Project number: 1986-010
Project Status:
Completed
Budget expenditure: $22,600.00
Principal Investigator: Richard Lewis
Organisation: Department of Agriculture and Fisheries EcoScience Precinct
Project start/end date: 28 Jun 1990 - 30 Dec 1990
Contact:
FRDC

Objectives

1. Define factors influencing ciguatoxin production by cultures of Gambierdiscus toxicus.
2. Examine reef disturbance effects & significance of genetic heterogeneity in G. toxicus in toxin production.
3. Establish requirements for growth & bloom formation by G. toxicus & other dinoflagellates

Final report

Author: Michael J. Holmes Richard Lewis Noel C. Gillespie
Final Report • 2011-08-01 • 3.92 MB
1986-010-DLD.pdf

Summary

This project confirmed that the benthic dinoflagellate Gambierdiscus toxicus is an origin of putative ciguatoxin precursors called gambiertoxins. It was recently found in French Polynesia that gambiertoxins could be extracted from biodetritus containing wild G. toxicus and that gambiertoxins were structural analogs of ciguatoxin. Ciguatoxin is the toxin found in the flesh of ciguateric fishes. It is demonstrated - for the first time- production of gambiertoxins in strains of G. toxicus grown in culture.

The production of gambiertoxins appears to be limited to certain genetic strains of G. toxicus, with the majority of strains not producing these toxins. It is proposed that ciguatera occurs when blooms of G. toxicus strains genetically capable of producing ciguatoxin precursors (gambiertoxins) enter the marine food chain. The type of maitotoxin produced by G. toxicus was also shown to be a stable characteristic within culture strains, but variable between strains.

Disturbance to coral reef environments has been suggested as a factor in promotion of ciguatera outbreaks. However, the researchers have been unable to find direct evidence to support this hypothesis. Translocation of ciguateric strains of G. toxicus (gambiertoxin producers) may explain the sudden appearance of ciguatera in areas previously free of the disease. The ability of living G. toxicus cells to be transported, either in ship ballast water or epiphytically upon the hulls of ships, had yet to be demonstrated. G. toxicus can survive rafting upon drift algae. Translocation by ships may be a mechanism for introduction of the causative organism to sites where reef damage occurs (eg. harbour works, anchorages and shipwrecks).

G. toxicus is a common component of reef benthos in Queensland. The researchers show that G. toxicus populations in Queensland generally do not produce ciguatoxin or ciguatoxin precursors. In addition, it is demonstrated that maitotoxin or non-toxic precursors in wild G. toxicus populations are not bioconverted to ciguatoxin in fishes. The majority of G. toxicus populations in Queensland are therefore probably not involved in ciguatera.

Platypus Bay is a major source of ciguateric fishes in Queensland. G. toxicus populations which produce gambiertoxins have been found in Platypus Bay biodetritus. A monoclonal strain of G. toxicus which produces gambiertoxins in laboratory culture was also isolated from Platypus Bay. This indicated that Platypus Bay wass probably the source of toxin in ciguateric fishes caught in Platypus Bay. However, gambiertoxins were not detected in the majority of biodetrital samples collected from Platypus Bay. Gambiertoxins therefore appear to be only infrequently pulsed into Platypus Bay.

Benthic dinoflagellates other than G. toxicus are suggested as potentially capable of producing toxins associated with ciguatera. Ciguatoxin or gambiertoxins were not produced by cultures of the benthic dinoflagellates Ostreopsis siamensis and Goolia monotis isolated from Queensland. These species produced water soluble and lipid soluble toxins, respectively. However, there is no evidence for the bioaccumulation of these toxins in the flesh of fishes.

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