlooked. Total lipid extracts were analyzed using hydrophilic interaction liquid chromatography-high resolution mass spectrometry (HILIC-HRMS), tandem mass spectrometry (MS/MS), and high-performance liquid chromatography (HPLC). The antioxidant capacity of lipid extracts was tested using DPPH and ABTS assays. Lipidomics identified 16 polar lipid classes, corresponding to glycolipids, betaine lipids, phospholipids, and sphingolipids, with a total of 191 lipid species, some of them recognized by their bioactivities. The most abundant polar lipids were glycolipids. Lipid classes less studied in algae were identified, such as diacylglyceryl-carboxyhydroxymethylcholine (DGCC) or hexosylceramide (HexCer). The pigment profile of A. acetabulum comprised carotenoids (17.19%), namely cis-neoxanthin, violaxanthin, lutein and β,β-carotene, and chlorophylls a and b (82.81%). A. acetabulum lipid extracts showed high antioxidant activity promoting a 50% inhibition (IC₅₀) with concentrations of 57.91 ± 1.20 μg · mL⁻¹ (438.18 ± 8.95 μmol Trolox · g⁻¹ lipid) in DPPH and 20.55 ± 0.60 μg · mL⁻¹ in ABTS assays (918.56 ± 27.55 μmol Trolox · g⁻¹ lipid). This study demonstrates the potential of A. acetabulum as a source of natural bioactive molecules and antioxidant compounds.     

Interspecific allelopathy in cyanobacteria: Cylindrospermopsin and Cylindrospermopsis raciborskii effect on the growth and metabolism of Microcystis aeruginosa

The biological role of cyanobacteria secondary metabolites is relatively unknown although several possible hypotheses have been discussed. In the following study the effect of cylindrospermopsin (CYN) and metabolites of non-CYN producing Cylindrospermopsis raciborskii strain on growth, alkaline phosphatase (ALP) activity and microcystin-LR (MC-LR) production in Microcystis aeruginosa was evaluated. Higher concentrations of CYN (10 and 50 μg L⁻¹) induced toxicity effects demonstrated by significant growth inhibition and M. aeruginosa cell necrosis. Lower concentrations of CYN (1 and 5 μg L⁻¹) slightly decreased growth rates but significantly up-regulated ALP activity. Moreover, under all studied CYN concentrations MC-LR production strongly decreased. Spent C. raciborskii medium mimicked the CYN action by inducing strong inhibition of M. aeruginosa growth and MC-LR production and through up-regulation of ALP activity. On the other hand, spent M. aeruginosa medium did not affect C. raciborskii growth and no alterations in ALP activity were observed. Co-culturing of these two species resulted in an increase of C. raciborskii contribution at the expense of M. aeruginosa. From the results we conclude that CYN can be involved in interspecific competition in cyanobacteria and that non-CYN producing C. raciborskii strains may produce a hitherto unknown bioactive compound(s) which can mimic CYN action.     

Contribution of omnivorous tilapia to eutrophication of a shallow tropical reservoir: evidence from a fish kill

SUMMARY 1. We examined whether a large stock of tilapia (>750 kg ha^?1, in littoral areas >1300 kg ha^?1), mostly Oreochromis niloticus (L.) and Tilapia rendalli (Boulenger), could contribute to the eutrophication of a tropical reservoir (Lago Paranoá, Brasília, Brazil) by enhancing P‐loading. 2. We took advantage of an extensive fish kill (>150 tons removed) during May–August 1997 in a hypereutrophic branch of the reservoir to compare water quality characteristics 1 year before and after this event by means of BACI statistics. We also measured P‐excretion rates in laboratory trials to assess the P‐loading of the reservoir by the tilapia relative to tributary inputs and loading from a sewage treatment plant. 3. Concentrations of chlorophyll a (decline from 84 to 56 μg L^?1, P=0.018) and total P (decline from 100 to 66 μg L^?1, P < 0.001) decreased significantly in the branch of the reservoir affected by the fish kill, compared with a similar but unaffected branch that served as a control. Because P‐loading by both a sewage treatment plant and tributaries remained high after the incidence, the fish kill was likely to contribute to the observed water quality improvement. 4. Removing 150 tons of dead tilapia corresponded to 20 days of external total phosphorus load (TP‐load) to the branch, and resulted in a reduction of 5.1 kg P day^?1 in internal recycling via tilapia excretion, which is equivalent to 12% of the external TP‐load. 5. Implementing professional tilapia cast‐net fisheries could be an efficient biomanipulation approach to improve water quality and limit the occurrence of cyanobacteria blooms and fish kills in hypereutrophic branches of Lago Paranoá and similar tropical lakes.     

