The Natural History Museum of Denmark houses a unique collection of 70,000 pieces of amber from various time periods. Surprisingly, while studying this collection, a team of researchers found an amazingly well-preserved fungus gnat inside 40-million-year-old amber.  

This is the first known fossil of Robsonomyia henningseni, a “rare and never-before-studied species” of gnat. According to the researchers, this ancient insect is a missing link between two living gnat species found in Japan and the United States, separated by an ocean and a distance of nearly 8,000 kilometers.

“This geographical separation was puzzling to us. Our discovery reveals that Robsonomyia also once inhabited Europe, which is approximately halfway between Japan and North America, This suggests that millions of years ago, the genus likely had a much broader distribution across the entire Northern Hemisphere,” Alicja Pełczyńska, first study author, and a PhD student pursuing a double doctorate at both the University of Łódź and the University of Copenhagen, told ZME Science. 

This finding also suggests that many other species with similar distribution patterns might have undergone the same migration. 

Amber is no less than a time capsule

Pełczyńska and her team weren’t looking for an ancient fungus gnat. They were studying the amber pieces to closely understand the impact of climate change on fauna that inhabited Earth during the early period of the Eocene epoch (~56 to 40 million years ago).

This is because, at the beginning of the Eocene, temperatures increased by up to eight degrees Celsius due to increased carbon levels in the atmosphere –- very similar to how our planet is currently experiencing global warming driven by massive carbon influxes. 

A close examination of the fauna of that epoch can help scientists better understand how such phenomena impacted the insect species we know today, particularly flies. But where can one find such fossils of such fauna in well-preserved condition? 

The answer to this question is “Baltic amber, which formed during the Eocene. It provides us with a wealth of data as this fossilized resin was once incredibly sticky, trapping insects — and even small vertebrates like lizards — that came into contact with it. Over millions of years, the resin hardened, preserving these organisms in stunning detail.” Pełczyńska said.

While studying the amber pieces and fossils, the researchers were trying to connect the dots of climate change but they had no idea they would find something unexpected.

“When we first found this specimen (R. henningseni), we knew it was unlike anything previously found in amber. However, we didn’t initially realize that we were dealing with such a rare and enigmatic genus. This rare specimen is perfectly preserved and appears almost alive, despite being millions of years old, proving that amber acts like a time capsule” Pełczyńska added.

Fungus gnat’s body is preserved but the DNA is lost 

Robsonomyia henningseni was a predatory insect that inhabited ancient Fennoscandia (present-day Northern Europe) 35 to 40 million years ago. It lived in a sub-tropical or tropical environment featuring dense humid forests, and used sticky webs coated with acidic fluids to trap and kill small invertebrates. 

The discovery of this fossil gives scientists the rare opportunity to study the migration and distribution patterns of the Robsonomyia genus.

“Robsonomyia is a little-known genus, with much of its biology still shrouded in mystery. Enhancing our understanding of how the distribution of organisms has evolved over time provides critical insights into the factors that shape the current patterns of flora and fauna,” Pełczyńska told ZME Science.

For instance, the resin that trapped the insect allowed for a unique form of fossilization, preserving the organism in three dimensions and retaining an astonishing level of morphological detail as if it were still alive.

By studying these well-preserved specimens, the researcher can compare them to their modern relatives with great precision. This would help them uncover evolutionary changes that have occurred over millions of years in response to environmental and climatic shifts since the Eocene epoch.

“However, despite their lifelike appearance, these insects have undergone significant chemical and physical transformations over millions of years. Consequently, their genetic material has degraded beyond the point of full restoration,” Pełczyńska said. 

This means that for now scientists can’t extract and study the DNA of the fungus gnat. The fossil represents the hollow body of the insect that is so fragile that any attempt to remove it from the amber can turn the insect into tiny pieces.    

“That said, advances in technology may one day allow us to recover fragments of DNA from these ancient remains,” Pełczyńska added.

The study is published in the journal Scientific Reports.