Clytia lomae (Torrey, 1909) (Medusa)

Common name(s): 

Synonyms: Phialidium lomae Clytia lomae
Phylum Cnidaria 
Class Hydrozoa 
Suborder Thecata (Leptomedusae) 
Family Companulariidae 
Clytia lomae captured in a surface plankton tow off Rosario Beach Marine Laboratory at night. Diameter 6 mm.
(Photo by: David Cowles, July 2017 )

Description:  This small hydromedusa has a flattened bell with a diameter greater than its height. Its numerous unbranched tentacles (up to 80) are evenly distributed around the bell margin. The highly extensily tentacles are all of similar size and do not have knoblike concentrations of nematocysts on them, nor do they have ocelli at their bases. Alternating between the tentacles around the margin of the bell are marginal vesicles including statoliths. There is no dark band around the margin of the bell. The stomach is attached directly to the subumbrella rather than suspended below it on a peduncle, and it has a short manubrium with 4 lobed lips. The medusa has 4 unbranched radial canals which run from the stomach to the bell margin, forming a characteristic cross pattern. The radial canals do not have conspicuous lateral diverticula.  The dark brown, gray, or yellow, elongated gonads are associated with the radial canals about 1/2 way or farther out to the margin of the bell and have a circular cross-section.  The medusa matures when the bell is about 1 cm diameter, at which time it has less than 10 tentacles per quadrant (and presumably less than 40 total?).

This type of medusa was formerly classified in genus Phialidium, until it was discovered by T.C. Frye that it is the medusa of polyps in genus Clytia.

How to Distinguish from Similar Species:Clytia gregarium is very similar but does not mature until the bell is 1.5 cm diameter, has light-colored, sometimes dark-striped gonads with an elliptical cross-section, and may have a dark ring around the margin of the bell. It has been speculated that C. gregarium and C. lomae are actually the same species.

Geographical Range:  At least from San Diego north to the Salish Sea. (Its sister species, C. gregaria, occurs coastally from Oregon to the Bering Sea)

Depth Range:  Pelagic

Habitat:  Coastal pelagic

Biology/Natural History:  Although the polyp stage of C. lomae has not yet been discovered, the hydroid (polyp) stage of other Clytia live on the shells of living snails or clams, but do not seem to occur on stones or on dead mollusk shells. Periodically the polyps release large numbers of medusae, which swim in energetic bursts (movie) followed by periods of passive sinking. Some have suggested that Clytia attenuata, which has known polyps and occurs from Vancouver Island to southern California, is the same species as C. lomae, but this has been disputed (Arai and Brinkmann-Voss 1980).

Some Clytia species are said to be brightly bioluminescent around the margin of the bell when disturbed at night.

Clytia sp. medusae are sometimes parasitized by the larva of the anemone Peachia quinquecapitata. The medusae capture and ingest the larvae, which then feed on the medusa's stomach and gonads before finally dropping off and becoming a benthic anemone.



Dichotomous Keys:
  Carlton, 2007
  Kozloff, 1987, 1996 (as Phialidium lomae, corrected to Clytia lomae)

General References:
  Johnson and Snook, 1955 (General information on Phialidium and Clytia)
  Morris et al., 1980 (General information on Clytia)
  Wrobel and Mills, 1998 (Information on C. gregaria)

Scientific Articles:
Arai, M.N. and A. Brinkmann-Voss, 1980. Hydromedusae of British Columbia and Puget Sound. Canadian Bulletin of Fisheries and Aquatic Sciences 204: 192 pp.

Web sites:

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

Authors and Editors of Page:
Dave Cowles (2017):  Created original page
CSS coding for page developed by Jonathan Cowles

Salish Sea Invertebrates web site provided courtesy of Walla Walla University