Although it does not breathe fire, the olm has several attributes fitting a dragon: It can live up to 100 years and survive without food for 10.

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Creatures resembling dragons dwell deep within the caves of Slovenia. With the help of biologists, a new brood is set to hatch at an unusual aquarium, accessible by underground train.

This crystal-clear egg is one of three recently laid by an olm, a cave amphibian whose long sinuous body, stubby legs and frilly gills led people in the 15th century to believe it was the offspring of dragons.

Although it does not breathe fire, the olm — a type of salamander — has several attributes fitting a creature of mythology. It can live up to 100 years and survive without food for 10. It is blind, but hunts using its incredible sense of hearing and smell, and it can detect electric and magnetic fields.

Female olms only reproduce once every six years, and it takes them ages to become sexually mature. The aquarium, at a tourist site known as Postojna Cave, last expected baby olms in 2013. But none of those eggs hatched and several were eaten by other olms in the tank, said Sašo Weldt, a biologist who works there.

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“It is rare and it is exciting,” Weldt said of this opportunity for a do-over. “I was jumping when I saw the first one and the second one. It’s something you don’t want to miss when working as a biologist in a cave.”

Weldt said that this time, employees at the cave have taken new measures to ensure that this batch of eggs has a better chance of developing. They have emptied the tank of all other creatures but the mother olm and her eggs. The mother is about a week into a 20-day period where she will lay 30 to 60 eggs. Several weeks later, they are expected to hatch.

“It’s the most iconic creature in the cave,” Weldt said. “We are hoping that in a couple of months we can state that we have baby dragons.”