Invasion History

First Non-native North American Tidal Record: 1977
First Non-native West Coast Tidal Record: 1977
First Non-native East/Gulf Coast Tidal Record: 1999

General Invasion History:

Ianiropsis serricaudis was described from the Pacific coast of Russia (Gurjanova 1936, cited by Hobbs et al. 2015), and is known to occur from the Korea Straits to the Sea of Okhotsk (Jang and Kwon 1990; Hobbs et al. 2015). In 1977, it was tentatively identified from San Francisco Bay by Carlton, Iverson, and Chapman (Carlton 1979), but was later not considered to be established because of taxonomic uncertainty (Cohen and Carlton 1995). In 2000, an unidentified Ianiropsis, the first of the genus to be found on the East Coast, was found in rapid assessment surveys of nonindigenous species in New England (MIT Sea Grant 2000-2008; Pederson et al. 2003). Collections of similar isopods were made from fouling communities in the Netherlands (in 2000, Faasse 2007, cited by Hobbs et al. 2015); England (in 2004, Hobbs et al. 2015); Puget Sound (in 2010, Cordell et al. 2012), and the Lagoon of Venice (in 2012, Marchini et al. 2015). Likely vectors for the spread of this isopod are ship fouling, ballast water, and oyster aquaculture (Hobbs et al. 2015).

North American Invasion History:

Invasion History on the West Coast:

Ianiropsis serricaudis was collected and identified from fouling communities in San Francisco Bay by Carlton, Iverson, and Chapman in 1977. It was found associated with the introduced tunicates Styela clava, Ciona robusta, and the isopod Dynoides dentisinus (Carlton 1979). Ianiropsis spp. continued to be collected, but identifications to species were difficult, owing to a large number of native species. Cohen and Carlton (1995) listed I. serricaudis among species whose establishment was uncertain. Specimens collected in the 1990s and 2000s from Treasure Island (1993), Richmond (2004), and the Presidio Yacht Club (2004) were verified as I. serricaudis (Hobbs et al. 2015), all in the central Bay. Additional collections were made in 2005 at Coyote Point Marina and San Mateo, in South San Francisco Bay (Foss 2009). In 2002, three specimens of I. serricaudis were identified from Elkhorn Slough, in Moss Landing. The isopods were found near reefs of the tubeworm Ficopomatus enigmaticus (Heiman and Micheli 2010; Hobbs et al. 2015). This isopod was reported from open coast areas at Point Arena and Purisima Point in 2004 (Maloney et al. 2006), but we do not know if populations are established there.

In 2010, I. serricaudis was found to be abundant in Puget Sound, Washington at one site: Taylor Shellfish Farms in Totten Inlet (Cordell et al. 2012). It was associated with Didemnum vexillum there, but was not found at other locations in Puget Sound (Cordell et al. 2012; Hobbs et al. 2015). Living specimens of I. serricaudis were found on a dock and a boat that drifted across the Pacific to the Oregon coast after the Japanese earthquake and tsunami of 2011, but these transports are not known to have resulted in established populations (Hobbs et al. 2015).

Invasion History on the East Coast:

There are no native Ianiropsis spp. in the Northwest Atlantic, but the small size of I. serricaudis makes it easy to overlook. On the East Coast, Ianiropsis serricaudis was first collected in 1999 in the Mystic River, a tributary of Long Island Sound, 'amongst the native bryozoan Amathia dichotoma', but not identified until 2012 (Hobbs et al. 2015). In New England, surveys conducted in 2000-2014 found I. serricaudis, identified as Ianiropsis sp., from Waterford, Connecticut to Bourne Marina, Massachusetts (MA) (MIT Sea Grant 2003-2008; Pederson et al. 2003; Janiak and Whitlach 2012). In 2007-2013, it was found in the Gulf of Maine, from Sandwich, MA (Cape Cod Bay) to Camden, Maine, (Penobscot Bay) (MIT Sea Grant 2009-2012; Wells et al. 2014). It was typically found on dock floats overgrown with Ulva sp. and tunicates, and rocky intertidal shores (Janiak and Whitlach 2012; Hobbs et al. 2015). In 2012-2013, I. serricaudis was found in Barnegat Bay, New Jersey, associated with the tunicate Botryllus schlosseri (Pallas, 1766), and the native bryozoans Einhornia crustulenta (Pallas, 1766) and Schizoporella sp., as well as the green alga Ulva lactuca (Hobbs et al. 2015). In 2012, this isopod was found in at one station in Sinepuxent Bay, Maryland, at only one of 13 stations in the Maryalnd Coastal Bays (Morales-Núñez, and Chigbu 2018).

