Moving from an aquatic environment to the land generates a list of biological problems with the intake of oxygen.  Anaerobic respiration, such as that occurring in water, provides 19 times less energy for the organism than that of aerobic respiration through air.  In optimal water conditions the diffused oxygen in water is around 15 ppm, compared to air which has around 200,000 ppm of oxygen.  Paragnetina media has some clever ways of solving this problem.  As with almost all insects water diffusion through the impermeable cuticle is very slow and almost nonexistent, but the nymph has a small body size optimizing its ability to intake oxygen.  The most important feature on the nymph is the gills located around the anus of the nymph.  The gills greatly increase the surface area for gas exchange making living under water possible for these insects.  In warmer, or slow moving waters where the dissolved oxygen is not as prevalent the nymphs will actually do a series of push-ups creating their own water flow and maximizing the intake of oxygen.   

Any angler will know the very prominent role that both the nymphs and the adults play in the ecology of a trout stream.  The number, or for that matter the presence of stone flies, in the streams is a great indicator for good water quality as they are intolerant to pollution.  The nymphs are also one of the trout's favorite meals and bait shops spend hundrededs of dollars trying to duplicate the appearance of a Paragnetina media nymph so that someone may catch their meal.  (Borror, D.J. and DeLong, D.M. and Triplehorn, C.A. 1976)

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