Cyanobacterial anabaenopeptin-B, microcystins and their mixture cause toxic effects on the behavior of the freshwater crustacean Daphnia magna (Cladocera)

Comparison of the toxic effects caused by the pure cyanobacterial cyclic hexapeptide anabaenopeptin-B (AN-B), the heptapeptides: microcystin-LR (MC-LR) and MC-LF as well as a binary mixture of AN-B with MC-LR on the swimming speed and hopping frequency - essential activities of Daphnia, was experimentally determined. Till now, no information on behavioral effects of AN-B and its mixture with microcystins, commonly produced by cyanobacteria, was available. Also MC-LF effect on aquatic crustaceans was determined for the first time. The results showed that AN-B exerted considerable inhibition of D. magna swimming speed and hopping frequency similar to MC-LR and MC-LF. The mixture of AN-B and MC-LR caused stronger toxic effects, than the individual oligopeptides used at the same concentration. The much lower 48 h- EC50 value of the AN-B and MC-LR mixture (0.95 +/- 0.12 mu g/mL) than those of individual oligopeptides AN-B (6.3 +/- 0.63 mu g/mL), MC-LR (4.0 +/- 0.27 mu g/mL), MC-LF (3.9 +/- 0.20 mu g/mL) that caused swimming speed inhibition explains the commonly observed stronger toxicity of complex crude cyanobacterial extracts to daphnids than individual microcystins. The obtained results indicated that AN-B, microcystins and their mixture exerted time- and concentration-dependent motility disturbances of crustaceans and they can be good candidates for evaluation of toxicity in early warning systems. Other cyanobacterial oligopeptides beyond microcystins should be considered as a real threat for aquatic organisms.

Automated summary

The study showed that AN-B exhibited significant toxicity towards Daphnia, similar to MC-LR and MC-LF. The mixture of AN-B and MC-LR was found to be more toxic than individual oligopeptides. This suggests that cyanobacterial extracts containing a combination of AN-B and microcystins may pose a greater threat to aquatic organisms than individual microcystins.