The microscopic view of a swarm cell of the fossil presented before the media on Wednesday. (PTI)

New Delhi, Nov. 2: Scientists in Lucknow have discovered 65-million-year-old fossils that show tiny, single-celled organisms engaged in the sexual act.

The scientists from the Birbal Sahni Institute of Paleobotany (BSIP) and Lucknow University dug out the fossils from ancient rock at the base of a nine-metre-deep dry well near the town of Padwar, about 20 km from Jabalpur in Madhya Pradesh.

The organisms are slime moulds known as Myxomycetes, a primitive class of fungi with characteristics of both plants and animals. The fungi have tail-like structures called flagella that help them swim through water. The fungal cells, which can be seen only under a microscope, fuse during sexual union to produce a spore that germinates into offspring.

The Lucknow scientists observed a pair of these fossilised fungi in sexual conjugation. “During the act of copulation, something happened, and the two cells died and were fossilised over time,” Ranajit Kar, a scientist at the BSIP, told The Telegraph.

The sexual union of fungi is a very short process and is very difficult to observe even in the laboratory today. “It’s amazing to see sexual union in the fossilised state because the sexual organs are delicate, the conjugation lasts for about a day,” Kar said.

Living Myxomycetes have been reported in India since the 1830s. They are commonly found during the rainy season, growing under dead wood or leaf litter. But until now there have been no reports of fossilised forms of these organisms.

Kar and his colleagues have also detected several fossilised fungal cells with flagella-like structures. Reporting their findings in the journal Current Science, the Lucknow scientists said the cells they detected do not closely resemble any fossil forms. While flagella-like structures have been detected in two-billion-year-old rocks in Canada, they do not appear connected to any kind of cells.

The fungi were picked up from layers of rock representing a lull in the Deccan volcanism ? a period of intense volcanic activity that lasted thousands of years in central India about 65 million years ago.

Scientists believe that during one of the lulls in volcanic activity, the organisms thrived in a lake in the region. Over time, they were buried under dust, rock or volcanic debris and turned into fossils.