Invasion History

First Non-native North American Tidal Record: 1979
First Non-native West Coast Tidal Record: 1979
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

The cyclopoid copepod Limnoithona sinensis was described from specimens taken from fresh waters in China, including the Suzhou Canal, the Huangpu River, and Yangtze River (or Chang Jiang) in 1898-1906. This copepod was also reported from the Wuli Lake, Jiangsu, in the Yangtze River Delta, and also occurs at least 300 km inland from the sea (Ferrari and Orsi 1984). In the late 1970s, it was found in the Sacramento-San Joaquin Delta, California. The highest salinity at which it was collected was 1.2 PSU (Ferrari and Orsi 1984). We consider it to be a stenohaline freshwater species.

North American Invasion History:

Invasion History on the West Coast:

Limnoithona sinensis was first collected in North America near Stockton, California, on the San Joaquin River in August 1979 (Ferrari and Orsi 1984). In the Delta, its most upstream occurrence was at Hood, on the Sacramento River in 1981, while it ranged downstream to the head of Suisun Bay (Ferrari and Orsi 1984). In 1993, the introduced copepod Limnoithona tetraspina appeared in Suisun Bay, and soon became the dominant cyclopoid in the Delta (Orsi and Ohtsuka 1999). 'L. sinensis continues to be collected in very low numbers, but is not recorded separately from L. tetraspina.' (Baxter and Heib 2006).

In 1979, L. sinensis was also collected in the Columbia River estuary (Sytsma et al. 2004). In 1993, L. tetrapsina appeared in the Columbia River, and appears to have replaced L. sinensis (Cordell et al. 2008). Limnoithona sinensis was not collected in 2002-2003 exotic species surveys (Sytsma et al. 2004); however, future invasions are possible. Limnoithona sinensis was one of the most abundant species found in low-salinity ballast water in the tanks of ships arriving to Vancouver, British Columbia (Levings et al. 2004).


Limnoithona sinensis has a shield-shaped prosome and four tapering thoracic segments. The final thoracic segment is conical and truncated, bearing the much reduced P5 swimming legs (pereiopods). The urosome is slender, consisting of 5 segments. (Ferrari and Orsi 1984).

In adult females, the rostrum is absent and the forehead is rounded dorsally. On the 1st urosome segment, there is a knob near the genital opening with 1 long and 1 short seta. The caudal rami have a length 6X the width, and are armed with one outward seta near the base and 5 seta at the tip. From the outward side inward, the 1st seta is shortest, while setae 2 and 3 are plumed and longer, 3 being the longest. On the antennule, there are 9 free segments. Adult females range from 0.47 to 0.55 mm in size (30 specimens examined) (Ferrari and Orsi 1984). The female, like other Oithonidae, often carries two symmetrical egg masses attached to the genital segment.

The adult male lacks a rostrum and the forehead is rounded dorsally. The length of the caudal rami is 5X the width, with setae like that of the females. Both 1st antennae are symmetrical and digeniculate (having two hinged joints) with 17 segments. The swimming legs (pereiopods) P1-P5 are slightly reduced, in size relative to female individuals. Adult males range from 0.41-0.51 mm in size (22 specimens examined) (Ferrari and Orsi 1984).

The copepodite and naupliar stages of this copepod have not been described. Morphology and development should be somewhat similar to that described for Oithona brevicornis by Uchima (1979).

In a redescription of L. tetraspina, Barroso do Abiahy et al. (2006) moved the genus Limnothona to the family Cyclopettidae, based on a morphological analysis.


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Maxillopoda
Subclass:   Copepoda
Order:   Cyclopoida
Family:   Cyclopettidae
Genus:   Limnoithona
Species:   sinensis


Limnoithona sinensis (Rosendorn, 1927)
Oithona sinensis (Burkhardt, 1912)

Potentially Misidentified Species

Limnoithona tetraspina
Limnoithona tetraspina has replaced L. sinensis in the San Francisco Bay Delta and the Columbia River estuary. In the San Francisco Bay Delta, 'L. sinensis continues to be collected in very low numbers, but is not recorded separately from L. tetraspina.' (Baxter 2006).

Oithona davisae
Oithona davisae is characteristic of meso-euhaline waters (Ferrari and Orsi 1984).



Planktonic cyclopoid copepods mate in the water column. Males use their modified antenules to grasp the female and transfer spermatophores to the female's genital segment. Female cyclopoid carry eggs in two symmetrical clusters under the abdomen (Barnes 1983). Eggs hatch into nauplii which go through six stages. The first stage, NI, has 3 pairs of appendages and is unsegmented - each molt has additional appendages and/or more differentiation of segments. The sixth stage (NVI) molts into a first copepodite stage (CI), with the basic form of the adult, and fully differentiated feeding structures, but with only two pairs of swimming legs and only one urosomal segment. The copepod goes through five additional molts, with increasing numbers of swimming legs, urosomal segments, and sexual differentiation. The sixth (CVI) stage is the male or female adult (Uchima 1979).

