Dr. W. Gary Anderson has found sharks continuously control the volume of their blood and other body fluids through the integration of a number of physiological systems.
“Much like humans, sharks need to regulate their body fluid volume and blood is one component of that,” says Dr. Anderson, Department of Biological Sciences. “Like us, a lot of the regulation of shark blood volume is achieved through the coordination of cardiovascular and renal systems. However, sharks also use their gills and a specialized salt secreting gland known as the rectal gland. They will also drink seawater to maintain body fluid balance.”
If salinity rises or falls, there is a decrease or increase of water movement into the shark which affects blood volume, he explains. For the most part, he adds, sharks are totally marine fish.
However, Dr. Anderson along with Drs. C. Franklin and R. Pillans, University of Queensland, Australia and Dr. N. Hazon, University of St. Andrews, Scotland looked at bull sharks in the three-year study and found the fish live in both freshwater and seawater and as a result are regularly faced with changes in salinity.
“Unlike other elasmobranch fish (sharks, skates and rays) we know that bull sharks can regulate body fluid volume regardless of salinity, but we are only just getting to grips with how they manage to do it so effectively,” says Dr. Anderson. “Because of this unique ability, bull sharks offer us an important insight into the evolution of body fluid volume regulation as a life-sustaining process.”
In addition to bull sharks, Dr. Anderson has conducted research on dogfish, bamboo sharks and skates for the past 15 years.