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Upon initial qualitative analysis, definite morphological differences were noted in the four groups. Data were collected and statistical analysis was used to clarify our observations. Trends of decreasing mass, head diameter, and beak length with increasing ethanol dosage were observed as seen by a negative slope in regression analyses (Figure 1, Figure 2, Figure 3). We proceeded to determine whether these differences were significant.

No significant differences existed between any of the chicks' masses (ANOVA: F-ratio = 1.3544, p=0.2923) (Table 1). A significant difference was measured in chick head diameter across the different dosage groups (ANOVA: F-ratio = 22.010, p<=0.0001) (Table 1). A Bonferroni post hoc analysis indicated significant differences between 5% to control (p=0.001244), 10% to control (p=0.000020), and 15% to control (0.000067) (Table 2). No significant differences were seen between any beak lengths (ANOVA: F-ratio = 3.0072, p=0.0612) (Table 1).

Although significant difference were not always observed, a great deal of variation within each measurement for each group was seen. Figure 4 illustrates the most notable superficial difference in size between a control and a 10% ethanol treated embryo. Figure 5 illustrates the difference in head size between a control and a 10% ethanol treated embryo. Figure 6 shows the difference in beak size between a control and a 10% ethanol treated embryo.


The eggs treated earlier, at 27-hours, were smaller in mass, head diameter, and had shorter beak length than those exposed to ethanol at 51-hours or the control eggs, consistent with Lawrence and Yoder's study. There were visible malformations particularly in the craniofacial region, including missing beaks, misshaped heads, and soft skulls (Figure 7).

From the set of eggs treated at 51-hours, two ethanol-treated embryos and three control embryos were harvested (Table 3). The eggs treated at 27-hours yielded seven experimental and one control embryo (Table 4). All treated embryos were smaller in mass and head diameter and had shorter beaks compared to their respective control embryos. One embryo exposed to ethanol at 27 hours was missing its beak (Figure 7).

Vital dye staining with Neutral Red revealed more specific areas of apoptosis in both ethanol-treated embryos, most prominently in the midbrain area of the embryo treated at 27 hours (Figure 8). The embryo treated at 51 hours with ethanol did not exhibit staining in the head region, but rather more caudally (Figure 9). Red dye was not present in the control embryos (Figure 10).

©Cebra-Thomas, 2000

Last Modified: 10 May 2004

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