Commentary on species of Hydrozoa, Scyphozoa and Anthozoa (Cnidaria)
Sometimes Listed as Non-Indigenous in Puget Sound
by Claudia Mills, October 1998

A number of lists of non-indigenous marine and aquatic species for Washington State have recently been developed without the specific guidance of taxonomic experts for various groups. I offer here my assessment of the cnidarian species that have been included on some of these lists, ending with a list of those species that should henceforth be included as either non-indigenous or cryptogenic in Puget Sound - see Summary at bottom of page. It is hoped that this list will eventually be adopted and used to emend the State of Washington website for non-indigenous aquatic nuisance species.


Bougainvillia muscus (Allman, 1863). Sometimes listed under its junior synonym B. ramosa. I collected hydroids of this species on floats of the town docks of Friday Harbor in 1978. Medusae from the hydroids were raised in the laboratory in order to positively identify this species. The status of this species, which has been recorded from all over the world, is uncertain, as it may in fact represent more than one cryptic species (Calder, 1988). It should be listed as cryptogenic in Washington.

Cladonema radiatum Dujardin, 1843. This very small hydromedusa and its polyp have been abundant amongst Zostera marina on the east shore of Padilla Bay during the past decade. It is considered to be a West-Atlantic boreal species, although it has also been collected at least in Bermuda, the Bahamas, Florida and perhaps Japan (Kramp, 1959; Calder, 1988). The species was first collected in Washington in 1988 by Eugene Kozloff, Judy Friesen and Francis Ambrose and identified by me. The population was probably established several to many years before it was noticed. I have continued to collect it regularly in Padilla Bay since 1988 and have made some unpublished observations on its natural history.

Cordylophora caspia (Pallas, 1771). Sometimes referred to by its junior synonym Cordylophora lacustris, this species is reported to have been collected in Lake Union by Trevor Kincaid about 1920 (Carlton, 1979). We found luxurious growths of this species at Edison, near the mouth of the Samish River, where the salinity was 3 psu. The Puget Sound Expedition site at Fishermen's Terminal was included in order to look for this species and I further searched during October 1998 at several sites on Lake Union and in the Montlake cut in Seattle, but none was found. This species is generally considered to be native to the Caspian and Black Seas, but has been found worldwide including a variety of low salinity sites from British Columbia to California (Carlton, 1979).

Ectopleura crocea (L. Agassiz, 1862). There are records of this Atlantic species in the San Juan Islands from the 1930s (see Carlton, 1979), but except for an unsuccessful attempt to introduce this species using East Coast material in the early 1980s, I know of no recent collections. Confusion with several of what are thought to be native species of Ectopleura, Tubularia or Hybocodon is likely, and species names should only be assigned to this group with great care. This species should be removed from the list of non-indigenous species in Washington until such time as new collections show that it is really present and established.

Gonothyraea clarki (Marktanner-Turneretscher, 1895). Originally described from Spitzbergen, this is one of several Gonothyraea species reported from the Pacific Coast by Fraser (1937), who records it from numerous locations between the Aleutian Islands and southern California including the San Juan Islands. The taxonomy of Gonothyraea is in need of further study; if all are a single species, it could be circumpolar in distribution; there may also be confusion of more than one species with at least one being a native eastern-Pacific species. This genus can be separated from other members of the family Campanulariidae based on its reproductive stuctures, which are also needed to make positive identification to species. This species should be removed from lists of non-indigenous west coast species pending further study.

Obelia spp. I remain skeptical that Obelia is an exotic genus in the eastern Pacific; in a poll of my colleagues at the September 1998 Workshop of the Hydrozoan Society in California, most hydrozoan taxonomists present felt confidant that this genus is cosmopolitan. Species identification within this genus is highly problematic and the number of valid species is hotly debated by specialists. At the Hydrozoan Workshop, Professor Wim Vervoort of the National Museum of Natural History in Leiden, Netherlands, identified both Obelia dichotoma (Linneaus, 1758) and Obelia longissima (Pallas, 1766) from the Puget Sound Expedition samples. Until someone does an in-depth molecular and genetic study of this genus, both O. dichotoma and O. longissima might best be listed as cryptogenic in Washington.

Sarsia tubulosa (M. Sars, 1835). This species should not be on any list of non-indigenous west coast species, as it almost certainly occurs natively on the west coast. All of the problems related to Sarsia identification, including early references to Syncoryne mirabilis, Coryne rosaria and others (see Carlton, 1979), actually reflect purely taxonomic (rather than biogeographic) problems. There are at least 4 species of Sarsia that seem to be native to the Puget Sound/Strait of Georgia region, including S. tubulosa, which appears to be a circumboreal species (see Arai and Brinckmann-Voss, 1980). Although the genus is well known and easily recognized, most species of Sarsia are very difficult to identify correctly, and detailed morphology of both the medusa and its polyp must be known in order to apply a species name in most cases.


