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For food safety, the concentrations and profiles of paralytic shellfish toxins (PSTs) and tetrodotoxin were examined in economically important scallops and bloody clams collected from the coast of the Miyagi Prefecture, Japan. PSTs were the major toxins in both species. The tetrodotoxin concentration in scallops increased in summer, although the highest value (18.7 μg/kg) was lower than the European Food Safety Authority guideline threshold (44 μg/kg). This confirmed the safety for tetrodotoxin in this area., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The content and composition of paralytic shellfish toxins (PSTs) in Japanese basket clam ( Corbicula japonica ) and mussels ( Mytilus galloprovincialis ) from Osaka Bay, Japan, were investigated using a mouse bioassay (MBA) and hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS), and the association between toxicity values of MBA and HILIC-MS/MS was verified based on research data. The overall toxicity in Japanese basket clam was lower than that in the mussel. The PSTs of Japanese basket clam and mussel consisted mainly of C1, C2, and gonyautoxins 1-4 (GTX1-4) taking toxins compositional differences as mol%. When multiplying the content of different toxins by the toxic equivalent factor (TEF), C2 and GTX1-4 accounted for more than 90% of total toxicity (MU TEF /g) based on the MU TEF score converted by TEF for the two species. The total content of C2 and GTX1-4 converted to toxicity was significantly correlated with the toxicity determined by MBA for the two species ( r 2  > 0.983). This study provides a suitable and ethical monitoring method to investigate toxicity in bivalves contaminated with A. tamarense by analysis of only predominant toxins, along with reducing use of MBA.

In the Great East Japan Earthquake of 11 March 2011, a magnitude 9.0 earthquake and accompanying tsunami struck the Tohoku region of Japan. The tsunami washed away old equipment containing polychlorinated biphenyls (PCBs) stored in the region's factories, and these PCBs may have leaked out of their casings into the marine environment. In this study, we evaluate marine PCB contamination by comparing mussels collected before (in 2005) and after (June 2011) the tsunami. PCB contamination levels were significantly elevated in mussel samples collected after the tsunami in June 2011 (3 months after the tsunami). This indicates that PCBs (specifically, formulation KC-400) leaked out of old equipment swept away by the tsunami and accumulated in mussels. PCBs were estimated to have an environmental half-life (EHL) in mussels of 4 months. Our results show that an earthquake and subsequent tsunami can cause elevated PCB contamination in the marine environment., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In order to investigate cadmium contents in foods sold in Japan, cadmium levels in 40 seafood samples and 30 chocolate samples were measured by means of atomic absorption spectrometry and ICP-OES. We first confirmed the validity of the method according to the guidelines of the Ministry of Health, Labour and Welfare. Among 40 seafood samples investigated, cadmium was detected in 31 samples, in which the concentration exceeded half the LOQ (0.025 mg/kg), and the level was ranged from 0.03 to 0.38 mg/kg. We could not find any sample containing cadmium in excess of 2 mg/kg, which the Codex Alimentarius sets as the maximum standard value. Among 30 chocolate samples, cadmium was detected in 21 samples, and the level ranged from 0.025 to 0.54 mg/kg.

From October to November 2004, the paralytic shellfish poison (PSP)-producing dinoflagellate Alexandrium tamiyavanichii was observed at Harima-Nada, Seto Inland Sea at a maximum cell density of 4,960 cells/L. The wild cells of the dinoflagellate collected from the same seawaters, and cultured cells derived from them showed toxicity scores of 6.25-15.4 x 10(-4) and 2.7-3.5 x 10(-4) MU/cell, respectively, both of which were much higher than those of previously reported strains. PSP of the wild cells was mainly composed of gonyautoxin (GTX) 5 (40.6-52.4 mol%) and GTX4 (15.6-24.8 mol%), showing a unique composition that was greatly different from those of the previously reported strains, or of the cultured cells, whose main toxin component was GTX3 (average 37.6 mol%). The mussel Mytilus galloprovincialis collected from the same area in the same period accumulated a relatively high level of PSP (13-28 MU/g), suggesting a risk that A. tamiyavanichii may induce high-level PSP contamination of bivalves even at a cell density as low as around 5,000 cells/L.

