Orthopyxis everta (Clark, 1876)

Common name(s): 

Synonyms: Eucopella everta Orthopyxis everta
Phylum Cnidaria 
Subclass Leptotheca (Leptomedusae; Thecata) 
Order Proboscoida 
Family Campanulariidae 
Orthopyxis everta, about 2 mm tall, on a tunicate.  Note the annulated pedicel and smooth rim to the hydrotheca.
(Photo by:  Dave Cowles, August 2010 )
Description:   As with all thecate hydroids, the hydranth of this species is partly enclosed by a hydrotheca.  The hydrotheca is bell-shaped and deeper than wide, and able to contain the entire hydranth when it contracts.  There is no operculum.  The rim of the hydrotheca is smooth and a diaphragm exists in the lower part of the hydrotheca.  The hydranths are on slender, annulated individual stalks (pedicels) (see photo above) connected to stolons.  The colony produces small medusae (<= 2 mm) that may or may not be released.  The medusae have no stomach.

How to Distinguish from Similar Species:  Several similar genera such as Campanularia and Clytia have cusps or undulations on the rim of the hydrothecaOrthopyxis compressa and O. integra have smooth, non-annulated pedicels

Geographical Range:  British Columbia to southern California.

Depth Range:  2-77 m.

Habitat: Sometimes found abundantly on kelp

Biology/Natural History:  The colonies grow in a stolon.  This hydroid retains its gametes.  The larvae of the pycnogonid Tanystylum duospinum live parasitically on this species.



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

General References:

Scientific Articles:

Web sites:

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

Another on same tunicate

Another indivudual on the same tunicate.  Note the diatoms attached to some stalks.

Authors and Editors of Page:
Dave Cowles (2010):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)

Rosario Invertebrates web site provided courtesy of Walla Walla University