Undigested matter in the alimentary canal passes through specialized rectal glands in the hindgut.
2.
Three conspicuously large oval unicellular rectal glands are present, one dorsal and two subventral.
3.
Bull sharks in freshwater environments decrease the salt-excretory activity of the rectal gland, thereby conserving sodium and chloride.
4.
All elasmobranchs have a rectal gland which functions in the excretion of excess salts accumulated as a consequence of living in seawater.
5.
In sharks, this includes a " rectal gland " that secretes salt to help the animal maintain osmotic balance with the seawater.
6.
The " "'rugogastridae " "'are parasites, and infect the rectal glands of various species of holocephalan fish.
7.
However, bull sharks in freshwater possess several organs with which to maintain appropriate salt and water balance; these are the rectal gland, kidneys, liver and gills.
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