Understanding the effects of anthropogenic eutrophication on coastal fisheries may help in the enhancement of fishery production by effective utilization of sewage effluents, as well as in the consequent reduction of eutrophication. In this study, it was revealed that the nitrogen stable isotope ratio (delta(15)N) in the soft tissues of the manila clam, Ruditapes philippinarum, can be used as an indicator of anthropogenic eutrophication levels in tidal flat environments by investigation of delta(15)N in dissolved inorganic nitrogen (DIN), particulate organic matter (POM), sedimentary organic matter (SOM) and soft tissues of the clam in five tidal flats in Japan with different levels of DIN concentration. In addition, it was found that the acid insoluble fraction of the shell organic matrix, conchiolin, can be used as a proxy for the soft tissues in delta(15)N analyses. This will contribute in easier storage handling and the expansion of chances for sample acquisition.

Organotin compounds (OTs) and representative booster biocides were measured in sediment and mussels from Otsuchi Bay, Japan. The mean amounts of tributyltin (TBT) and triphenyltin (TPT) compounds in sediment were 13 microg kg(-1) dry and 3 microg kg(-1) dry, respectively. Representative booster biocides (Sea-Nine 211, Diuron, Dichlofluanid, Irgarol 1501, M1, which is a degradation compound of Irgarol 1051, and Copper pyrithione) were also detected in sediment from Otsuchi Bay. OT concentrations were higher than those of the measured booster biocides. Otsuchi Bay was divided into four parts by cluster analysis based on OT concentrations in sediment sampled from the bay. These areas included the vicinity of a shipyard, a small fishing port, the closed inner area of the bay, and the mouth of the bay. Higher concentrations of TBT and TPT and a higher ratio of TBT to total BTs were observed in the vicinity of the shipyard. A higher concentration of TPT in comparison with TBT was detected in a small fishing port. Furthermore, OT concentrations in the mouth of the bay were higher than those in the closed-off section. OT concentrations in mussels decreased with distance from the shipyard. Otsuchi Bay was then divided into three parts by cluster analysis based on the concentrations of representative booster biocides found in the bay's sediment. These areas included the vicinity of a shipyard, a small fishing port, and other sites. Concentrations of Diuron and Irgarol 1051 in the vicinity of a shipyard and a small fishing port were dramatically high in comparison with the other sites. Copper pyrithione and Dichlofluanid in addition to Diuron and Irgarol 1051 were also detected in the area of a small fishing port. The concentrations of antifouling biocides were highest in the water in front of the shipyard and showed a marked decrease with distance from the shipyard.

Sterol composition in muscle and viscera tissues of the marine bivalve Megangulus zyonoensis was investigated. Among 13 different sterols identified by gas chromatography-mass spectrometry of their trimethylsilyl ether derivatives, cholesterol was the most abundant sterol, followed by 24-methylenecholesterol, in both muscle and viscera tissues. In this study, the proportion of brassicasterol, in addition to that of cholesterol, differed between the muscle and viscera.

