Do the total mercury concentrations detected in fish from Czech ponds represent a risk for consumers?

Mercury is one of the important pollutants of the environment. Therefore, it’s necessary to monitor quantity of mercury especially in aquatic ecosystems. The main goal of the presented study was to compare the content of total mercury in tissues of fish coming from the Czech Republic, an important carp exporter, with focus on comparison of mercury content between 3 different ponds, its comparison between different fish species and between different tissues of the same species, and estimation whether the mercury content in tissues meets the limit given in the Commission Regulation (EC) No. 1881/2006 or not. Total mercury concentration was measured in 90 fish specimen sampled from three ponds (Velky Kocelovicky, Mysliv and Zehunsky) in autumn 2018. The values of total mercury in fish tissues was measured by atomic absorption spectrometry. The content of total mercury in the tissues decreased as follows: muscle > liver > gonads > scales. The highest average content of total mercury in muscle was 0.1517 ± 0.0176 mg/kg coming from pike caught in Velky Kocelovicky pond. In contrast, the lowest average content of total mercury in muscle 0.0036 ± 0.0003 mg/kg was found in carp tissue coming from the locality of Zehunsky pond. We confirmed that the predatory fish are more exposed to mercury than non-predatory fish. None of the monitored localities exceeded the set regulatory limit. Thus, our study shows that fish coming from these ponds are safe in terms of total mercury content.

Influence of citrate and PEG coatings on the bioaccumulation of TiO2 and CeO2 nanoparticles following dietary exposure in rainbow trout

Background This study was conducted to provide much needed information on the potential of low solubility, highly biodurable nanoparticles (NPs) (TiO2 and CeO2 NPs), to bioaccumulate in fish and to investigate the relationship between an engineered nanomaterials surface coating, uptake and biokinetics in vivo. Rainbow trout (Oncorhynchus mykiss) were fed diets spiked with uncoated or surface coated (polyethylene glycol (PEG) or citrate (CIT)) TiO2 and CeO2 NPs (100 mg NPs/kg feed) for 10 days and thereafter fish were allowed to depurate for 42 days. Special care was taken to measure the real dispersed and actual administered concentrations, taking into consideration any potential losses from leaching, and to characterise the form (size, aggregation state, charge) of the NPs to which the fish were exposed. Results The coatings had an influence on levels of uptake and distributions. Most notably a higher uptake of PEG and CIT coated TiO2 and CeO2 NPs compared to fish exposed to uncoated materials was observed. The elimination of any Ti from tissues was rapid during the first day of depuration, whereas Ce levels remained in fish tissues (stomach, intestine and liver) with differences in depuration and redistribution of the three types of CeO2 NPs. However, no bioaccumulation potential for both tested metal oxide NPs in fish irrespective of coatings is expected according to BMF values < 1. Conclusions Distinct uptake, distribution and depuration kinetics in rainbow trout have been evidenced for different metal oxide NPs (TiO2 and CeO2 NPs). Coatings influenced uptake and in some cases led to slower depuration and distinct distributions, but do not make the uncoated NPs studied bioaccumulative (BMF > 1). Graphical Abstract

Insights Into Amino Acid Metabolism and Incorporation by Compound- Specific Carbon Isotope Analysis of three-Spined Sticklebacks

Interpretation of isotope data is of upmost importance in ecology to build sound models for the study of animal diets, migration patterns and physiology. However, our understanding of isotope fractionation and incorporation into different consumer tissues is still limited. We therefore measured the δ13C values of individual amino acids from muscle and liver tissue of three-spined sticklebacks (Gasterosteus aculeatus) over time in a controlled feeding experiment. The isotope signatures of amino acids in the liver quickly responded to even small shifts in dietary isotope compositions, whereas muscle tissue remained isotopically constant over time. No significant fractionation between diet and fish tissues was observed for half of the amino acids in both liver and muscle tissue, supporting the idea of direct nutrient routing on a protein rich diet. Small isotopic differences were observed for alanine, glycine and serine between diet and liver, indicating that metabolic processes such as glycolysis or gluconeogenesis can be tracked by the isotope signatures of their main substitutes. We demonstrate that compound-specific isotope analysis has great potential to investigate the main metabolic pathways of organisms and suggest further investigations using isotopically enriched materials to facilitate the correct interpretation of ecological field data.

