Eupolymnia crassicornis is a tropical species of annelid, commonly known as a spaghetti worm.

Eupolymnia crassicornis are deposit feeders that primarily feed at evening or night.

They extend their ciliated tentacles out and along the sea-floor to gather dead organic matter (detritus) that originated as diatoms and other planktonic microorganisms.

Spaghetti worms have a well-developed gut consisting of an oesophagus, fore-stomach, closed circulatory system, hind-stomach and intestine, and use enzymes to help carry out digestion.

Unusually, both males and females have been observed to release gametes even when the other sex was not in the vicinity.