Freshwater Sponges (Porifera: Spongillidae) Of Western Montana: Distribution And Ecology
Thirty-seven freshwater sponge populations were found in 25 lakes in Western Montana. Three species were identified: Eunapiusfragilis (E.f.), Spongilla lacustris (SI), and Ephydatia muelleri (E.m.). In an effort to describe factors correlating with sponge distribution, limnological data were obtained from 16 ofthe lakes which contained sponges and an additional 9 lakes where no sponges were found. New limits oftolerance with respect to hardness (E.m.,E.f), magnesium (E.m., S.I.), silica (E.m., S.I.), calcium (E.m ), and conductivity (E.m.) were established . Reasons for the lack offindings in regard to differences between species habitats are discussed and attributed to the similar habitat requirements for the three species found in Western Montana. These species are essentially cosmopolitan and are commonly found in association with one another. Spicule measurements greatly expanded previously recorded size ranges. This great size variation plus spicule malformation are discussed as points which lead to the difficulty of using spicule morphology as the major indicator for species identification. The need to look more closely at factors such as food preference and interspecific competition is discussed as a means for more specifically defining a species' ecological niche, especially in species which commonly associate with one another.