Invasion History

First Non-native North American Tidal Record: 1978
First Non-native West Coast Tidal Record: 1978
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

The marine isopod Eurylana arcuata was first described from Port Jackson, New South Wales, Australia. However, its range and abundance in Australia is limited, with most collections being in the vicinity of Sydney, Newcastle, and Twofold Bay, while it is more abundant and widespread in New Zealand (Jansen 1981; Bowman et al. 1981; Bruce 1986; Bruce 2001). Eurylana arcuata has also been reported from many sites along the coast of Chile (Menzies 1962). However, specimens from Chile showed some minor morphological differences from those in Australia and New Zealand (Bowman 1981; Bruce 1986). Tentatively, we follow Bruce (1986) in treating New Zealand as the likeliest native region. However, further morphological and molecular studies will be needed to determine the origin of this isopod. It is clearly introduced on the West Coast of North America, where it is only known from San Francisco Bay, where it was first collected in 1978 (Bowman et al. 1981; Cohen and Carlton 1995).

North American Invasion History:

Invasion History on the West Coast:

Eurylana arcuata was first collected on the West Coast on the intake screens of the Oleum Power Plant, in Rodeo, California, in San Pablo Bay on May 16, 1978 (USNM 1163795, U.S. National Museum of Natural History 2015; Bowman et al. 1981). It was collected in only 8 of 52 samples at this power plant in May 1978 to April 1979, and was not seen in samples from four other power plants on the Bay. Other collections were from floating docks on Coast Guard Island, Oakland, in San Francisco Bay, in 1993-1994 (Cohen and Carlton 1995), and from Mears Beach, in San Pablo Bay in January 2004 (CAS-IZ 111591.00, California Academy of Sciences 2015). Likely vectors for introduction are ballast water or hull fouling.

Invasion History Elsewhere in the World:

Eurylana arcuata is abundant and widespread in New Zealand, and is regarded as a native species (Jansen 1981; Bruce 1986; Bruce 2001). In Australia, it appears to be rare and confined to port areas in the southeastern corner of the continent, in South Australia, Victoria and New South Wales. Although it was described from Port Jackson, near Sydney in 1925, it is treated as an introduced species there (Bowman et al. 1981; Bruce 1986; Furlani 1996). Menzies (1962b) identified isopods from a 1948-1949 expedition to Chile as Cirolana concinna and C. robusta. Bowman et al. (1981) considered these and later specimens from Chile to be synonymous with E. arcuata, although he and Bruce (1986) noted small morphological differences. The Chilean Eurylana spp. could represent an introduction to the Chilean coast, a cryptic species, or an alternative native region for the species (Bowman et al. 1981; Bruce 1986). We have treated the Chilean occurrences as cryptogenic, but further molecular studies may change the status of these populations.


Eurylana arcuata is a marine isopod of the family Cirolanidae, which are characterized by a rather streamlined elliptical-oval cephalothorax (peraeon) but a distinct abdomen (pleon) of 4-5 segments, which is more rectangular in outline. Like many cirolanids, it has fairly prominent eyes, a large telson, and outward-spreading uropods. The coxal plates are prominent in a side view. The cephalon (head-shield) of Eurylana arcuata lacks a rostrum. The frontal lamina of the head is wider than long, and expanded anteriorly. The clypeus, forming the front of the 'face', is narrow, with concave sides, and is at an acute angle to the frontal lamina, projecting downward in lateral view. Segment 2 of Antenna 1 is the longest segment in the peduncle. Antenna 1 reaches back to the middle of pereonite 1. Antenna 2 is longer, extending back to the middle of pereonite 2 or the posterior edge of pereonite 3. The coxal plates increase in size posteriorly, with lateral and posterior margins rounded. The pereiopods are robust, and armed with setae and spines. The telson is triangular, but with a broad rounded apex, lined with fined setae and short, stout spines. Adults are 10.5 to 19 mm in size. A photographed specimen is dark brown, with yellow-brown edging between peraeonites and pleonites. Description based on: Schultz 1969, Bowman et al. 1981, Jansen 1981, Bruce 1986, Bruce 2001, and Brusca et al. 2007.


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Malacostraca
Subclass:   Eumalacostraca
Superorder:   Peracarida
Order:   Isopoda
Suborder:   Flabellifera
Family:   Cirolanidae
Genus:   Eurylana
Species:   arcuata


Cirolana concinna (Menzies, 1962)
Cirolana arcuata (Hale, 1925)
Cirolana robusta (Menzies, 1962)
Eurylana arcuata (Jansen, 1981)

Potentially Misidentified Species

Cirolana harfordi
Northeast Pacific native, from British Columbia to Baja California, introduced in Australia (Schultz 1969; Bruce 1986).