Feed intake and tissue distribution of florfenicol in cod (Gadus morhua) administered feed with different fat contents

This study was performed to examine the appetite and the corresponding plasma and tissue distribution of florfenicol when administered to healthy groups of cod using medicated and non‐medicated salmonid and marine feeds. Marine feed contains approximately 18% fat whereas salmonid feed contains approx. 30% fat. Two groups of fish were medicated with florfenicol at a dosage of 10 mg kg^?1 day^?1 for 10 consecutive days when the drug was administered either via marine or salmonid pellets. Two groups of fish also received either non‐medicated marine or salmonid pellets. Twenty‐four hours after giving the medicated marine feed, 14 out of 20 fish contained detectable concentrations of florfenicol with mean values (n = 14) of 4.67 ± 4.02 μg ml^?1 in plasma, 2.29 ± 2.11 μg g^?1 in muscle and 0.79 ± 0.69 μg g^?1 in the liver. In the fish given medicated salmonid feed, 18 of 20 fish contained detectable concentrations of florfenicol with mean values (n = 18) of 1.77 ± 1.84 μg ml^?1 in plasma, 0.75 ± 0.66 μg g^?1 in muscle and 0.30 ± 0.25 μg g^?1 in the liver. Decreased feed intake of the salmonid feed, both medicated and non‐medicated, was noted when compared to medicated and non‐medicated marine feed. No difference in feed consumption was registered between medicated and non‐medicated marine feed, however a difference was noted between the medicated and non‐medicated salmonid feed.     

Effects of nonylphenol on hematological parameters and immune responses in immature rainbow trout (Oncorhynchus mykiss)

ABSTRACT

This study investigated the effects of nonylphenol (NP) on hematological and immunological parameters in both male and female rainbow trout (Oncorhynchus mykiss). Fish were randomly distributed into six groups and administered with NP (10, 50 and 100 μg g^-1 week^-1 BW) and a single dose of 17-β estradiol (E2; 2 μg g^-1 week^-1 BW, positive control). The solvent controls received ethanol and coconut oil as a vehicle, while the controls were not injected. Red blood cells (RBCs) count, hematocrit (Hct), hemoglobin (Hb), white blood cells (WBCs), and lymphocytes demonstrated a NP dose-dependent decrease, whereas mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), monocytes, and neutrophils showed an increasing trend in both male and female fish 21 days post-treatment. Also, RBCs, Hb, MCHC, WBCs, and lymphocytes were significantly reduced (p<0.05) in E2 treated fish. Lysozyme, complement components (C3 and C4) and immunoglobulin M (IgM) were increased in fish sera subjected to 10 and 50 μg g^-1 NP, while these decreased in groups administered with 100 μg g^-1 NP and 2 μg g^-1 E2. Except for C4 level at 10 μg g^-1 NP, no significant differences were observed in hematological and immunological parameters of male and female in each treatment. Overall, a frequent exposure to NP could lead to adverse effects on fish immune-physiological functions which may cause serious ecological threats of fish natural population sustainability.     

Uptake of organic mercury and selenium from food by nordic shrimp Pandalus borealis

Abstract

In an attempt to improve our understanding of the transfer process of organic mercury (mainly methyl mercury) from the prey to the consumer, the uptake of mercury in edible muscle of shrimps, Pandalus borealis, from contaminated mussels used as food supplies was studied. Shrimps bioaccumulated rapidly mercury in their abdominal muscle when submitted to a highly contaminated diet (6 μg Hg g^?1) but biomagnification was not observed and Hg concentration in shrimps never exceeded 1.8 μg g^?1. The assimilation efficiency during the uptake period was estimated to about 42% When shrimps received moderately contaminated diet (2.5–2.9 μg Hg g^?1), a two-stage bioaccumulation process was observed in which mercury concentration began to increase in shrimp muscle after 15 days of contaminated diet and at the end of the experiment it seemed to level off. This process can be represented by a two-compartment conceptual model in which mercury rs first eliminated and/or accumulated in the compartment 1 (digestive organs) and then transferred to the compartment 2 (abdominal muscle) following a mechanism and under conditions not yet clearly understood. The use of selenium biologically incorporated into the diet had no apparent effect on the uptake of mercury     

Follicle-stimulating hormone stimulated differentiation and progesterone production of bovine granulosa cells in culture

