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Campostoma anomalum, Clinostomus elongatus, Notropis photogenis, and Fundulus notatus in Canada are confined to a few streams in southern Ontario and are considered rare or threatened in this country. The distribution of C. anomalum shows dramatic expansion in the Thames River drainage over the past decade. Clinostomus elongatus has a disjunct distribution and has apparently been extirpated from several watersheds owing to habitat degradation. Information on the stability of N. photogenis and F. notatus populations is lacking. Both C. anomalum and N. photogenis are rheophilic and occur in relatively high gradient streams. Clinostomus elongatus occurs mainly in cool, clear headwaters. Fundulus notatus is confined to turbid and sluggish or stagnant streams. Factors affecting the vulnerability of these species, based on habitat requirements, are described and measures to conserve their habitats are suggested. Observations on growth, reproduction, feeding, predation, and parasitism are also described.

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The fingernail clams Sphaerium occidentale and Musculium securis often inhabit the same temporary pond. Sphaerium occidentale occurs only in temporary aquatic habitats and M. securis in both temporary and permanent aquatic habitats. Both burrow into the sediment and aestivate when the habitat dries in summer. While aestivating, S. occidentale is more resistant to drying than M. securis, although both species require relative humidities near 100% to survive prolonged atmospheric exposure. A soil moisture level of at least 15% by weight is required by both species to resist desiccation during aestivation in the laboratory. In the dry pond, microhabitats characterised by moist, organic soils support the highest survival rates for both species. To survive aestivation, resistance to desiccation is developed by all length classes of S. occidentale. Only newborn M. securis are able to aestivate.

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