Found: Subtropical water around the world
Size: 1 millimeter-long (0.03 inches)
Their protection is really nuanced. When an ostracod is pulled into the mouth of a cardinal fish, it immediately releases a chemical that combine to give off light called bioluminescent chemical. This chemical also turns makes the ingested easier to spot in the blackness of a nighttime sea, and so an easier meal. Most fish will shun eating the ostracods and their shining liquid, as it might attract even bigger, more perilous fish. The light warns predators to remain aside.