Invasion History Elsewhere in the World:

In Europe, I. serricaudis was first observed in the Oosterschelde, the Netherlands in 2000 (Faasse 2007, cited by Hobbs et al. 2015). It was later found at another site, near the port of Rotterdam. In England, it was found in 2004 at Southampton, in the Solent estuary, off the English Channel (Hobbs et al. 2015), and at Plymouth, on the southwest coast (Hobbs et al. 2015). In 2012, it was found in the Lagoon of Venice, its first reported occurrence in the Mediterranean (Marchini et al. 2015). As with the invasions in North America, hull fouling and ballast water are probably the likeliest modes of long-distance transport, but aquaculture sites are likely areas of colonization and a source of local dispersal (Hobbs et al. 2015).


Ianiropsis serricaudis has a lozenge-shaped body, about 3X as long as wide, with the sides nearly parallel, broadest in pereaonal segment 3, and slightly tapered towards the head. The margin of the cephalon is slightly concave and has an inconspicuous rostrum on the frontal margin. The pleotelson has a small median lobe, with 3 or 4 spine-like serrations on each side (sometimes up to 7) and 2 or 3 unequal setae at the base of each serration. The uropods are slightly longer than the pleotelson. Antenna 1 is comparatively short, reaching segment 5 of Antenna 2 and about 1/4 of the body length. The Antennae 2 of I. serricaudis are about equal to body length, and peduncle segments 6 and 7 are especially elongated, totaling about 1/2 body length. In mature males, the maxilliped palps are elongated, with 5 segments, extending well beyond the basal segments of Antenna 2 and visible in dorsal view. The pereiopods are long, 1X-2X body maximum width. Pereiopods 1 have 3 claws each, while Pereiopods 7 have 2-3 claws. Antenna 2 is 6/10 of body length, with a flagellum of 24 segments. In males, Pleopod pairs 1 and 2 are modified for copulation. Pleopods 1 are fused to form a narrow appendage (the sympod),widening near the tip and ending in a pair of thick spines, each bearing 4 outer setae, a group of short setae on the inner side of the spine, and a longer, medial group of 6-7 longer setae. Pleopods 2 are not fused, but the inner ramus of each is modified into a needle-like stylus. Males are up 3.2 mm long and females are at least 2.4 mm. Reported colors vary, apparently with substrate. Gurjanova (1936, cited by Hobbs et al. 2015), reported that the isopods in Pacific Russia were pale, but with black eyes, spotted with black melanophores, giving a gray appearance. Korean specimens had brown melanophores (Jang and Kwon 1990), while Dutch animals often had red eyes and brown melanophores. New England animals varied from greenish to yellowish, and reddish, according to the color of the bryozoans and sponges on which they were feeding. Description based on: Jang and Kwon 1990, Wilson and Wagele 1994, Doti and Wilson 2010, Hobbs et al. 2015.


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Malacostraca
Subclass:   Eumalacostraca
Superorder:   Peracarida
Order:   Isopoda
Suborder:   Asellota
Family:   Janiridae
Genus:   Ianiropsis
Species:   serricaudis


Ianiropsis sp. (Pederson et al., 2003)
Ianiropsis notoensis (Nunomura, 1985)

Potentially Misidentified Species

Ianiropsis analoga
Menzies 1952, Northeast Pacific (Schultz 1969; Brusca et al. 2007; Hobbs et al. 2015)

Ianiropsis breviremis
Sars 1883, Northeast Atlantic (Hobbs et al. 2015)

Ianiropsis derjugini
Gurjanova 1952, Northwest Pacific, Bering Sea, Northeast Pacific (Jang and Kwon 1990; Brusca et al. 2007; Hobbs et al. 2015)

Ianiropsis epilittoralis
Menzies 1952, Northwest Pacific, Northeast Pacific (Schultz 1969; Jang and Kwon 1990; Brusca 2007; Hobbs 2015)

Ianiropsis kincaidi
Richardson 1904, Northeast Pacific (Schultz 1969; Brusca 2007)

Ianiropsis minuta
Menzies 1952, Northeast Pacific (Schultz 1969; Brusca 2007)

Ianiropsis montereyensis
Menzies 1952, Northeast Pacific (Schultz 1969; Brusca 2007)

Ianiropsis tridens
Menzies 1952, Northwest Pacific, Northeast Pacific, Chile (Schultz 1969; Jang and Kwon 1990; Brusca 2007; Hobbs et al. 2015)



Ianiropsis serricaudis has separate sexes, with internal fertilization, and direct development. Kussakin (1988, cited by Hobbs et al. 2015) observed breeding of I. serricaudis in Russia, in August-October, with 7-32 (average 18) eggs per female.

