Toxic effects of PCB126 and TCDD on shortnose sturgeon and Atlantic sturgeon

The aquatic food web of the Great Lakes has been contaminated with polychlorinated biphenyls (PCBs) since the mid-20th century. Threats of PCB exposures to long-lived species of fish, such as lake sturgeon (Acipenser fulvescens), have been uncertain because of a lack of information on the relative sensitivity of the species. The objective of the present study was to evaluate the sensitivity of early-life stage lake sturgeon to 3,3',4,4',5-pentachlorobiphenyl (PCB-126) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure. Mortality, growth, morphological and tissue pathologies, swimming performance, and activity levels were used as assessment endpoints. Pericardial and yolk sac edema, tubular heart, yolk sac hemorrhaging, and small size were the most commonly observed pathologies in both TCDD and PCB-126 exposures, beginning as early as 4 d postfertilization, with many of these pathologies occurring in a dose-dependent manner. Median lethal doses for PCB-126 and TCDD in lake sturgeon were 5.4 ng/g egg (95% confidence interval, 3.9-7.4 ng/g egg) and 0.61 ng/g egg (0.47-0.82 ng/g egg), respectively. The resulting relative potency factor for PCB-126 (0.11) was greater than the World Health Organization estimate for fish (toxic equivalency factor = 0.005), suggesting that current risk assessments may underestimate PCB toxicity toward lake sturgeon. Swimming activity and endurance were reduced in lake sturgeon survivors from the median lethal doses at 60 d postfertilization. Threshold and median toxicity values indicate that lake sturgeon, like other Acipenser species, are more sensitive to PCB and TCDD than the other genus of sturgeon, Scaphirhynchus, found in North America. Indeed, lake sturgeon populations in the Great Lakes and elsewhere are susceptible to PCB/TCDD-induced developmental toxicity in embryos and reductions in swimming performance. Environ Toxicol Chem 2017;36:988-998. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Section: Developmental Toxicity Of Dioxin-like Compounds To Sturgeoncontrasting

confidence: 94%

Sensitivity of lake sturgeon (Acipenser fulvescens) early life stages to 2,3,7,8‐tetrachlorodibenzo‐P‐dioxin and 3,3′,4,4′,5‐pentachlorobiphenyl

Tillitt

Buckler²,

Nicks

et al. 2016

“…Elonen et al [15] reported high hatchability in 6 of 7 species exposed to TCDD (0.005-4.77 ng TCDD/g egg), with only lake herring (Coregonus artedii) showing a significant decrease in hatch at the highest (2.09 ng TCDD/g egg) dose tested. Reduced hatchability in other fish species [30][31][32], including 2 species of Acipenser sturgeon [33], has been related to total PCB or TCDD exposure. Shovelnose sturgeon, and presumably pallid sturgeon, have larger posthatch yolk reserves than some lotic species [22].…”

Section: Discussionmentioning

confidence: 99%

Sensitivity of shovelnose sturgeon (Scaphirhynchus platorynchus) and pallid sturgeon (S. albus) early life stages to 3,3′,4,4′,5‐pentachlorobiphenyl and 2,3,7,8‐tetrachlorodibenzo‐P‐dioxin exposure

Buckler

Candrl

McKee

et al. 2015

Concern exists that polychlorinated biphenyls (PCBs) may be contributing to the current decline of shovelnose sturgeon (Scaphirhynchus platorynchus) and the US federally endangered pallid sturgeon (Scaphirhynchus albus). Waterborne exposures with newly fertilized eggs were used to assess developmental and morphological effects of 2 of the most potent aryl hydrocarbon receptor (AhR) agonists, 3,3',4,4',5-pentachlorobiphenyl (PCB-126) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), on early life stage shovelnose and pallid sturgeon. No dose-related effects of PCB-126 were observed on percent development or hatch in either species at concentrations as high as 1711 ng/g egg. Effects of TCDD on percent development were not assessed in shovelnose sturgeon. However, percent development was not affected by TCDD in pallid sturgeon, and percent hatch was unaffected by TCDD doses as high as 60 ng/g egg to 81 ng/g egg in either species. Morphological pathologies such as yolk sac edema and craniofacial deformities were typical of AhR agonist exposure and were similar in both species. Calculated PCB-126 50% lethal dose (LD50, 95% fiducial limits) values were 196 ng/g egg (188-203 ng/g) for shovelnose and 159 ng/g egg (122-199 ng/g) for pallid sturgeon. Likewise, calculated TCDD LD50 values were 13 ng/g egg (11-15 ng/g) for shovelnose and 12 ng/g egg (10-14 ng/g) for pallid sturgeon. These LD50 values are among the highest recorded in early life stage fish, suggesting that early life stage Scaphirhynchus sturgeon may be comparatively insensitive to AhR agonists.

“…This suggests that up-regulation of CYP1A in liver explants could be predictive of in vivo responses of regulatory relevance, such as embryo lethality. Embryos of Atlantic sturgeon (Acipenser oxyrinchus), shortnose sturgeon (Acipenser brevirostrum), shovelnose sturgeon (Scaphirhynchus platorynchus), and pallid sturgeon (Scaphirhynchus albus) have been shown to differ significantly in their sensitivity to exposure to TCDD [14,33]. However, nothing is currently known regarding sensitivity of embryos of white sturgeon or lake sturgeon to TCDD or other dioxin-like compounds.…”

Section: Relative Sensitivity Of Fishes To Dioxin-like Compounds In Vmentioning

confidence: 99%

Cross‐species comparison of relative potencies and relative sensitivities of fishes to dibenzo‐p‐dioxins, dibenzofurans, and polychlorinated biphenyls in vitro

Eisner

Doering

Beitel

et al. 2015

Dioxin-like compounds of varying toxicities are found in complex mixtures. The toxic equivalency factor (TEF) approach was developed based on the potency of a dioxin-like compound relative to the potency of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) to streamline risk assessment. One limitation of the TEF approach is uncertainty regarding differences in the relative potency of dioxin-like compounds among different species. Relative potencies among fishes are limited, relative to relative potencies among birds and mammals, and TEFs for fishes are based entirely on the model species, rainbow trout (Oncorhynchus mykiss). An in vitro liver explant assay was used to characterize species-specific responses with regard to up-regulation of CYP1A transcript after exposure to 6 dioxin-like compounds in rainbow trout, white sturgeon (Acipenser transmontanus), lake sturgeon (Acipenser fulvescens), and northern pike (Esox lucius). Differences in sensitivities were observed among species after exposure to dioxin-like compounds. The relative potencies developed from liver explants of rainbow trout were comparable to relative potencies developed from embryo toxicity assays. Differences in relative potencies between species with the least and greatest relative potencies were up to 40-fold. To compare relative potencies among species, concentrations of dioxin-like compounds in fish eggs in the Fraser River and in Lake Ontario were used to calculate toxic equivalency quotients (TEQs) determined from TEFs or TCDD equivalents determined from relative potencies. The TEQs underestimated TCDD equivalents for white sturgeon, lake sturgeon, and northern pike, indicating uncertainty in application of TEFs to diverse fishes.