ACCUMULATION OF SOME HEAVY METALS IN LARVAE OF CONTRACAECUM SP. AND THEIR HOST TIGRIS CATFISH SILURUS TRIOSTEGUS HECKEL, 1843 IN BAGHDAD, IRAQ

This study was achieved to investigate the accumulation of some heavy metals included: Cadmium, Lead and Nickel in the tissues (gill, intestine, liver, muscles and skin) of Silurus triostegus Heckel, 1843 (Siluriformes, Siluridae) and its larval stage of the nematode Contracaecum sp. (Rhabditida, Anisakidae). As well as to assess the infection patterns of Contracaecum among S. triostegus specimens which were purchased fresh from the local market in Baghdad. One hundred and nine nematodes specimens in larval stage were recovered from the fish host; the overall prevalence of Contracaecum sp. was 38.6%. The sex of the host was not significantly (P ˃ 0.05) associated with the infection of this nematode. Results showed that the overall mean intensity of Contracaecum sp. was 6.41; mean intensity did not differ significantly (P ˃ 0.05) between the fish sexes.The lead (Pb) was the only element detected in all fish tissues investigated as well as in the parasite, while the cadmium and nickel elements were not detected in all specimens. Skin and muscles of the fish, as well the parasite Contracaecum sp. contained the lowest lead levels compared to other fish tissues (gill, intestine and liver), although no significant differences were noticed among all investigated tissues and the parasite regarding the concentration of Pb.

Bioaccumulation of heavy metals in the water, sediment and the tissues of Carassius gibelio (Bloch, 1782) from Eber Lake

In this research, in order to observe the seasonal change between April 2014 and February 2015, heavy metal contents in the water, sediment and the Carassius gibelio (Bloch, 1782) tissues (muscle, gill and liver) growing in Eber Lake were determined. The obtained results showed that trace elements were founded in water, sediment and fish tissues. Among the average annual concentrations of water samples, the highest concentration was found for Mn (0.1584 mg/L) element and the lowest concentration was found for Pb element in the spring season. the maximum Average annual concentration was calculated for Mn (0.1584 mg/L, Spring) and the minimum was determined for Pb in water. In the sediment, Fe (16245.84 mg/kg, Spring) was found to be maximum and Co was the minimum. In fish, the highest concentrations were found in liver (Mo, Ni, Pb, Co, Cu, Fe), while the lowest concentrations were found in gill (Mn, Zn) and muscle (Cd, Cr, Se) tissues While the highest heavy metal concentrations were observed in the sediment, the minimum was found in the fish tissues (the ranking was the following; liver, gill and muscle). It was concluded that the heavy metal levels measured in the Lake Eber have no risk to the environment and to the public health.

Assessment of physiological and biochemical indicators of the state of the so-iuy mullet Liza haematocheilus (Temminck & Shlegel, 1845) in the Azov-Black Sea Basin

A comprehensive analysis of the physiological state of the so-iuy mullet, inhabiting the Sea of Azov, has been carried out during its pre-spawning period in 2020–2021. The hematological characteristics of the investigated individuals have been evaluated. It has been revealed that the content of protein and lipids in fish tissues was at the level of average longterm values. The content of protein and lipids in the gonads of females was significantly higher than that of males, which is explained by the forthcoming stage of spawning. It has been determined that the contribution of albumin to the total blood serum protein was minimal, which could be a consequence of the low feeding rate of the fish. At the same time, no stress effect was identified-glucose was within its normal range.