A case of paralytic shellfish poisoning caused by consumption of visceral balls from geoduck Panopea japonica in Japan.

In the end of March 2018, an unprecedented food poisoning incident due to ingestion of the visceral balls of geoduck Panopea japonica occurred in Japan. The patient, presented with symptoms of numbness on the lips and general weakness, was diagnosed as paralytic shellfish poisoning (PSP). The patient immediately treated with the mechanical ventilation recovered and left the hospital after 3 days treatment. Saxitoxins (STXs) in the plasma and urinary samples collected from the patient on the first and second day after hospitalization were analyzed by ultra high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC/MS/MS) and liquid chromatography with post-column fluorescent detection (LC/FLD). The STXs levels of 499.1 and 6.0 µg/L of STX dihydrochloride equivalent (STX·2HCl eq.) were quantitated by LC/FLD in the urinary samples on the first and second day, respectively. In addition, geoducks harvested from the same areas of the PSP causative specimens after the incident were analyzed by LC/FLD, and the results showed the level of STXs in their whole bodies of the geoducks exceeding 0.8 mg STX·2HCl eq./kg which is the maximum levels of STX in CODEX STAN 292-2008. Prominent toxins in STXs that detected in urinary and geoduck samples and identified by UHPLC/MS/MS and LC/FLD were gonyautoxin-1+4 (GTX1+4). These results concluded that the incident was the food poisoning due to STXs accumulated in the geoducks. This is the first PSP case caused by consumption of geoducks in Japan. This is also the first PSP case that causative toxins are detected in urinary samples of patients involved in PSP in Japan.

Method for obtaining reliable R-waves in fish electrocardiograms by utilizing conductivity of seawater.

A simple method for measuring bioelectric signals of fish in seawater is expected for managing the health of farmed fish and clarifying the ecophysiology of natural fish. We previously proposed a simple and unique method for measuring bioelectric signals of fish by inserting only one special internal electrode (which can be isolated from seawater) into the fish's body and by sinking an external electrode in seawater (for utilizing the conductivity of seawater). However, the proposed method could not obtain fish electrocardiograms (ECGs) with reliable R-waves in the same manner as the conventional method. In this study, we thus experimentally investigated whether the R-waves of ECGs could be observed by optimizing the insertion position of the internal electrode into the fish's body. The results of the experiment show that for four species of fish (each slightly longer than 10 cm) with different body shapes, reliable R-waves could be observed by inserting the internal electrode near the heart. We also investigated the possibility of simultaneously measuring ECGs of multiple fish by the proposed method. The results of the investigation show that the fish ECGs with R-waves of three fish could be observed simultaneously even when one single common external electrode replaced multiple external electrodes. This result indicates the advantage of the proposed method in reducing the total number of bioelectrodes compared to the conventional method for ECG measurements of multiple fish.

Utilizing conductivity of seawater for bioelectric measurement of fish.

To manage health conditions of farmed fish and other living creatures, a simple method to measure bioelectric signals of the creatures in seawater is expected. A novel method to measure bioelectric signals by utilizing the conductivity of seawater surrounding the entire body of a fish is proposed. As for the proposed method, a needle-type internal electrode is inserted into the fish's muscle at a certain measurement point, and an external electrode is sunk in seawater. The internal electrode is isolated from the seawater by virtue of being inserted in the fish. Bioelectric signals generated between the external and internal electrodes are then measured. By sharing the external electrode with the internal electrode, it is possible to measure bioelectric signals with half the number of bioelectrodes used by conventional methods. To demonstrate the practicality of the proposed method, two internal electrodes were inserted into different parts (above the gills and near the tail) of three fish (Parajulis poecilepterus, ca. 20 cm fork length) kept in a tank. The proposed method obtained reliable bioelectric signals corresponding to electrocardiograms (ECGs) and electromyograms (EMGs) from each part of the individual fish.