Giant Mitochondria (Megamitochondria)

Mitochondria are extremely sensitive indicators of the health of their host cells. Even slight perturbations in cellular metabolism can evoke morphological alterations in these organelles. One way in which mitochondria respond to metabolic disturbances is by increasing in size, often to a point where they outstrip the cell nucleus in diameter. Such outsize organelles are also referred to as megamitochondria, a term that appears to have found increasing favor. Hepatic megamitochondria can measure,14 μm, giving them a volume >1400 mm 3 , compared to the volume of 0.5 mm 3 exhibited by typical liver mitochondria. Enlarged mitochondria can be induced by various nutritional and pharmacological manipulations. They occur naturally in certain human disease states and in a few cell types in exotic organisms; for example, the larger of the paired mitochondria in the spermatozoan tail of the hemipteran Gerris has a volume of 10 000 mm 3 .