Year of Publication

2005

Document Type

Dissertation

College

Arts and Sciences

Department

Biology

First Advisor

Wesley J. Birge

Abstract

A series of acute (96h) toxicity tests were conducted on six species of crayfish inthe family Cambaridae. Toxicity values fell into a sensitive group comprising Orconectesplacidus and Procambarus acutus (LC 50= 0.368mg Cd/L - 0.487mg Cd/L; LC10= 0.048mg Cd/L - 0.092 mg Cd/L) and tolerant group comprising O. juvenilis, O. virilis, P.alleni, and P. clarkii (LC 50= 2.44 mg Cd/L - 3.30 mg Cd/L; LC10= 0.386 mg Cd/L -0.947 mg Cd/L). For juvenile crayfish, the LC50 and LC10 values were as follows: O.juvenilis, 0.060 and 0.014 mg Cd/L; O. placidus, 0.037 and 0.002 mg Cd/L; P. clarkii,0.624 and 0.283 mg Cd/L. Cd exposure decreased molting success highlighting theimportance of this sensitive process. Behavioral responses were assessed in O. placidus,O. virilis, P. acutus, P. alleni, and P. clarkii. The tail-flip predator avoidance behaviorwas significantly reduced by cadmium exposure. In most species tested, the claw raisedefensive behavior was significantly increased by Cd exposure. Between species, as bodymass increased, the tail-flip response frequency decreased, and the claw-raise responseincreased in frequency. P. clarkii was also analyzed for the effect of Cd exposure onheart rate and response to two stimuli. The data indicate that heart rate may be a usefulphysiological marker of Cd toxicity. The major organ systems were dissected fromsurvivors of four adult crayfish toxicity tests (O. juvenilis, O. placidus, P. acutus, P.clarkii) and analyzed for metal content. Cadmium tissue content correlated with Cdexposure. Cadmium accumulated more in the hepatopancreas, gills and green glands ofsensitive species than in tolerant species. Zn showed negative correlations with Cdexposure in the hepatopancreas. Cu increased in green glands, gills, and hemolymph and,in some cases, decreased in the hepatopancreas. Ca, Fe, Mg, and Zn also showedsignificant trends. Zn accumulated in the exposure water over 24h. These data indicatethat Cd may displace Cu and/or Zn in the hepatopancreas and the displaced metal thenmay move into other tissues, especially the gills and green glands, possibly to beexcreted.

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