The relationship between fine rings in the statolith and growth of the cubomedusa Chiropsalmus quadrigatus (Cnidaria: Cubozoa) from Okinawa Island, Japan

Sixty-nine Chiropsalmus quadrigatus medusae were collected from Okinawa Island, Japan, in June-August 2000. The bell height ranged from 2.5 to 97.6 mm. The numbers of fine rings on polished statoliths were counted, and the coefficient of variation for the within-individual counts for the four statoliths was 3.3± 1.9% (mean::tSD, n=17). The slope of the linear regression of the number of rings against collecting date in 61 medusae was near 1.0, suggesting that the statolith rings are daily increments. The relationship between bell height and number of rings fitted a logistic growth curve. And, the relationship between statolith length and number of rings fitted the Gompertz growth curve. A check ring was present at a position of 5-10 rings from the center of each statolith. The backcalculated dates of check ring formation dated mainly from early to mid June, suggesting that the polyp of C. quadrigatus finished the metamorphosis to medusa and the medusa was liberated from a substratum during this period

Ciguatera in the Philippines: Examining Reef Fish Vectors and Its Causative Benthic Dinoflagellates in Visayan and Sibuyan Seas

Ciguatera Fish Poisoning (CFP) is primarily caused by ingesting reef fishes contaminated with ciguatoxins (CTX) produced by the Gambierdiscus species. The unpredictability of this type of food poisoning poses risks to public health and adversely affecting the fish trade industry. This study aimed to provide useful information on ciguatera in the Philippines. Different reef fish species and host-macroalgae for benthic dinoflagellates were collected in Visayan and Sibuyan Seas. Ciguatoxins were extracted from reef fish samples, and toxicity was determined qualitatively using mouse bioassay. Meanwhile, cell density estimation of toxic benthic dinoflagellates isolated from the host-macroalgae was done through microscopy. It was observed that 4.46% of the total reef fish samples were positive with ciguatoxins. Spatially, Carles, Iloilo in Visayan sea had the highest number of toxic specimens belonging to Epinephelus merra, Lethrinus lentjan, Lutjanus campechanus, Scarus quoyi, Siganus guttatus, and Sphyraena barracuda. Based on data gathered from three sampling sites, fish toxin occurrence is observed to be site-specific. Geographical conditions affect the frequency of toxic samples. Moreover, fish weight is not a good predictor of fish toxicity. For toxic benthic dinoflagellates, Gambierdiscus spp. were observed to have the lowest cell density count among other dinoflagellates averaging 7-115 cells per 100 g macroalgae. On the other hand, Ostreopsis spp. had the highest average cell density of 118-1,455 cells per 100 g macroalgae, followed by Prorocentrum spp. (207-594 cells per 100 g macroalgae). Fish toxicity is directly proportional to the occurrence of benthic dinoflagellates in areas as seen during dry season. Monitoring and management of CFP on identified reef fish vectors and its causative benthic dinoflagellates in the area are necessary to promote food safety and fair trade practice

A Protein Phosphatase 2A-Based Assay to Detect Okadaic Acids and Microcystins

Okadaic acids (OAs) are causative agents of diarrhetic shellfish poisoning, produced by the dinoflagellates Dinophysis spp. and Prorocentrum spp. Microcystins (MCs) are cyclic heptapeptide hepatotoxins produced by some cyanobacteria genera, including Microcystis spp. Traditionally, toxicity detection and quantification of these natural toxins were performed using a mouse bioassay (MBA); however, this is no longer widely employed owing to its lack of accuracy, sensitivity, and with regard to animal welfare. Therefore, alternative toxicity analyses have been developed based on MCs’ and OAs’ specific inhibition of protein phosphatase 2A (PP2A), using p-nitrophenylphosphate (p-NPP) as a substrate. The assay is simple, inexpensive, ready for use on site, and can be applied to several samples at once. For OA detection, this assay method is appropriate for widespread application as a substitute for MBA, as evidenced by its alignment with the oral toxicity of MBA. In this review, we summarize the structure and function of PP2A, the inhibitory activities of OAs and MCs against PP2A, and the practical applications of the PP2A assay, with the aim of improving understanding of the PP2A assay as an OAs and MCs detection and quantification method, as well as its suitability for screening before confirmatory chemical analysis

Detection of Extremely Low Level Ciguatoxins through Monitoring of Lithium Adduct Ions by Liquid Chromatography-Triple Quadrupole Tandem Mass Spectrometry

