Abietinaria inconstans (Clark, 1876)

Common name(s): Sea fir, Coarse sea fir

Synonyms:Abietinaria amphora, A. costata Abietinaria inconstans
Phylum Cnidaria 
Subclass Hydroidolina 
Order Leptothecatae 
Family Sertulariidae 
Abietinaria inconstans colony, about 8 cm tall, found at 90 m depth in the San Juan Channel.  This colony is heavily encrusted with small bryozoans and tubeworms.
(Photo by:  Dave Cowles, August 2014)

Description:  This colonial hydroid forms distinctive pinnately-shaped colonies with a thick stem and coarsely branching side stems.  The species is thecate, meaning that the polyps are enclosed within a chitinous hydrotheca into which they can completely retract. The hydrothecae are approximately alternating (not paired), protruding at an angle from opposite sides of the stalk, but they are not on individual stalks (photo).   The stalk is about twice as wide as the individual hydrothecae (photo).  The hydrotheca is longer (deeper) than it is wide, and the opening can be closed by a single operculum which is attached to the hydrotheca on the side closest to the stalk (photo).

How to Distinguish from Similar Species:  Several other Abietinaria species (not distinguished in Kozloff's key) have a stalk only about as wide as the individual hydrothecaeThuiaria sp. has the operculum attached to the side of the hydrotheca opposite the stalk. Sertularia and Sertularella spp. have an operculum consisting of 2-4 flap plus they are more finely branched. Aglaophenia has a similar pinnate colony but it is much more finely branched, has the distinctive corbulae structures for reproduction, and the polyps are on only one side of each branch.

Geographical Range:  Alaska to Baja California, Mexico

Depth Range:  Low intertidal to 313 m

Habitat:  In areas out of direct sun such as under ledges and boulders

Biology/Natural History:  The reproductive polyps of this species produce sessile (attached) medusae.  They occur on the main stalk and the lower parts of the branches.



Dichotomous Keys:
  Carlton, 2007
  Kozloff, 1987, 1996 (as Abietinaria spp)

General References:
  Harbo, 2011
  Kozloff, 1993
  Morris et al., 1980

Scientific Articles:

Web sites:

General Notes and Observations: Locations, abundances, unusual behaviors:

This closer view of the colony shows the polyps (within their hydrothecae) along the two sides of each branch.  Notice that the branches are about twice as wide as the hydrothecae are.

The individual hydrothecae can be clearly seen in this closer view.  The colony is a bit fouled by diatoms and other debris.

In this photo of an individual hydrotheca, the darker operculum which is attached on the side nearest the stalk can be seen.

Authors and Editors of Page:
Dave Cowles (2014):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)

Salish Sea Invertebrates web site provided courtesy of Walla Walla University