Answer
Freshwater fish have more and longer glomeruli. Saltwater fish typically have fewer and shorter glomeruli.
Work Step by Step
Freshwater fish are all osmoregulators, meaning they have a greater need for their kidneys to be able to create a specific blood electrolyte concentration that is different from their environment. Saltwater fish have body fluid concentrations more similar to their environments and have less need for strict regulation via the kidneys.
