Moray eel

Several species of the moray eel (Gymnothorax) have caused toxic reactions, especially ki Japan. The toxic principle appears to be protekiaceous and is found predominately ki the blood but it may occur ki the flesh as well. Its exact stmcture remains somewhat uncertain. 

Ciguatoxin. The toxin was isolated from moray eels and purified to crystals by Scheuer s group (1). Structural determination of the toxin by x-ray or NMR analyses was unsuccessful due to the unsuitability of the crystals and due to the extremely small amount of the sample. The toxin was presumed to have a molecular formula of C Hg NO from HRFAB-MS data (MH+, 1111.5570) and to have six hydroxyls, five methyls, and five double bonds in the molecule (2). The number of unsaturations (18 including the five double bonds) and the abundance of oxygen atoms in the molecule point to a polyether nature of the toxin. The toxin, or a closely related toxin if not identical, is believed to be the principal toxin in ciguatera. Ciguatoxin was separable on an alumina column into two interconvertible entities presumably differing only in polarity (J). 

Murata, M., et ah. Structures and configurations of ciguatoxin from the moray eel Gymnothroax javanicus and its likely precursor from the dinollagellate Gambierdiscus toxicus, J. Am. Chem. Soc., 112, 4380, 1990. 

Moray eels (Muraenidae) of tropical reefs possess a water-soluble poison. Poisoning occurs from eating the flesh. 

Nakajlma and coworkers (20) reported an ether soluble extract from concavum to be slightly toxic to mice but provided little additional information. Crude fractions containing ciguatoxin obtained from moray eel (Gymnothorax javanicus) and toxlcus from the Pacific were reported to have LD q s of 12.2 mg/kg and 28.1 mg/kg, respectively (37). These compare well with the LD q of 8.3 mg/kg for similarly purified ESAF from concavum. 

Finally, it is clearly evident that no one dinoflagellate species should be singled out as the major ciguatera causative organism nor should it be assumed that a single toxin is the major cause of ciguatera in the Caribbean. This is especially important in view of the fact that no species has been shown conclusively to produce ciguatoxin as described from moray eel by Scheuer and coworkers (6) and Tachibana (37). 

Extraction of cultured G. toxicus. To prepare the harvested dinoflagellate cells (about 1 x 10 cells) for shipment from Hawaii to South Carolina, absolute methanol was added to effect a final concentration of approximately 25 (v/v). Upon receipt of the culture, additional methanol was added to attain a final concentration of 80% (v/v). After extraction at room temperature for J days, the suspension was clarified by centrifugation. The supernatant was dried and the resultant solids were weighed and resuspended in absolute methanol. The suspension was filtered and the filtrate designated as the crude dinoflagellate extract used in this study. Subsequent fractionation of this extract by HPLC (Higerd et al., manuscript in preparation) showed that the material responsible for toxicity eluted in a fraction well removed from the fraction that exhibited toxicity when extracts of either Pacific moray eel or Caribbean fish were chromatographed. In all cases, the body temperature depression effect was evident only in those fractions which also exhibited toxicity. 

Source of Extracted Fish Toxin. Two different extracts of ciguatoxic fish were used in this study. Partially purified ciguatoxin was derived from the liver and viscera of the Pacific moray eel (Gymnothorax Javanicus) and was a side fraction of the... 

Figure 1. Dose-response curve of the lethality of the three different extracts used in this study. The extracts were administered to mice i.p. in PBS with 57o Tween-80. Lethality was assessed at 48 h. for animals maintaine d at 24 C. Extracts were Gambierdiscus toxicus, fish of Caribbean origin, and partially purified moray eel ciguatoxin.

B From Coska Maya, arrange a trip to snorkel the largest coral reef in Mexican waters. Banco Chinchorro lies off the coast of the southern Yucatan and is home to rare black coral, sea turtles and moray eels. 

Ciguatoxin (exotic fish, Moray eel) and batrachotoxin (South American frogs) bind in the Na+ channel, keeping it open to cause a persistent depolarization and channel inactivation. 

From ciguateric Moray eels. Acts like batra-chotoxin qv. Ciguatera is also the term applied to the syndrome (headache, paraesthesiae, lassitude, haematuria, pruritis, cardiac dysrhythmias, vomiting, diarrhoea) caused sporadically by the consumption of a range of reef-dwelling fish. In both types, the source of the poison may be the blue-green algae or other components of the diet but detailed descriptions of the chemical identity of the poison(s) are not available. 

Moray eels Gymnothorax javanicus) have also been reported to be occasionally toxic. The symptoms resemble ciguatera but additionally often include excessive salivation. As moray eel toxicity seems most common in eels caught on coral reefs when other fish are ciguatoxic, it seems most likely that moray eel poisoning is actually ciguatoxin accumulated by this formidable predator. 

Lewis, R.J., M. Sellin, M.A. Poli, R.S. Norton, J.K. MacLeod, and M.M. Sheil (1991). Purification and characterization of ciguatoxins from moray eel (Lycodontis javanicus, Muraenidae). Toxicon 29, 1115-1127. 

Ciguatoxin (CTX, 18) was first isolated in 1980 and its structure was finally elucidated in 1989 [ 18,19]. For that study, 4000 kg of moray eels (Gymnothrax javanicus) were collected in French Polynesian water and 124 kg of viscera were extracted to obtain 0.35 mg of pure CTX. The G. toxicus collected in the Gambier Islands yielded 0.75 mg of a precursor toxin that was coded... 

Crayfish nerve cord (CNC) has been used successfully as an assay for the extracts of the dinoflagellate Prorocentrum concavum (Miller et al. 1986). Three of the P. concavum extracts reduced the activity of the CNC. Purified CTX from moray eel induce spontaneous action potentials upon the node of Ranvier of frog isolated nerve fibers under current and voltage clamp conditions. This spontaneous activity Is reversible upon removal of the toxin from the external solution (Benoit et al. 1986). The postulated reason for this activity will be explained in the pharmacology section of this chapter. 

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