Effects of cyanobacterial toxins and aqueous crude extracts of cyanobacteria on the development of fish and amphibians

The effects of cyanobacterial hepatotoxins microcystin-LR, -RR, and -YR, of the neurotoxins saxitoxin and anatoxin-a, and of crude aqueous extracts of cyanobacteria were determined on the embryos of fish and amphibians from c leavage up to advanced stages of embryonic development, No acute toxic effe cts were observed after exposure to microcystins at 0.5, 5, and 50 mu g/L, but the timing of hatching was altered in rainbow trout: earlier hatching o ccurred with 0.5, 5, and 50 mu g/L microcystin-RR, 5 and 50 mu g/L microcys tin-YR, and 50 mu g/L microcystin-LR; a minor delay in hatching was observe d at 0.5 and 5 mu g/L microcystin-LR. In axolotl, a delay in feeding was ob served (microcystin-LR at 5 and 50 mu g/L; microcystin-YR at 50 mu g/L). Af ter termination of exposure and rearing in toxin-free tanks, survival rate and growth were adversely affected in zebrafish larvae preexposed to microc ystin-LR at 5 and 50 mu g/L, At the highest applied concentration of microc ystin-LR (10 mg/L), morphological effects were detected. Saxitoxin at 10 mu g/L and above delayed hatching in zebrafish and led to malformations and m ortalities at 500 mu g/L. Hatching was also delayed in axolotl at 500 mu g/ L saxitoxin. Anatoxin-a (400 mu g/L) altered the heart rate in zebrafish, b ut no chronic effects were observed. Far more pronounced effects, compared to those obtained with pure toxins, were observed following exposure to var ious aqueous crude extracts of cyanobacteria from field samples and batch c ultures: similar malformations combined with high mortalities and adverse e ffects on outer egg structures were observed concomitantly in all species. HPLC data showed that these effects cannot be attributed to microcystin con tent alone, (C) 1999 by John Wiley & Sons, Inc.