Jellyfish
Craspedacusta sowerbii
"Peach Blossom Jellyfish Clones"
On the topic of jellyfish in general, even a small amount of research produces a sense of awe for these small creatures. According to the website oneearth.org there are about 300,00 species of jellyfish and they have existed for some 700 million years. Comprised mainly of water and with no brain, their existence is summed up by "oneearth.org" in the following text excerpt:
“Before the dinosaurs, trees, or even fungi, there were jellyfish. They are the oldest multi-organ animal, surviving all five of Earth’s mass extinction events. “
Previously on this website information concerning the freshwater jellyfish in Hotel Lake was limited to an October 2020 article in the Harbour Spiel which you can now find in the library by clicking here.
This webpage presents information on this small freshwater jellyfish called Craspedacusta sowerbii or as it is more popularly dubbed: "Peach Blossom Jellyfish Clones”
To understand a bit more about the history and naming of this jellyfish we refer to the following explanation, quoted from a recent paper by Professor Evgeny Pakhomov and Dr. Florian Luskow:
"In ancient Chinese, there are four dialects or local names of FWJ [freshwater jellyfish]: 士淑水母: The pronunciation of this name is similar to ‘dead-water jellyfish’ in the Hangzhou dialect where it was found; 马鼻子 – Horse nose or horse nasal mucus; 桃花扇 – Peach Blossom Fan; 桃花鱼 – Peach Blossom Fish. The last one, 'Peach Blossom Fish' is the most common name. It is unknown who first coined these names. Old notes mention these FWJ were found at the time of peach bloom, and the jellyfish look like falling petals of the flowers. Kimura (1937) reviewed ancient Chinese literature – some dating back to the Song dynasty in the year 1250. Despite centuries-old written proof of existence, FWJ were kept aside as an 'abnormality' by many GZ researchers and limnologists."
From here, we delve into the spread, and life cycle of the Peach Blossom Jellyfish as well as an update on current research efforts to understand its impact on our ecosystem.
In BC, sightings of freshwater jellyfish in lakes have been concentrated in the Lower Mainland and Vancouver Island areas. On the Sunshine Coast, the first reports of Peach Blossom Jellyfish Clones in Hotel Lake date back to 2001.
Hotel Lake Jellyfish video taken in August 2024
The freshwater jellyfish with the scientific name, Craspedacusta sowerbii, is now thought to inhabit every continent except Antarctica. This jellyfish is indigenous to the Yangtze River Valley in China and experts theorize that it has made its way around the world on the hulls of boats, through aquarium dumping, in bait buckets and by hitching rides on stocked fish, aquatic plants, and even waterfowl.
The diagram below, of Craspedacusta sowerbii, is from plos.org. PLOS is a nonprofit, open Access publisher empowering researchers to accelerate progress in science and medicine by leading a transformation in research communication.
What we see in Hotel Lake in the warmth of July, August and September is the medusa, a whitish, translucent bell that is approximately one inch in diameter. Composed of at least 90% water the medusa have no lungs, heart or brain. Oxygen is absorbed through their thin skin. They have no blood for a heart to pump. The nerve net found just below the epidermis allows them to respond to changes in their environment.
A group of jellyfish, which can be in the thousands, is called a bloom, a swarm or a smack of jellyfish. Except for the warmest summer months, the freshwater jellyfish exists as a polyp found underwater attached to vegetation, rocks or even tree stumps. Often existing in small colonies, they are cylindrical in shape and look much like like tiny bowling pins. These “bowling pins” have one end fixed to the ground, and the other end extending up into the water with a ring of tentacles surrounding its mouth/anus. In this phase, the jellyfish polyp has a fully developed digestive system and is able to catch prey and feed itself efficiently.
According Professor Pakhomov: "Polyps are very small, usually around a millimetre in size, and it is challenging to locate them. They inhabit shallow areas and can be found on rocks and submerged wood debris. Hence, we usually know about jellyfish introduction when we see the floating medusa form produced by polyps appear in the water, which appear only when water temperature is higher than 21degrees Celsius —so polyps could be in many more lakes without us knowing about it. We do not know how and when introduction of the species occurred, but it was likely through medusa-producing polyps carried on recreational boats or on the bills or feet of birds when feeding.” It seems that locating polyps in Hotel Lake is the next big task, one that will advance our understanding of our local jellyfish.
