A long loop of henle becomes important in terrestrial organism as they need to retain as much water as possible. The long loop(seen in juxtamedullary nephrons in mammals) helps with extreme reabsorption of water and creating urine with osmolarity higher than plasma osmolarity(which is something you do not see in a lot of other organism as their urine is hypo-osmolar or iso-osmolar to their body fluids). So they basically get rid of waste and ions with smallest amount of water possible.
