Carcharhinus Lumbatus
(Blacktip Shark)
The blacktip shark is a timid shark common in tropical and subtropical waters throughout the world; it is noted for its ability to jump out of the water and spin three or four times before landing. The excretory system of the blacktip shark has to combat due to osmosis. Because of its high tolerance for its own nitrogenous waste in its blood and cytoplasm, high amounts of urea and trimethylamine oxide can stay in the blood stream of the blacktip shark; this allows the blood to be isotonic to sea water. Eventually, the shark’s tubules reabsorb both the urea and the trimethylamine and it is excreted. A unique aspect of the blacktip shark’s excretory system is the fact that the shark’s gills regulate the pH balance. The kidney regulates the pH balance in most other vertebrate, but sharks’ kidneys are limited in their ability to excrete H+ ions. Finally, male blacktip sharks lack ureters, so it has an accessory urinary duct in order to drain urine from the kidney.