Toxicity screening of 13 Gambierdiscus strains using neuro-2a and erythrocyte lysis bioassays

Abstract

Species in the epi-benthic dinoflagellate genus Gambierdiscus produce ciguatoxins (CTXs) and maitotoxins (MTXs), which are among the most potent marine toxins known. Consumption of fish contaminated with sufficient quantities of CTXs causes Ciguatera Fish Poisoning (CFP), the largest cause of non-bacterial food poisoning worldwide. Maitotoxins, which can be found in the digestive system of fish, could also contribute to CFP if such tissues are consumed. Recently, an increasing number of Gambierdiscus species have been identified; yet, little is known about the variation in toxicity among Gambierdiscus strains or species. This study is the first assessment of relative CTX- and MTX-toxicity of Gambierdiscus species from areas as widespread as the North-Eastern Atlantic Ocean, Pacific Ocean and the Mediterranean Sea. A total of 13 strains were screened: (i) seven Pacific strains of G. australes, G. balechii, G. caribaeus, G. carpenteri, G. pacificus, G. scabrosus and one strain of an undetermined species (Gambierdiscus sp. Viet Nam), (ii) five strains from the North-Eastern Atlantic Ocean (two G. australes, a single G. excentricus and two G. silvae strains), and (iii) one G. carolinianus strain from the Mediterranean Sea. Cell pellets of Gambierdiscus were extracted with methanol and the crude extracts partitioned into a CTX-containing dichloromethane fraction and a MTX-containing aqueous methanol fraction. CTX-toxicity was estimated using the neuro-2a cytoxicity assay, and MTX-toxicity via a human erythrocyte lysis assay. Different species were grouped into different ratios of CTX- and MTX-toxicity, however, the ratio was not related to the geographical origin of species (Atlantic, Mediterranean, Pacific). All strains showed MTX-toxicity, ranging from 1.5 to 86pg MTX equivalents (eq) cell. All but one of the strains showed relatively low CTX-toxicity ranging from 0.6 to 50 fg CTX3C eq cell. The exception was the highly toxic G. excentricus strain from the Canary Islands, which produced 1426 fg CTX3C eq cell. As was true for CTX, the highest MTX-toxicity was also found in G. excentricus. Thus, the present study confirmed that at least one species from the Atlantic Ocean demonstrates similar toxicity as the most toxic strains from the Pacific, even if the metabolites in fish have so far been shown to be more toxic in the Pacific Ocean.

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

“…, Pisapia et al. ; Table ). Recent work has shown G. silvae can be as toxic as G. excentricus (Robertson et al.…”

“…, Pisapia et al. ) located 160 km west of the Tortugas Ecological Reserve in the Northeastern Gulf of Mexico and from the Bahamas (N 26°38.849, W 78°04.839; Bahamas Gam5 = BahamaGam5 in Litaker et al. ).…”

Ciguatera Fish Poisoning: The Risk from an Aotearoa/New Zealand Perspective

“…Three species have been identified as potential producers of CTXs or CTX-like compounds: CTXs production has been confirmed for G. polynesiensis [19] by liquid chromatography tandem mass spectrometry (LC-MS/MS). G. silvae Fraga & Rodriguez [20] and G. excentricus Fraga [21][22][23][24] were reported as positive for CTXs using the neuro-2a assay, with G. silvae being highly toxic in this assay (2.1-4.8 pg Caribbean-CTX-1 equivalents; C-CTX) [20,21].…”

“…Over the last decade these species have been reported not only from tropical and subtropical waters, but also from more temperate regions, including the coastal waters of New South Wales, Australia [20,[25][26][27][28], and additional species have been reported from more sites throughout the Pacific region ( Figure 1) [6,13,23]. Of the eighteen described Gambierdiscus species, only G. silvae and G. carolinianus have not been reported in the Pacific region.…”

“…Toxins 2020, 12, 50 3 of 21 production has been confirmed for G. polynesiensis [19] by liquid chromatography tandem mass spectrometry (LC-MS/MS). G. silvae Fraga & Rodriguez [20] and G. excentricus Fraga [21][22][23][24] were reported as positive for CTXs using the neuro-2a assay, with G. silvae being highly toxic in this assay (2.1-4.8 pg Caribbean-CTX-1 equivalents; C-CTX) [20,21]. Over the last decade these species have been reported not only from tropical and subtropical waters, but also from more temperate regions, including the coastal waters of New South Wales, Australia [20,[25][26][27][28], and additional species have been reported from more sites throughout the Pacific region ( Figure 1) [6,13,23].…”