Nephridium


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Related to Nephridium: Malpighian tubules, prostomium, clitellum

nephridium

[nə′frid·ē·əm]
(invertebrate zoology)
Any of various paired excretory structures present in the Platyhelminthes, Rotifera, Rhynchocoela, Acanthocephala, Priapuloidea, Entoprocta, Gastrotricha, Kinorhyncha, Cephalochorda, and some Archiannelida and Polychaeta.

Nephridium

 

an excretory organ that is characteristic of invertebrates. The nephridium regulates osmotic pressure, extracts and removes harmful metabolites from the body, and sometimes transports gonad products. The most primitive nephridia are those of flatworms, rotifers, gastrotrichs, nemerteans, and some polychaetes. These nephridia, which are called protonephridia, are branched tubules of ectodermal origin. They are closed at the internal ends by terminal cells, or solenocytes, and open to the exterior by means of excretory pores, or nephridiopores. Upon losing its solenocytes and opening into the coelom, the protonephridium is transformed into a metanephridium (primarily in annelids). In some annelids the nephridium coalesces with the mesodermal ciliated gonad funnels, or coelomo-ducts, forming an organ of mixed origin, the nephromyxium.

A. V. IVANOV

References in periodicals archive ?
This vessel, which corresponds to the left anterior aorta (9) in the juvenile, is associated with Hatschek's nephridium, the first excretory organ to appear in the ontogeny of amphioxus.
Morphology of Hatschek's nephridium in larval and juvenile stages of Branchiostoma virginiae (Cephalochordata).
The early development of the nephridia in amphioxus: introduction and part I, Hatschek's nephridium. Q.