Malpighian vessels

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.

The Malpighian vessels (after Marcello Malpighi ) can be regarded as the kidneys of insects and other land-living arthropods (arthropods) and thus as efficient excretory organs .

You are Blindausstülpungen of the midgut (in arachnids ) or the rectum (for Tracheentieren ). Therefore they are of endodermal origin in arachnids and ectodermal in origin. The evolution of the Malpighian vessels is a convergent development, which can also be seen in the different ontogenetic origins. The intestine and Malpighian vessels are separated by a peritrophic membrane .

Epithelial transport active potassium - and sodium - ions from the hemolymph of the body cavity in the Malpighian tubules. A water import is linked to the potassium transport. Due to the built-up electrochemical gradient , uric acid can be transported into the vessels despite the difference in concentration. Since uric acid is sparingly soluble in water, it is in crystalline form in the vessels, which saves water. Amino acids , sugar , urea and other salt ions are also released passively . The pH value in the Malpighian vessels is around 6.8 to 7.5. From the iso-osmotic urine that is formed , salt ions are actively pumped into the hemolymph of the body cavity in the rectum and rectum , with water flowing again passively. The pH value in the rectum is 3.5 to 4.5. Substances like amino acids and sugar are recovered here and in the rectum. The inner gastric water cycle contributes to a large extent to the success of insects as land creatures, as it enables a large amount of water to be saved. The regulation of the water and ion balance ( osmoregulation ) is carried out using the system described.

A big difference to mammalian kidneys , proto - and metanephridia is that the removal of the substances does not take place by means of ultrafiltration , but through (secondary) active transport processes and filtration does not play a role.

The Malpighian vessels emerged at least twice in the history of the arthropods: in the arachnida as a protuberance of the endodermal midgut and in the antennas as a protuberance of the ectodermal rectum.

Individual evidence

1. ↑ Volker Storch, Ulrich Welsch: Systematic Zoology. 6th edition. Spektrum Verlag, Munich 2004, ISBN 3-8274-1112-2 , pp. 246, 266.