[4] Platynereis dumerilii is today an important lab animal,[5] it is considered a living fossil,[6][7][8] and it is used in many phylogenetic studies as a model organism.

[9] Like a number of invertebrate phyla, Platynereis dumerilii has an axochord, a paired longitudinal muscle that displays striking similarities to the notochord regarding position, developmental origin, and expression profile.

Larvae have segmental multiciliated cells that regularly display spontaneous coordinated ciliary arrests, which compose the ciliomotor circuitry in the worms.

Unlike other polychaetes, in Platynereis larvae, the parapodia are used only for navigation while the cilia are responsible for propulsive force.

The cirri are thin thread-like head appendages and are specialized in tactile sensation, but can also give spatial information from were a chemical cue is coming, since a single stimulus can elicit in the left and right cirrus a response at a different times.

[30] Platynereis dumerilii commonly lives in depths of 0 to 5 meters,[31][32][26][25] and so is typical for shallow bright infra-littoral environments.

[31] However, it has been also found on a buoy at 50 meters[33] and on rotting seaweed at 100 m.[34] It may also live in less favorable environments, like at thermal vents[35][36] or polluted areas near sewer outfall pipes.

[41] Larvae feed on plankton, and migrate vertically in the ocean in response to changes in light, causing a daily transport of biomass.

The adult worms rise en masse to the water surface a few days after the full moon, during a one- to two-hour dark portion of the night between sunset and moonrise.

In the worm’s natural environment, it is important to synchronize spawning to increase the potential for gametes to meet and fertilize.

By detecting nighttime lighting in accordance with the lunar cycle, the worms synchronize reproductive activity.

Worms that make L-Cry protein are better able to detect appropriate light conditions and synchronize the release of gametes.

Some combination of signals from r-Opsin and L-Cry is believed to help the worms to coordinate rising at a common time to spawn.

[2] Therefore, the following developmental times are given with 18 °C as reference temperature: After 24 hours, a fertilized egg gives rise to a trochophore larva.

However, compared to many classical invertebrate molecular model organisms, this genome size is rather large and therefore it is a challenge to identify gene regulatory elements that can be far away from the corresponding promoter.

[50] Bristle worms contain the complex protein haemoglobin, found in vertebrates, annelids (e.g. earthworms), molluscs (e.g. pond snails) and crustaceans (e.g. daphnia).