title: A rapid bioassay for detecting saxitoxins using a Daphnia acute toxicity test.
abstract: Bioassays using Daphnia pulex and Moina micrura were designed to detect cyanobacterial neurotoxins in raw water samples. Phytoplankton and cyanotoxins from seston were analyzed during 15 months in a eutrophic reservoir. Effective time to immobilize 50% of the exposed individuals (ET50) was adopted as the endpoint. Paralysis of swimming movements was observed between approximately 0.5-3 h of exposure to lake water containing toxic cyanobacteria, followed by an almost complete recovery of the swimming activity within 24 h after being placed in control water. The same effects were observed in bioassays with a saxitoxin-producer strain of Cylindrospermopsis raciborskii isolated from the reservoir. Regression analysis showed significant relationships between ET50 vs. cell density, biomass and saxitoxins content, suggesting that the paralysis of Daphnia in lake water samples was caused by saxitoxins found in C. raciborskii. Daphnia bioassay was found to be a sensitive method for detecting fast-acting neurotoxins in natural samples, with important advantages over mouse bioassays.
authors.affiliation: Laboratório de Avaliação e Promoção da Saúde Ambiental, Departamento de Biologia, Instituto Oswaldo Cruz, FIOCRUZ, Av. Brasil 4365, Manguinhos, Rio de Janeiro, RJ 21045-900, Brazil. aloysio@ioc.fiocruz.br
authors.forename: Aloysio da S
authors.initials: Ada S
authors.lastname: Ferrão-Filho
authors.forename: Maria Carolina S
authors.initials: MC
authors.lastname: Soares
authors.forename: Valéria Freitas
authors.initials: VF
authors.lastname: de Magalhães
authors.forename: Sandra M F O
authors.initials: SM
authors.lastname: Azevedo
mesh_terms: D000818:Animals; D001681:Biological Assay; D018533:Biomass; D000458:Cyanobacteria / Q000737:chemistry / Q000254:growth & development; D003621:Daphnia / Q000187:drug effects* / Q000502:physiology; D005618:Fresh Water / Q000032:analysis / Q000382:microbiology; D012044:Regression Analysis; D015203:Reproducibility of Results; D012530:Saxitoxin / Q000032:analysis*; D013550:Swimming / Q000502:physiology; D023382:Toxicity Tests, Acute; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D012530:Saxitoxin