In the coldest months of the year, or in other harsh environmental conditions such as drought, polyps can shrink into tiny dome shaped bodies known as podocysts. This resting, dormant stage allows jellyfish to survive detrimental conditions for lengthy periods and rebound when circumstances become more favourable.
Freshwater jellyfish have three major stages: egg, polyp, and medusa.
Sexual reproduction happens when medusae release sperm and eggs into the water. Asexual reproduction is more common and occurs when polyps “bud”. The complexity and adaptability of this life cycle play significant roles that contribute to 700 years of survival for this resilient jellyfish. However, this life cycle still has a few question marks that we cannot answer. Future work and study in this area will likely provide greater understanding.
The medusa feeds on zooplankton including water fleas and copepods. To catch and digest this prey, the jellyfish has tentacles lining the rim of the bell and a large stomach structure (manubrium) hanging down from the centre of the inside of the bell with a mouth-opening and four frilly lips. The many tentacles each contain thousands of cells called cnidocytes which are the source of barbs and venom. Dangling its tentacles, the jellyfish drifts along until prey touches a tentacle.The prey is then stung, paralyzed, coiled by a tentacle and brought to the mouth. Food is taken into the mouth opening, digested in the stomach and waste is finally expelled through the same opening. This sounds like a water fleas’ worst nightmare.
So, if freshwater jellyfish eat zooplankton, what eats jellyfish? It is believed that fish avoid jellyfish. Turtles and crayfish are mentioned as the only interested predators.
The tentacle’s stinging cells are used for paralyzing very tiny prey and have not been proven to have the capacity to pierce human skin. Recently concern has been expressed for allowing freshwater jellyfish to get close to our eyes (e.g accidentally being scooped up in googles) or near open wounds as has happened in a couple of incidents. On Vancouver Island, two children needed to go the hospital and undergo a week or so of antibiotic treatment.
Science and Jellyfish
Craspedacusta sowerbii and other freshwater jellyfish hold a place of special interest for the scientific community. Jellyfish are known as an indicator species, meaning changes in their populations represent greater changes in the ecosystem. Around the world today, jellyfish are thriving in record numbers.
A local zoologist Dr. Florian Lüskow, became interested in freshwater jellyfish when they were reported in Killarney Lake near Victoria. Today, working with Professor Evgeny Pakhomov at UBC the aim of their research is to understand the distribution and impacts of the jellyfish on lake ecosystems in B.C. An initial study analyzed polyp and medusa responses to different temperatures. In our library, you can read his article: “Increasing Temperature Facilitates Polyp Spreading and Medusa Appearance of the Invasive Hydrozoan Craspedacusta sowerbii “ by clicking here.
Recognizing that medusae bloom in the warmth of July, August and even September the possibility exists that climate change will affect both life cycle stages and their food web impacts. Luskow surmises that increases in temperature due to environmental warming “will favour the expansion of the species in the future to higher latitudes.”
Many researchers emphasize how much can be learned from citizen scientists who document their findings. Florian Luskow asks if you find medusae to email him at flueskow@eoas.ubc.ca. Observers are asked to share the place, time, conditions and if possible, even a picture of the jellies.
Researchers lament that many questions remain and much is not known. Many articles end with the thought that “The ecological impacts of this non-native species are unclear”. Some of the questions revolve around the concerns that non-native species with few predators can outcompete the local residents for food. If these jellyfish were to cause a major decline in planktonic algae, daphnia, and other organisms that form the basis of aquatic food chains, they might indeed have an indirect impact on populations of fish and other larger animals.
In 2022 we took great interest, because we were frequently seeing these jellyfish in Hotel Lake during the summer months. This motivated us to contact Dr. Florian Lüskow at UBC for information so that we could publish this webpage about Jellyfish. Over time Dr Lüskow and Professor Evgeny Pakhomov, at UBC, outlined a research study of freshwater jellyfish that would require the help of local volunteers and happily six local Hotel Lake volunteers came forward to assist in the summer of 2023. This project began with Dr. Lüskow and Professor Pakhomov visiting Hotel Lake to provide training to the 6 volunteers. The 2023 project involved 17 sorties out onto the lake to collect data and samples; these sorties dubbed “Stations” took place every 4 days. At each station volunteers conducted a number of measurements and sample-taking and associated processing for later analysis. In 2024, the local volunteers assumed the mantle: “Hotel Lake Stewards” and this project continued to evolve with new protocols. This proved to be a very active year as a great many jellyfish samples and other data were collected.
