Springtail's Globe-Trotting Secret Caught in Amber

Researchers have found new evidence showing a springtail taking a ride on the wings of a mayfly.

A team of researchers led by David Penney from the University of Manchester, UK, analyzed the fossils of two tiny creatures trapped in a 16-million-year-old amber (globules of fossilized resins). The amber was discovered by miners in the Dominican Republic in 2008.

Scientists said this discovery suggest the descendants of these tiny creatures might still hitchhike flights today to move around the globe, reported LiveScience.  

Using a high resolution CT scanner, they took over 3,000 X-rays of the springtail (small wingless insects that are 0.04 to 0.2 inch long) fossil from different angles and made 3D digital images to precisely analyze the behavior of the springtail. They found clear evidence of a springtail hitchhiking on a mayfly using its prehensile antennae. The antennae were used to hook on to the base of the mayfly's wing.

"The images are really impressive. This pioneering approach to studying fossils has allowed us an insight into the behavior of one of the world's most prevalent organisms," Penny said in a statement.

Researchers observed minute details of the animal using the 3D images taken. Magnified observation of the images showed that the springtail was slightly detached (by just 50 micrometers) from the mayfly. This suggests that the arthropod was attempting to spring away when the amber covered both the creatures.

As the resin flowed over the mayfly it died instantaneously and wasn't moved from its resting place. The springtail resting on its back was in contact with the mayfly in the same position. This shows that the resin did not bring the two creatures together when it moved down the tree.

This is the first record of phoresy (transportation of one organism by another) in adult mayflies, considering the fact that they have a short lifespan. Mayflies live for periods ranging from one hour to a few days. They spend their adulthood in reproduction and they are unable to feed.

The new discovery also sheds light on how springtails migrate across the globe. Springtails hop around when the soil is disturbed, but it is not known how they manage to migrate to other places.  They are nervous creatures and have the ability to escape from danger using its springing organ (the furca) on the underside of the abdomen. This makes observing their behavior very difficult.

In a previous discovery, a piece of Baltic amber showed evidence of five springtails hooked in a row on the leg of a harvestman (daddy longlegs) arachnid. This new study reveals that springtails can use mayflies as well, to migrate from place to place.

Experts are further analyzing the amber using CT scans. They hope the study will give insights into the unknown behavior of these tiny creatures that are commonly found in the soil.

The findings of the study, "Ancient Ephemeroptera-Collembola Symbiosis Fossilized in Amber Predicts Contemporary Phoretic Associations," are published in the journal PLOS ONE.