The larva of an ocean sunfish (Mola mola).  The spines are probably used for defense and/or to reduce sinking rate.  Sunfish eggs are produced ~30,000,000 at a time.  

The larva of an ocean sunfish (Mola mola).  The spines are probably used for defense and/or to reduce sinking rate.  Sunfish eggs are produced ~30,000,000 at a time.