Well, the food is in the environment. I would like to compare it with how bacteriae feed (however my biology is quite rusty), that is, they engulf their food and they "digest" -- not the proper term, since there are no organs to do real digestion -- it.
Shark,big fish, small fish,algae,plankton hope this helped
Answer: the capillaries.
<span>The blood capillaries are blood vessels with very small caliber. They form the blood distribution and collection network in cells. They are the communication between branches
originating from the arteries and with the smaller
veins. It is on the walls of the capillaries that occurs <span>the exchange of water, oxygen, CO2,
other nutrients and chemical residues.</span></span>