Taxon Description (Wikipedia)
File:VasesAaRiverCirca1990.jpg|thumb|left|200px|Tubifex, in Aa River (north of France) in a polluted zone, circa 1990.species of tubificid segmented worm that inhabits the sediments of lakes and rivers on several continents.
Tubifex probably includes several species, but distinguishing between them is difficult because the reproductive organs, commonly used in species identification, are resorbed after mating, and because the external characteristics of the worm vary with changes in salinity. These worms ingest sediments, selectively digest bacteria, and absorb molecules through the body wall.
The worms can survive with little oxygen by waving hemoglobin rich tail-ends to exploit all available oxygen, they can also exchange carbon dioxide and oxygen through their thin skin,...
full article at Wikipedia
