According to a team of genetic researchers headed by Prof David Denlinger of the Ohio State University, the Antarctic midge (Belgica antarctica) has the tiniest insect genome sequenced so far.
An adult male of the Antarctic midge, Belgica antarctica. Image credit: Richard E. Lee Jr.
The Antarctic midge is a small, wingless fly. It was first described by a naturalist aboard the S.Y. Belgica, an exploratory ship that plied the waters off the Antarctica Peninsula at the end of the 19th century.
The midge is the southernmost insect and the only insect species endemic to Antarctica.
Its larvae develop over not one but two winters, losing nearly half their body mass each time.
It endures high winds, salt and intense UV radiation. As an adult, the midge gets by without wings and lives for only a week or so before starting the life cycle all over again.
Surprisingly, its genome has only 99 million base pairs (building blocks of DNA), making it smaller than other tiny reported genomes for the body louse (105 million base pairs) and the winged parasite Strepsiptera (108 million base pairs). By comparison, the human genome has 3.2 billion base pairs.
The Antarctic midge genome lacks many of the segments of DNA and other repeat elements that don’t make proteins, which are found in most animal genomes.
“The lack of such baggage in the genome could be an evolutionary answer to surviving the cold, dry conditions of Antarctica,” said Prof Denlinger, who is the senior author on a paper published in the Nature Communications.
Small in architecture but not in the number of genes, the midge genome contains about 13,500 functional genes.
In looking at the genes and comparing them with their known functions in other animals, Prof Denlinger’s team found an abundance of genes geared towards regulation and developmental processes.
On the other hand, it has few odorant receptors. This could be because it rarely ventures far, having no wings, and doesn’t need to detect things much further than it can walk.
“It’s a pretty exciting fly,” said Dr Joanna Kelley of Stanford University and the Washington State University, who is the lead author on the study.
“Overall, its genome opens up a lot of questions for me about genome evolution, and I’m looking at other related organisms to try and get at that question.”
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Kelley, J. L. et al. 2014. Compact genome of the Antarctic midge is likely an adaptation to an extreme environment. Nat. Commun. 5: 4611; doi: 10.1038/ncomms5611
