Air fern

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Air fern
Sertularia argentea, Haeckel.jpg
Colony of Sertularia argentea
Scientific classification edit
Kingdom: Animalia
Phylum: Cnidaria
Class: Hydrozoa
Order: Leptothecata
Family: Sertulariidae
Genus: Sertularia
S. argentea
Binomial name
Sertularia argentea
  • Sertularia cupressina argentea (Linnaeus, 1758)
  • Thuiaria argentea (Linnaeus, 1758)

Air fern (Sertularia argentea) is a species of marine animal in the family Sertulariidae. It also known as the sea fir and Neptune plant.

These so-called "ferns" are dead and dried colonies of hydrozoans, colonies of marine hydroids, class Hydrozoa, phylum Cnidaria. Hydroids are related to corals and jellyfish.

These dried hydroid colonies are commonly sold as a curiosity, as a decorative "indoor plant", or as underwater decorations for aquaria in stores. They are sometimes labeled as "Neptune plants". Despite a superficial resemblance to plants, they are actually animal skeletons or shells. The dried colonies are often dyed green, but, when soaked in water, the coloring will dissolve.

An air fern on display

The fernlike branches of S. argentea are composed of many small, chitinous chambers where individual animals once lived. When the colony was alive, a polyp with numerous tentacles occupied each of the chambers, called hydrotheca.

Also note that sometimes dried bryozoa are sold as "air ferns."[1]

Most commercially sold air ferns are collected as a by-product by trawlers in the North Sea.


  1. ^ Frank K. McKinney. "The Bryozoa". International Bryozoology Association. Archived from the original on 2006-12-13. Retrieved 2007-02-17.

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