Antarctic Midge Has Tiniest Insect Genome to Date in Order to Survive Harsh, Icy Conditions

Scientists may have just found the smallest insect genome to date--and it's in Antarctica. Researchers have sequenced the genome of the Antarctic midge and believe that its comparatively tiny genome could be the reason why it can survive under harsh living conditions.

The midge is a small, wingless fly that spends most of its two-year larval stage frozen within the Antarctic ice. Once it finally grows into an adult, it has only 10 days to mate and lay eggs before it dies.

What's surprising, though, is that the midge genome is so small. It contains only 99 million base pairs of nucleotides. In comparison, the louse has 105 million base pairs and the winged parasite Strepsiptera has 108 million base pairs.

That's not to say that the midge doesn't have a large number of functional genes. It has about 13,500 of those. Yet the fact that it's small in architecture is intriguing.

"It has really taken the genome down to the bare bones and stripped it to a smaller size than was previously thought possible," said David Denlinger, one of the researchers, in a news release. "It will be interesting to know if other extremophiles-ticks, mites and other organisms that live in Antarctica-also have really small genomes, or if this is unique to the midge. We don't know that yet."

The midge does have genes that allow it to survive the harsh conditions of Antarctica, though. It has a host of genes called aquaporins, which are involved in water transport into and out of cells. These allow the midge to tolerate a loss of up to 70 percent of their water.

"They look like dried up little raisins, and when we pour water on them they plump up and go on their merry way," said Denlinger. "Being able to survive that extreme level of dehydration is one of the keys to surviving low temperatures. This midge has some mechanism that enables it to both be dehydrated and stay alive, with its cells functioning normally."

The findings reveal a bit more about this midge and show how it manages to thrive within the Antarctic. Currently, the scientists hope to see if other Antarctic species share the midge's small genome, or if it's unique to this insect.

The findings are published in the journal Nature Communications.