Ichthyotoxism by a paralytic toxin produced by marine dinoflagellates of the genus Ceratium: relationship to fraction beta isolated from the sponge Tedania ignis.

Two hundred tons of the plankton feeding sardine Cetengraulis edentulus died in March 1982, in Carenero (10 degrees 10' N, 66 degrees 05' W), Venezuela. A fraction was extracted from this fish that was toxic to mice by i.p. injection. The animals died in less than 4 min and showed generalized flaccid paralysis. Gel filtration on Sephadex G15 and Bio Gel P2 showed that the toxicity is related to a fraction that blocks the release of acetylcholine in frog (Rana pipiens) neuromuscular junctions. This toxin is similar in chemical properties and presynaptic effect to fraction beta isolated from the sponge T. ignis by Sevcik and Barboza. Fractions of the same biological action and chemical properties were isolated from plankton samples collected in the area of the ichthyotoxism. The correlation analysis between the presence of toxin and a plankton species in a sample, was carried out with a feasibility index (as %) defined by Sevcik and Mijares. Random samples of plankton (29) were collected in 3 locations (11 degrees 50' N, 68 degrees 15' W; 10 degrees 36' 24'' N, 67 degrees 14'7'' W and 10 degrees 21' N, 64 degrees 21' W). The correlation carried out over 167 species of phytoplankton present in the samples indicates that the species most likely to be responsible for the production of the fraction beta, in order of feasibility index (in parentheses) are: Ceratium furca (54%), Protoperidinium sp. (1.7%) and Protoperidinium pallidum (1.6%). In some samples a fraction similar to fraction alpha from T. ignis was also found. The identification of the phytoplankton responsible for this fraction is, however, less conclusive. The feasibility indexes are: Protoperidinium sp. (58%), Ceratium inflatum (30%), Podolampas sp. (23%), Ornithocercus steini (21%). The genus Ceratium was the second most abundant in Carenero at the time of the fish death. These results suggest that the toxins isolated from C. edentulus and T. ignis have a planktonic origin.