Fish Hybridization Leads to Uncertainty Regarding Ciguatera Fish Poisoning Risk; Confirmation of Hybridization and Ciguatoxin Accumulation with Implications for Stakeholders

Abstract

Globally, ciguatera fish poisoning (CFP) avoidance efforts rely primarily on local knowledge of the fish being consumed, its collection location, and association with illnesses. In 2016, several fish that appeared to be hybrids between a local commercially prized species, Ocyurus chrysurus, and a regionally prohibited species Lutjanus apodus (due to CFP concerns), were caught nearshore in United States Virgin Islands waters, leading to confusion regarding the safety of consuming the fish. The hybrid status of the fish was verified as O. chrysurus (male) × L. apodus (female) by comparing two sets of gene sequences (mitochondrial CO1 and nuclear S7). Using an in vitro mouse neuroblastoma (N2a) assay, one of the hybrid fish exhibited a composite cytotoxicity of 0.038 ppb Caribbean ciguatoxin-1 (C-CTX-1) equivalents (Eq.); a concentration below the US Food and Drug Administration (FDA) guidance level for safety in fish products for CFP (0.1 ppb C-CTX-1 Eq.) but approximately 2× above the maximum described in the commercially prized parent species (0.019 ppb C-CTX-1 Eq./g). C-CTX-1 was confirmed in the hybrid sample by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The second hybrid fish tested negative for CTXs. This research confirms hybridization between two species with contrasting commercial statuses, discusses CTX accumulation implications for hybridization, and provides a methodology for future studies into novel CFP vectors, with the goal of providing critical information for fishermen and consumers regarding CFP risk management.

Revisiting the Neuroblastoma Cell-Based Assay (CBA-N2a) for the Improved Detection of Marine Toxins Active on Voltage Gated Sodium Channels (VGSCs)

“…The accuracy of the data provided by this revisited CBA-N2a, relies, in part, on the availability of five viability controls, i.e., RCV, COV − , COV + , QCOV − and QCOV + that were established throughout the various stages of CBA-N2a in order to verify: (i) the initial (RCV control) and final viability of N2a cells (COV − controls), (ii) the efficiency of O/V treatment (COV + controls) and (iii) the detection of the specific mode of action of VGSC activators vs. inhibitors (QCOV − and QCOV + controls). If the use of percentages is recurrent in most studies to express cell viability results [7,8,32,33,36,37,43,46,53,59,62,63,[66][67][68]70,73,74,76,81,83,85,87,88,90,91,95,97,103,[106][107][108][109][110][111][112], the originality of our revisited CBA-N2a is to recommend the use of absorbance data by establishing a RCV control that characterizes the baseline viability of N2a cell layer prior to O/V treatment and toxin exposure. This RCV control serves as a reference from which all other viability controls as well as viability data of standard and samples depend.…”

Ciguatera Mini Review: 21st Century Environmental Challenges and the Interdisciplinary Research Efforts Rising to Meet Them

“…However, species implicated in CP can have wide geographical ranges, e.g., the Nassau grouper ( Epinephelus striatus ) transcend the jurisdictions of 43 nations or territories [ 142 ], or have a relatively small spatial home and hunting ranges, with occasional sporadic movements for spawning aggregations and migrations. Consumer avoidance of CP risk species can become complicated when identifiable characteristics used for phenotypically determining a species, like the head or skin, are removed during processing [ 143 , 144 ] or when species hybridize [ 145 ]. Therefore, the policies guiding CP harvest restrictions can be subverted by deliberate or inadvertent species substitution [ 146 ], or by falsifying capture location information [ 147 ].…”

“…So far, a meal remnant analysis remains the best scenario for confirmation of potential poisoning. In trace back instances from CP outbreaks, DNA-barcoding is a critical tool for the identification of the ciguatera-causing species [ 145 , 186 , 187 , 188 , 189 , 190 , 191 , 192 , 193 ]. Toxin identification, quantification, and DNA barcoding [ 194 ] can still be performed on the meal remnant even after cooking, yielding valuable information for cataloging CP events and causative fish species [ 114 , 186 , 195 ].…”

Advances and Current Challenges in Marine Biotoxins Monitoring

“…Novoveská and Robertson [2] by identifying spherical cells, most likely a morphological stage of the toxin-producing dinoflagellate Karenia brevis, as a source of brevetoxins in Mobile Bay, Gulf of Mexico, USA, suggesting that monitoring programs relying only on microscopy are not sufficient to properly evaluate the risk and that data on toxin occurrence is needed. Similarly, Loeffler et al [3] highlighted the importance of determining the toxin content, in this case regarding ciguatoxins, and not relying only on species identification, in this case fish species that are commonly recognized as toxin vectors. In their work, Loeffler and colleagues [3] revealed the presence of C-CTX-1 in a hybrid between a local commercially prized species Ocyurus chrysurus (male) and a regionally prohibited species Lutjanus apodus (female), collected from nearshore US Virgin Islands waters.…”

“…Similarly, Loeffler et al [3] highlighted the importance of determining the toxin content, in this case regarding ciguatoxins, and not relying only on species identification, in this case fish species that are commonly recognized as toxin vectors. In their work, Loeffler and colleagues [3] revealed the presence of C-CTX-1 in a hybrid between a local commercially prized species Ocyurus chrysurus (male) and a regionally prohibited species Lutjanus apodus (female), collected from nearshore US Virgin Islands waters. Finally, Rodrigues et al [4] reported the first study investigating the presence of tetrodotoxin (TTX) and TTX analogues in bivalve mollusks from the Portuguese coast.…”