How do crustaceans survive in freshwater, seawater, and highly salty inland brines?

Crustaceans survive in diverse aquatic environments—ranging from freshwater to highly saline inland brines—by employing complex osmoregulation strategies to maintain internal salt and water balance.12

Because their respiratory surfaces are permeable to water and ions, crustaceans must counteract osmotic pressure that would otherwise cause them to lose or gain water uncontrollably. They manage this through several physiological mechanisms:2

• Active Transport: Crustaceans maintain internal salinity by actively transporting inorganic ions, such as sodium and chloride, across specialized tissues. This process is energy-intensive and is regulated by various endocrine factors.21
• Specialized Organs: The gills, antennal glands, and the intestine play critical roles in regulating ionic balance. These organs are controlled by factors originating from the brain, thoracic ganglion, and eyestalk complex.1
• Adaptability: Many species are euryhaline, meaning they can tolerate a wide range of external salinities. For example, fiddler crabs can control their osmotic concentration when exposed to freshwater for short periods. Specialized crustaceans like brine shrimp (Artemia) have evolved to thrive in extremely high-salinity environments.234

These adaptations allow crustaceans to function as either osmoconformers, matching their internal environment to the surroundings, or osmoregulators, which keep their internal chemistry constant despite external changes.2