Practice question

Insect excretion is performed by Malpighian tubules, slender blind-ended tubules opening at midgut-hindgut junction, derived from endodermal or ectodermal origin depending on order. Epithelium actively transports potassium, uric acid, excess ions and nitrogenous wastes from hemolymph into lumen via active secretion, water follows osmotically, then hindgut and rectal glands reabsorb water and ions producing semi-dry frass. Tubule number ranges from two to over two hundred. Nephridia characterize annelids, antennal green glands crustaceans, coxal glands arachnids. Malpighian tubule-rectal complex supports uricotelism conserving water essential for terrestrial life.