Progesterone production of granulosa cells cultured in vitro is stimulated and cell differentiation increased, by follicle-stimulating hormone (FSH). This study examined whether the increased progesterone production observed when bovine granulosa cells are cultured occurs because (1) progesterone production by undifferentiated and/or differentiated cells is increased or (2) the differentiation of granulosa cells is stimulated. Viable bovine granulosa cells (2−3×10⁵) from follicles 5–8 mm in diameter were cultured in the presence of 0, 1, 10 and 100 μu FSH (1 μu ≡ 1 μg NIH-FSH-S1) for 6 days at 37°C in a humidified atmosphere of 5% CO₂ in air in 1 ml of a 1:1 mixture of Dulbecco's modified Eagle medium: Ham's F10 medium supplemented with 365 μg ml⁻¹ l-glutamine, 100 U ml⁻¹ penicillin and 100 μg ml⁻¹ streptomycin. Progesterone production, total DNA and protein, and cell diameter were determined sequentially over the culture period. The increases in progesterone production (ng μg⁻¹ DNA per 24 h), cytoplasmic:nuclear ratio (μg protein μg⁻¹ DNA) and cell diameter (μm) over 6 days culture indicated that granulosa cells underwent differentiation in the presence of FSH. Progesterone production of undifferentiated granulosa cells (diameter 14 μm or less) was stimulated by FSH (P < 0.01) in a dose dependent manner (1.0±0.2, 2.9±0.3, 3.7±0.3 and 4.9±0.4 ng μg⁻¹ DNA per 24 h for 0, 1, 10 and 100 μu ml⁻¹ FSH respectively) but remained constant within dose (P > 0.05) during a 6 day culture period. FSH stimulated (P < 0.05) the rate of granulosa cell differentiation (10±3%, 53±13%, 74±21% and 82±10% differentiating cells per well for 0 μu, 1 μu, 10 μu and 100 μu ml⁻¹ FSH respectively) but did not stimulate (P > 0.05) progesterone production by differentiating granulosa cells (8.7±0.5 ng μg⁻¹ DNA per 24 h). In conclusion, the increase in progesterone production of FSH-stimulated granulosa cells cultured in vitro appears to be mainly due to an increase in the number of differentiating cells with a constant rather than an increasing progesterone production per cell.     

Contaminants in tilapia (<Emphasis Type="Italic">Oreochromis mossambicus</Emphasis>) from the Salton Sea,California, in relation to human health,piscivorous birds and fish meal production

A summary of all existing information collected since 1980 on contaminants in tilapia from the Salton Sea is presented and risks to humans and fish-eating birds assessed. Of the 17 trace elements, 42 organic pesticides and 48 polychlorinated biphenyls (PCBs) analyzed in tilapia whole body and fillet samples, only selenium (Se), arsenic (As) and possibly dichlorodiphenyltrichloroethane (DDE) were found at levels high enough to be of concern for fish, birds or humans. Average current concentration of arsenic (As) was 0.7 μg g⁻¹ wet weight (ww) in whole body samples and 1.2 μg g⁻¹ ww in fillet samples, or 2.8 and 5.7 μg g⁻¹ dry weight (dw), respectively. Inorganic As averaged 0.006 μg g⁻¹ ww (0.03 μg g⁻¹ dw) in fillet samples, which represented 0.3% of total As. By U.S. Environmental Protection Agency (U.S.EPA) guidelines, As levels in tilapia pose no threat of non-cancerous adverse health effects in children and adults. As is a known human carcinogen, however, and U.S.EPA cancer risk assessment procedures indicate that a weekly consumption of 540 g (19 oz) or more for 70 years would increase the upper bound cancer risk by 1 in 100,000 consumers exposed. Average current Se concentration was 2.2 μg g⁻¹ ww in tilapia whole body samples and 1.9 μg g⁻¹ ww in fillet (8.3 and 9 μg g⁻¹ dw, respectively). Consumption of Se-contaminated tilapia was found to present no unacceptable risk for adverse health effects for adults consuming up to 1000 g (35 oz) of fillet per week even when additional intakes of Se from other food items were taken into account. Similarly, children weighing 30 kg or more could safely eat up to 430 g (15 oz) of tilapia fillet on a weekly basis. A health advisory issued by the State of California in 1986 recommended, on the basis of Se levels, that consumption of any fish from the Salton Sea be limited to 114 g (4 oz) every 2 weeks, but the rationale and calculations on which that advisory was based are unavailable. We suggest that the existing health advisory for Salton Sea tilapia be revised by the state in light of this new information and updated risk parameters for As and Se. Dichlorodiphenyltrichloroethane (DDE) was detected in all samples of tilapia, with current levels averaging 0.085 μg g⁻¹ in whole tilapia and 0.032 μg g⁻¹ in fillet ww. Compared to screening values proposed by the U.S. EPA, these concentrations are unlikely to cause non-cancerous health effects in anglers, but one might exceed a 1 × 10⁻⁵ increase in cancer risk by consuming more than 4 meals of tilapia per week. Similarly, polychlorinated biphenyls (PCBs) were detected in tilapia fillets at levels that may increase the cancer risk for those anglers also eating more than 4 meals of tilapia per week. These determinations are based, however, on DDE concentrations reported from a small sample size (n = 4), and on screening values recommended by U.S.EPA. The paucity of DDE and total DDT analyses carried out in recent times on the edible portion of Salton Sea tilapia warrants additional analyses in order to evaluate the need for issuance of a fish consumption advisory with regards to long term exposure to total DDT via consumption of Salton Sea fish. With regards to the potential impact on fish and piscivorous birds, we cannot conclude whether concentrations of As in tilapia could pose a threat to the fish and the birds feeding on them. Se concentrations, however, may be elevated enough to negatively affect fish health, and reproduction and immune systems of piscivorous birds, but definitive studies are lacking. Total DDT and PCB concentrations in whole tilapia are not elevated enough to have adverse effects on fish and piscivorous birds. Fish harvesting for fish meal production has been proposed for the Salton Sea. Based on whole fish dry weight values of 61% protein and 21% ash, and the determined contaminant levels, tilapia could yield a meal of reasonable quality for use in formulating poultry, livestock and aquaculture feeds. Guest Editor: John M. Melack Saline Waters and their Biota     

