Histopathology and microcystin distribution in Lymnaea stagnalis (Gastropoda) following toxic cyanobacterial or dissolved microcystin-LR exposure.
The accumulation of hepatotoxic microcystins (MCs) in gastropods has been demonstrated to be higher following grazing of toxic cyanobacteria than from MCs dissolved in ambient water. Previous studies, however, did not adequately consider MCs covalently bound to protein phosphatases, which may represent a considerably part of the MC body burden. Thus, using an immunohistochemical method, we examined and compared the histopathology and organ distribution of covalently bound MCs in Lymnaea stagnalis following a 5-week exposure to (i) dmMC-LR, dmMC-RR, and MC-YR-producing Planktothrix agardhii (5 microg MC-LReqL(-1)) and (ii) dissolved MC-LR (33 and 100 microgL(-1)). A subsequent 3-week depuration investigated potential MC elimination and tissue regeneration. Following both exposures, bound MCs were primarily observed in the digestive gland and tract of L. stagnalis. Snails exposed to toxic cyanobacteria showed severe and widespread necrotic changes in the digestive gland co-occurring with a pronounced cytoplasmic presence of MCs in digestive cells and in the lumen of digestive lobules. Snails exposed to dissolved MC-LR showed moderate and negligible pathological changes of the digestive gland co-occurring with a restrained presence of MCs in the apical membrane of digestive cells and in the lumen of digestive lobules. These results confirm lower uptake of dissolved MC-LR and correspondingly lower cytotoxicity in the digestive gland of L. stagnalis. In contrast, after ingestion of MC-containing cyanobacterial filaments, the most likely longer residual time within the digestive gland and/or the MC variant involved (e.g., MC-YR) allowed for increased MC uptake, consequently a higher MC burden in situ and thus a more pronounced ensuing pathology. While no pathological changes were observed in kidney, foot and the genital gland, MCs were detected in spermatozoids and oocytes of all exposed snails, most likely involving a hemolymph transport from the digestive system to the genital gland. The latter results indicate the potential for adverse impact of MCs on gastropod health and reproduction as well as the possible transfer of MCs to higher trophic levels of the food web.
Lance
Emilie
E
UMR CNRS 6553 ECOBIO, Université de Rennes 1, 263 Avenue du Général Leclerc, CS 74205, 35042 Rennes, France. Electronic address: emilie.lance@live.fr.
Josso
Celine
C
UMR INRA Bio3P, Université de Rennes 1, 263 Avenue du Général Leclerc, CS 74205, 35042 Rennes Cedex, France.
Dietrich
Daniel
D
Human & Environmental Toxicology Group, University of Konstanz, D-78457 Konstanz, Germany.
Ernst
Bernhard
B
Human & Environmental Toxicology Group, University of Konstanz, D-78457 Konstanz, Germany.
Paty
Chrystelle
C
UMR INRA Bio3P, Université de Rennes 1, 263 Avenue du Général Leclerc, CS 74205, 35042 Rennes Cedex, France.
Senger
Fabrice
F
UMR CNRS 6026, Université de Rennes 1, 263 Avenue du Général Leclerc, CS 74205, 35042 Rennes Cedex, France.
Bormans
Myriam
M
UMR CNRS 6553 ECOBIO, Université de Rennes 1, 263 Avenue du Général Leclerc, CS 74205, 35042 Rennes, France.
Gérard
Claudia
C
UMR CNRS 6553 ECOBIO, Université de Rennes 1, 263 Avenue du Général Leclerc, CS 74205, 35042 Rennes, France.
D000818:Animals; D000458:Cyanobacteria / Q000472:pathogenicity*; D004064:Digestive System / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D004781:Environmental Exposure / Q000009:adverse effects*; D005835:Genitalia / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D007150:Immunohistochemistry; D008195:Lymnaea / Q000187:drug effects* / Q000378:metabolism*; D008387:Marine Toxins; D052998:Microcystins / Q000378:metabolism* / Q000633:toxicity*; D012098:Reproduction / Q000187:drug effects; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity
D008387:Marine Toxins; D052998:Microcystins; D014874:Water Pollutants, Chemical; C057862:cyanoginosin LR