Mollusca excretory system uses which structures?

• A. Nephridia
• B. Malpighian tubules
• C. Flame cells
• D. Kidneys

Answer: (A)

Mollusks rely on nephridia, specifically metanephridia, to remove waste. These are tubule-based excretory organs that take in coelomic fluid through a ciliated funnel (the nephrostome), pass it through the tubule where useful substances are reabsorbed, and then excrete the wastes into the mantle cavity or to the outside via an excretory pore. This contrasts with other invertebrate systems: Malpighian tubules are used by insects to dump wastes into the gut, flame cells form protonephridia in flatworms and some other groups, and kidneys are the vertebrate excretory organs.