Panamic Fan Worm, Parasabella rugosa

Panamic Fan Worm, Parasabella rugosa. Underwater photograph taken in Zihuantanejo Bay, Guerrero, March 2018. Photograph courtesy of Ron Woheau, Zihuantanejo. Identification courtesy of Bob Hillis, Ivins, Utah.

Panamic Fan Worm, Parasabella rugosa. Underwater photographs taken in Zihuantanejo Bay, Guerrero, March 2020. Colony approximately 60 cm (2 feet 0 inches) x 91 cm (3 feet 0 inches). Photographs and identification courtesy of Ron Woheau, Zihuantanejo.

Phylogeny:  The Panamic Fan Worm, Parasabella rugosa (Moore, 1904), is a member of the Sabellidae Family of Feather-duster Worms. The genus Parasabella is one of forty-one genera in this family, and there are twenty-eight species in this genus. Historical this species was name Bispira monroi,  Bispira rugosa, and Bispira rugosa monterea, but was renamed in 2010. It is known in Mexico as Gusano Abanico Panámico. The family Sabellidae is currently undergoing much needed taxonomic revision. Additionally, many species in this family have been introduced to multiple locations, making range a less valuable tool in determining species identification. Positive identification of species in this family is difficult. As a result many identification are stopped at at the genus level.

Morphology: Panamic Fan Worms, similar to their cousins the earthworms,  have bodies that are composed of ringed segments. They have distinct thoracic and abdominal segments. Most of that body is hidden inside in a parchment-like tube. These tubes are made of mucoprotien, which may be mixed with silt, sand, or fine shell particles. Extending from the tube, when submerged, are two fan-shaped structures. These “fans” are made up of feather-like radioles. The radioles consist of paired side branches, and are used for respiration and food gathering. The radioles curve dorsally and are whitish, with thin, dark, reddish-brown bands. This species quickly withdraws into the tube when approached. Panamic Fan Worms reach a maximum of 5.0 cm (2.0 inches) in length.

Habitat and Distribution: Panamic Fan Worms are found attached to rocks in the intertidal and subtidal regions. They rare found at depths up to 60 m (197 feet). They are a tropical  Eastern Pacific species. In Mexican waters they are found throughout the Gulf of California, and extend south along the coast to Guatemala. They are absent from the west coast of the Baja Peninsula.

Diet: Panamic Fan Worms are suspension feeders, using their tentacles to grab plankton and suspended detritus from the water column. Once caught, the plankton are swept down a groove, by currents generated by cilia, to the mouth. This filtering process also secures fine particles that are used in tube building.

Predators: Panamic Fan Worms are a poorly studied and understood species. Very little has been documented regarding their predators. Other species within this genus are eaten by crabs, fish, gastropods and starfish.

Reproduction:  Panamic Fan Worms are gonochoric ( male or female for life). They can reproduce asexually by architomy  (splitting into multiple fragments, which regenerate the missing organs needed to become a mature individual)), or sexually. They reproduce sexually by either casting their eggs and sperm, through a rupture in the body wall, into the surrounding water, or into a section of the tube. The fertilized eggs produce planktonic larvae which settle on to hard substrates and begin tube building. From this point forward, they are confined to their tube.

Ecosystem Interactions: There are no documented examples of Panamic Fan Worms engaging in commensal, parasitic, or symbiotic relationships.

Human Interactions:  Panamic Fan Worms have no direct impact on human activities. From a conservation perspective they have not been formally evaluated however they are fairly common with a wide distribution and should be consider to be of Least Concern.

Synonyms: Bispira monroi, Bispira rugosa, Bispira rugosa monterea, Demonax rugosa, Distylia rugosa, Distylidia monroi, and Distylidia rugosa.