Gonionemus vertens A. Agassiz, 1862

Common name(s): Clinging jellyfish, Orange-striped jellyfish, Angled hydromedusa

Phylum Cnidaria
Class Hydrozoa
Order Thecata (Leptomedusae)
Suborder Limnomedusae
Family Olindiasidae
Gonionemus vertens, 2 cm diameter, found on eelgrass in Padilla Bay, WA.  The 4 radial canals with attached frilly gonads, and the hanging manubrium can be seen.
(Photo by: Dave Cowles, July 2007)
Description:  This bell-shaped hydromedusa (usually just slightly broader than tall) has about 60-80 unbranched tentacles which evenly spaced around the margin of the bell.  The tentacles have large rings of nematocycts all along their length (photo), and partway back from the tip of each tentacle is a larger adhesive knob or pad used for attachment to objects (photo).  The tentacle tends to bend at the disk (photo).  The tentacle bulbs at the base of the tentacles are yellowish-tan (photo)(photo).  The 4 radial canals are unbranched and continue all the way to the margin of the bell.  There are no centripetal canals.  Ruffled flaplike orange, red, violet (in females), or yellow-brown (in males) gonads hang down along the 4 radial canals and form a clearly visible X shape (see photo above)(photo)(photo).  The manubrium is colored tan and hangs down about to the bell margin, with 4 slightly frilly lips(photo). The bell may be clear or light green. (It is unusual for a hydrozoan medusa to be colored but the light green appears to be algae coating the outside of the bell).  Diameter to 2.5 cm.

How to Distinguish from Similar Species:Eperetmus typus is also deep bell-shaped and has nematocyst rings on the tentacles but it has no adhesive pads on the tentacles and the radial canals usually have many centripetal canals.

Geographical Range:  Alaska to southern California, Kamchatka, northern Japan, Arctic Ocean, N Atlantic to Cape Cod. On our Pacific coast not common south of Puget Sound but some blooms have appeared farther south such as near Santa Barbara, CA.

Depth Range:

Habitat:  Attached to kelp, eelgrass, and other substrates (in summer); in at least partly protected waters.

Biology/Natural History:  Feeds on small crustaceans, especially copepods.  The  polyp is seldom seen.  The polyps of this species found in Kamchatka are highly venomous but those along our coast are not.

Older references list this species as a member of the Trachyline medusae.



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

General References:
  Harbo, 1999
  Kozloff, 1993
  McConnaughey and McConnaughey, 1985
  Wrobel and Mills, 1998

Scientific Articles:

Daniel, Thomas L., 1985.  Cost of Locomotion: Unsteady Medusan Swimming.  Journal of Experimental Biology 119,149-164

Mills, C.E., 1993.   Natural mortality in NE Pacific coastal hydromedusae: Grazing predation, wound healing and senescence.   Bulletin of Marine Science 53(1):

Singla, C.L., 1977.  Fine structure of the adhesive pads of Gonionemus vertens.  Cell Tissue Res. 181(3):395-402

Westfall JA., 1970.  The nematocyte complex in a Hydromedusan, Gonionemus vertens.  Z Zellforsch Mikrosk Anat. 110(4):457-470.

Web sites:

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

In this view of a swimming individual the kneelike articulation of several of the tentacles at the adhesive pad can be seen. Note the tan color on the manubrium, the gonads, and on the tentacle bulbs.

This closeup of several tentacles shows the distinct nematocyst rings and also the adhesive pads.

In this closeup the velum can be clearly seen along the margin of the bell.  The manubrium is at top center, a gonad is seen along a radial canal down through the center of the photo,
and the bell margin with velum and single row of tentacles with tan tentacle bulbs is visible across the bottom third.

In this view of the subumbrella, the frilly lips of the manubrium can be seen.

Another view of the subumbrella, showing the manubrium and gonads. Photo by Dave Cowles, June 2020

Tentacular bulbs
A closeup of the rim of the bell, showing the tentacles and tentacular bulbs. Photo by Dave Cowles, June 2020

Authors and Editors of Page:
Dave Cowles (2007):  Created original page
Jonathan Cowles (2007):  Updated page with CSS