To assess levels of shellfish intoxication by the paralytic shellfish poison (PSP)-producing dinoflagellate Alexandrium tamarense, potential health risks to human shellfish consumers and the possible need for regulatory intervention, yearly variations of maximum cell density of this species were examined from 1993 to 2004 in Kure Bay and Kaita Bay, which are located within Hiroshima Bay, Hiroshima Prefecture, Japan. The seawater temperature was determined concomitantly. In Kure Bay, maximum concentrations of 1,400 and 1,300 cells/mL at 0 and 5 m depths were observed on 21 and 24 April 1997. In Kaita Bay, remarkably high concentrations above 1,000 cells/mL of A. tamarense were observed in two out of three years investigated. These facts suggest that the environment in both bays is favorable for the propagation of A. tamarense. The temperature range at which the natural population of A. tamarense blooms was generally from 12 to 16 degrees C. Four strains (ATKR-94, -95, -97 and -01) from Kure Bay and one strain (ATKT-97) from Kaita Bay were established. The strain ATKR-94, cultured in modified SW-2 medium at 15 degrees C for 15 days, showed a specific toxicity of 33.8 x 10(-6) MU/cell. The toxins in all five strains exist almost exclusively as beta-epimers (C2 (PX2 or GTX8), GTX3, dcGTX3 and GTX4), which accounted for 54.9 to 73.0 mol% of the total. The corresponding a-epimers (C1 (PX1 or epi-GTX8), GTX2, dcGTX2 and GTX1) accounted for 6.0 to 28.9 mol%. The toxin profiles of ATKR-97 and ATKT-97 were characterized by unusually high proportions of low-potency sulfocarbamoyl toxin, which comprised 62.4 and 68.2 mol%, respectively, of total toxins. In the toxic bivalves, the low-toxicity sulfocarbamoyl components, major components of A. tamarense, were present in amounts of only a few percent, suggesting that in vivo conversion of PSP occurs after ingestion. A comparison of the toxin profiles of the causative dinoflagellate and contaminated bivalves showed that PSP components exist in the bivalves in the form of alpha-epimers, presumably owing to accumulation or storage of the toxins.

Six new carotenoids, named corbiculaxanthin (1), corbiculaxanthin 3'-acetate (2), 6-epiheteroxanthin (3), 7',8'-didehydrodeepoxyneoxanthin (4), cyclopyrrhoxanthin (5), and hydratoperidinin (6), were isolated from the corbicula clam (Shijimi in Japanese), Corbicula japonica. Their structures were determined by chemical and spectral data.

The mussel Mytilus edulis and the cultured ark shell Anadara broughtonii in the southeast coasts of the Seto Inland Sea were contaminated with paralytic shellfish poison (PSP) following the appearance of the dinoflagellate Alexandrium tamiyavanichii in early December 1999. A. tamiyavanichii plankton collected around the Straits of Naruto on December 3, 1999 showed PSP toxicity, of which 83 mol% was accounted for by GTX2, GTX3 and GTX4. Its specific toxicity was 112.5 fmol/cell, and one MU was equivalent to 7,200 cells. Toxicity values at the beginning of toxification were 4.7 MU/g for the ark shell and 7.3 MU/g for the mussel. In the former, the value remained at almost 4 MU/g, resulting in prohibition of marketing for about two months. In the latter, it sharply decreased to less than 4 MU/g. These bivalves collected during the toxification period were dissected into five tissues, mantle, adductor muscle, hepatopancreas, gills and "others", and submitted to high-performance liquid chromatography (HPLC). The cultured ark shell accumulated GTX2, GTX3 and STX as major components and GTX1, GTX4, GTX5, neoSTX, dcSTX and PX1-3 (C1-C3) as minor ones. The amount of GTX3 decreased with time, while STX tended to increase. At the early stage of PSP toxification, toxins were accumulated in the gills and "others", most of which were quickly detoxified. On the other hand, PSP of the toxified mussel consisted of GTX4 as a main component, and GTX1, GTX2, GTX3, GTX5, STX and PX1-2 (C1-C2) as minor ones. Its toxin composition pattern was similar to that of the ingested causative plankton. Its total toxin decreased soon after disappearance of the dinoflagellate. During the decrease of toxicity, PSP tended to be retained in the hepatopancreas, resulting in accumulation of 50 mol% of total toxin.

Ten samples of commercial blue mussels (Mytilus edulis) from Japan were analyzed for domoic acid by an indirect competitive enzyme immunoassay (idc-EIA) based on an anti-domoic acid monoclonal antibody. Domoic acid was found in all samples at low concentrations (0.11-1.81 ng/g mussel tissue). The presence of domoic acid was confirmed by liquid chromatography coupled with immunoaffinity chromatography using an anti-domoic acid monoclonal antibody as ligand. To our knowledge, this is the first reported detection of domoic acid, a causative agent of amnesic shellfish poisoning, in Japanese mussels.

