Believe it or not, some people make a career out of wrestling jellies. But this bunch of jelly enthusiasts take it to a whole other level. They wrestle jellies that have arms laced with venomous harpoons. Sounds dangerous? That’s just the way they roll out at James Cook University, Cairns.

Behind the scenes there is some serious science going on and the talented team of jelly wranglers have just added another world first to their belt. They’ve unlock a key stage of the Irukandji jellyfish lifecycle and have grown the polyp form in the laboratory.

Postgraduate student Robert Courtney and Professor Jamie Seymour, both from the Australian Institute of Tropical Health and Medicine (AITHM), now have a culture of more than a million polyps, which have so far produced around 100 tiny jellyfish.

Since polyps reproduce asexually, budding off clones of themselves, JCU now has a perpetual source of early-lifecycle jellyfish, which will be used to better understand the factors that drive the timing and intensity of the Irukandji season.

“Having a culture of Carukia barnesi polyps is a huge step forward in Irukandji research because it allows us to study the rest of the lifecycle of this species, which has not been observed before,” Mr Courtney said.

Carukia barnesi is the species originally identified in 1964 by Cairns doctor Jack Barnes as causing what we now know as Irukandji Syndrome. To understand the excitement about growing Irukandji polyps in the lab, it helps to understand the complex lifecycle of jellyfish in general.

“The jellyfish, or medusa, stage is what most people are familiar with, and that’s the stage in which some species pose a threat to humans,” Associate Professor Seymour said.

During this stage jellyfish grow to maturity and reproduce sexually, producing fertilised eggs. The eggs hatch as small larvae, which swim for a few days before attaching to a hard surface such as rocks or coral.

The larvae then develop into small polyps, which remain attached to one spot and reproduce asexually, budding off clones of themselves. The polyps are small (a millimetre across) and have short tentacles, which they use to catch prey. Eventually the polyps produce medusae (jellyfish).

“Species differ in how and when the polyps produce jellyfish, but the trigger is environmental,” Associate Professor Seymour said.

“Having this culture in the lab means we can investigate what the trigger is for Carukia barnesi, and better understand the timing and intensity of Irukandji season.”

The researchers are also gaining insight into where Irukandji polyps might be found in the marine environment – a detail that is currently unknown.

“Although it’s early days, the results from a series of experiments indicate that the polyps have a high tolerance to both temperature and salinity, but they do best at around 25 degrees Celsius,” Mr Courtney said.

“What’s really interesting is that they also seem to do best at low salinity levels – conditions much closer to what we find in estuaries and river mouths, rather than on the Great Barrier Reef.”

Associate Professor Seymour said this was an exciting observation. “The adult Carukia barnesi is considered an oceanic species, occurring mostly offshore. These results indicate that in the polyp stage it might actually be a coastal animal, similar to the larger box jellyfish species such as Chironex fleckeri.”

From their culture of Carukia barnesi, the researchers have grown about 100 baby jellyfish, which initially measure just one millimetre across.

“Even at that size they’re dangerous and could cause Irukandji syndrome,” Associate Professor Seymour said. “Eventually they grow to a maximum of around 3.5 centimetres across the bell, with tentacles up to 1.2 metres long.”

Understanding how different water quality parameters affect the polyp stage will also help researchers to determine how the length and intensity of Irukandji season might change in response to projected climate change scenarios.

Check out a video on the polyps here: Irukandji Polyps