Clytia gregaria (A. Agassiz, 1862)

Common name(s): Gregarious jellyfish

Synonyms:  Phialidium gregarium Clytia gregaria
Phylum Cnidaria 
Order Hydroida 
Suborder Thecata (Leptomedusae) 
Family Campanulariidae 
Clytia gregaria, 1.5 cm diameter, trawled in vertical night trawl to 100 ft depth off Rosario July 2023.
(Photo by: Dave Cowles, July 2023 )

Description:  As a hydromedusa, this small medusa has a velum and short manubrium. This species is wider than high and  has 4 unbranched radial canals which have no lateral diverticula but run all the way to the bell margin. The stomach is held tightly to the subumbrella rather than hanging down well away from it with the manubrium.  The lips of the mouth are relatively short and the manubrium does not hang down very far. The many (up to around 80), unbranched tentacles are of similar length as one another, do not have prominente rings of nematocycts, and are distributed evenly around the margin of the bell. There are no ocelli at the base of the tentacles. The light-colored, sausage-shaped gonads are associated with the outer ends of the radial canals and are mostly attached along the canals rather than hanging free under the subumbrella. Mature individuals are generally around 1.5 cm diameter.

How to Distinguish from Similar Species:  Clytia lomae matures at about 1 cm diameter. It has dark brown, gray, or yellowish gonads, and only up to about 40 tentacles. Mitrocoma cellularia has up to 350 tentacles which alternate long and short; its lips are long and extended, the gonads and/or the exumbrella may be pale blue, and the gonads may be associated with the entire length of the radial canals, especially the inner canal ends.

Geographical Range:  Alaska to central Oregon

Depth Range:  Epipelagic

Habitat:  Midwater.

Biology/Natural History:  Originally this medusa was known as Phialidium gregarium, but later it became known that it is the same genus as a Clytia hydroid species, so now it is known as Clytia gregaria. The medusa can often be found in large aggregations. It swims in bursts interspersed with slowly sinking while upside-down. The hydroid (polyp) form of this species also occurs along our coast.



Dichotomous Keys:
  Carlton, 2007
  Flora and Fairbanks, 1966
  Kozloff, 1987, 1996

General References:
  Kozloff, 1993

Scientific Articles:

Web sites:

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

Authors and Editors of Page:
Dave Cowles (2018):  Created original page
CSS coding for page developed by Jonathan Cowles

Salish Sea Invertebrates web site provided courtesy of Walla Walla University