1. Specialized Kidneys: Bull sharks have kidneys that can adjust their function to regulate salt levels in their blood. In saltwater environments, their kidneys conserve water and excrete excess salt. In freshwater, they conserve salt and excrete excess water.
2. Chloride Cells: These specialized cells in their gills help regulate salt levels by actively pumping salt out of their bodies in freshwater environments and absorbing salt from the surrounding water in saltwater environments.
3. Blood Osmolality: Bull sharks can maintain a relatively stable blood osmolality (the concentration of dissolved substances) even when moving between saltwater and freshwater environments. This is crucial because a significant difference in osmolality between the blood and the surrounding water can cause water to move in or out of the shark's cells, potentially causing damage.
4. Behavioral Adaptations: Bull sharks are known to spend time in both saltwater and freshwater environments. They may even travel up rivers and estuaries for extended periods, further showcasing their euryhaline nature.
These adaptations allow bull sharks to thrive in a variety of habitats, from coastal waters to freshwater rivers and estuaries. This gives them a significant advantage in terms of food availability and reduces competition with other species.