Tissue Distribution and Oral Dose Effects of Microcystin in the Freshwater Pulmonate Snail Lymnaea stagnalis jugularis (Say)

Abstract

Microcystin (MC) concentrations were measured in the alimentary tract, digestive gland, and remaining visceral mass of adult pulmonate snails (Lymnaea stagnalis) exposed to cyanobacteria known to contain MC. The highest proportion of total body MC content was measured within the alimentary tract (83%), though an appreciable proportion (17%) was also found within the digestive gland tissue. This provides conclusive evidence for the limited digestion of toxic cyanobacteria and subsequent uptake and accumulation of MC by the digestive gland of L. stagnalis. Additionally, pure microcystin-LR was orally administered to adult L. stagnalis to investigate the potential for toxic effects. Exposure to microcystin-LR induced histopathological alterations of the digestive glands consistent with those reported elsewhere for mammals and fish, indicating a common mode of toxicity to both vertebrates and invertebrates.

Our thanks to: K. Powell for assistance during field collection of phytoplankton and gastropods for use in the tissue distribution study; M. Keohane for the subsequent preparation of samples for MC analysis; N. Torrieri for her assistance with the oral dose study; and Randy Mandryk of the Histology Laboratory (University of Alberta) for direction and assistance with the histology preparations. We also thank Meanook Biological Research Station for the use of field equipment; Kawtikh Resort (Hastings Lake) for providing its boat launch; B. Rolseth, R. Rudy, and P. Burgess of the Limnology Lab (University of Alberta) for assistance; C. Paszkowski for use of the aquatics laboratory space; and K. Baier and M. Craig for guidance and assistance during the analyses of phytoplankton and gastropod tissues for MC via colorimetric PP1c assay. Special thanks also go to J. Burke for her critical reviews of earlier manuscripts. This study was funded by a Natural Sciences and Engineering Research Council (NSERC) Research (Discovery) Grant to E. E. Prepas.