Examples of Commensalism

 

Barnacles adhering to the skin of a whale or shell of a mollusk:  Barnacles are crustaceans whose adults are sedentary.  The motile larvae find a suitable surface and then undergo a metamorphosis to the sedentary form.  The barnacle benefits by finding a habitat where nutrients are available.  (In the case of lodging on the living organism, the barnacle is transported to new sources of food.)  The presence of barnacle populations does not appear to hamper or enhance the survival of the animals carrying them.

Remora sharks:  Remora sharks are endowed with an adhesive disk on the dorsal surface of their heads.  They use this adhesive disk to “hitch a ride” on larger animals, usually whales, which tend to be sloppy eaters.  When food floats away from the whale’s mouth, the remora can unhitch itself and collect the scraps of food floating by. 

 

Note sucker on dorsal surface of head