How do lice breathe? - briefly
Lice obtain oxygen via two spiracles on the thorax that open into a tracheal network delivering air directly to their cells. The tracheal system provides respiration without lungs or gills.
How do lice breathe? - in detail
Lice obtain oxygen through a network of tracheae that open to the exterior via tiny spiracles located on the thorax and abdomen. These spiracles are minute pores, each surrounded by a thin cuticular ring that prevents water loss while allowing gas exchange. Air enters the spiracles, travels through progressively finer tracheal tubes, and diffuses directly to body tissues, eliminating the need for a circulatory transport system.
Key features of the respiratory system:
- Spiracle placement: Typically one pair on each side of the thorax and a pair on the abdomen; the exact number varies among species.
- Tracheal branching: Primary tracheae bifurcate into secondary and tertiary branches, ending in tracheoles that contact individual cells.
- Cuticular reinforcement: Each spiracle is equipped with a valve-like structure that can close to reduce desiccation during unfavorable conditions.
- Gas diffusion: Oxygen diffuses down the concentration gradient from the external environment through the tracheal network; carbon dioxide follows the reverse path.
Because lice are ectoparasites living on warm, moist hosts, their spiracles remain open most of the time, relying on the host’s temperature to maintain a favorable diffusion gradient. During periods of host grooming or environmental stress, the valve mechanism can partially close spiracles, temporarily limiting gas exchange but preserving moisture.
Metabolic rates in lice are relatively low, matching the limited oxygen supply provided by the tracheal system. Consequently, these insects can sustain prolonged periods without feeding, as their energy demands are modest and efficiently met by the diffusion-based respiration.