Figure 4. Developmental Cd exposure affects survival and brain size in longitudinal adult fish.

Fish treated with 10 μM CdCl₂ during development showed significantly lower survival at 6 months than untreated controls (4A). This experiment was carried out a minimum of 6 times for each treatment group (a: p < 0.05 when compared to the 0 μM, 0.1 μM and 1.0 μM groups and b: p < 0.01 compared to the 0.01 μM group). The telencephalons of longitudinal adult GFP⁺ fish were imaged and the area measured as described in methods (4B). Body length and telencephalic area are strongly correlated (3C, p < 0.0001, n = 152). The telencephalon to body length ratio (TA/BL) did not vary significantly between the different longitudinal treatment groups (4D this experiment was done 3 times with an n = 35 for each Cd group, except the 10 μM Cd, which had much lower survival and an n = 10, p < 0.52). However, the shape of the concentration response curve was similar to that for survival (4A) and larval telencephalic area (2C), with a slight, but statistically insignificant, increase at the lower concentrations (0.01 μM), and a decrease at higher concentrations (1.0 and 10 μM). Brain weight was strongly correlated with body length when all groups were considered together (3E, p < 0.0001, n = 103). The brain weight to body length ratio differed between CdCl₂ treatment groups. Fish treated with 0.1 μM, 1.0 μM and 10 μM CdCl₂ during development had proportionally heavier brains than untreated controls (n = 21-24 for each Cd group except the 10 μM group, which had an n =12, a: p < 0.01 compared to the 0 μM group, b: p < 0.001 compared to the 0 μM group, c: p < 0.01 when compared to the 0.01 μM group and d: p < 0.05 compared to the 1.0 μM fish).