Sweeney, B.W., D.H. Funk, and L.J. Standley. 1993. Environmental Toxicology and Chemistry 12(1):115–125.
The stream mayfly Cloeon triangulifer is well suited as a bioassay organism because it has a relatively short egg and larval stage and can be readily cultured under laboratory conditions. Moreover, the species is widely distributed and reproduces as parthenogenetic clones. Nineteen distinct clones have been isolated from natural populations with Nei’s genetic distance between clones ranging from 0.004 to 0.183. Clonal reproduction gives research scientists the option of including or excluding genetic variation from the experimental design. The present study involved exposing individuals from a single clone to initial technical chlordane levels ranging between 4.3 and 56.3 μg/L. No effect of chlordane was observed for the egg stage; eggs required 9 d to hatch at 20°C, and >95% of the eggs hatched in all controls and treatments. Egg hatch success was also tested at higher concentrations (89.0 and 158.3 μg/L), with no effect being observed. In contrast, larval survivorship decreased significantly from about 80% for control groups to 18.0 and <0.6% when larvae were exposed to initial chlordane levels of 4.3 μg/L and 9.4 μg/L, respectively. All larvae died when initial concentrations of chlordane were >15.4 μg/L. Sublethal effects on larvae exposed to 4.3 μg/L of chlordane included significantly longer developmental time (37 vs. 34.8 d) and larger adult size (1.5 vs. 1.1 mg) relative to controls. Body burdens of chlordane in adult tissue for individuals reared in the 4.3-μg/L treatment ranged from 51 to 140 ppb. Chlordane-related compounds found in adult mayfly tissue were cis-nonachlor (6%), trans-nonachlor (45%), cis-chlordane (4%), trans-chlordane (5%), oxychlordane (21%), and heptachlor epoxide (18%).