Two toxigenic Ostreopsis species, O. cf. ovata and O. siamensis (Dinophyceae), from the South China Sea, tropical Western Pacific.

In the dinophyte genus Ostreopsis, seven out of 11 described species are known to produce various toxic compounds that were characterized in the palytoxins family. Species in the genus shared identical thecal plate patterns but differed in size, shape, and thecal plate ornamentation. Two species, O. cf. ovata and O. siamensis, have been reported from the Western Pacific, but information on toxin production is scarce. Here, we established nine strains of Ostreopsis from six localities in the South China Sea (SCS), covering the Gulf of Thailand, northern SCS (Hainan Island, Beibu Bay), and southern SCS (Peninsular Malaysia). Their morphology was examined by light and electron microscopy and the molecular phylogeny was inferred based on the LSU rDNA (D1-D3) and ITS rDNA sequences using maximum likelihood and Bayesian inference. Both O. cf. ovata and O. siamensis, albeit morphologically closely related, can be distinguished by a feature of the thecal pores with pronounced ridges in the latter. Molecular data further supported their species identity. Toxin production in the strains was examined by LC-MS/MS. O. cf. ovata strain T5PRBost02 was observed to produce Ovatoxin-k and Ovatoxin-j2 only; while Ostreocin-B and Ostreocin-D was produced by O. siamensis strain T10PRBost04. This is the first report confirming the production of palytoxins analogs in Ostreopsis species from the region.

Rapid and Accurate Species-Specific PCR for the Identification of Lethal Chironex Box Jellyfish in Thailand.

Box jellyfish are extremely potent venom-producing marine organisms. While they have been found worldwide, the highest health burden has been anticipated to be the tropical Indo-Pacific of Southeast Asia (SEA). At least 12 Cubozoan species have now been documented in Thai waters, and many of them inflict acutely lethal strings, especially those under the order Chirodropida. Our previous study has successfully differentiated species of box jellyfish using DNA sequencing to support the morphological study. In this study, we specifically designed polymerase chain reaction (PCR) primers for the 16S ribosomal RNA (rRNA) gene and the mitochondrial DNA cytochrome oxidase subunit I (COI) gene of lethal Thai Chironex species. The SYBR green-based real-time PCR panel was performed for rapid species identification. The sensitivity and specificity of the panel were determined by testing samples of different species. Moreover, we applied the panel to the tentacle sample from a real patient, which helped confirm the animal-of-cause of envenomation. Our results show a success for species identification of box jellyfish using 16S rRNA and COI PCR panel, which revealed congruence between molecular and morphological identification. Furthermore, the panel worked very well with the unknown samples and jellyfish tissue from the real envenomation case. The results demonstrated that molecular panels were able to identify three species of Chironex box jellyfish both rapidly and accurately, and can be performed without having a complete specimen or morphological study.