Characterization of a Strain of Fukuyoa paulensis (Dinophyceae) from the Western Mediterranean Sea

A single cell of the dinoflagellate genus Fukuyoa was isolated from the island of Formentera (Balearic Islands, west Mediterranean Sea), cultured, and characterized by morphological and molecular methods and toxin analyses. This is the first report of the Gambierdiscus lineage (genera Fukuyoa and Gambierdiscus) from the western Mediterranean Sea, which is cooler than its eastern basin. Molecular analyses revealed that the Mediterranean strain belongs to F. paulensis and that it bears LSU rDNA sequences identical to New Zealand, Australian, and Brazilian strains. It also shared an identical sequence of the more variable ITS‐rDNA with the Brazilian strain. Toxin analyses showed the presence of maitotoxin, 54‐deoxyCTX1B, and gambieric acid A. This is the first observation of the two latter compounds in a Fukuyoa strain. Therefore, both Gambierdiscus and Fukuyoa should be considered when as contributing to ciguatera fish poisoning. Different strains of Fukuyoa form a complex of morphologically cryptic lineages where F. paulensis stands as the most distantly related nominal species. The comparison of the ITS2 secondary structures revealed the absence of CBCs among strains. The study of the morphological and molecular traits depicted an unresolved taxonomic scenario impacted by the low strains sampling.     

Ciguatoxins activate specific cold pain pathways to elicit burning pain from cooling

Ciguatoxins are sodium channel activator toxins that cause ciguatera, the most common form of ichthyosarcotoxism, which presents with peripheral sensory disturbances, including the pathognomonic symptom of cold allodynia which is characterized by intense stabbing and burning pain in response to mild cooling. We show that intraplantar injection of P-CTX-1 elicits cold allodynia in mice by targeting specific unmyelinated and myelinated primary sensory neurons. These include both tetrodotoxin-resistant, TRPA1-expressing peptidergic C-fibres and tetrodotoxin-sensitive A-fibres. P-CTX-1 does not directly open heterologously expressed TRPA1, but when co-expressed with Na_v channels, sodium channel activation by P-CTX-1 is sufficient to drive TRPA1-dependent calcium influx that is responsible for the development of cold allodynia, as evidenced by a large reduction of excitatory effect of P-CTX-1 on TRPA1-deficient nociceptive C-fibres and of ciguatoxin-induced cold allodynia in TRPA1-null mutant mice. Functional MRI studies revealed that ciguatoxin-induced cold allodynia enhanced the BOLD (Blood Oxygenation Level Dependent) signal, an effect that was blunted in TRPA1-deficient mice, confirming an important role for TRPA1 in the pathogenesis of cold allodynia.     

Toxicological characterization of Fukuyoa paulensis (Dinophyceae) from temperate Australia

Dinoflagellates of the genus Gambierdiscus are known to produce neurotoxins that cause the human illness ciguatera, a tropical and sub‐tropical fish poisoning. Some species from the Gambierdiscus genus were recently re‐classified into a new genus, Fukuyoa based on their phylogenetic and morphological divergence, however, little is known about their distribution, ecology and toxicology. Here we report the first occurrence of F. paulensis in the temperate coastal waters of eastern Australia and characterize its toxicology. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) did not detect the presence of ciguatoxins, however, a putative maitotoxin congener (MTX‐3) was present. Similarly, high maitotoxin‐like activity was detected in High Performance Liquid Chromatography (HPLC) fractionated cell extracts using a Ca²⁺ influx bioassay on a Fluorescent Imaging Plate Reader (FLIPR), but no ciguatoxin‐like activity was detected.     

Isolation and some properties of ciguatoxin

Ciguatoxin, the principal toxin of ciguatera produced by a toxic dinoflagellate and accumulated through the food chain in the viscera of moray eels, was purified. The probable molecular formula C₆₀H₈₆O₁₉ was obtained for the first time by high resolution mass spectrometry. ¹H NMR spectra suggested the presence of a primary hydroxyl group suitable for preparing an antigen necessary to develop an enzyme immunoassay. author for correspondence     

Ciguatera — Parameters of a tropical health problem

Ciguatera fish poisoning is a significant health and resource problem in the tropical world, largely because of its uneven and unpredictable distribution in space and through time. Here, the problem is reviewed with evidence from the Pacific Basin. The contemporary distribution of ciguatera and the species commonly perceived to be toxic are considered and a hypothesis relating the greater prevalence of ciguatera in the eastern Pacific to reduced species diversity is presented. The problem is also considered as a public health phenomenon (the mean reported incidence for the Pacific region as a whole in 1981 was 109/100,000) and attention is given to island dwellers' adaptation to the problem, their explanations of its etiology, as well as its detection, prophylaxis, and cure.The primary research was made possible by a Fulbright-Hays Research Aboard Grant (#.441Ah70055); subsequent research was supported by a University of Hawaii Research and Training Revolving Fund Award.     

Species‐specific PCR assays for Gambierdiscus excentricus and Gambierdiscus silvae (Gonyaulacales,Dinophyceae)

The two most toxic Gambierdiscus species identified from the Caribbean are G. excentricus and G. silvae. These species are the primary causes of ciguatera fish poisoning and likely contribute disproportionately to the toxicity of marine food webs. While Gambierdiscus species are difficult to distinguish using light or scanning electron microscopy, reliable species‐specific molecular identification methods have been developed and used successfully to identify a number of other Gambierdiscus species. Corresponding species‐specific assays are not yet available for G. excentricus and G. silvae, which imposes limitations on species identification and related ecological studies. The following note describes species‐specific polymerase chain reaction assays for G. excentricus and G. silvae that can be used for these purposes.