Scientists have for long wondered how some aquatic bugs and micro-organisms get enclosed in amber. Aquatic organisms - as their name suggests - are usually found in the water, and amber is formed from tree resin.
Assuming that tree resin hardens on the tree, it isn't obvious how water-loving creatures get trapped inside. Scientists have put forth theories that perhaps resin still flowing in trees with water-logged holes trap some organisms or that wind blows dried-out remains of aquatic creatures into blobs of resin.
Now, the team of Alexander Schmidt from the Museum of Natural History in Berlin, Germany, and David Dilcher of the University of Florida in Gainsville, the US, has provided a different yet simpler theory for this phenomenon.
They said that for trees standing in water, resin dropping into the water stayed firm enough to retain its shape and act as a trap, but soft enough for an insect to wander through the shell of the hydrophobic resin blob. "It is so logical and easy an answer that we didn't think of it. This provides an easy and very plausible answer to how insects get caught in resin," said Michael Balke of the Bavarian State Collection of Zoology in Munich, a researcher specializing in the taxonomy of aquatic insects, who has been studying this question for quite some time.
As part of their study, the two researchers cut some trees standing in water to induce a resin flow, and then watch what happens. They found that when the resin reached the water line, some spread out and floated on the water. The majority of the resin, however, slid all the way down to the floor of the pond as pillow-shaped blobs. These formed a thin hard shell after a few days, but remained liquid inside.
The duo found that small microorganisms could penetrate the blob before its shell hardened, while largish insects that blundered into the blob by breaking the shell got stuck inside. "People thought it was very hard to get tiny soft-bodied organisms into the resin," said Schmidt.
During the course of their research, the duo collected a menagerie of Florida swamp-dwellers in their resin, which hardened as the summer wore on and the water dried up, exposing the resin to the air.
They found that along with water beetles, algae, diatoms, flagellated microorganisms, nematodes and mites, fungi and bacteria actually grew inside the resin - until it solidified.
The study appears online in the week's issue of the journal Nature.