Effects of cyanobacterial biomass and purified microcystins on malformations in Xenopus laevis: teratogenesis assay (FETAX).
Xenopus laevis (African clawed frog) embryos in a 96-h teratogenesis assay (FETAX) were exposed to 0-250 microg/L and 500 microg/L of purified microcystin-LR (MCYST-LR) for the estimation of lethality, as well as to equivalent concentrations of biomass containing MCYST-LR (natural water bloom dominated by Microcystis aeruginosa) and biomass without MCYST-LR (bloom dominated by Microcystis wesenbergii). The highest tested concentrations of purified MCYST-LR caused up to 30% lethality after a 96-h exposure, corresponding to a LC(25) of 380 microg/L. Cyanobacterial biomass containing MCYST-LR caused significant lethality up to 50% at the highest tested concentrations (300 mg/L, i.e., 250 microg/L of MCYST-LR). The estimated 96-h LC(25) values varied from 125 mg/L (biomass containing MCYST-LR) up to 232 mg/L (biomass without MCYST-LR). A statistically significant increase in the number of malformed embryos was observed after exposure to cyanobacterial samples. Purified MCYST-LR at and above 25 microg/L significantly increased the number of malformations, with 53% of surviving embryos malformed in the highest tested concentration, 250 microg/L (EC(25) = 27 microg/L). Exposure to the highest concentration of MCYST-LR containing biomass resulted in more than 60% of the embryos being malformed and an EC(25) of 52 mg/L (i.e., 43 microg of MCYST-LR/L). Cyanobacterial biomass with no natural microcystin also induced substantial malformations-about 50% aberrant embryos at the highest concentration, 300 mg/L (EC(25) = 75 mg/L). External additions of purified MCYST-LR to the biomass that was originally without microcystins resulted in a slight additional increase in the rate of malformations (80% at the highest concentration, 300 mg of biomass plus 250 microg of MCYST-LR per liter). A comparison of lethality and effects on malformations (teratogenic index, TI = LC(25)/EC(25)) showed that all samples had significant teratogenic potential in the FETAX assay (TI(MCYST-LR) = 14; TI for biomass with and without microcystin ranged between 2.4 and 3.1, respectively). We conclude that cyanobacterial water blooms can significantly alter the normal development of amphibian embryos.
Dvoráková
Dagmar
D
University of Veterinary and Pharmaceutical Sciences, Palackého 1-3, CZ 612 42 Brno, Czech Republic.
Dvoráková
Katerina
K
Bláha
Ludek
L
Marsálek
Blahoslav
B
Knotková
Zora
Z
D000818:Animals; D001427:Bacterial Toxins / Q000009:adverse effects; D018533:Biomass; D000013:Congenital Abnormalities / Q000209:etiology* / Q000662:veterinary*; D000458:Cyanobacteria; D004305:Dose-Response Relationship, Drug; D047108:Embryonic Development; D005068:Eutrophication; D007928:Lethal Dose 50; D008387:Marine Toxins / Q000009:adverse effects; D052998:Microcystins; D010456:Peptides, Cyclic / Q000633:toxicity*; D013723:Teratogens / Q000633:toxicity; D014982:Xenopus laevis / Q000196:embryology
D001427:Bacterial Toxins; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic; D013723:Teratogens; C057862:cyanoginosin LR