Chronic Toxicity of Diethylenetriamine Pentaacetic Acid to Crimson-Spotted Rainbowfish (Melanotaenia fluviatilis): Effects on Reproduction, Condition, and EthoxyresorufinO-Deethylase Activity

Abstract

The chronic effects of the chelating agent diethylenetriamine pentaacetic acid (DTPA) on reproduction, condition factor, liver somatic index (LSI), gonad somatic index (GSI), and ethoxyresorufinO-deethylase (EROD) activity of adult Australian crimson-spotted rainbowfish (Melanotaenia fluviatilis) were assessed. Breeding groups of three females and two males were exposed to 0, 1, 10, or 100 mg/liter DTPA (nominal) in a 28-day “static-renewal” experiment. Overall, the toxicity of DTPA to adult crimson-spotted rainbowfish was relatively low. Reproduction was not affected at concentrations up to 100 mg/liter DTPA, although an early effect on hatchability was potentially attributed to direct toxicity to rainbowfish eggs. DTPA also had little effect on the condition of adult rainbowfish, with condition factor and GSI being unaffected at concentrations up to 100 mg/liter, the latter finding supporting the reproduction results. However, LSI in male rainbowfish exposed to 100 mg/liter was significantly lower than in those exposed to 1 mg/liter DTPA (P≤0.05), but not controls. LSI was not affected in female rainbowfish. The major effect of exposure to DTPA was an approximate 50% inhibition of EROD activity in female rainbowfish exposed to 100 mg/liter DTPA (mean±SE: 6.39±1.56 pmol/min/mg protein) compared with controls (12.29±1.80 pmol/min/mg protein;P≤0.05). DTPA had no effect on EROD activity in male rainbowfish. The apparent inhibition of EROD by DTPA appears to be the first such effect of a chelating agent to be reported in the external literature, and may have consequences for aquatic organisms exposed to multiple-contaminant situations. However, the concentration of DTPA required to produce inhibition of EROD activity (i.e., 100 mg/liter) is not likely to occur in Australian aquatic environments, and thus the risk to fish appears minimal. The lowest-observed-effect and no-observed-effect concentrations of DTPA (nominal) for adult crimson-spotted rainbowfish were 100 and 10 mg/liter, respectively.