Eurylana arcuata is a marine isopod with separate sexes and internal fertilization. Eggs are brooded in a ventral pouch covered by plates, called oostegites, which arise from the base of the pereiopods on peraeonal segments 1-5. Development is direct, and the young hatch as postlarvae, in which the last peraeonal segment and its pair of pereiopods are undeveloped (Schultz 1969; Barnes 1983).

Eurylana arcuata is known from intertidal and shallow subtidal habitats, including soft mud, sandy beaches, rocks, boulders, and floating docks (Menzies 1962; Bowman et al. 1981; Jansen 1981; Bruce 1986). It is associated with cold-temperate to warm-temperate climates, and mesohaline to euhaline salinities. In San Francisco Bay, it was collected at 7.9 to 22.4°C, and 6.8 to 26.2 PSU (Bowman et al. 1981). Isopods of the family Cirolanidae are well-known as scavengers, often attacking dead or injured fishes, and can be pests in fish nets or traps (Bruce 2001; Brusca et al. 2007).


Invertebrates, carrion




Cirolana harfordi

Trophic Status:




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

Tolerances and Life History Parameters

Minimum Temperature (ºC)7.9Field, Rodeo power plant, San Francisco Bay (Bowman et al. 1981)
Maximum Temperature (ºC)22.4Field, Rodeo power plant, San Francisco Bay (Bowman et al. 1981)
Minimum Salinity (‰)6.8Field, Rodeo power plant, San Francisco Bay (Bowman et al. 1981)
Maximum Salinity (‰)31.2New Zealand, Jansen 1981
Maximum Length (mm)19Bowman et al. 1991
Broad Temperature RangeNoneWarm temperate
Broad Salinity RangeNoneMesohaline-Euhaline

General Impacts

No ecological or economic impacts have been reported from introduced populations of Eurylana arcuata.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NZ-IV None 0 Native Estab
AUS-VII None 1981 Def Estab
AUS-X None 1925 Def Estab
SEP-B None 1962 Crypto Estab
NEP-V Northern California to Mid Channel Islands 1978 Def Estab
P090 San Francisco Bay 1978 Def Estab
SEP-C None 1962 Crypto Estab
P093 _CDA_P093 (San Pablo Bay) 1978 Def Estab
NZ-V None 0 Native Estab
AUS-VIII None 2010 Def Unk
SEP-A' None 1949 Crypto Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
28392 Cohen and Carlton, 1995 1994 1994-01-01 Oakland Eastuary - Coast Guard Island, Oakland Es Def 37.7810 -122.2459
29489 California Academy of Sciences 2005 2005-06-09 McNears Beach Def 37.9962 -122.4556
29963 Foss 2009 2005 2005-09-09 Coyote Point Marina Def 37.5905 -122.3177
33415 Bowman et al. 1981 1978 1978-01-01 San Pablo Bay Def 38.0446 -122.2483


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

Bowman, T. E., Bruce, N. L., Standing, J. D. (1981) Recent introduction of the cirolanid isopod crustacean Cirolana arcuata into San Francisco Bay, Journal of Crustacean Biology 1(4): 545-557

Bruce, Niel L. (1986) Cirolanidae (Crustacea: Isopoda) of Australia, Records of the Australian Museum Supplement 6.: 1-239

Bruce, Niel L. (2001) Marine isopod crustaceans in New Zealand, NIWA Water and Atmosphere 9(3): 13-14

Brusca, Richard C.; Coeljo, Vania R. Taiti, Stefano (2007) The Light and Smith Manual: Intertidal invertebrates from Central California to Oregon (4th edition), University of Calfiornia Press, Berkeley CA. Pp. 503-542

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

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>

Foss, Stephen (2009) <missing title>, California Department of Fish and Game, Sacramento CA. Pp. <missing location>

Furlani, Dianne M. (1996) A guide to the introduced marine species in Australian waters., In: (Eds.) . , Hobart, Australia. Pp. <missing location>

Jansen, K. P. (1981) Eurylana, a new genus of Cirolanidae (Isopoda: Flabellifera)with two species, Eurylana cookii (Filhol) and Eurylana arcuata (Hale), Journal of the Royal Society of New Zealand 11(1): 5-10

Menzies, Robert James (1962b) The zoogeography, ecology, and systematics of the Chilean marine isopods, Lunds Universitets Arsskrift 57(11): 1-162

Schultz, G.A. (1969) The Marine Isopod Crustaceans, Wm. C. Brown Company, Dubuque, Iowa. Pp. <missing location>

U.S. National Museum of Natural History 2002-2021 Invertebrate Zoology Collections Database.