A new bacterial species belonging to the genus Pseudoalteromonas is described on the basis of phenotypic characterization, and sequence analysis of its 16S rRNA-coding and gyrase B (gyrB) genes. Ten strains, isolated from sea water of Yamato Island, Sea of Japan, were Gram-negative, yellow, motile, polarly flagellated, aerobic, rod-shaped eubacteria and had a G + C content of 42 mol%. Analysis of the 16S rDNA sequence revealed a clear affiliation between these strains and members of the gamma-Proteobacteria. High similarity values were found with members of the genus Pseudoalteromonas and this was supported by fatty acid profiles. The 16S rDNA sequence similarity between strain F12-50-A1T and Pseudoalteromonas piscicida was very high (99.1%). However, molecular characterizations employing small subunit 16S rDNA sequences were at the limits of resolution for the differentiation of species in this genus. As a result, DNA-DNA hybridization and sequence analyses of a more rapidly evolving gyrB gene were performed. Our assertion that this strain represents a distinct bacterial species within the genus Pseudoalteromonas was supported by both of these molecular analyses. Species-specific PCR probes were designed for the gyrB gene and used for the rapid screening of F12-50-A1T-like strains, thereby confirming the species. As these strains cleave complex protein compounds of the Mytilus edulis foot by secreting proteases, the name Pseudoalteromonas peptidolytica sp. nov. is proposed, with strain F12-50-A1T (= MBICC F1250A1T) as the type strain.

Concentrations of Hg and other metals such as Ag, Cr, Co and Ni in soft tissues and byssi of the blue mussel (Mytilus edulis) from three sites along the east coast of Kyushu Island, Japan, were determined by a cold-vapor technique. Large inter-regional differences in metal concentrations in both soft tissues and byssi were observed. The tissue concentrations of Hg were significantly greater in M. edulis from the most contaminated locations (Saganoseki) compared to those from a non-industrialized area (Urashiro). It is evident that, compared to the soft tissue, byssus is a more sensitive biomonitor for Hg, Cr, Co and Ni. From the data obtained in the present study evidently results that the soft tissue and especially byssi of M. edulis appear to be good bioindicators for identification of coastal areas exposed to Hg contaminants.

In May 1996, during surveillance on the toxicity of invertebrates such as bivalves inhabiting the coasts of Hiroshima Bay, the starfish Asterias amurensis collected in the estuary of the Nikoh River was found to contain toxins which showed strong paralytic action in mice; the maximum toxicity (as paralytic shellfish poison, PSP) was 8.0 MU/g for whole body and 28.7 MU/g for viscera throughout the monitoring period, March to July 1996. Attempts were made to identify the paralytic toxins in the starfish. They were extracted with 80% ethanol acidified with acetic acid, followed by defatting with dichloromethane. The aqueous layer obtained was treated with activated charcoal and then applied to a Sep-Pak C18 cartridge. The unbound toxic fraction was analyzed by high-performance liquid chromatography techniques. The starfish toxin was rather unexpectedly identified as PSP. It was comprised of high toxic components (gonyautoxin-1; GTX1, GTX2, GTX3, GTX4, decarbamoyl-GTX3; dcGTX3 and dcSTX) as the major components, which accounted for approximately 77 mole% of all components, along with protogonyautoxin-1, 2, 3 and 4 (PX1-4), which are N-sulfocarbamoyl derivatives. Of the high toxic components, GTX1 was present in the largest amounts. It was concluded that the toxin of starfish collected in the estuary of Nikoh River in May 1996 consisted of PSP, which supposedly came via the food chain from toxic bivalves living in the same area. To our knowledge, this is the first report of the occurrence of PSP in starfish.

Some experiments on the preservability of chemicals in environmental samples such as atmospheric particulate matters and mussel meat have been conducted by National Institute for Environmental Studies (NIES), Japan, as a preliminary study for future establishment of environmental specimen bank. NIES also has been operating a small experimental sample bank, storing several kinds of environmental samples. Closely cooperating with NIES, Environment Agency of Japan has been performing several types of nationwide environmental monitoring of chemical substances and some parts of the collected samples have been stored in the cold storage room for future use. A retrospective analysis of TBT and TPT in the fish using these stored samples showed an availability and usefulness of specimen bank for the long term monitoring of pollutants.