Fig. 3. Localization of NADH fluorescence in Daphnia magna. To obtain satisfactory fluorescence images, the excitation light was concentrated on the central portion of the animal. The body region in focus comprised the mandible (Mand), the base of the large antenna (A2M) and the bases of the thoracic limbs (1–5). Switching from normoxia (A) to anoxia (B) resulted in a strong increase in fluorescence intensity, indicating an accumulation of mitochondrial NADH. The difference image (C) reveals that this increase in intensity derived from various groups of muscles associated with the respective appendages (D).