The gossamer worm (Tomopteris, Neo-Latin from Greek meaning "a cut" + "wing" but taken to mean "fin")[3] is a genus of marine planktonic polychaetes.

All described species are known to be holoplanktic, meaning that they spend their entire life cycles in the water column.

[4] E. Newton Harvey had noted the unusual yellow bioluminescence[5] occurring from the parapodia.

It is thought that this mode is to distract predators, analogous to chaff or flares dispensed from military aircraft during evasive maneuvers.

Generally, gossamer worms grow to only a few centimeters in overall length, or 20 millimetres (0.79 in) to 40 millimetres (1.6 in) in total length, though this is likely to reflect the size of those amenable to being caught in trawl nets.