ABSTRACT
Freshwater bryozoans (Class Phylactolaemata) constitute a well-defined group of sessile invertebrates. With about 80 described species inhabiting a wide range of freshwater habitats, they are among the most common metazoans living on submerged substrates. Like their marine counterparts, phylactolaemates are exclusively modular in structure, composed of many identical zooids all freely sharing a common coelom (Wood 2001). The group displays an impressive diversity of colony morphology, ranging from diffuse branching tubules to compact, globular masses. Freshwater bryozoans often cause serious fouling of irrigation pipes and water cooling systems (Wood & Marsh 1998, Smith et al. this volume). Several species are implicated as final hosts to a serious myxozoan parasite of salmonid fish (Canning et al. 1999).