Ianiropsis serricaudis occurs in cold-temperate to warm-temperate climates, and has been collected at temperatures ranging from -1.8 C to 24 C. It has been collected at salinities from 16.9 to 35 PSU (Hobbs et al. 2015). This isopod occurs on a wide range of fouling organisms which provide shelter, including algae (red algae-Pachyarthron cretaceum, Chondrus crispus, Grateloupia turuturu; brown algae- Laminaria sp., green algae- Ulva spp.); sponges (Halichondria bowerbanki, Clathria prolifera); bryozoans (Amathia dichotoma, Einhornia crustulenta, Schizoporella sp., Tricellaria inopinata); and tunicates (Botrylloides violaceus, Ciona robusta, Didemnum vexillum, Diplosoma listerianum, Styela clava). Many of the organisms used by I. serricaudis are native to the Northwest Pacific, the native region of I. serricaudis (Hobbs et al. 2015). The feeding habits of this isopod is not known, but it may feed on the fecal material of colonial invertebrates, as well as, the surface microbiota and detritus associated with colonial invertebrates and algae.


Microalgae, protozoans, pseudofeces

Trophic Status:




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)-1.8Field, Pacific Russia (Hobbs et al. 2015)
Maximum Temperature (ºC)24Field, Pacific Russia, Narragansett Bay (Hobbs et al. 2015)
Minimum Salinity (‰)16.9Field (Hobbs et al. 2015)
Maximum Salinity (‰)35Field (Hobbs et al. 2015)
Maximum Length (mm)3.2Hobbs et al. 2015
Broad Temperature RangeNoneCold-temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Impacts of Ianiropsis serricaudis have not been studied. However, in some cases this isopod can reach extraordinary abundances within fouling communities, and could have impacts as a competitor, as prey, or in some other ecological role (Hobbs et al. 2015).

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NWP-4a None 1937 Native Estab
NEP-V Northern California to Mid Channel Islands 1977 Def Estab
P090 San Francisco Bay 1977 Def Estab
P067 _CDA_P067 (San Antonio) 2004 Def Unk
P116 _CDA_P116 (Big Navaro-Garcia) 2004 Def Unk
P080 Monterey Bay 2002 Def Estab
NEP-III Alaskan panhandle to N. of Puget Sound 2010 Def Estab
P290 Puget Sound 2010 Def Estab
NA-ET3 Cape Cod to Cape Hatteras 1999 Def Estab
M010 Buzzards Bay 2000 Def Estab
M020 Narragansett Bay 2000 Def Estab
M040 Long Island Sound 1999 Def Estab
NA-ET2 Bay of Fundy to Cape Cod 2007 Def Estab
N140 Hampton Harbor 2013 Def Estab
N170 Massachusetts Bay 2007 Def Estab
N180 Cape Cod Bay 2013 Def Estab
N100 Casco Bay 2007 Def Estab
N070 Damariscotta River 0 Def Estab
N050 Penobscot Bay 2007 Def Estab
NWP-3a None 0 Native Estab
M070 Barnegat Bay 2012 Def Estab
NEA-II None 2004 Def Estab
NEA-III None 2015 Def Estab
MED-VII None 2012 Def Estab
NWP-5 None 0 Native Estab
MED-II None 2015 Def Estab
NEA-V None 2011 Def Estab
NEP-V Northern California to Mid Channel Islands 2013 Def Estab
P170 Coos Bay 2013 Def Estab
M110 Maryland Inland Bays 2012 Def Estab
M023 _CDA_M023 (Narragansett) 2013 Def Estab
M060 Hudson River/Raritan Bay 2019 Def Estab
NEP-IV Puget Sound to Northern California 2015 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
767353 Ruiz et al., 2015 2012 2012-08-21 Porto Bodega, Bodega Bay, California, USA Def 38.3333 -123.0525
767375 Ruiz et al., 2015 2012 2012-08-21 Tomales-Nick's Cove, Bodega Bay, California, USA Def 38.1980 -122.9222
767394 Ruiz et al., 2015 2012 2012-08-16 Tomales-SNPS, Bodega Bay, California, USA Def 38.1359 -122.8719
767604 Ruiz et al., 2015 2013 2013-09-05 Launch Ramp, Morro Bay, CA, California, USA Def 35.3577 -120.8508
768191 Ruiz et al., 2015 2012 2012-09-07 Jack London Square Marina, San Francisco Bay, CA, California, USA Def 37.7940 -122.2787


