Lancelets respiration relies on which mechanism?

• A. Lungs
• B. Gills
• C. Diffusion through body surfaces
• D. Tracheal system

Answer: (C)

Gas exchange in lancelets happens by diffusion across a moist, thin body surface. They lack specialized respiratory organs such as lungs or gills, and their small, simple form relies on direct diffusion between seawater and their body fluids to move oxygen in and carbon dioxide out. The surrounding water keeps the skin moist and provides the diffusion gradient needed for this gas exchange. A tracheal system, like in insects, isn’t present, and the pharyngeal slits used for feeding aren’t used for respiration. So diffusion through the body surface is the mechanism that fits their anatomy and lifestyle.