Ecological interactions between Nile tilapia (Oreochromis niloticus, L.) and the phytoplanktonic community of the Furnas Reservoir (Brazil)

1. Exotic invasive species modify natural food webs in a way frequently hard to predict. In several aquatic environments in Brazil the introduction of Oreochromis niloticus (tilapia) was followed by changes in water quality. Yet, because of its rapid and easy growth, this fish has been used in many aquaculture programmes around the country. 2. To measure the effects of tilapia on the phytoplankton community and on water conditions of a large tropical reservoir in south‐eastern Brazil (Furnas Reservoir), we performed two in situ experiments using three controls (no fish) and three tilapia enclosures (high fish density). Abiotic and biotic parameters were measured at 4 day intervals for 28 days. 3. Fish presence increased nitrogen (N) and phosphorus (P) availability (ammonium 260 and 70% mean increase – first and second experiment; and total phosphorus 540 and 270% mean increase) via excretion. Nutrient recycling by fish can thus be significant in the nutrient dynamics of the reservoir. The higher chlorophyll a concentration in the experimental fish tanks (86 and 34 μg L^?1, first and second experiment, respectively) was the result of a positive bottom‐up effect on the phytoplankton community (approximately 2 μg L^?1 in the reservoir and control tank). 4. Because tilapia feed selectively on large algae (mainly cyanobacteria and diatoms), several small‐sized or mucilaginous colonial chlorophyceans proliferated at the end of the experiments. Thus, the trophic cascade revealed strong influences on algal composition as well as on biomass. 5. Tilapia can contribute to the eutrophication of a waterbody by both top‐down and bottom‐up forces. In particular, by supplying considerable amount of nutrients it promotes the increase of fast growing algae. Tilapia must be used cautiously in aquaculture to avoid unexpected environmental degradation.     

Individual variations and interrelationships in feeding rate,growth rate,and spontaneous activity in hybrid tilapia (Oreochromis niloticus × O. aureus) at different feeding frequencies

A 30‐day growth trial was conducted to investigate the individual variations in feeding rate, growth rate, spontaneous activity, and their possible interrelationships in hybrid tilapia (Oreochromis niloticus × O. aureus) reared individually at feeding frequencies of one and two meals daily. Results show that the feeding rate in energy (FRe), specific growth rate in energy (SGRe), and food conversion efficiency (FCE) of fish fed twice a day were significantly higher than that of fish fed only once. However, no significant differences in distance or in time spent swimming were observed between the groups. SGRe was positively correlated with FRe in fish fed only once daily, and SGRe was positively correlated with food conversion efficiency in energy (FCEe) between the two groups. SGRe was only inversely correlated with the distance that fish swam when fed once daily. The results suggest that the individual growth differences of hybrid tilapia could be attributed mainly to variations in FRe, and that the energy costs of spontaneous activity play an important role in the differences at feeding frequency of one meal a day. However, at feeding frequencies of two meals a day, individual growth differences in fish may be caused by variations in FCEe, and energy costs of spontaneous activity have only marginal effects on the differences.     

