Aglaophenia sp. (probably latirostris or struthionides)

Common name(s): Ostrich plume hydroid

Phylum Cnidaria
 Class Hydrozoa
  Order Hydroida
   Suborder Thecata
    Family Aglaopheniidae
Aglaophenia sp. colony collected at 5 m depth off Sares Head.
(Photo by: Dave Cowles, Jule 2006)
Description:  Aglaophenia sp is a large benthic, colonial hydroid with a distinctive pinnate growth form.  Its polyps have a hydrotheca into which they can withdraw.  The perisarc margins on the hydrotheca are toothed and the hydrotheca is deeper than wide and attached directly to the main hydroid stalk.  The hydrotheca has no operculum.  The gonophores are within corbulae, which occur in series on some branches of the hydroid and can readily be seen without magnification (they look like small clusters of eggs deposited on the hydroid (photo).  Plumes may be up to 15 cm long.

How to Distinguish from Similar Species:  There are several species of Aglaophenia, which need more systematic work.  Cladocarpus has gonophores which are on slender branches instead of within corbulae.  The genus Aglaophenia has hydroids with sessile nematophores, hydrothecae with toothed margins, and gonophores enclosed in basketlike corbulae made of overlapping leaf-like structures.

Geographical Range:  British Columbia, Canada to San Diego, CA.

Depth Range:

Habitat:  Rocky subtidal habitats, especially where exposed to current.

Biology/Natural History:  This hydroid retains the medusae within the corbulae. Corbulae containing male and female gonophores look slightly different.  The medusae, which are highly modified, release eggs and sperm (the eggs are retained in the female medusae until fertilization, and it is the planula that is released).  The planula larva settles to the bottom, crawls for awhile, and grows into a new hydroid.   Caprellid "skeleton shrimp" and pycnogonids can often be found climbing on hydroids such as this species.

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Dichotomous Keys:
  Flora and Fairbanks, 1966
  Kozloff 1987, 1996
  Smith and Carlton, 1975

General References:
  Gotshall and Laurent, 1979
  Hinton, 1987
  Johnson and Snook, 1955
  Kozloff, 1993
  Morris et al., 1980
  Niesen, 1994
  Niesen, 1997
  Ricketts et al., 1985

Scientific Articles:

Web sites:

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

A closer view of two Aglaophenia plumes.  The upper plume has corbulae with the reproductive gonophores.

This closeup of a plume shows the individual polyps in their hydrothecae (note some polyps are open and actively feeding while others are retracted).
The large structures are a string of corbulae with the reproductive gonophores (and captive medusae) inside.

Authors and Editors of Page:
Dave Cowles (2006):  Created original page