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Trapped in 99-Million-Year-Old Amber, a Beetle With Pilfered Pollen

A mid-Cretaceous beetle had a cavity filled with hair at the base of its mandibles for collecting pollen from plants known as cycads.

Bees and butterflies are praised for their pollination prowess. But millions of years before they ever flirted with a flower, beetles were one of the world’s pre-eminent pollinators.

Among the plethora of prehistoric plants they helped fertilize were cycads, which look like a mix between palms and ferns, though they are more closely related to pines. They have thick trunks, pineapple-shaped cones and they are crowned with feather-like leaves.

Researchers knew from studying modern cycads that they were pollinated by beetles. Now, for the first time, paleontologists have found trapped in amber from Myanmar a 99-million-year-old beetle preserved with pilfered pollen from a cycad. They reported their find Thursday in the journal Current Biology.

“Finding this ancient relationship, it’s like a dream come true,” said Chenyang Cai who is a research fellow at the University of Bristol in England.

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Dr. Cai first started studying the amber while doing research in China. Stuck inside was a two-millimeter-long insect, known as a boganiid beetle. These beetles have a tiny cavity filled with hair at the base of their mandibles that acts like a pocket for collecting pollen.

When he was done cutting, trimming and polishing the amber, Dr. Cai had what was essentially a biological sample mounted on a golden glass slide. He placed the fossil under a microscope and examined it at 400 times magnification. There, he found the beetle’s mandible pocket. And surprisingly, he saw dozens of specks of pollen, some even clustered in clumps, alongside the beetle.

“I was very excited. I just wanted to know what was this pollen,” Dr. Cai said. “It’s not on the body of the beetle, but it’s very close to the beetle and to its mouth part,” he said.

He noted that the pollen may have once been on the beetle, but it could have slid off as the pair were engulfed by tree resin.

Dr. Cai contacted Liqin Li, who studies ancient pollen at the Chinese Academy of Sciences and is an author on the paper. By observing the long grooves on the oval-shaped grains, Dr. Li identified the pollen as belonging to an ancient cycad.

Though scientists in Spain had previously found beetles and pollen preserved together in amber from a different deposit, the researchers were not sure if the pollen came from a cycad or a ginkgo plant. The authors of the new paper also found that the ancient beetle’s closest living relative is one in Australia that also pollinates cycads.

Cycads, unlike most flowering plants, have distinct male and female plants. When a beetle flies to the cones of a male plant, perhaps seeking pollen to eat or for a place to lay its eggs, it brushes against the pollen. Then while visiting dozens of other cycads, it may happen upon a female cycad and deliver that pollen.

“It’s inadvertently and innocently pollinating the plant,” said Michael Engel, a paleoentomologist at the University of Kansas and an author on the paper. “It works well — the plant gets pollinated and the insect gets fed.”

Though this piece of amber is 99-million-years-old, Dr. Cai and Dr. Engel think it provides a snapshot of a pollination process that may be much older, possibly dating to the Triassic Period. If so, that may mean that beetles were pollinating plants more than a hundred million years before butterflies and bees were first pollinating flowers, which may have been around 130 million years ago.

“Insects and plants are the two dominant titans of our world,” said Dr. Engel. “The intimate, love-hate relationship between these two behemoths of diversity through time is a major tale to tell, and this fossil is just one component of that.”

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