Invasion History

First Non-native North American Tidal Record: 1974
First Non-native West Coast Tidal Record: 1974
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Catriona rickettsi, described from San Francisco Bay, is considered introduced to the West Coast, but is of unknown origin (Cohen and Carlton 1995). It has been collected from Oregon to Mexico, but has not been reported from other parts of the world. However, its relatively recent discovery (1974) in San Francisco Bay, and its association with and feeding on the introduced hydroid Ectopleura (= Tubularia) crocea (Behrens 1984; Cohen and Carlton 1995) are indicative of introduced status. Ectopleura crocea is native to the Western Atlantic, but C. rickettsi is not known from that region, so its original food source is likely a different, but related hydroid.

North American Invasion History:

Invasion History on the West Coast:

Catriona rickettsi was described from specimens collected in Pete's Harbor, Redwood City, in South San Francisco Bay, California in 1974 (Behrens 1984). It was also found in the central part of San Francisco Bay at Hunters Point, Treasure Island, and South Hampton Shoal in 2000 (Ruiz et al., unpublished data). It has been found at several spotty locations on the West Coast, including tidepools in La Jolla, CA in 1980; a jetty at the mouth of the Umpqua River in Reedsport, Oregon in 1994; and Punta Eugenia, Baja California, Mexico (Cohen and Carlton 1995; Bertsch et al. 2000; Behrens 2004, in Miller 2014; California Academy of Sciences 2014).


Catriona rickettsi is a slender nudibranch, tapering posteriorly, with a tail forming about one fifth of its length. This animal reaches approximately 20 mm in size. The anterior portion of its foot is flared and rounded, and the whole foot is about 10X longer than it is wide. The oral tentacles are long, but the rhinophores are longer, at about 17-20% of the body length. Both pairs of appendages are smooth or slightly warty and tapering. The cerata (dorsal and lateral club-like structures) are arranged in 8-10 rows, varying with body width, with the widest row consisting of six cerata. The cerata vary somewhat in shape, from spindle to club-shaped, and when fully extended, are about as long as the rhinophores. The penis lacks a stylet or other spines. The body is translucent, and some of its organs are visible. In some larger animals, the region between the rhinophores and pericardium is yellow to orange. The distal third of the rhinophores and oral tentacles are white, as are the tips of the cerata. There is a band of orange below the white pigment on the rhinophores and oral tentacles, but the extent of this pigment is highly variable. The color of the cores of the cerata varies from yellow to orange-pink, red-brown, burgundy, or brownish green. Description from: Behrens 1984; Behrens 1991; and McDonald 2007.

Catriona rickettsi lays its eggs in a spiral of tightly folded strings, enclosed in a clear gelatinous mass, which forms a thicker tangled string. The eggs are yellowish, each contained in a capsule within the string. A typical egg mass measures 2 X 6 mm, and is attached to a substratum, usually the stalk of a hydroid (Behrens 1984).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Mollusca
Class:   Gastropoda
Subclass:   Opisthobranchia
Order:   Nudibranchia
Family:   Tergipedidae
Genus:   Catriona
Species:   rickettsi


Cuthona rickettsi (None, None)
Trinchesia rickettsi (Miller, 2005)

Potentially Misidentified Species

Catriona columbiana
Native to the Northeast Pacific, from San Diego to southeast Alaska, also reported from Japan (Behrens 1991).



Catriona rickettsi is a nudibranch found in open coastal regions and harbors. Nudibranchs are simultaneous hermaphrodites, and copulate reciprocally or unilaterally. Catriona rickettsi lays its eggs in a gelatinous mass, enclosing a spiral of tightly folded strings. Most Northeast Pacific nudibranchs hatch out as planktotrophic larvae, but some have lecithotrophic larvae (Barnes 1983; Behrens 1984; Goddard 2007).

