Invasion History

First Non-native North American Tidal Record: 1970
First Non-native West Coast Tidal Record: 1970
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Climacocodon ikarii is a remarkable, completely planktonic hydrozoan, first described from Oshoro, Hokkaido, on the Sea of Japan, and later collected from Muroran and Akkeshi on the Pacific coast of Hokkaido (Kubota 1979). This hydrozoan, although planktonic, appears to be confined to coastal waters, and has not been collected in the open ocean (T. Uchida 1970, in a letter to DeBoyd L. Smith, James T. Carlton, personal communication). It has been 'occasionally' collected off Central California and Coos Bay, Oregon.

North American Invasion History:

Invasion History on the West Coast:

Climacocodon ikarii was first collected in 1970 off a wharf in Santa Cruz, California by DeBoyd L. Smith, and illustrated in a book on plankton identification (Smith 1977). Several more specimens were collected off Dillon Beach, Tomales Bay (D. L. Smith, 1987, personal communication to James T. Carlton). This species was also collected and photographed in 2002 from Coos Bay, OR (R. Emlet, personal communication to James T. Carlton 2010). The photograph was published in Mills et al. (in Carlton 2007; plate 42I, page 138). This hydrozoan was probably introduced in ballast water.


Climacocodon ikarii is a hydrozoan whose polyp and medusa forms are both planktonic (Smith 1977; Kubota 1979; Mills et al., in Carlton 2007). Polyps, when first released, are very small (0.4-0.5 mm) and shaped like a truncated cone, with three circlets of short, blunt tentacles radiating outwards. As the polyp grows, the hypostome becomes elongated and the oral tentacles are well-separated from the two circlets of aboral tentacles. A second whorl of blunt oral tentacles develops above the first. Medusa buds are produced around the base of the hypostome. Mature polyps are 1.6-2.3 mm long, and resemble the detached hydranth of a benthic hydroid, though the tentacles remain short and blunt, and the base of the hypostome is surrounded by medusa-buds.

The medusa of C. ikarii is between cubical and ovoid in shape, and when mature, a little taller than wide. In young medusae, the manubrium is cylindrical, but it becomes flask-shaped as the medusa grows. When extended, it can reach to the opening of the bell cavity. The middle of the manubrium is surrounded by gonadal tissue. In females, clusters of eggs develop on the manubrium. There are four radial canals, which form swellings when they join the ring canal. The velum is well-developed. A unique feature of C. ikarii is the presence of tentacles arising from the middle sides of the umbrella as well as from the margin. Four sets of about eight tentacles project from the radial canals, three of these from the sides of the bell. Depending on maturity of the medusae, the total number of tentacles varies from about 23 to 46. Mature medusae are about 3 mm in height (description from: Kubota 1979).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Cnidaria
Class:   Hydrozoa
Subclass:   Hydroidolina
Order:   Anthoathecatae
Suborder:   Capitata
Family:   Margelopsidae
Genus:   Climacocodon
Species:   ikarii


Potentially Misidentified Species



Climacocodon ikarii is a hydrozoan whose polyp and medusa forms are both planktonic. The polyp drifts in the plankton, and buds off medusae as it grows (Smith 1977; Kubota 1979; Mills et al., in Carlton 2007). Presumably, the polyp captures zooplankton, although its tentacles are short and blunt. The medusa also feeds on zooplankton and develops eggs in its ovaries. When fertilized, these eggs develop into planulae, which develop into polyps. Kubota (1979) described the development of this organism from preserved specimens. To our knowledge, C. ikarii has not been reared, so many details of its life history are unknown.



Trophic Status:

Suspension Feeder



General HabitatUnstructured BottomNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Vertical HabitatPlanktonicNone

Tolerances and Life History Parameters

Maximum Width (mm)3Medusa diameter (Kubota 1979)
Broad Temperature RangeNoneCold-temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

No impacts have been reported for native or introduced populations of Climacocodon ikarii.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NEP-V Northern California to Mid Channel Islands 1970 Def Estab
P080 Monterey Bay 1970 Def Estab
P110 Tomales Bay 1976 Def Estab
NEP-IV Puget Sound to Northern California 2002 Def Estab
P170 Coos Bay 2002 Def Estab
NWP-4a None 1924 Native Estab
NWP-4b None 0 Native Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Carlton, James T. (Ed.) (2007) The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon Fourth Edition, Completely Revised and Expanded, University of California Press, Berkeley. Pp. <missing location>

Kubota, Shin (1979) Morphological notes on the polyp and medusa of Climacocodon ikarii Uchida (Hydrozoa, Margelopsidae) in Hokkaido, Journal of the Faculty of Science, Hokkaido University, Series VI 22(1): 122-139

Mills, Claudia; Marques, Antonio; Migotto, Alvaro E; Calder, Dale R.; Hand, Cadet (2007) The Light and Smith Manual: Intertidal invertebrates from Central California to Oregon (4th edition), University of California Press, Berkeley CA. Pp. 118-168

Smith, DeBoyd L. (1977) <missing title>, Kendall/Hunt Publishing Company, Dubuque, Iowa. Pp. <missing location>