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

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>

Cordell, Jeffery R.; Levy, Claire; Toft, Jason D. (2012) Ecological implications of invasive tunicates associated with artificial structures in Puget Sound, Washington, USA, Biological Invasions 15(6): 1303-1318

Doti, Brenda Lía; Wilson, George D. F. (2010) The genera Carpias Richardson, Ianiropsis Sars and Janaira Moreira & Pires (Isopoda: Asellota: Janiridae) from Australia, with description of three new species, Zootaxa 2625: 1-39

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

Fuller; . Pam L.; Whelan, Gary E (2021) The flathead catfish invasion of the Great Lakes, Journal of Great Lakes Research 44(5): 1081-1092

Heiman, Kimberly W.; Micheli, Fiorenza (2010) Non-native ecosystem engineer alters estuarine communities, Integrative and Comparative Biology 50(2): 226-236

Hobbs, Niels-Viggo and 8 authors (2015) Going global: The introduction of the Asian isopod Ianiropsis serricaudis Gurjanova (Crustacea: Peracarida) to North America and Europe, Aquatic Invasions 10: In press

Jang, In Kwon; Kwon, Do Heo (1990) Ianiropsis (Isopoda, Ianiridae) from Korea, with description of a new species, Korean Journal of Systematic Zoology Molluscan Research 6(2): 193-208

Janiak, Dean S.; Whitlatch, Robert B. (2012) Epifaunal and algal assemblages associated with the native Chondrus crispus (Stackhouse) and the non-native Grateloupia turuturu (Yamada) in eastern Long Island Sound, Journal of Experimental Marine Biology and Ecology 413: 38-44

Kennedy, C., Pappal, A. L.; Bastidas, C.; ; Carlton, J. T.; David, A. A.; Dijkstra, J.A.; Duffey, S; Gibson, J.; Grady, S. P.; Green-Gavrielidis, (2020) Report on the 2018 Rapid Assessment Survey of Introduced, Cryptogenic, and Native Marine Species at New England Marinas: Massachusetts to Maine, <missing publisher>, Boston MA. Pp. <missing location>

Maloney, E.; Fairey, R.; Lyman, A.; Reynolds, K.; Sigala, M. (2006) <missing title>, California Department of Fish and Game, Office of Spill Prevention and Response, Sacramento. Pp. <missing location>

Marchini, Agnese; Ferrario, Jasmine; Sfriso, Adriano; Occhipinti-Ambrogi Anna (2015) Current status and trends of biological invasions in the Lagoon of Venice, a hotspot of marine NIS introductions in the Mediterranean Sea, Biological Invasions <missing volume>: In press

MIT Sea Grant 2003-2008 Introduced and cryptogenic species of the North Atlantic. <missing URL>

MIT Sea Grant 2009-2012 Marine Invader Tracking and Information System (MITIS). <missing URL>

Morgan, David L.; Gill, ;Howard S.; Maddern, Mark G; Beatty. .; Stephen J. (2004) Distribution and impacts of introduced freshwater fishes in Western Australia, New Zealand Journal of Marine and Freshwater Research 38: 511-523

Moschenko, Alexander V.; Zvyagintsev, Alexander Yu. (2004) Composition, structure, and distribution features of fouling community in the water intake tunnel of Vladivostok heat and power plant, Ocean and Polar Research 26(4): 619-633

Pederson, Judith and 15 authors (2003) <missing title>, MIT Sea Grant College Program, Cambridge. Pp. <missing location>

Pederson, Judith, and 13 authors (2021) 2019 Rapid Assessment Survey of marine bioinvasions of southern New England and New York, USA, with an overview of new records and range expansions, Bioinvasions Records 10(2): 22-–237

Russell, D. J. Thuesen, P. A. Thomson, F. E. (2012) A review of the biology, ecology, distribution and control of Mozambique tilapia, Oreochromis mossambicus (Peters 1852) (Pisces: Cichlidae) with particular emphasis on invasive Australian populations, Review of Fish Biology and Fisheries 22: 533-554

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

Ulman, Aylin and 17 authors (2017) A massive update of non-indigenous species records in Mediterranean marinas, PeerJ 5( e3954): <missing location>

Wells, Christopher D. and 23 authors (2014) Report on the 2013 rapid assessment survey of marine species at New England bays and harbors, Massachusetts Office of Coastal Zone Management, Boston MA. Pp. 32

Wilson, George D. F.; Wagele, Johann-Wolfgang (1994) Review of the family Ianiridae (Crustacea: Isopoda: Asellota), Invertebrate Taxonomy 8: 683-747

Zambrano, René; Ramos, John (2021) Alien crustacean species recorded in Ecuador, Nauplius 29: e2021043