Excretion of Foreign Substances in Sea Horses

 

Functions of an Excretory System      There are four basic functions of an excretory system.  First, an excretory system maintains the proper solute concentration of an organism. Second, the system maintains proper water content in the body.  Third, the excretory system removes metabolic products.  Lastly, it removes foreign substances or the metabolic products of the foreign substances (Schmidt - Nielsen 1998).  This last function of the excretory system has provided the focus for research in the aglomerular kidney of the sea horses.

Sea Horses' Removal of Immune Products and Macromolecules      Recent research by Tsujii and Seno (1990) and just Tsujii in (1988) in excretion physiology has focused on how aglomeruli marine teleosts dispose of immune products and exogenous macromolecules.  Tsujii and Seno's research (1990), though published later, was done before and made a foundation for Tsujii's research (1988).

Tsujii and Seno (1990)      Tsujii and Seno (1990) set forth to examine how and why melano-macrophage centers formed in the sea horse's kidney.  They found that sea horses have hemopoietic foci surrounding the renal tubules in the interstitial tissue of the kidney.  Inside each hemopoietic focus is an artery and sinusoids along with macrophages without melanin pigments.  The individual macrophages remained attached to the sinusoids at all times; however, melano-macrophage centers, large clusters of macrophages filled with cell debris and some melanin pigments, could be found in the hemopoietic foci.  The melano-macrophage centers had formed after the individual macrophages picked up foreign particles - horse-spleen ferritin and carbon particles.  The macrophages then come together to form the melano-macrophage center to aide the digestion and removal of these foreign particles.

Tsujii (1988)      Tsujii's later research (1988) was able to tie together other information about the excretion of foreign particles.  He found that the foreign particles - in this experiment anionic and cationic horse-spleen ferritin - were not removed by the gills.  This shows that all the particles must either remain in the body or be removed by the excretory system.  Also, he learned more about the melano-macrophage centers.  The macrophages removed the ferritins by pinocytosis and decompose the ferritins in their phagolysosome.  Then after degrading all the ferritins, the macrophages and melanin come together to form the melano-macrophage center.  The melano-macrophage centers of the kidney are also used to remove damaged hemopoietic cells from the renal hemopoietic tissue.  Tsujii was able to connect other research about melano-macrophage centers to show that the centers are also formed in the hemopoietic tissue of the spleen and liver.  He showed that melano-macrophage centers form in glomerular and aglomerular teleosts but not in higher vertebrate.

 

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