Figure 1

Survival, developmental delays, and heart rates of reference (Kings’ Creek – blue) and resistant (Elizabeth River – red ) Fundulus embryos. A) Embryo survival (2-way ANOVA, p = 0.97) among five treatment groups within reference and resistant embryo populations at developmental stage 31 (late organogenesis). Sensitive and resistant embryo’s survival is not affected by any treatment at the stage 31. B) Hatching success and survival to stage 40 (2-way ANOVA, p < 0.01) among reference and resistant embryos. The cumulative effects in both combined treatments have significant effect among sensitive embryos, as they fail to hatch, while the resistant embryo survival is largely unaffected. C) Development among control and five treatment groups of reference and resistant embryos at 144–150 hours post-fertilization: although most of the embryos reached stage 31 within the expected time period, significant developmental delays were noted among reference embryos exposed to both low and high ANF + BNF treatments (2-way ANOVA, P <0.01). Reference embryos were significantly delayed (on average 3 developmental stages, ~ 40 h) relative to resistant embryos in both combined treatments (Bonferroni post-test analysis, p < 0.01), while embryo development in discrete treatments did not significantly differ. D) Embryo heart rates: reference and resistant embryos’ heart rates during stage 31: significant bradycardia (2-way ANOVA, p < 0.01) were noted among reference embryos at both lower (p < 0.04; t = 4.12) and higher (p < 0.05; t = 8.03) BNF/ANF dose exposures relative to resistant embryos. Asterisks (*) represent statistically significant within-treatment differences (Student’s t-test, p < 0.05) between Elizabeth River (resistant) and King’s Creek (reference) embryos.