Comparative Ecology and Physiology of the Crayfish, Orconectes propinquus and Cambarus fodiens

Abstract

The crayfish Orconectes propinquus and Cambarus fodiens overlap in their geographical ranges but are ecologically isolated; the former is typically a clear stream form and the latter is characteristic of mud-bottomed, often temporary ponds. Annual comparison of a temporary forest pond and a contiguous small stream in the Chicago area show marked differences in several pertinent physical and chemical factors. It is inferred that the absence of each sp. from the reciprocal habitat is related causally to their environmental differences. This conclusion is largely corroborated by evidences from comparative physiological and behavioral experiments. These latter indicate a greater tolerance by C. fodiens to exposure to air and decreased oxygen concentration, a selectivity for a mud substratum and the ability to burrow in the mud under conditions of summer drying. Q. propinquus was found to be relatively intolerant to desiccation and lowered oxygen tensions and was unable to burrow in mud; it oriented strongly towards a rocky substratum and was highly tolerant of strong water currents. The pond species, C fodiens, appeared the more tolerant of increased temps. Both spp. could be acclimatized to water of greater than natural temps. These differences, when related to the known facts of the life histories, are sufficient to explain at least partly the restriction of these two species to their respective habitats.