Sublethal responses in Melanoides tuberculata following exposure to Cylindrospermopsis raciborskii containing cylindrospermopsin

Sublethal effects in the aquatic snail Melanoides tuberculata were examined during exposure to whole cell extracts of Cylindrospermopsis raciborskii and live C. raciborskii cultures, containing varying concentrations of algal cells, cellular debris, and the blue-green algal toxin, cylindrospermopsin (CYN). Exposure to whole cell extracts or live algal cultures did not result in significant changes in adult snail behaviour or relative growth rates. However, clear changes in the number of hatchlings released from parent snails were observed. Exposure to whole cell extracts containing ≥200 μg L⁻¹ extracellular CYN resulted in an increase in the number of hatchlings. In contrast, decreases in hatchling number were recorded from treatments containing ≥200 μg L⁻¹ CYN during exposures to live C. raciborskii cultures, compared with controls. This suggests that CYN may be more toxic to grazing invertebrates if present in the intracellular form. Since CYN is a protein synthesis inhibitor, it is possible that CYN may be especially toxic to rapidly developing tissues such as snail embryos. This may also explain the lack of effects observed in adult snails.     

Mercury in blood,hair, and feces from subsistence fish-eating riverines of the Madeira River Basin (Western Amazon)

BackgroundThe Madeira River (Amazon Basin) has been impacted by activities related to artisanal and small-scale gold mining (ASGM), deforestation and burning (for timber, agriculture, and hydroelectric dam projects). All these activities contribute to environmental mercury (Hg) release and cycling into the Amazon ecosystem and thus to changing lifestyles.MethodWe assessed exposure to total and MeHg in two small riverine communities of the Madeira River (Amazon): Lago Puruzinho (LP, n = 26 families) and São Sebastião do Tapurú (SST, n = 31 families). Samples of human hair (n = 137), blood (n = 39), and feces (n = 41) were collected from adults and children (0–15 years of age).ResultsIn women of childbearing age from LP village, the mean blood total-Hg (THg) (45.54 ± 24.76 μg.L⁻¹) and MeHg (10.79 ± 4.36 μg.L⁻¹) concentrations were significantly (p = 0.0024; p < 0.0001, respectively) higher than in women from SST village (THg: 25.32 ± 16.75 μg.L⁻¹; MeHg: 2.32 ± 1.56 μg.L⁻¹) village; the trend in hair-Hg persisted but was statistically significant (p < 0.0145) only for THg (LP, 11.34 ± 5.03 μg. g⁻¹; SST, 7.97 ± 3.51 μg. g⁻¹). In women, the median hair:blood ratio of total Hg was 269. In children, the mean hair THg concentrations were 6.07 ± 3.60 μg. g⁻¹ and 6.47 ± 4.16 μg. g⁻¹ in LP and SST; thus, not significantly different (p = 0.8006). There was a significant association (p < 0.001) between hair-Hg concentrations of mothers and their respective children. The excretion of Hg in feces of women (0.52 μg. g⁻¹ dw) was not significantly different from children (0.49 μg. g⁻¹ dw). The only statistically significant correlation between Hg in feces and in hair was found in children, (n = 16, r_s = 0.38, p = 0.005). Significant relationship was seen between the levels of THg in blood and hair of women from LP and SST. Based on hair-Hg concentrations, fish consumption rate ranged from 94.5 to 212.3 g.day⁻¹.ConclusionWomen and children excrete THg in feces in comparable concentrations. However, the mean fish consumption rate and blood MeHg are higher in the most remote villagers. Mother`s hair-Hg concentration is a good predictor of children’s hair-Hg.     

Evolving water quality in a common carp and blue tilapia high production pond

Intensive polyculture of blue tilapia, Oreochromis aureus, and common carp, Cyprinus carpio was conducted to determine their growth capacity and the accompanying water quality transitions in a 376 m² (207 m³) fish pond without aeration or water exchange. A total of 485 fingerlings (290 tilapia and 195 carp) averaging 72 g each (total 35 kg) was stocked and fed commercial floating pellets (36% protein-6%-N) at the approximate daily rate of 3% of the fish biomass six days each week. The total net fish growth was 159.4 kg (4.2 t ha^–1) with an average growth of 199.5 g per fish through the 96 days feeding period — 6 June to 7 September 1984. The s conversion ratio for the commercial feed was 1.3.Physiochemical patterns in the pond water were directly related to the rise and fall of turbidity through the course of the production trial. During one period of low turbidity, a biological inversion was evident with pH and dissolved oxygen measured at higher levels near the pond bottom and increasingly lower toward the surface. It is postulated that settled phytoplankton formed a photosynthetically-active algal mat on the pond bottom. The implications for potential fish kills can be significant.