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Fig. 5
Inter-specific divergence in apoptosis.
(A) Hierarchical clustering of zebrafish/tilapia divergently expressed genes contained in the GO term “regulation of apoptotic process”. Log2 transformation of gene fold change is indicated by the color-coded scale. (B) TUNEL assays in the gills of two fishes, indicating an earlier onset and more aggravated apoptosis in tilapia than in zebrafish at the same cold temperature. The nucleus was counterstained with DAPI. Scale bar is 100 µm. (C) Increased apoptotic cell populations in the gills of tilapia and zebrafish over time at 8 °C. Significant differences between the two fishes are indicated by an asterisk (Student’s t test, P < 0.05) and are based on at least three biological replicates, with each replicate having at least 3 individuals at each time point.