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(P636) Variation in the toxicity of cadmium between two related crayfish species.
Wigginton, Andrew*,1, Brammell, Ben1, Shaw, Joseph2, Birge, Wesley1, 1 University of Kentucky, Lexington, KY, USA2 Dartmouth College, Hanover, NH, USA
ABSTRACT- Crayfish species are potentially useful organisms for studying the effects of heavy metal pollution in invertebrates. They are omnivorous and thus are open to toxicant exposure from a variety of sources including the water column, adsorbed onto food stuff, or bioaccumulated in prey. Crayfish can serve as an excellent model species to increase the knowledge-base for invertebrate ecotoxicology. To that end, a series of toxicity tests have been conducted on two related species of crayfish, Orconectes rusticus and Orconectes placidus. In tests with juveniles of both species, the 48 hour LC50 was 2.3 times greater in O. placidus than O. rusticus (0.127 mg Cd/L versus 0.56 mg Cd/L, respectively). The 48 hour LC10 values were 0.014 mg Cd/L and 0.007 mg Cd/L for O. placidus and O. rusticus, respectively. Additional work has been done with O. rusticus. Two acute toxicity tests with adults have been conducted, yielding LC10: 0.037 mg Cd/L; LC50: 0.197 mg Cd/L (120 h) in the first test and LC10: 0.623 mg Cd/L; LC50: 2.442 mg Cd/L (96 h) for the second. The difference in the toxicity of these two test may be attributed to the difference in size and molt activity between the two tests. The individuals in the first test molted with much greater frequency (at least 21 molts) than in the second test (total of one molt), and the individuals in the second test were several times the size of those in the first test. In the first test, 21 of the 73 total mortalities (28.8%) occurred in concert with molting. There were no mortalities associated with molting in the second experiment. Both juvenile toxicity tests demonstrated a similar pattern, though less striking, to the first adult test. In the juvenile O. rusticus test, 15 of 112 total mortalities (13.4%) were associated with molting, while in the juvenile O. placidus test 11 of 82 total mortalities (13.4%) were associated with molting. This indicates that molting may be a time of increased vulnerability to cadmium toxicity.
Key words: crayfish, cadmium, body burden, molting
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