Fig 2. Survival, developmental delays, and heart rates of sensitive and resistant embryos developing in clean and polluted sediment extracts.

(A) Survival rates of sensitive and resistant embryos exposed to clean and polluted sediment extracts at stages 31 and 35. Survival rates are significantly different among treatment groups (one-way ANOVA; Bonferroni post-test, p < 0.05). Sensitive embryos developing in clean sediment extracts during stages 31, 35, and hatching, had the highest survival rates (87.5%). Resistant embryos exposed to clean and polluted sediment extracts (PC and PP) and sensitive embryos exposed to polluted extracts (CP) had significantly lower survival rates (57.5–65%). (B) Time-to-stage for embryos from two populations developing in clean and polluted sediment extracts. Significantly slower development of sensitive embryos exposed to polluted sediment extracts is noted for both stages 31 and 35 (one-way ANOVA; Bonferroni post-test, p < 0.01). (C) a–Developmental delays of sensitive embryos exposed to polluted sediment extracts (CP) before hatching (stage 35). CC, PC, and PP embryos reached pre-hatching stage 35 within the expected time (approximately 212 hours), while the CP embryos were 3 stages (52 hours) behind. b–Pairwise differences in gene expression between CP and CC embryos at stage 35 based on the anatomical and morphological similarities and not the time-to-stage. c–Pairwise differences between CP embryos at stage 31 and CC embryos at stage 35 considering development of two treatment groups at the same time frame only. Significances of differences as -log₁₀(p-values) are plotted against log2 differences in expression of adjacent stages. -log₁₀(p-values) range from 0 to 5 and log2 differences in expression range from -2 to 3 (-4-fold to 8-fold differences in expression). Distribution of differentially expressed genes (p < 0.01) between the developmental stages of treatment groups are shown. (D) Heart rates (bpm) of sensitive and resistant embryos. Significantly lower heart rates are detected among sensitive embryos developing in contaminated sediment extracts and resistant embryos developing in clean sediment extracts (one-way ANOVA; Bonferroni post-test, p<0.01). *, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001.