Obelia spp.

click on image for more illustrations

The genus Obelia is distributed worldwide.
Nearshore coastal waters all along the coast of the western United States.
2-6 mm bell diameter, as adults.
Small zooplankton.
Useful Facts or Characters: 

Nearly flat with a central stomach and 4 sac-like gonads at the end of the radial canals.  At least 16 short, thick tentacles.

Natural History: 

The hydroid phase of the life history is better known than the medusa stage.  The hydroids grow in branching stalks and are commonly found as part of coastal benthic fouling communities.  The medusae are small and are often found during the summer.


Torrey, H.B. (1909) The Leptomedusae of the San Diego Region. University of California Publications in Zoology 6: 11-31.