Sufficient pure ciguatoxin (0.5 mg of CTX-1) has been isolated from moray eel viscera to allow the immunisation of mice and screening of antibodies to ciguatoxin. It is determined that in vivo immunisation techniques were most likely to yield antibodies using related toxins as models of ciguatoxin. The model toxins used included brevetoxin, okadaic acid and tetrodotoxin. Using the same approach it was determined that the in vitro immunisation techniques investigated were inappropriate. It appears essential that ciguatoxin be conjugated to a carrier protein to allow production and screening of antibodies to ciguatoxin. The use of unconjugated toxin, either for immunisation or screening, appears inappropriate. The conjugation of ciguatoxin to a carrier protein has not been achieved despite considerable effort. Consequently, it was not possible to achieve the overall goal of the project. Until it is confirmed that ciguatoxin possesses the functional groups that allow the toxin to be conjugated to a carrier protein, work towards the development of antibodies to ciguatoxin cannot proceed.

During this project 595 potentially toxic fish samples were tested for toxin content. This included numerous samples of moray eel viscera and numerous portions of fish involved in ciguatera in Australia.

During this project two new ciguatoxins (CTX-2, 0.3 mg; CTX-3, 0. 1 mg) were also isolated from moray eel viscera. These toxins were determined to be less oxidised forms of ciguatoxin. Analysis of moray eel toxicity indicated that these fish may excrete ciguatoxin over time.

Using mouse bioassay, the efficiency of extraction of ciguatoxin was determined to be > 50% in fish flesh spiked with ciguatoxin. Mouse assay is not suitable to detect low toxicity fish flesh samples but is useful as a confirmatory assay for fish with a toxicity high enough to demonstrate moderate to severe clinical effects.

Future studies are required to resolve questions on the chemistry of ciguatoxin. These studies are presently underway. With this information the project can proceed to the production of antibodies to ciguatoxin using the procedures and protocols developed during this project.

Seagrasses are of immense ecological importance in marine ecosystems. Primary production rates for seagrass beds are amongst the highest recorded for marine and terrestrial systems. They have a well documented role as animal habitat, nursery grounds, and as substrate stabilizers.

The proximity of population centres to many of the seagrass­ colonised estuaries and embayments of the Australian coast has catalyzed research of the effects of pollution and erosion on these marine angiosperms. Although the importance of seagrass habitat and the potential for its loss has been recognized in these studies, ecological research remains surprisingly sparse. This is particularly so in the northern regions of Australia.

In northern Queensland, seagrass-vegetated areas are important as habitats for the juveniles of commercial penaeid prawn species. The tiger prawns, Penaeus esculentus and P. semisulcatus, and the endeavour prawn, Metapenaeus endeavouri, form the major component of an otter trawl fishery for prawns in this region worth around $60 million annually.