Limnoithona sinensis is characteristic of inland fresh waters, but also occurs in tidal fresh and oligohaline waters (Ferrari and Orsi 1984). Adult and juvenile cyclopoid copepods feed raptorially, seizing particles, and may be carnivorous or omnivorous, feeding on algae, ciliates, rotifers, and copepod nauplii (Barnes 1983). Limnoithona sinensis probably feeds similarly to L. tetraspina, feeding primarily on aloricate ciliates and flagellates, while not significantly grazing diatoms or dinoflagellates (Gifford et al. 2007).


phytoplankton; microzooplakton

Trophic Status:

Suspension Feeder



General HabitatUnstructured BottomNone
Salinity RangeLimnetic0-0.5 PSU
Salinity RangeOligohaline0.5-5 PSU
Tidal RangeSubtidalNone
Vertical HabitatPlanktonicNone

Tolerances and Life History Parameters

Minimum Salinity (‰)0None
Maximum Salinity (‰)1.2CA/Sacramento-San Joaquin Delta (Ferrari and Orsi 1979)
Minimum Length (mm)0.4None
Maximum Length (mm)0.6None
Broad Temperature RangeNoneWarm temperate
Broad Salinity RangeNoneNontidal Limnetic-Oligojhaline

General Impacts

Limnoithona sinensis was briefly abundant, reaching 71,000 m-3 in the Sacramento-San Joaquin Delta, in 1981, but by 1994, it was largely replaced by L. tetraspina, and is now only a trace component of the zooplankton (Ferrari and Orsi 1984; Orsi and Ohtsuka 1999; Baxter 2006). Any impact that it may have had on planktonic food webs were transient.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
P260 Columbia River 1979 Def Failed
P090 San Francisco Bay 1979 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
26920 Ferrari and Orsi 1984 1979 1979-08-01 Delta - Port of Stockton Def 37.9510 -121.3266
27697 Cohen and Carlton, 1995 1980 1980-01-01 Suisun Bay Def 38.0713 -122.0581
27698 Ferrari and Orsi 1984 1979 1979-01-01 Disappointment Slough Def 38.0407 -121.4460
30992 Ferrari and Orsi 1984 1979 1979-10-01 Hood, Sacramento River Def 38.3682 -121.5174


Barroso do Abiahy, Bernard; da Rocha, Carlos Falavigna; Ferrari, Frank D. (2006) Redescription of Limnoithona tetraspina Zhang et Li 1976 (Copepoda, Cyclopoida) with a discusssion of character states shared with the Oithonidae and older cyclopoids., Invertebrate Zoology 3(3): 115-135

Baxter, Randall; Heib, Katherine (2006) Zooplankton Monitoring 2005, IEP Newsletter 19(2): 13-16

Bouley, P.; Kimmerer, W. J. (2006) Ecology of a highly abundant, introduced cyclopoid copepod in a temperate estuary., Marine Ecology Progress Series 324: 219-228

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, Jeffrey; Bollens, Stephen M.; Draheim, Robyn; Sytsma, Mark (2008) Asian copepods on the move: Recent invasions in the Columbia-Snake River system, USA, ICES Journal of Marine Science 65: 753-758

Ferrari, Frank D., Orsi, James (1984) Oithona davisae, new species, and Limnoithona sinensis (Burckhardt, 1912) (Copepoda: Oithonidae) from the Sacramento-San Joaquin Estuary, California, Journal of Crustacean Biology 4(1): 106-126

Levings, C. D.; Cordell, J. R.; Ong, S.; Piercey, G. E. (2004) The origin and identity of invertebrate organisms being transported to Canada's Pacific coast by ballast water., Canadian Journal of Fisheries and Aquatic Science 61: 1-11

Orsi, James J., Ohtsuka, Susumu (1999) Introduction of the Asian copepods Acartiella sinensis, Tortanus dextrilobatus (Copepoda:Calanoida), and Limnoithona tetraspina (Copepoda: Cyclopoida) to the San Francisco Estuary,California, USA., Plankton Biology and Ecology 46(2): 128-131

Sytsma, Mark D.; Cordell, Jeffrey R.; Chapman, John W.; Draheim, Robyn, C. (2004) <missing title>, Center for Lakes and Reservoirs, Portland State University, Portland OR. Pp. <missing location>

Uchima, Mittsuaka (1979) Morphological observations of developmental stages in Oithona brevicornis, Bulletin of the Plankton Society of Japan 26(2): 59-76

Winder; Monika; Jassby, Alan D.; Mac Nally, Ralph (2011) Synergies between climate anomalies and hydrological modifications facilitate estuarine biotic invasions, Ecology Letters 14: 749-757