Life at the depths of the ocean has extraordinary twist to cope up with the

eternal darkness, high water pressure and the permanent cold.

More than half the inhabitants in the lower depths are luminous.

It serves to attract a mate a well to find its prey.

Others act as hosts to colonies of glowing bacteria

which light up parts of their bodies from within.

The Indian ocean fish Photoblepharon has a large spot under each eye

which is full of blood vessels and packed with these glowing bacteria.

Each ‘headlight’ has its own black curtain too.

The fish can raise a black fold of skin to shut off this light when danger threatens.