Chronic toxicity of diethylenetriamine pentaacetic acid to crimson-spottedrainbowfish (Melanotaenia fluviatilis): Effects on reproduction, condition, and ethoxyresorufin O-deethylase activity

The chronic effects of the chelating agent diethylenetriamine pentaacetic a cid (DTPA) on reproduction, condition factor, liver somatic index (LSI), go nad somatic index (GSI), and ethoxyresorufin O-deethylase (EROD) activity o f adult Australian crimson-spotted rainbowfish (Melanotaenia fluviatilis) m ere assessed. Breeding groups of three females and two males were exposed t o 0, 1, 10, or 100 mg/liter DTPA (nominal) in a 28-day "static-renewal" exp eriment. 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 ef fect on the condition of adult rainbowfish, with condition factor and GSI b eing unaffected at concentrations up to 100 mg/liter, the latter finding su pporting the reproduction results. However, LSI in male rainbowfish exposed to 100 mg/liter was significantly lower than in those exposed to 1 mg/lite r DTPA (P less than or equal to 0.05), but not controls LSI was not affecte d in female rainbowfish. The major effect of exposure to DTPA was an approx imate 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 wit h controls (12.29 +/- 1.80 pmol/min/mg protein; P less than or equal to 0.0 5), DTPA had no effect on EROD activity in male rainbowfish, The apparent i nhibition of EROD by DTPA appears to be the first such effect of a chelatin g agent to be reported in the external literature, and may have consequence s 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 environm ents, 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, (C) 1999 Academ ic Press.