Eunice aphroditois is a benthic bristle worm of warm marine waters. It lives mainly in the Atlantic Ocean, but can also be found in the Indo-Pacific.^[1][2] It ranges in length from less than 10 cm (4 in) to 3 m (10 ft).^[3] Its exoskeleton displays a wide range of colors, from black to purple and more. This species is an ambush predator; it hunts by burrowing its whole body in soft sediment on the ocean floor and waiting until its antennae detect prey.^[4] It then strikes with its sharp mandibles.^[5] It may also be found among coral reefs.

Quick Facts Scientific classification, Binomial name ...

Eunice aphroditois
A burrowed Eunice aphroditois
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Annelida
Clade:	Pleistoannelida
Subclass:	Errantia
Order:	Eunicida
Family:	Eunicidae
Genus:	Eunice
Species:	E. aphroditois
Binomial name
Eunice aphroditois Pallas, 1788

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Eunice aphroditois is also known as the bobbit worm^[6][7] or bobbitt worm.^[8] The name is believed to be taken from the John and Lorena Bobbitt case;^[9] however, another proposed reason is due to its jaw. It is sometimes called the sand striker.^[8] Another name associated with them is trap-jaw worm. Traces of their burrows have been noted in 2021 to have been found among fossils near Taiwan dating back twenty million years.^[10]

These ambush predators have five antennae on their head that are used to sense prey.^[11] The body is covered by a hard exoskeleton.^[12] The mandibles can be retracted inside the body and are responsible for striking and stunning prey; they are capable of snapping some prey in half.^[13] Typically, E. aphroditois ranges from deep purple to black, with an iridescent skin. The largest known specimen on record reached 299 centimeters (9.81 ft) in length,^[3] making it the longest known member of the polychaete class. Despite these great lengths, the worms are slim, with the body only about 25.5 millimeters (1.00 in) wide.

This species may be found prowling among the prey-rich environment of coral reefs, where its coloration allows it to blend in and its slim body enables it to hunt in tight places.^[13] It inhabits a wide range of other habitats,^[14] particularly sandy and muddy sediments, as well as around rocks and sponges.^[13] It has been recorded at depths of up to 95 meters (312 ft).^[7]

Eunice aphroditois's sexual reproduction organs have not been fully studied, therefore there is no clear answer of how they reproduce, though a proposed idea is that they reproduce similarly to Polychaetes.

The lifespan of E. aphroditois is believed to be three to five years.^[17]

While not commonly kept in aquaculture, individuals of E. aphroditois are occasionally found in home aquaria, where smaller specimens can evade detection by being transported into the tank in live rocks, where they then grow in size.^[19] As E. aphroditois hunts fish, it cannot be kept as part of a community tank and should be removed when found, as it will deplete the aquarium's stock by direct predation.^[20]

E. aphroditois can be difficult to remove from aquariums due to their abilities to split into new individuals when cut in half,^[18] dig holes into rocks, and curl up and hide in small rocks, despite their length.^[21]

Fossil burrows from the Miocene of northeastern Taiwan have been likened to E. aphroditois. The burrows, classified in the ichnogenus Pennichnus, have been found preserved in fine-grained sandstone. They are L-shaped and can reach up to 2 metres (6 ft 7 in) in length, with a vertical section covered in feather-like collapse structures comprising around 40% of the burrow length, connected by a short intermediate section to a horizontal section amounting for 50% of the length. The burrows are on average 2.5 centimetres (0.98 in) wide at the entrance, and taper down to 2 centimetres (0.79 in) at the end of the horizontal section.^[22]