Nephridium

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Related to nephridia: Malpighian tubules, parapodia

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 ?
One or two pairs of anterior nephridia, in 6/7-8/9, with compact spindle-shaped postseptale (up to 90 [micro]m x 40 [micro]m) tapering into short (35 [micro]m) ectal duct in its posterior end.
Thus, digestive gland tubules, intestine, nephridia, gills, gonad, and connective tissue of the mantle were the main sites invaded.
During an initial stage, gills, nephridia, connective tissue of mantle, gonad, and digestive system were infiltrated by hemocytes, and a few neoplastic cells were apparent (Fig.
The attached figures clearly showed two pairs of nephridia, the gizzard in segment 6, and holandry as the generic characters for Brachydrilus, although a pair of spermathecae in 12/13 was evaluated as being in an 'abnormal position'.
And also the nephridia are present only as rudiments.
Nephridia, in posterior segments two pairs per segment, coiled; the dorsal pair larger and the ventral smaller, this varying between segments, in some the dorsal smaller and the ventral larger.
Tissue samples were embedded in Paraplast, and oblique transverse sections, approximately 5-mm thick, were taken from each specimen including mantle, gills, gonad, digestive gland, nephridia and foot.
Based on nephridia characteristics, Korniushin (1998) suggested that all African Sphaerium spp.