noun, plural: Malpighian tubules
Malpighian tubules are small slender tubes located posteriorly in the alimentary canals of arthropods, such as insects, myriapods, arachnids, and tardigrades. The tubules are extensions of the alimentary canal to the exterior. Each tubule is lined with a single layer of cells and with microvilli that propel the contents along the tubules. Most of them are highly convoluted and are bathed in hemolymph. These tubes are involved in osmoregulation; they absorb solutes, water, and wastes from the hemolymph and release wastes as solid nitrogenous compounds to the outside of the organism. Most of the Malpighian tubule systems have accessory musculature that help mix the contents of the tubules. In certain insects, the Malpighian tubules are modified. For instance, the Malpighian tubules of the larvae of the glowworm, Arachnocampa luminosa, are capable of emitting a blue-green light that attract prey.1
1 Green, L.B.S. (1979) The fine structure of the light organ of the New Zealand glow-wormArachnocampa luminosa (Diptera: Mycetophilidae).Tissue and Cell 11: 457–465.