WILLIAMSBURG — Biology students at William & Mary have been observing a recent freshwater Jellyfish bloom in the pond known as Crim Dell on campus. This has been the first jellyfish bloom at William & Mary since 2019.
Known by their scientific name Craspedacuta, nicknamed by the school “the crim jellies”, these very small animals are surprisingly resilient. The species is actually native to China but over hundreds of years, they have found their way to over 40 states in the United States and some regions in Canada. In fact, they have been recorded on every continent except Antarctica.
William & Mary Biology Professor John Allen is a marine biologist and an invertebrate specialist who has been studying this species on campus. The recent freshwater jellyfish bloom occurred right outside the school’s science building.
“It was actually a student in the class that was the first one to spot them this year. I think it was the first day of class when a student came up to me and said, ‘I think we saw Jellyfish in the Crim Dell.'” said Allen. “Then we went out and started looking for them more intentionally. There was a huge number of them. The students were really the ones who spotted them before they even knew that they existed.”
Since the initial spotting, Allen and his biology students have been collecting samples and collaborating with one of Allen’s former students, who works out of a laboratory in Kansas, and several colleagues from a laboratory in British Columbia, Canada. All the collaborators are very involved with the research of the animal and have been working with Allen’s students in an effort to gather more data.
Allen admits there are still many unknowns about the animal. At this point, one can only hypothesize how the animal is able to travel all over the world.
“That’s one of the mysteries about them. How’d they get distributed? They obviously have been so successful in terms of their distribution globally and in North America. ” said Allen.
One theory is that when the jellyfish are in the polyp stage of their life before they bloom into jellyfish, they get on the feet of birds who are swimming or fishing. These birds will then carry the polyps to another body of freshwater where the polyps end up living the rest of their life.
The polyp phase is the main phase of the animal’s life cycle. When they are in this phase the animal looks like a small stock with tentacles on it. This phase is where the animal spends the majority of its life. The polyps reproduce asexually. They simply bud off new individuals of those polyps.
Allen and his students speculate that the bloom may be triggered by a temperature change in the water.
“It seems like there is a temperature trigger. If it warms up enough above 21 celsius then they switch from asexual reproduction to sexual reproduction and they start making these little jellyfish,” said Allen. “Those jellyfish feed on plankton and they swim around and the whole cycle repeats.”
Research is still going into the freshwater jellyfish’s impact on the local ecosystem. Biologists know that these jellyfish are known to eat mosquitos, plankton, and sometimes even small fish.