How do invertebrates eat?
A northern sea anemone feeding
Ring of tentacles
In order to eat, a northern sea anemone opens wide the ring of white tentacles around its mouth.
Its tentacles wave slightly to create a current and attract plankton.
When the tentacles have trapped enough plankton, they relay it to the anemone’s mouth.
Anemones often close up completely when digesting their food.
A polar seastar feeding
Detecting its prey
There is a light-sensitive structure on the tip of each of the seastar’s arms. It uses its sense of smell to detect its prey, for instance a mussel or other bivalve mollusc.
Grasping its prey
It covers its prey and grips its shell with the tube feet on the underside of its arms. It pries the shell open and then everts its stomach (turns it inside out) into the mussel’s shell.
The seastar secretes gastric juices that liquefy its prey’s tissues so that it can suck them up and digest them.
A sand dollar feeding
Food from above!
A sand dollar burrows into the sand or mud and lets food drop onto and accumulate on its body.
Spines to carry its food
Its body is covered in small moveable spines that move in a synchronized fashion with its tube feet to direct the food towards its mouth, located in the middle of its underside.
A sea cucumber feeding
When it wants to eat, a sea cucumber extends its ten feathery tentacles and waits for food to accumulate on them.
Then a slow dance starts, with the tentacles taking turns reaching toward its central mouth, which traps the food. It literally “licks” its tentacles.