Craspedacusta sowerbii
Lankester, 1880
Common Name:
Freshwater jellyfish
Synonyms and Other Names:
peach blossom fish (China); Craspedacusta sowerbyi Lankester, 1880
Identification:
Craspedacusta sowerbii is a hydrozoan (Phylum Cnidaria, Class Hydrozoa), which is most easily identified when it takes the form of a small, bell-shaped jellyfish, known as a hydromedusa. The hydromedusa measures about 5–25 mm in diameter, and is translucent with a whitish or greenish tinge (Peard, 2002; Pennak, 1989). It possesses five opaque-white canals, which form the gastrovascular cavity; four are radial and one is medially dorsoventral. Tentacles of varying lengths protrude from the upper margin of the velum, arranged with three to seven short tentacles between longer ones (Pennak, 1989; Slobodkin and Bossert, 1991). Freshwater jellyfish exhibit four very long tentacles, each parallel to a radial canal at the edge of the velum. Shorter tentacles facilitate feeding, while the longer ones give stability for swimming. The total number of tentacles varies from 50 to 500 (Pennak, 1989). Conspicuous swarms of hydromedusae appear sporadically, but are only one part of the animal's life cycle. Craspedacusta sowerbii more often exist as microscopic podocysts (dormant "resting bodies"), frustules (larvae produced asexually by budding), planulae (larvae produced sexually by the hydromedusae), or as sessile polyps, which attach to stable surfaces and can form colonies consisting of two to four individuals and measuring 5 to 8 mm (Angradi, 1998; Acker and Muscat, 1976; Pennak, 1989; Peard, 2002).
Size:
hydromedusa is 5–25 mm in diameter
Native Range:
Craspedacusta sowerbii is indigenous to the Yangtze River valley in China, where it can be found in both the upper and lower river valley (Slobodkin and Bossert, 1991).
Great Lakes Nonindigenous Occurrences:
Craspedacusta sowerbii was discovered in the Huron River near Ann Arbor, MI, in 1933, and in Lake Erie shortly thereafter (Mills et al., 1993). It has since been recorded in Lake Huron and Lake St. Clair, as well as dozens of inland lakes and streams throughout the region. In Canada, freshwater jellyfish have been known in Quebec since 1955 and in Ontario since 1980 (Peard, 2002).
Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Craspedacusta sowerbii are found here.
Full list of USGS occurrences
Table last updated 4/9/2026
† Populations may not be currently present.
Ecology:
Craspedacusta sowerbii occupies a range of freshwater habitats. In its native range, it typically inhabits shallow pools along the Yangtze River, sometimes coexisting with a related species, C. sinensis, which occurs in the upper river valley (Slobodkin and Bossert, 1991). In this environment, changing conditions in the main river system expose jellyfish to fluctuating water levels, temperatures and plankton populations. Where it is introduced, C. sowerbii is most commonly found in shallow, slow moving or stagnant artificial water bodies such as ornamental ponds, reservoirs, gravel pits, and quarries (Pennak, 1956; DeVries, 1992; Peard, 2002). They prefer still or slow moving freshwater bodies of mesotrophic character between 12 and 33 degrees Celsius (Galarce et al., 2013). It has also been reported in large river systems, including the Allegheny, Ohio and Tennessee River systems, natural lakes, aquaria, and ornamental ponds (Beckett and Turanchik, 1980; DeVries, 1992; Peard, 2002). A study by Caputo et al. 2018, demonstrated that higher turbidity or increase in color of the water ‘‘brownification’’ would provide more favorable conditions for the invasion process of this hydroid.
Craspedacusta sowerbii is able to reproduce both sexually and asexually. Mature hydromedusae reproduce sexually by broadcasting gametes into the water. Fertilized eggs grow into ciliated planulae (larvae), which then settle and metamorphose into the polyp form. Polyps are capable of budding to produce hydromedusae, as well as either daughter polyps that remain attached to the parent, forming a colony, or frustule larvae which move to new locations before metamorphosing into new polyps (Pennak, 1989; Slobodkin and Bossert, 1991; Peard, 2002).