Ciguatera poisoning (CP) is the most common type of marine biotoxin food poisoning worldwide, and it is caused by ciguatoxins (CTXs), thermostable polyether toxins produced by dinoflagellate Gambierdiscus and Fukuyoa spp. It is typically caused by the consumption of large fish high on the food chain that have accumulated CTXs in their flesh. CTXs in trace amounts are found in natural samples, and they mainly induce neurotoxic effects in consumers at concentrations as low as 0.2 µg/kg. The U.S. Food and Drug Administration has established CTX maximum permitted levels of 0.01 µg/kg for CTX1B and 0.1 µg/kg for C-CTX1 based on toxicological data. More than 20 variants of the CTX1B and CTX3C series have been identified, and the simultaneous detection of trace amounts of CTX analogs has recently been required. Previously published works using LC-MS/MS achieved the safety levels by monitoring the sodium adduct ions of CTXs ([M+Na]+ > [M+Na]+). In this study, we optimized a highly sensitive method for the detection of CTXs using the sodium or lithium adducts, [M+Na]+ or [M+Li]+, by adding alkali metals such as Na+ or Li+ to the mobile phase. This work demonstrates that CTXs can be successfully detected at the low concentrations recommended by the FDA with good chromatographic separation using LC-MS/MS. It also reports on the method’s new analytical conditions and accuracy using [M+Li]+

Specification of the Okadaic Acid Equivalent for Okadaic Acid, Dinophysistoxin-1, and Dinophysistoxin-2 Based on Protein Phosphatase 2A Inhibition and Cytotoxicity Assays Using Neuro 2A Cell Line

Diarrhetic shellfish poisoning (DSP) is a globally occurring disease threatening public health and trade. The causative toxins, okadaic acid (OA), dinophysistoxin-1 (DTX1), and dinophysistoxin-2 (DTX2) are collectively called OAs, and are quantified using the LC-MS/MS method. The hazardous effect of total OAs is expressed as the sum of OA equivalents defined for respective OAs based on mouse lethality, produced by either intraperitoneal (OAip) or oral administration (OAor). OAs are potent inhibitors of protein phosphatase 2A (PP2A) and are cytotoxic, necessitating expansion of the concept of OA equivalents to all relevant bioactivities. In this study, we determined OA equivalents for respective OA members in PP2A inhibition and cytotoxicity assays. To secure result credibility, we used certified OAs, reference materials, and PP2A produced using genetic engineering. The relative ratio of the OA equivalents determined by PP2A inhibition assays for OA, DTX1, and DTX2 were 1.0:1.6:0.3, while the ratio determined using the cytotoxicity assays indicated 1.0:1.5:0.5. OA equivalents showed a similar tendency in the PP2A inhibition and cytotoxicity assays, and matched better with oral toxicity data than intraperitoneal toxicity in mice. The PP2A inhibition assay, which measures the core activity of the OAs, suggested a higher OA equivalent for DTX1 than that currently used

Chemistry, Toxicology and Etiology of Marine Biotoxins

Marine biotoxins refer to bioactive natural products primarily produced by microalgae and bacteria and may affect aquatic organisms and human health [...

沖縄島産のノコギリガキ(二枚貝綱、カキ目、イタボガキ科)とカイヤドリヒドラクラゲ(ヒドロ虫綱、軟クラゲ目、マツバクラゲ科)の共生の初記録

An association is reported for the first time between Dendrostrea japonica (Bivalvia, Ostreidae) and Eugymnanthea japonica (Hydrozoa, Leptomedusae). Based on specimens collected in Okinawa in 2002. A brief description of the mature medusa of the latter species, obtained by laboratory-culture, is also given

A smartphone-controlled amperometric immunosensor for the detection of Pacific ciguatoxins in fish

Ciguatoxins (CTXs) are marine neurotoxins produced by microalgae of the genera Gambierdiscus and Fukuyoa. CTXs may reach humans through food webs and cause ciguatera fish poisoning (CFP). An immunosensor for the detection of Pacific CTXs in fish was developed using multiwalled carbon nanotube (MWCNT)-modified carbon electrodes and a smartphone-controlled potentiostat. The biosensor attained a limit of detection (LOD) and a limit of quantification (LOQ) of 6 and 27 pg/mL of CTX1B, respectively, which were 0.001 and 0.005 μg/kg in fish flesh. In the analysis of fish samples from Japan and Fiji, excellent correlations were found with sandwich enzyme-linked immunosorbent assays (ELISAs), a cell-based assay (CBA) and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Stability of at least 3 months at −20 °C was predicted. In just over 2 h, the biosensor provides reliable, accurate and precise Pacific CTX contents in fish extracts, being suitable for monitoring and research programs.info:eu-repo/semantics/acceptedVersio