Mitochondria

Definition

Double-membraned organelles in eukaryotic cells that carry out aerobic respiration, generating ATP through oxidative phosphorylation. In arthropods, mitochondria are especially abundant in metabolically active tissues such as flight muscle, where their density and cristae surface area scale with metabolic demand; they also contain their own circular DNA (mtDNA), which is widely used in molecular systematics and phylogeography of insects and arachnids due to its maternal inheritance and rapid evolution.

Etymology

From Greek mitos (thread) + khondrion (small granule), coined by Carl Benda in 1898 to describe their thread-like and granular appearance under light microscopy.

Example

The synchronous flight muscles of blow flies (Calliphoridae) contain densely packed giant mitochondria with highly folded cristae to sustain the rapid ATP turnover required for wing beating.

Synonyms

• chondriosome

Related Terms

• ATP
• cristae
• mtDNA
• oxidative phosphorylation
• flight muscle
• sarcosome

Usage Notes

Specialists reserve 'sarcosome' for the exceptionally large mitochondria of insect flight muscle. Mitochondrial density varies dramatically across arthropod tissues and life stages; dormant or anaerobic stages may show reduced mitochondrial volume. In systematics, 'mitochondrial DNA' or 'mtDNA' specifically refers to the maternally inherited circular genome, distinct from nuclear DNA.