How sharks recycle toxic ammonia to keep their skin moist

(University of British Columbia) The Pacific spiny dogfish shark is a master at recycling the ocean's toxic ammonia and converting it into useful urea, according to new research from University of British Columbia zoologists. Animals typically eat protein in order to grow, but sharks also require protein to continually replenish urea in their tissues. The urea keeps the fish from drying out in salty seawater.