6-7-2024 ROTTERDAM ZOO, NETHERLANDS - FRINGED CERIANTHID (Pachycerianthus fimbriatus)

Pachycerianthus fimbriatus is a cerianthid anemone that burrows in substrate and lives in a semi-rigid tube made of felted nematocysts. The anemone is often seen in bright orange to red.

Like most anemones, the tube-dwelling anemone contains stinging cells or nematocytes along its tentacles, however, the cells are not toxic to humans.

The ceriantharia possess two whorls of tentacles, one surrounding the mouth (labial tentacles) and one at the edge of the oral disc (marginal tentacles).

This species was described from Indonesia. It is considered to be synonymous with Pachycerianthus plicatus which was described from the Pacific Ocean coast of North America.

Pachycerianthus fimbriatus feeds on small crustaceans. The giant nudibranch Dendronotus iris has been documented to prey upon P. fimbriatus. 

9-12-2021 CITY OF ARTS AND SCIENCES, VALENCIA - FRINGED CERIANTHID (Pachycerianthus fimbriatus)

The Fringed Cerianthid (Pachycerianthus fimbriatus) is a tube-dwelling sea anemone belonging to the order Ceriantharia.

Key Characteristics

• Appearance: Features a bright orange, red, cream, or purple coloration. It grows up to 35 cm in length with a tentacle spread of around 30 cm.

• Tentacles: Possesses two distinct rings of tentacles:

• Marginal (outer) tentacles: Long, fine, and flowing; used for defense and catching prey.

• Labial (inner) tentacles: Short and tightly packed around the mouth; used to handle and ingest food.

• Tube Dwelling: Lives inside a long, semi-rigid, and slimy tube made of mucus and specialized stinging threads called ptychocysts. The tube is buried vertically in soft mud, sand, or gravel.

• Toxicity: Contains stinging cells (nematocysts), but they are not toxic to humans.

Habitat and Distribution

• Range: Found along the Pacific coast of North America (from Southern Alaska to Baja California) and parts of the Indo-Pacific/Indonesia.

• Depth: Typically found in subtidal zones down to 54 meters or more, inhabiting soft mud banks, bays, and harbors.

• Diet & Predators: Feeds on small crustaceans and zooplankton; it is known to be preyed upon by the giant nudibranch Dendronotus iris.