Aurelia aurita (Linnaeus, 1758) and Aurelia labiata Chamisso and Eysenhardt, 1821. Recent unpublished work by Lisa Gershwin of the University of California at Berkeley has convinced me that both species are good and that both have been found in recent times on the west coast. Certainly both species can presently be found on display in public aquariums on the west coast, sometimes in the same tank. Although the name A. labiata has been used in various publications including Light's Manual Third Edition, it is Gershwin's new morphological observations that indicate this species to be distinctly different from A. aurita. New unpublished molecular data by a number of scientists appears to support that conclusion. I summarize what are believed to be valid morphological species descriptions in Wrobel and Mills (1998). Most Aurelia medusae on the west coast, including all specimens known from Puget Sound, seem to be A. labiata, which was originally described from near San Francisco. Specimens of A. labiata collected in Port Orchard during the Puget Sound Expedition were sent to Werner Schroth of Johann Wolfgang Goethe-University, Frankfurt am Main, Germany, for molecular analysis. Aurelia aurita should be removed from the list of non-indigenous species in Washington until such time as new collections show that a second species is also present here.


Diadumene lineata Merrill, 1870. Often listed as its junior synonym Haliplanella luciae, this anemone with worldwide distribution was collected by the Puget Sound Expedition at the Shelton Marina where it occurred in great numbers at the waterline of the floats. It has also been collected by Jim Carlton, Art Siebert, and me on separate occasions in the 1970s on rocks in the high intertidal at the Friday Harbor Laboratories, below the library. Bruno Pernet collected it in Padilla Bay in May 1998 on cobbles just beyond the boulders supporting the beginning of the dyke trail, along with lots of non-indigenous Batallaria snails. Carlton (1979) gives a fairly cohesive argument that it is likely to be non-indigenous to Washington State, favoring the theory of an Asian Pacific origin, but since its real origin may never be understood, it might fairly be listed as either non-indigenous or cryptogenic in Washington.

Nematostella vectensis Stephenson, 1935. Known in Puget Sound from Jaekle's Lagoon on San Juan Island and a lagoon near Camp Casey on Whidbey Island. This estuarine species has an extremely broad worldwide distribution, not so different from Diadumene lineata. Hand and Uhlinger (1994) have located it in all but two of the United States with coastlines. There is some question of whether or not this species with widespread global distribution is native or non-indigenous, but Hand and Uhlinger weigh-in slightly favoring the spread of this low salinity, quiet water species with mariculture and shipping. So far only female Nematostella vectensis have been collected in Washington (Hand and Uhlinger (1994) and Tammy McGovern, personal communication), which implies that Washington populations are likely to be clonal introductions and not native. Listing this species as cryptogenic in Washington seems the most conservative way to treat it until more is known.


In summary, the following non-indigenous (NIS) and cryptogenic (C) species should be listed as present and established in Puget Sound:


Bougainvillia muscus .......... C
Cladonema radiatum ......... NIS
Cordylophora caspia ......... NIS
Obelia dichotoma ................ C
Obelia longissima ............... C



Diadumene lineata ............. NIS or C
Nematostella vectensis ........... C


Literature Cited

Arai, M. N. and A. Brinckmann-Voss, 1980. Hydromedusae of British Columbia and Puget Sound. Canadian Bulletin of Fisheries and Aquatic Sciences, Bulletin 204: 1-192.

Calder, D. R. 1988. Shallow-water hydroids of Bermuda: the Athecatae. Royal Ontario Museum Life Sciences Contributions 148: 1-107.

Carlton, J. T. 1979. History, Biogeography, and Ecology of the Introduced Marine and Estuarine Invertebrates of the Pacific Coast of North America. Ph.D. dissertation, University of California, Davis, 903 pages.

Fraser, C. M. 1937. Hydroids of the Pacific Coast of Canada and the United States. University of Toronto Press, Toronto, 207 pages and 44 plates.

Hand, C. and K. R. Uhlinger, 1994. The unique, widely distributed, estuarine sea anemone, Nematostella vectensis Stephenson: a review, new facts, and questions. Estuaries 17: 501-508.

Kramp, P. L. 1959. The hydromedusae of the Atlantic Ocean and adjacent waters. Dana Report 46: 1-283.

Website for Non-indigenous Aquatic Nuisance Species (ANS), Washington State Department of Fish and Wildlife, located at (as of October 28, 1998).

Wrobel, D. and C. Mills, 1998. Pacific Coast Pelagic Invertebrates: a Guide to the Common Gelatinous Animals. Sea Challengers and the Monterey Bay Aquarium, Monterey, California, 108 pages.

** This site is maintained by C. E. Mills;
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