Briefly explain the role of Malpighian tubules in arthropods.

Malpighian tubules absorb uric acid, salts, water, and wastes from the hemolymph. Some materials are selectively reabsorbed into the hemolymph, and the rest is emptied into the gut. Uric acid is excreted as a paste, and thus minimal water is lost. This efficient conservation of body fluids has contributed to the success of insects.