Hydromedusae are produced only sporadically, and a given location may go several years between blooms (Peard, 2002). Blooms are thought to be temperature dependent, requiring water of at least 25° C, and are most common in summer and fall (Kato and Hirabayashi, 1991; Dodson and Cooper, 1983; Anonymous, 1997; McGaffin, 1997; Peard, 2002). Other factors that may affect hydromedusa blooms include zooplankton populations, alkalinity, and calcium carbonate (Acker and Muscat, 1976; Koryak and Clancy, 1981; McCullough et al., 1981; Angradi, 1998). The more cold tolerant polyp form may have a wider distribution than the hydromedusa form, but because it is inconspicuous and easily overlooked, its range is difficult to determine (Kato and Hirabayashi, 1991; Angradi, 1998). Polyps overwinter by contracting into resting bodies called podocysts, which are essentially dormant cellular balls surrounded by a protective chitin-like membrane that allows them to withstand more extreme conditions than the active forms (Peard, 2002). When conditions are favorable, the podocysts grow into polyps again.
Like other cnidarians, C. sowerbii is an opportunistic predator, feeding on small organisms that come within its reach. A study in Northern Italy found that C. sowerbii feed on zooplankton with a preference for the Daphnia complex of species (Stefani et al., 2010). Both polyp and hydromedusa forms use nematocysts (stingers) to capture prey. Polyps are able to camouflage themselves by secreting a sticky mucous that adheres particles to their body (Pennak, 1989; Peard, 2002).
Great Lakes Means of Introduction:
Initially, C. sowerbii was probably transported with ornamental aquatic plants, especially water hyacinth (Eichhornia crassipes), from its native region in China (Slobodkin and Bossert, 1991). In the United States, polyps and resting bodies are probably translocated accidentally with stocked fish and aquatic plants or by waterfowl (Angradi, 1998; Wynett and Wynett, pers. comm. 1998).
Great Lakes Status:
Widespread, overwintering and reproducing throughout the Great Lakes and inland Lakes of the region. This species has not been reported from the open waters of Lake Ontario or Lake Huron, though it is in tributaries and inland lakes of those basins. Most reports are of the medusa form - the less conspicuous but more persistent hydra are underreported and potentially far more widespread. The number of sightings has increased considerably since 2010 (Luskow et al 2021).
Great Lakes Impacts:
Craspedacusta sowerbii has a moderate environmental impact in the Great Lakes. Craspedacusta sowerbii medusa represent a new functional guild in most freshwater systems which it has invaded (Schachtl 2019), one which shunts energy away from the native food chain. Medusae have triggered trophic cascades (Schachtl 2019) and crustacean zooplankton have declined following a bloom (Dumont 1994). Medusa also transport phosphorus from the benthos to the water column at high rates (Schachtl 2019).
There is little or no evidence to support that Craspedacusta sowerbii has significant socio-economic impacts in the Great Lakes.
There is little or no evidence to support that Craspedacusta sowerbii has significant beneficial effects in the Great Lakes.
Management:
Regulations Regulations pertaining to Craspedacusta sowerbii in the Great Lakes region | Jurisdiction | Regulation | Law | Description | Date Effective |
| Illinois | Other | 515 ILCS 5/20-90 | Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions. | 7/9/2015 |
Note: Check federal, state/provincial, and local regulations for the most up-to-date information.
Control
Craspedacusta sowerbii has spread across temperate climates for more than a century, but despite experimental observation of its possible contribution to trophic cascade effects (Jankowski et al. 2005), and studies on predation habits (Dodson and Cooper 1983, Spadinger and Maier 1999, Dendy 1978), little research on control is available.
Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.
Remarks:
Freshwater jellyfish are not considered dangerous to humans. Although its stings can paralyze macroinvertebrates and small fish, its small nematocysts are not likely to penetrate human skin (Peard, 2002).
Populations of C. sowerbii are frequently all male or all female, making sexual reproduction rare (Pennak, 1989).
Pennak (1989) gives several useful line drawing of C. sowerbii. For an illustrated description of the lifecycle, see Thorp and Covich (1991), or visit Sexual Reproduction in Freshwater Jellyfish (Sasaki, 1999). Spelling variations of the specific epithet include sowerbyi, but in his paper describing the species Lankester (1880) gives the spelling as sowerbii.
References
(click for full reference list)
Author:
McKercher, E., O; Connell, D., Fuller, P., Liebig, J., Larson, J., Makled, T.H., Fusaro, A., and Daniel, W.M.
Contributing Agencies:
Revision Date:
4/1/2026
Citation for this information:
McKercher, E., O; Connell, D., Fuller, P., Liebig, J., Larson, J., Makled, T.H., Fusaro, A., and Daniel, W.M., 2026, Craspedacusta sowerbii Lankester, 1880: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/GreatLakes/FactSheet.aspx?Species_ID=1068, Revision Date: 4/1/2026, Access Date: 4/10/2026
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.