Infestation of the North American freshwater mussel Elliptio complanata (Head Lake, Canada) by the euendolithic cyanobacterium Plectonema terebrans Bornet et Flahault
Tribollet, Aline; Veinott, Geoff; Golubic, Stjepko; Dart, Ray
This study reports for the first time, the infestation of shells of the fresh-water mussel Elliptio complanata by the euendolithic cyanobacterium Plectonema (Leptolyngbya) terebrans in North America. The infestation, observed in numerous shells from Head Lake (Canada), occurs around areas of the shell where the periostracum has been softened and/or eroded by other mechanical or biodegradational causes. The tunnels produced by P. terebrans spread from the point of entry predominantly perpendicular to the shell surface, but are consistently deflected at internal conchiolin layers. The cyanobacterium penetrates easily through carbonate mineral layers but shows reduced ability in penetrating organic lamellae. The average maximal depth of penetration of the endolithic filaments is 0.7 ± 0.3 mm, which represents 22 % to 100 % of the shell thickness. The infestation of Elliptio complanata is, therefore, important and inflects damages to the structure of shells despite the presence of conchiolin 'barriers'. We suggest that the occurrence of P. terebrans in freshwater Elliptio complanata shells may be a new invasion in North American freshwater mollusk shells.