Catriona rickettsi inhabits tidepools, rocky shores, and harbors of warm-temperate to cold-temperate regions. In San Francisco Bay, it occurs in 'a variety of fouling communities' (Behrens 1984). It has been found repeatedly on the introduced hydroid Ectopleura crocea (Behrens 1984; Behrens 2004, in Miller 2014), but the range of its diet is not known. In many nudibranchs which feed on cnidarians, the nematocysts (stinging cells) are ingested, and are then incorporated into the cerata, as a defensive mechanism (Barnes 1983). This is probably the case in C. rickettsi.


Hydroids (Ectopleura crocea)

Trophic Status:




General HabitatMarinas & DocksNone
General HabitatRockyNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Vertical HabitatEpibenthicNone

Tolerances and Life History Parameters

Maximum Length (mm)20Behrens 1984
Broad Temperature RangeNoneCold temperate-Warm temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

No impacts have been reported for Catriona rickettsi in North American waters.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NEP-V Northern California to Mid Channel Islands 1974 Def Estab
NEP-VI Pt. Conception to Southern Baja California 1980 Def Estab
NEP-IV Puget Sound to Northern California 1994 Def Estab
P022 _CDA_P022 (San Diego) 1980 Def Estab
P090 San Francisco Bay 1974 Def Estab
P180 Umpqua River 1980 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
2832 Cohen and Carlton 1995 1980 1980-01-01 La Jolla Def 33.8575 -117.2733
2833 Cohen and Carlton 1995 1974 1974-01-01 Pete's Harbor Def 37.7083 -122.2792
2834 Cohen and Carlton 1995 1994 9999-01-01 Reedsport Def 43.7025 -124.0956
2836 Ruiz et al. unpublished data 2000 2000-09-07 Hunters Point Def 37.7165 -122.3632
2837 Ruiz et al. unpublished data 2000 9999-01-01 Southhampton Shoals Def 37.8819 -122.4002
2838 Ruiz et al. unpublished data 2000 2000-09-11 Treasure Island Def 37.8203 -122.3626
768037 Ruiz et al., 2015 2012 2012-08-27 Port of San Francisco Pier 31, San Francisco Bay, CA, California, USA Def 37.8078 -122.4060


Barnes, Robert D. (1983) Invertebrate Zoology, Saunders, Philadelphia. Pp. 883

Behrens, D.W. (1991) Pacific Coast Nudibranchs, In: (Eds.) . , Monterey, California. Pp. <missing location>

Behrens, David W. (1984) Notes on the Tergipedid nudibranchs of the northeastern Pacific, with a description of a new species, Veliger 27(1): 65-71

Bertsch, Hans; Campillo, Orso Angula; Arreola. Jose Luis (2000) New distributional records of opisthobranches for the Punta Eugenia region of the Baja California Peninsula: A report based on 1977-1998 Conabio-sponsored expeditions, Festivus 32(7): 99-104

California Academy of Sciences 2005-2015 Invertebrate Zoology Collection Database. <missing URL>

Carlton, James 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. Pp. 1-904

Cohen, Andrew N.; Carlton, James T. (1995) Nonindigenous aquatic species in a United States estuary: a case study of the biological invasions of the San Francisco Bay and Delta, U.S. Fish and Wildlife Service and National Sea Grant College Program (Connecticut Sea Grant), Washington DC, Silver Spring MD.. Pp. <missing location>

Goddard, Jeffrey H. R. (2007) The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon, University of California Press, Berkeley CA. Pp. 781-782

Goddard, Jeffrey H. R.; Green, Brenna (2013) Developmental mode in opisthobranch molluscs from the Northeast Pacific Ocean: Additional species from southern California and supplemental data, Bulletin of the Southern California Academy of Sciences 112(2): 49-62

McDonald, Gary R. (2007) The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon, University of California Press, Berkeley CA. Pp. 788-807

Miller, M. C. (2004) An appraisal of the identity of the New Zealand species of the aeolid nudibranch family Tergipedidae (Gastropoda: Opisthobranchia)., Journal of Natural History 38: 1183-1192

Miller, Michael D. 2004-2014 Slug Site. <missing URL>