First report of neurotoxic effect of the cyanobacterium Cylindrospermopsis raciborskii on the motility of trematode metacercariae

Abstract

Cylindrospermopsis raciborskii (Woloszynska) is a photosynthetic cyanobacterium that can produce cytotoxic (cylindrospermopsin) and neurotoxic cyanotoxins (saxitoxins). In Brazil the strains of C. raciborskii are reported to produce only saxitoxins (STX) and their effect on fish parasites has not been tested to date. The fish Poecilia vivipara Bloch and Schneider is a common host for the trematode Pygidiopsis macrostomum Travassos off the coast of Rio de Janeiro, and this fish-parasite interaction is a model for behavioural and ecotoxicological studies. The aim of this work was to evaluate the motility of metacercariae of P. macrostomum from P. vivipara exposed to 40 mg l-1 and 400 mg l-1 of crude lyophilized extract of the cyanobacterium C. raciborskii (CYRF-01) for 48 h. The fish were separated into groups of ten individuals and, after exposure, five fish from each group were dissected for counting and checking the motility of metacercariae. The other five fish were dissected after 48 h in clean water. The detection and quantification of STX in the solutions of cyanobacteria, and the gills and guts of fish, were performed by an enzyme-linked immunosorbent assay. The crude extract of C. raciborskii caused temporary paralysis in metacercariae of P. macrostomum after exposure of fish to both concentrations, and the motility recovered after the fish were kept for 48 h in clean water. STX was detected in the guts and gills of all fish analysed, suggesting that this toxin is involved in the paralysis of metacercariae. This is the first report on the action of neurotoxins in metacercariae of fish.

Current Knowledge of Small Flukes (Digenea: Heterophyidae) from South America

“…The fish Poecilia vivipara is a common host of Pygidiopsis macrostomum off the coast of Rio de Janeiro. This fish-trematode interaction was tested as a model for ecotoxicological studies with the cyanobacterium Cylindrospermopsis raciborskii (CYRF-01) [71,72]. Changes in the motility of metacercariae of P. macrostomum occurred after their fish host was exposed to different concentrations of crude lyophilized extract of the cyanobacterium CYRF-01 producer of neurotoxic saxitoxins (STX), resulting in a temporary paralysis [72].…”

“…This fish-trematode interaction was tested as a model for ecotoxicological studies with the cyanobacterium Cylindrospermopsis raciborskii (CYRF-01) [71,72]. Changes in the motility of metacercariae of P. macrostomum occurred after their fish host was exposed to different concentrations of crude lyophilized extract of the cyanobacterium CYRF-01 producer of neurotoxic saxitoxins (STX), resulting in a temporary paralysis [72]. Interestingly, their motility recovered after the fish were kept for 48 hr in clean water, suggesting that blooms of cyanobacteria may interfere with the motility of both the fish host and its parasites.…”