TABLE 8 Crayfish Mortality After 2 Weeks at 150%, 140%, 120%, and 100% Total 

 Gas Saturation at 12 C, and Observed Signs of Gas Bubble Disease 1 (Test 7) 



late instar nymphs of each species, were placed in 

 each test chamber. All stoneflies appeared well 

 adjusted to the test system. Bubbles were seen 

 adhering to stoneflies during the first few hours 

 after supersaturated water was introduced into the 

 aquaria. Three hours after the test began two 

 Acroneuria were floating and covered with bubbles; 

 the other animals also had bubbles adhering to their 

 bodies. They were checked every 4 hr during the 

 next 2 days and were apparently unaffected. How- 

 ever, Acroneuria had a few bubbles clinging exter- 

 nally. One Acroneuria successfully molted after 

 24 hr at 125% and appeared normal. Most Acro- 

 neuria had some bubbles clinging to them, and they 

 would periodically rise to the surface when they lost 

 hold of the substrate, but would manage to get back 

 to the bottom as many bubbles would burst when 

 they struck the water surface. Pteronarcys had few 

 bubbles on the external body wall, but did have 

 many small bubbles adhering to the ventral tracheal 

 gill masses (Fig. 13); however, bubbles did not 

 appear to greatly affect behavior or movements. 



FIG. 13 Ventral view of stonefly with bubbles on the gills. 



62 Nebeker, Stevens, Brett 



