## 1 Introduction
While _Gambierdiscus_ remains the principle genus producing ciguoxins in the Pacific Ocean, with _Gambierdiscus polynesiensis_ confirmed as a ciguatoxin producer [79; 82; 83; 84; 85; 86], other dinoflagellate species of the genus _Fukuyoa_ might also contribute to ciguatera risk in the Atlantic Ocean [81; 87; 88]. These less polar ciguatoxins, originally referred to as gambierotoxins, initiate upstream contamination of the ciguatera food chain [1; 75; 89]. Furthermore, they are primarily transferred and metabolized into more polar ciguatoxins through different trophic levels [1; 77] to generate species-specific profiles of ciguatoxins [23; 42; 43; 90; 91]. In the marine food chain, CTXs are known to undergo bioaccumulation and concentration [16; 51; 58; 59; 64; 92; 93]. While fishes at lower trophic levels, such as herbivorous and dettritivores fishes and invertebrates feeders, generally exhibit lower CTX concentrations, those at higher trophic levels, such as carnivorous fishes, tend to have higher concentrations [58; 68; 94; 95]. This transfer and accumulation process has been quantified in recent studies conducted by [PERSON] et al. [75; 89]. The P-CTXs are well-known and well-studied toxins, both chemically and pharmacologically [20; 96; 97]. However, there is a general lack of knowledge regarding C-CTXs. Isolation and characterisation of P-CTXs were successfully in the 1990s [98; 99; 100]. Caribbean ciguatoxin was first isolated in 1994 from locally caught barracuda (_Sphruena barracuda_) and horse-eye jack (_Caranx latus_) [101; 102]. The structures of C-CTX-1 and its epimer, C-CTX-2 were elucidated using pure C-CTX-1 isolated from the liver, viscera, and flesh of horse-eye jack (_C. latus_), a fish often implicated in ciguatera fish poisoning and collected from Saint-Barthelemy (Lesser Antilles) in the Eastern Caribbean Sea [35; 38]. The multiplicity of C-CTXs analogues was first identified using chromatographic behavior [103] and/or the mouse bioassay (MBA), with fast-acting ciguatoxins (FATs) in addition to classical slower-acting ciguatoxins [104]. However, due to insufficient quantity, FATs have not been definitively characterised [19; 23; 38; 41]. Recently, the likely algal precursor of C-CTX-1/-2 was identified in _Gambierdiscus silvae_ and _Gambierdiscus caribaeus_ strains from the Caribbean [43]. This ketone variant of C-CTX-1/-2 known as C-CTX-5 could be bio-transformed in vitro by fish liver microsomes directly to C-CTX-1/-2, the dominant CTX in cigiatoxic fish from the Caribbean. Importantly, C-CTX-5 from _G. silvae_ was confirmed to have voltage-gated sodium-channel-specific activity [43], indicating its potential contribution to ciguatera. Caribbean ciguatoxins have also been identified in the Eastern Atlantic, including the Canary Islands (Spain) and Madeira (Portugal) [105; 106; 107; 108; 109; 110; 111; 112; 113]. These include CP outbreaks due to the consumption of a 26-kg amberjack (_Seriola rivoliana_) from the Canary Islands in 2004 [105], a 30-kg amberjack (_Seriola_ sp.) caught near the Selvagens Islands (Portugal) in 2008 [107], and many ciguatoxin-positive fish from the Madeira and Selvagens Archipelagos [113]. The influence of climate change are expected to bring ciguatera closer to Europe [6; 114; 115; 116; 117]. Reflecting this increasing risk in ciguatera in Europe, the remainder of this review provides an update on the chemical and biochemical properties of ciguatoxins in the Atlantic Ocean, and the potential of analytical chemistry to mitigate the public health impacts and advance our knowledge of the origin and biotransformation of C-CTXs.