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DescriptionFicopomatus enigmaticus is a fan-worm that forms thin, white, calcareous tubes that turn yellowish-brown with age and are up to 8 cm in length and 0.1-0.2 cm in diameter. Tubes are marked by fine, transverse rings that spread outwards, reflecting previous growth. Thousands of individuals grow together at an individul rate of up to 2 cm per month to form huge reefs up to 50 cm in height and 4 m across, varying in shape from circular to elongate depending on water flow. The worm's body consists of a head, a seven segmented thorax, a 50-120 segmented abdomen and a tail segment. It grows to up to 2.5 cm in length and is greenish or reddish-orange in colour. The head has paired lobes, each bearing green, darkly banded, feather-like feeding tentacles up to 0.3 cm long and arranged in a semi-circle. One or more of the tentacles are modified into a yellowish-brown, fig-shaped operculum with dark spines. The base of the head is surrounded by a tall, faintly ribbed collar. The segments of the thorax, except for the first, are marked by a dorsal faecal groove and bear bundles of chaetae in two rows. The segments of the abdomen, except for the first to third, bear bundles of two to five chaetae also in two rows. The pygidium bears two small lateral lobes.Ficopomatus enigmaticus is a suspension-feeder. It has a planktonic larvae and reproduces by external fertilization. This species lacks true gonads and, although generally gonochoristic, hermaphroditism has been recorded in some populations.