Strange umbrella-shaped transparent organisms were first noticed a few months back in a well at Galamuna School of Medirigiriya. The bell shaped creatures visible to the naked eye, could be seen floating or swimming gently just below the surface of the water. The organisms were able to move in any direction through pulsating contractions along its bell surface. The organisms around the size of a 50 cent coin, started appearing in the well towards the end of 2008 monsoon season.
According to the principal of the school the Ven. Pansalgodalle Somaratne Thera, persons bathing at the school well first complained of strange creatures which got entangled on their bodies. “When they were thrown out of the water, the organisms jumped around using their tentacles.
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| Team members investigating samples |
Subsequently when farmers pumped water into a nearby vegetable field, hundreds of creatures were washed out attracting the attention of villagers…” The Ven. Pansalgodalle Thera said at this stage he isolated the well and informed the authorities. On receipt of this information, Dr Kamal Ranatunga of the University of Sri Jayewardenepura and Sumedha Abesinghe of Aquariums - National Zoological Gardens rushed to Polonnaruwa to investigate the mystery. They collected samples and carried out an investigation.
On completion of the investigation Dr. Ranatunga identified the creature as a rare freshwater jellyfish exhibiting a medusa stage in its life cycle.
Dr. Ranathunga said the creature begins its life cycle as a tiny polyp, which lives in colonies attached to underwater vegetation, rocks, or tree stumps, feeding and reproducing. He said when they reached this medusa stage they become visible to naked eye.
The freshwater “jellyfish” is not a true jellyfish as are some of its marine relatives.
It differs slightly from the true marine jellyfish scientifically identified as Craspedacusta sowerbii. Unlike the marine jellyfish, the freshwater jellyfish is harmless. They can grow up to 20 - 25 mm 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 according to literature. Hanging down from the center of the inside of the bell, is a large stomach structure with a mouth-opening with four frilly lips that help it feed on zooplanktons.
Dr. Ranatunga said he presumed this to be the first recorded sighting of freshwater jellyfish in Sri Lanka as no previous literature is available on the subject.
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Craspedacusta sowerbii.
Pic courtesy
(www.soe-townsville.org) |
While they were at Galamuna the research team investigated many other bodies of fresh water such as lakes, tanks and wells in the area but did not sight any fresh water jellyfish. The well at Galamuna to is now free of the jellyfish.
Villagers in the area tend to believe that the jellyfish may have been accidentally introduced into the well at Galamuna which is now free of the species. They appeared from nowhere and disappeared without a trace. Researchers point out that this is the normal behaviour of these mysterious creatures. They can still be hidden as tiny invisible organisms at polyp stage of their lifecycle and suddenly return to the medusa stage when they can be observed by the naked eye.
According to Dr. Ranatunga this life cycle is sporadic, unpredictable and varies from year to year depending on the local conditions. The researchers request the public in all parts of the country and especially in the Polonnaruwa district to be vigilant and inform them (researchers) if there are any further sightings of these creatures in fresh water. |
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