Bobbit Worm (Eunice aphroditois): Reproduction and Pest Notes

Eunice aphroditois is not a cultivated species but a feared live-rock hitchhiker. This guide outlines the limited published biology of its broadcast spawning and explains why it is treated as a reef-tank pest.

Overview

Eunice aphroditois is a large eunicid polychaete of the family Eunicidae. Recorded lengths span from under 10 cm to nearly 3 m, with the longest specimen measured at 299 cm, while the body remains only about 25 mm wide. It is an ambush predator that burrows in soft sediment and strikes passing prey with sharp mandibles. In aquaria it is regarded purely as a pest.

Spawning & Egg-brooding

Published biology indicates broadcast spawning rather than parental care. During spawning, individuals release sperm and eggs into the water column, where external fertilisation occurs. There is no den-building or egg-brooding stage, which separates this worm from cephalopods that tend their clutches.

Hatchling/Juvenile Care

Fertilised embryos develop into planktonic trochophore larvae that drift before settling and metamorphosing into juvenile worms. Because the species is treated as a pest, there is no established captive rearing protocol; small specimens most often enter tanks already as juveniles concealed in live rock.

Common Challenges

• Small individuals evade detection by hiding inside live rock when introduced to a tank.
• The worm hides in narrow burrows, making physical removal difficult.
• It depletes fish and invertebrate populations through ambush predation.
• It shows limited regeneration, primarily of posterior (tail) segments; claims of asexual reproduction by splitting are not scientifically supported.