Craspedacusta sowerbii is a freshwater jellyfish in the phylum Cnidaria. Since it is classified as a hydrozoan, it is one of many jellyfish that are also known as hydromedusae. Hydromedusan jellyfish differ from scyphozoan jellyfish because they have a muscular, shelf-like structure called a velum on the ventral surface, attached to the bell margin. Originally from the Yangtze basin in China, C. sowerbii is an invasive species now found throughout the world in bodies of fresh water.
C. sowerbii medusae are about 20–25 mm (approximately 1 in.) in diameter, somewhat flatter than a hemisphere, and very delicate, when fully grown. They have a whorl of up to 400 tentacles tightly packed around the bell margin. Hanging down from the center of the inside of the bell is a large stomach structure called a manubrium, with a mouth-opening with four frilly lips. Circulation of nutrients is facilitated by four radial canals which originate at the edges of the stomach (manubrium), and which are also connected to a ring canal, located near the bell margin. Most of the body is transparent or translucent, with a whitish or greenish tinge. The (usually) four large flat sex organs (gonads) are attached to the four radial canals, and are usually opaque white. The many tentacles each contain thousands of cells called cnidocytes, which contain nematocysts (also known as cnidocysts), and are used to capture prey and pass it to the mouth. Food is taken in the mouth opening, and waste is finally expelled out of the same opening.
Habitat and distribution
C. sowerbii is native to the Yangtze basin in China, but has been introduced widely around the world (the only continent where not found is Antarctica). It is usually found in calm, freshwater reservoirs, lakes, impoundments, gravel pits or quarries. They have also been seen in slow-moving backwaters of river systems such as the Allegheny River, the Ohio River and the Tennessee River in the United States and the Wang Thong River of Thailand. They prefer standing water, and are not generally seen in fast flowing streams or rivers.
C. sowerbii has a global distribution - it has been found in countries on almost every continent and nearly every state in the United States (no reports yet from Montana, Wyoming, North Dakota, South Dakota, Alaska or Hawaii) and most provinces in Canada (no reports yet from Alberta, Saskatchewan).
The medusa's appearance is sporadic and unpredictable from year to year. It is not uncommon for C. sowerbii to appear in a body of water where it had never been documented before, in very large numbers, and its appearance may even be reported on the local news.
On August 21, 2010, C. sowerbii was spotted and captured on the northwest corner of Falcon Lake in Manitoba, Canada. Scientists believe this is due to a recent heat wave in the Whiteshell Provincial Park area. It is proposed the C. sowerbii came to Falcon Lake on waterfowl originating from Star Lake, Manitoba, Canada. Falcon Lake along with Star Lake remain the only two confirmed sightings of C. sowerbii in Manitoba.
C. sowerbii has been seen in Pennsylvanian lakes and reservoirs including Marsh Creek Lake, Downingtown/Eagle, PA Turnpike/Rt 100/Rt 401, SR 282 (2007,2008).
It was reported in Panama in 1925, Chile in 1942, Argentina in 1950, Brazil in 1963, and in Uruguay in 1971.
In June 2018 C. sowerbii was found by Curtis (Oceans Fury Unleashed) and Skott (NaturesTemper) during their filming of the St Helens canals in the UK. 
C. sowerbii is a predator on zooplankton including daphnia and copepods. Prey is caught with their stinging tentacles. Drifting with its tentacles extended, the jelly waits for suitable prey to touch a tentacle. Once contact has been made, nematocysts on the tentacle fire into the prey, injecting poison which paralyzes the animal, and the tentacle itself coils around the prey. The tentacles then bring the prey into the mouth, where it is released and then digested.
Just like salt water jellyfish they do have stinging cells. However, these cnidocytes cells are used for paralyzing very tiny prey and have not been proven to have the capacity to pierce human skin.
C. sowerbii begins life as a tiny polyp, which lives in colonies attached to underwater vegetation, rocks, or tree stumps, feeding and asexually reproducing during spring and summer. Some of these offspring are the sexually reproducing medusae. Fertilized eggs develop into small ciliated larvae called planula. The planula then settle to the bottom, and develop into polyps. However, the majority of C. sowerbii populations existing in the United States are either all male or all female, so there is no sexual reproduction in those populations.
During the cold winter months, polyps contract and enter dormancy as resting bodies called podocysts. It is believed that podocysts are transported by aquatic plants or animals to other bodies of water. Once conditions become favorable, they develop into polyps again.
- Didžiulis, Viktoras. "NOBANIS – Invasive Alien Species Fact Sheet – Craspedacusta sowerbyi" (PDF). Archived (PDF) from the original on 17 May 2014. Retrieved 19 December 2014. Cite uses deprecated parameter
- Peard, Terry. "Distribution of the freshwater jellyfish". Archived from the original on 2008-07-28. Retrieved 2008-08-11. Cite uses deprecated parameter
- "Families find Manitoba's first jellyfish". Winnipeg Free Press. Retrieved 2010-08-21.
- "What is the distribution of the freshwater jellyfish in Pennsylvania". Dr. Terry Peard. Retrieved 2016-12-29.
- "Tiny African jellyfish in S.A. reservoir". Mail (Adelaide, SA : 1912 - 1954). 1950-03-11. p. 3. Retrieved 2017-08-05.
- "Jellyfish live in lake". Canberra Times (ACT : 1926 - 1995). 1967-03-01. p. 1. Retrieved 2017-08-05.
- Parent, G.H (1982). "Une page d'histoire des sciences contemporaines : un siècle d'observations sur la méduse d'eau douce, Craspedacusta sowerbii Lank". Bulletin mensuel de la Société linnéenne de Lyon (in French). 51 (2): 47–63. doi:10.3406/linly.1982.10519. ISSN 0366-1326.
- "ZJJ Cili Zhaojiaya Reservoir Appeared Freshwater Jellyfish". Zhangjiajie City Information Center. Archived from the original on 2014-08-19. Retrieved 2013-09-10. Cite uses deprecated parameter
- "Photographs of C. Sowerbii in India".
- "Az édesvízi medúza (Craspedacusta sowerbii Lankaster, 1880) magyarországi előfordulása | The freshwater jellyfish (Craspedacusta sowerbii Lankester, 1880) in Hungarian waters - REAL - az MTA Könyvtárának Repozitóriuma". Retrieved 2016-08-06.
- "Man nets seven jellyfish in Moscow River". RIA Novisti. Archived from the original on 2011-07-15. Retrieved 2010-08-04. Cite uses deprecated parameter
- Oceans Fury Unleashed, July 2018, <iframe width="560" height="315" src="https://www.youtube.com/embed/hM4qpHVWQMk" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe> Electronically Accessed 09/10/2018
- "Will freshwater jellyfish sting me?". Archived from the original on 2012-07-22. Cite uses deprecated parameter
|Wikimedia Commons has media related to Craspedacusta sowerbii.|
- http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=1068 USGS' page about C. sowerbyi
- http://www.freshwaterjellyfish.org/ An authoritative and detailed website about Craspedacusta sowerbyi
- Kaeng Bang Rachan at Tourism Authority of Thailand (reference to freshwater jellyfish in the Wang Thong River in Thailand)
- GLANSIS Species FactSheet