THE EFFECTS OF EDTA (ETHYLENEDINITROTETRAACETIC ACID) ON THE SURVIVAL AND DEVELOPMENT OF SHRIMP NAUPLII (Penaeus stylirostris STIMPSON) AND THE INTERACTIONS OF EDTA WITH THE TOXICITIES OF CADMIUM,CALCIUM, AND PHENOL

To examine the hypothesis that EDTA increases hatching rates and survival of penaeid shrimp larvae by decreasing the toxicities of heavy metals through chelation, the toxicity of cadmium, a highly toxic metal, was compared to the toxicities of calcium and phenol in both the presence and absence of EDTA. In addition, the toxicity of EDTA at higher concentrations was examined. The toxicities of EDTA, cadmium, calcium, and phenol were evaluated in terms of the percentage of nauplii surviving after 24 hours of exposure and the percentage of nauplii which metamorphosed to protozoea. The toxicities of cadmium, calcium, and phenol were also determined in the presence of EDTA. EDTA concentrations of 1.34 mM were lethal to nauplii. At 0.67 mM, EDTA reduced the percentage of nauplii which metamorphosed to protozoea but below 0.3 mM neither survival nor metamorphosis were affected. Cadmium, phenol, and calcium were lethal to nauplii at concentrations of 20 μM, 7 mM, and 400 mM, respectively. Metamorphosis was blocked by concentrations of 1 μM, 0.9 mM, and 200 mM, respectively. However, in the presence of 0.3 mM EDTA, the toxicities of cadmium and calcium were reduced. Cadmium concentrations of 20 μM did not affect either survival or metamorphosis in the presence of EDTA. In calcium concentrations of 50 and 100 mM, the percentage of nauplii that metamorphosed to protozoea was increased by the addition of EDTA. The interaction of EDTA and phenol toxicity was not significant.