Morphologic characterization of the ice worm Mesenchytraeus solifugus

Ice worms occupy a unique position in metazoan phylogeny in that they are t he only known annelid that completes its life cycle in ice. The mechanism(s ) associated with this adaptation are likely to occur at different levels, ranging from modification of their metabolism to changes in morphology. In this study, we examined specimens of Mesenchytraeus solifugus by scanning e lectron microscopy (SEM) and transmission electron microscopy (TEM) in an e ffort to identify morphologic structures that may aid in its glacial habita tion We report that M. solifugus contains an elongated head pore at the tip of its prostomium, numerous sensory structures, and differentially oriente d setae that curve abruptly at their distal end. (C) 2000 Wiley-Liss, Inc.