The Antarctic midge has the smallest genome ever sequenced by molecular biologists.
Antarctic midges are one of the hardiest animals on Earth, able to withstand freezing temperatures, high salt concentrations and extreme exposure to ultraviolet radiation. They eat biological waste from penguins, as well as algae and bacteria.
Larvae of the animals form over two winters. During each of these harsh, frigid seasons, the developing creatures lose up to half their body mass. After developing into adults, the small wingless flies mate, and die within a week to ten days.
The tiny genome could be a response to the harsh life of the animals, allowing them to live in conditions that would cause most animals to perish.
"[I]t opens up a lot of interesting hypotheses to hopefully test by sequencing additional Antarctic organisms or sub-Antarctic organisms, because there are other flies, or Diptera, on some of the sub-Antarctic islands. We're really interested to see whether or not they have similar genomes," Joanna Kelley, an assistant professor at Washington State University (WSU) said.
The genome of the Antarctic midge contains just 99 million base pairs of nucleotides, subunits of DNA. By comparison, a body louse possesses roughly 105 million pairs, and humans have around 3 billion pairs. The Antarctic fly does not possess many pieces of code that do not direct production and management of proteins.
Non-coding DNA is used in many living creatures in order to regulate genes, but they can also be responsible for genetic diseases. These strands of code were once known as "junk DNA" by researchers that did not understand their purpose.
Heat shock proteins, normally only triggered as a last-ditch survival method in larger animals, appears to be active at all times during larvae development in Antarctic midges.
Midges are able to lose up to 70 percent of the water in their bodies during the harsh winter. Insects typically perish after water in their cells is reduced by just 20 percent. Aquaporins, genes which direct water transport in and out of cells, also appear to place a key role in assisting survival of the larval flies. After dehydration, the tiny animals can be revived with warm water.
"It has really taken the genome down to the bare bones and stripped it to a smaller size than was previously thought possible. 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," David Denlinger of Ohio State University, said.
Investigation of the genome of the Antarctic midge was detailed in the journal Nature Communications.
