From UC Berkeley
All fishes have a brain protected by a braincase and an obvious head region with eyes, teeth, and other sensory organs
Most fishes
- are vertebrates with vertebrae protecting the spinal cord
- live in water
- breathe primarily with gills rather than lungs
- have paired limbs, in the form of fins that aid in locomotion
- are unable to regulate their own internal body temperatures
- are covered with scales that protect their bodies