RP9 Terrestrial Ecotoxicology
Thursday, 17 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(AUG-1117-821209) Embryotoxicity of 2,3,7,8-TCDD to the wood duck (Aix sponsa).

Augspurger, T¹, Di Giulio, R², Tillitt, D³, ¹ U.S. Fish and Wildlife Service, Raleigh, NC, USA² Duke University, Durham, NC, USA³ U.S. Geological Survey, Columbia, MO, USA

ABSTRACT- Eggs of wood ducks (Aix sponsa) collected from uncontaminated sites were injected with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to determine the wood duck's sensitivity relative to other birds. Four separate groups of 66 to 97 eggs (split into six treatments) were injected in 2004 and 2005. TCDD was dissolved in triolein which was injected at 0.1 microliters per gram egg. Injections were made into the yolk at embryonic day 0 and eggs were incubated with weekly assessments of mortality. Treatments included doses from 0 to 4,600 pg TCDD /g egg. Statistically significant embryo mortality was not observed at these concentrations through incubation day 25 (representing 90% of the incubation period for this species). Among 13 other avian genera for which egg-injected TCDD or polychlorinated biphenyl congener embryo lethality data are available (from the literature), our 4,600 pg/g No Observed Adverse Effect Level (NOAEL) ranks near the middle. Because this NOAEL for embryo mortality is unbounded (no higher concentrations were assessed), the wood duck appears to be among the more TCDD-tolerant of the species that have been assessed by egg injection. There was about a 9-fold increase in hepatic EROD activity over controls in the 4,600 pg/g treatment. Significant hepatic P4501A induction was observed at doses of 1,500 pg/g and 4,600 pg/g based on immunohistochemical staining. When exposures were extended to 2-weeks post-hatch (to allow total resorption of yolk and therefore exposure to all yolk-associated TCDD), there was still no statistically significant embryo mortality (doses from 0 to 3,200 pg/g). Liver, heart, eye and brain histology and hepatic EROD measurements from the longer exposures are pending.

Key words: birds, avian, dioxin, TCDD