Some pearl fish seek shelter inside the sausage shaped sea cucumber.

They locate the sea cucumber’s opening at the anus.

The fish then inserts its tail and wriggles the whole body inside.

Several pearl fish with their transparent and pigment dotted bodies may share the same sea cucumber.

The fish get safety, shelter and food. They even eat the internal organs of the sea cucumber.

But sea cucumber has the ability to regenerate its internal organs and

hence suffers no damage, nor does it benefit by the uninvited live-in-guests!