Production and biological characteristics and genotoxic status of clam <i>Corbicula japonica</i> (Bivalvia, Corbiculidae) in the estuary of Avvakumovka River (Olga Bay, northwestern Japan Sea)

In the mesohaline estuary of the Avvakumovka River (43°42’ N), the clam Corbicula japonica inhabits sand and silt-sandy grounds on the depths > 0.5 m in the main channel and tributaries from the mouth to 5 km upstream. The highest density (up to 175 ind./m2, 3882 g/m2) is observed in the mouths of tributaries with low velocity of the flow. Settlements in different parts of estuary differ by abundance of C. japonica , its size-age structure, and growth rates. The maximum observed shell size was 53 mm, the maximum weight of mollusk - 43 g, the maximum age - 13 years. The growth rate variability within the estuary is comparable with its latitudinal variation. The clam has the maximal linear increment of shell length in the first year of its life and the maximal weight increment - in the age of 5-7 years. It reaches the commercial size (shell length 20 mm) in 3-4 years old. The annual secondary production of C. japonica does not exceed 17.8 gС/m2, with P/B-ratio 0.37. Its annual consumption exceeds its biomass in 2.0-2.4 times. Corbicula japonica in the Avvakumovka River is practically unaffected by genotoxic influence; the estuary is defined as a clean, low-polluted area

DNA damage in gill cells of Corbicula japonica exposed to natural and anthropogenic stressors

Bivalve mollusks are sensitive biomarkers of aquatic ecosystem pollution. The impact of human activities on the environmental is an ongoing and increasing problem. There are many potentially dangerous chemicals that dissolve in water. Aquatic organisms are exposed to these chemicals, which can lead to morphological alterations and change certain physiological processes in their organs. The monitoring of changes in various biochemical parameters at the individual species level of organisms may be useful for identifying and delineating the impact of pollutants. C. japonica have been regarded as the most useful sentinels for chemical pollution studies in the aquatic environment. They are filter-feeding organisms able to bioaccumulate and concentrated most pollutants even if these are present at fairly low concentrations. Several bivalves, such as C. japonica have proven to be potential bioindicators. Oxidative DNA damage is considered to be one of the crucial steps in ageing and disease. Various factors such as chemical, physical and human activity inducting oxidative stress are known to cause DNA strand breaks through oxygen species and free radical action. The increasing genotoxic risk in marine environmental is motivating intense and continuous ecosystem research in an effort to develop and apply new biomonitoring tools. As a molecular biomarker for genetic effects DNA damage, integrity and repair processes introduce a highly specific and very early signal of genotoxic effects in some organisms. Under the constant influence of various stressors on living organisms, measured DNA damage, as a point in space-time, represent the dynamic state between constant DNA damage that occurs and its repair. In such cases DNA damage could reflect the level of marine pollution or human activity. The Comet assay or single gel electrophoresis (SCGE) assay is a simple, sensitive and rapid technique for detection of DNA damage in individual cells, and therefore, can be very useful in studies of genetic toxicology, especially ecogenotoxicology. Genotoxic damage, expressed as DNA strand breaks, was measured in cells isolated from gill from the C. japonica using the single gel electrophoresis (Comet assay). The gill tissue may have shown the highest level of DNA damage as substantial quantity of contaminated water, because of the water interface passed over the gill during the breathing, continuosly exposing the gill membranes. The mollusks were collected from polluted (estuary Razdolnaya river, lagoon Tihaya) and a ‘clean’ areas (estuary Artemovka river, estuary Partizanskaya river) from Peter the Great Bay. A total of 100 nuclei from each of the two replicates were examined and classified in one of the five damage classes, as described by Mitchelmore (1998), according to the migration distance and the fluorescence rate between the head and the tail of the nucleus: Class 0, intact nucleus with no migrated fragments (75% fragmented DNA). The results are presented as the percentage distribution of nuclei in the various damage classes and summarized in an index of DNA integrity or genetic damage index GDI) (Cavas, Kohen, 2008): The results from our study showed significant level of DNA damage from the C. japonica which were collected from polluted sites. Unpolluted sites were described as with no or minimal DNA strand breaks. Mollusks collected at polluted areas (estuary Razdolnaya river, lagoon Tihaya) showed high levels of DNA damage, GDI is equal to 3.22±0.2 and 3.11±0.7 in gills respectively. C. japonica obtained from a ‘clean’ areas (estuary Artemovka river, estuary Partizanskaya river) demonstrate less high level of DNA damage destruction, GDI is equal to 0,6±0,08 and 0,71±0,12) in gills respectively. Lipid peroxidation level was assayed measurement of malondialdehyde (MDA), a decomposition product of polyunsaturated fatty acids hydro peroxides were determined by the TBA reaction. The absorbance was read at 532 nm after removal of substances (TBARS) formed was calculated by using an extinction coefficient of 1.56*105 M-1 cm -1 formed per g dry weight. C. japonica sampled at Artemovka estuary, Partizanskaya estuary, Razdolnaya estuary, Tihaya lagoon showed LPX level (3.46±0.59, 5.62±0.82, 12.85±0.52, 15.32±1.13 nmol TBARS/g dry wt) in gills respectively. In conclusion, it can be noted that in the course of the experiment we found a clear relationship between the amount of DNA damage and the level of peroxidation products (MDA) in the gills of bivalve C. japonica, collected from sites with varying degrees of anthropogenic load. It should be emphasized that the shellfish that live in polluted areas are likely to be in a state of oxidative stress, which is one of the causes the degradation of DNA

