Fig. 2. Hearts from three species of notothenioid fishes. The channichthyid icefish Chaenocephalus aceratus has a pale yellow ventricle (far left) and lacks myoglobin (Mb) protein expression. The channichthyid icefish Chionodraco rastrospinosus expresses myoglobin protein and displays a rose-colored ventricle (middle). The related notothenioid species Notothenia coriiceps has a characteristically red ventricle (far right) associated with the presence of myoglobin protein. Note that both channichthyid hearts are considerably larger than that from the red blooded species despite all having been dissected from animals of equivalent body mass. (Figure is from Moylan and Sidell, 2000.)