First report on okadaic acid production of a benthic dinoflagellate Prorocentrum cf. fukuyoi from Japan

Abstract

The consumption of bivalves contaminated with diarrhetic shellfish toxins (DSTs) such as okadaic acid and dinophysistoxins has caused serious economic hardship to shellfish industries worldwide including Japan. Several benthic species of the genus Prorocentrum have been confirmed to produce DSTs. There have been no published studies of Japanese strains of Prorocentrum species that include a three-way characterization of morphological characteristics, molecular phylogenetic data, and toxin profiles. In the present study, a benthic Prorocentrum strain isolated from Japanese temperate shallow water (depths < 3 m) was characterized using morphological, phylogenetic, and toxicological methods. Cell size of the Japanese Prorocentrum strain KSK4P was 27.2 AE 1.3 μm in length, 22.4 AE 0.9 μm in width, and had a length-to-width ratio of 1.22 AE 0.04. The thecal surface was smooth and covered with large and small thecal pores lying in rows, and the pores were lacking in the central area of the theca. The right theca had a deeply excavated periflagellar area that was narrow V-shaped. Nine platelets and two wings were in the periflagellar area. These morphological features of the strain KSK4P are similar to those of P. fukuyoi. Phylogenetic trees based on the LSU rDNA D1/D3 sequences revealed that the strain KSK4P forms a new subclade F2f belonging to P. fukuyoi complex (subclade F2). The sequence analysis revealed that the strain KSK4P (subclade F2f) diverges from a subclade F2e to which the strain used for the description of P. fukuyoi belongs. Based on the results of morphological and phylogenetic analyses of the strain KSK4P, the strain was designated as P. cf. fukuyoi. The results of the LC/MS/MS analysis revealed that the strain KSK4P produced okadaic acid (1.5-2.7 fg cell −1 ). This is the first report that a strain belonging to the P. fukuyoi complex can produce okadaic acid.

Cryptic speciation of benthic Prorocentrum (Dinophyceae) species and their potential as ecological indicators

“…The morphology of strains from ribotype C appears variable. Strains Dn34EHU from Brazil (Laza-Martinez et al, 2011), KSK4P from Japan also fit the original description in terms of the sparse pores (Nishimura et al, 2020b), but strains Dn33EHU from Brazil (Laza-Martinez et al, 2011), IFR13-113 from the Caribbean Sea show dense pores (Chomérat et al, 2018). The molecular sequences of true P. emarginatum are still not available, therefore, these strains have been named P. cf.…”

“…However, molecular sequences were not provided in these studies. Subsequent surveys were performed combining morphology and molecular characterization of samples collected from Dongho, Korea (Kim et al, 2015), Hainan, China (Luo et al, 2017;Zou et al, 2021), Perhentian Island, Malaysia (Lim et al, 2019), and Japan (Nishimura et al, 2020a;Nishimura et al, 2020b). Detailed examinations on benthic Prorocentrum species in many parts of the Western Pacific, such as northern China and Indonesia, are still missing.…”

“…OA production is known in P. caipirignum (Nascimento et al, 2017;Lim et al, 2019), P. lima (Murakami et al, 1982;Lim et al, 2019), P. concavum (Dickey et al, 1990), P. steidingerae (as P. rhathymum) (An et al, 2010), P. cf. fukuyoi (Nishimura et al, 2020b), P. hoffmannianum (Morton and Bomber, 1994), P. leve (Faust et al, 2008), and P. belizeanum (Morton et al, 1998). OA production in many epibenthic Prorocentrum species has not yet been examined and may help to differentiate closely related species or cryptic species.…”

Degradation of okadaic acid in seawater by UV/TiO2 photocatalysis – Proof of concept

“…Fraction with the highest purity and content of OA was 17 (>90%, 25.3 mg), for DTX1 fraction 19 (>35%, 11.6 mg) and for DTX1 analogue fraction 22 (>45%, 13.2 mg). Prorocentrum species produce different DSP content depending on the species and/or strains ( An et al, 2010 ; Aquino-Cruz et al, 2018 ; Ben-Gharbia et al, 2016 ; Lee et al, 2016 ; Luo et al, 2017 ; Nishimura et al, 2019 ; Nishimura et al, 2020 ; Pan et al, 2017 ). Previous studies on large-scale culture of P. lima and separation and purification of OA and DTX1 were published.…”

Spatial-Temporal Distribution of Prorocentrum concavum Population in Relation to Environmental Factors in Xincun Bay, a Tropical Coastal Lagoon in China

“…Benthic Prorocentrum is a harmful benthic dinoflagellate group, which is widely distributed from tropical to temperate zones (Hoppenrath et al, 2013;Luo et al, 2017;Chomérat et al, 2019;Zou et al, 2021). To date, nine species of epibenthic Prorocentrum have been identified that produce okadaic acid (OA), and/or its analogs (Dickey et al, 1990;Morton et al, 1998;Ten-Hage et al, 2002;An et al, 2010;Rodríguez et al, 2018;Nishimura et al, 2020). This toxin causes diarrhea, vomiting, abdominal pain, and nausea in humans that ingest shellfish contaminated by OA (Toyofuku, 2006), which called as diarrhetic shellfish poisoning (DSP).…”