Accumulation and Tissue Distribution of Dinophysitoxin-1 and Dinophysitoxin-3 in the Mussel Crenomytilus grayanus Feeding on the Benthic Dinoflagellate Prorocentrum foraminosum

A DTX-1-producing microalga, Prorocentrum foraminosum, from Peter the Great Bay, Sea of Japan, was fed to Gray’s mussels, Crenomytilus grayanus, for 12 days. An increase in DTX-1 and 7-O-acyl-DTX-1 (DTX-3) was observed in the digestive gland, kidneys, and gills. The digestive gland accumulated 91–100% of DTX-1 + DTX-3; and kidneys and gills accumulated, up to 8.5% and 4.3%, respectively. The kidneys had a distinctive pattern of toxin accumulation where the concentration of DTX-1 did not grow significantly after the eighth day of feeding, indicating the potential of DTX-1 elimination. The digestive gland and gills predominantly accumulated DTX-1, with a dramatic increase between Days 8 and 12. The DTX-3 content was highest in the digestive gland. The composition of DTX-3 in the acyl groups was similar for the digestive gland and kidneys, and did not change during feeding. The total toxin uptake of mussels exceeded the total toxin content from ingested cells by 2.4 times, showing that toxins may have accumulated from the seawater. This assumption needs to be further proved. The muscle, gonads, and mantle remained free of toxins. No genotoxic effect was observed in the gills and digestive gland

Zinc Oxide Nanoparticles Induce DNA Damage in Sand Dollar Scaphechinus mirabilis Sperm

Products containing nanomaterials are becoming more and more common in everyday life. Zinc oxide nanoparticles (ZnO NPs), meanwhile, are among the most widely used NPs. However, their genotoxic effect on the germ products of marine organisms is poorly understood. Therefore, the effects of ZnO NPs and zinc ions (20, 50, 100, 200 &micro;g/L) on the sperm of sand dollar Scaphechinus mirabilis were compared. Comet assay showed that both tested pollutants caused an increase in DNA damage to 6.57 &plusmn; 2.41 and 7.42 &plusmn; 0.88% DNA in the comet tail, for zinc ions and ZnO NPs, respectively. Additionally, a different pattern was shown by the increase in DNA damage, with increasing concentration of pollutants, in different experimental groups

Copper Induced DNA Damage in the Gills of the Mussel <i>Mytilus trossulus</i> and Reversibility after Depuration

The pollution of coastal water areas by heavy metals is constantly growing; therefore, the study of the mechanisms of impact of these toxicants on the organisms of hydrobionts is a topical direction of toxicology. Particularly pertinent are questions about the state of the reparation system in the aquatic organisms, which make it possible to assess the resistance, survival of hydrobionts, and the probability of remote consequences under the impact of heavy metals. Therefore, in this work, we investigated genome integrity and DNA repair ability in the gill cells of Mytilus trossulus, under conditions of copper (Cu2+) accumulation, and in the process of tissue depuration from this metal. Although the biochemical detoxification system was functioning, it is noted that destructive processes developed, including the accumulation of lipid peroxidation products (MDA) and DNA damage. It was also found that in all of the experimental groups of Mytilus trossulus, in the process of depuration from Cu2+ for 24 h, the levels of DNA damage and MDA content were markedly reduced, and further reduction was less intense