Biological effects of chronic exposure to low-level radiation in bullhead catfish (Ameiurus natalis)
Abstract
Free-ranging animals that inhabit contaminated environments provide unique opportunities to evaluate the effects of contaminant exposure. In this case, yellow bullhead catfish (Ameiurus natalis) were used as biomonitors of low-level environmental radiation exposure. Biomarkers of oxidative damage, namely pronephric pigmented macrophages (PMs) and the oxidative DNA adduct 8-hydroxy-deoxyguanosine (8-OH-dG) were related to $\sp{137}$Cs burdens of fish inhibiting an abandoned reactor reservoir (Pond B, Savannah River Site, Aiken, SC). Equilibrium $\sp{137}$Cs burden in muscle (3604 Bq/kg) was acquired in approximately 2.94 yrs in these fish. Muscle $\sp{137}$Cs was unrelated to sex (P = 0.859) or mass of fish (P = 0.224), but was related to age (P = 0.036). Dose to fish due to tissue $\sp{137}$Cs was estimated as 0.54 rads/yr; sediment related dose, at 10 cm above the sediment plane, was estimated as 1.50 rads/yr. Among 671 Pond B bullheads, 13 (1.94%) had congenital lesions as compared to 2 of 521 (0.38%) brown bullheads (A. nebulosus) inhabiting an uncontaminated reservoir. Mean PMs, per 0.15 mm$\sp2$ of tissue section, differed by sex (P = 0.0261, Males: 13.45 $\pm$ 1.21 SE, N = 84; Females: 9.31 $\pm$ 0.80, N = 61), age (P = 0.0001), and with muscle $\sp{137}$Cs concentration (P = 0.0003). Among males, PMs were positively correlated with age (P = 0.0001, R$\sp2$ = 0.42) and $\sp{137}$Cs concentration (P = 0.0002, R$\sp2$ = 0.15); among females, PMs were also correlated to age (P = 0.0001, R$\sp2$ = 0.36) and $\sp{137}$Cs concentration (P = 0.0087, R$\sp2$ = 0.11). Adduct concentration (8-OH-dG/100,000 dG) differed by tissue (gill: 20.90 $\pm$ 2.33, brain: 33.73 $\pm$ 1.49, N = 103, P = 0.0001). Gill adducts were associated with fish condition (P = 0.0124) and the interaction between age and condition (P = 0.0575). As body-condition increased, gill adducts declined in 2 yr old fish (P = 0.0116, R$\sp2$ = 0.34, $B\sb1$ = $-$83.0); this was not evident in older fish (4 yrs: P = 0.3117, R$\sp2$ = 0.06, $B\sb1$ = $-$26.5; 6 yrs: P = 0.8056, R$\sp2$ = 0.00, $B\sb1$ = $-$4.1). Brain adduct concentration was positively correlated with muscle $\sp{137}$Cs concentration in females (P = 0.0062, R$\sp2$ = 0.26), but was unrelated to muscle $\sp{137}$Cs concentration in males. That is, at lower $\sp{137}$Cs concentrations females tended to have fewer DNA adducts in brain tissue. These results suggest that oxidative injury, in bullhead catfish, can be associated with exposure to low-level $\gamma$-radiation. Although life history traits of these fish may moderate their response to contaminants, they appear to be sensitive biomonitors of oxidative insult.
Degree
Ph.D.
Advisors
Glickman, Purdue University.
Subject Area
Environmental science|Aquaculture|Fish production|Toxicology
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