Can ingested cyanobacteria be harmful to the signal crayfish (Pacifastacus leniusculus)?

Abstract

1. A sample of adult signal crayfish were taken from a pond with a hepatotoxic bloom of the benthic cyanobacterium Oscillatoria sancta. Cyanobacteria were found in the stomachs of thirty-one out of thirty-two crayfish examined. 2. To examine the effect of hepatotoxic cyanobacteria on crayfish a 14-day feeding trial was carried out with thirty-six animals. There were three treatments: (i) hepatotoxic and (ii) non-toxic Planktothrix agardhii; and (iii) crayfish pellets as a control. 3. High-performance liquid chromatography (HPLC) showed that microcystins (the toxins of P. agardhii) had accumulated in the hepatopancreas of 50% of the animals in the toxic treatment. 4. The cyanobacteria did not appear to have any negative impact on the crayfish. All crayfish survived, remained motile and ate throughout the experiment. 5. During the experiment blood samples were taken and the total number of haemocytes counted. At the end of the experiment glucose concentration and relative wet weight of the hepatopancreas were measured. No differences between crayfish fed on toxic and non-toxic P. agardhii and the controls were found. 6. The fact that microcystin accumulates in the crayfish hepatopancreas indicates that the toxin may be transferred further up the food chain.