
To complete the interesting animal trifecta I bring you the Brownsnout Spookfish (Dolichopteryx longipes).
This animal is an incredible testament to the amazing power of evolution. Living very deep in the ocean means that the ability to collect light with its eyes is very important. It has two adaptations that each help with this task.
First it has developed a second eye chamber (they both share the same retina covered in light receptive cells). This allows one chamber to collect light from above in order to catch a glimpse of predators before they attack while the other chamber collects light from below where bioluminescent food may be found.
Second, the new downward facing chamber originally had no lens which made it only somewhat effective at collecting light. Likely it could only see things below which were very close or very bright. However, over the eons the creature has evolved a mirror-like array of crystals in the second chamber that allow it to effectively collect light from below. Very cool.
This post over at Science Blogs has more info.