This Extreme Antarctic Insect Has the Tiniest Genome

[Buster's Uncle]

This Extreme Antarctic Insect Has the Tiniest Genome
LiveScience.com
By Stephanie Pappas, Live Science Contributor  16 minutes ago



A female (left) and male (right) Antarctic midge mate. These animals are the only true insects native to Antarctica, and they have the smallest genome ever sequenced.



The Antarctic midge is a simple insect: no wings, a slender black body and an adult life span of not much more than a week.

So perhaps it's fitting the bug is now on record as the owner of the tiniest insect genome ever sequenced. At just 99 million base pairs of nucleotides (DNA's building blocks), the midge's genome is smaller than that of the body louse — and far more miniscule than the human genome, which has 3.2 billion base pairs. (Though the midge's genome still dwarfs the smallest of all genomes on record, which belongs to a bacterium that lives inside insects and contains just 160,000 base pairs.)

"It's a pretty exciting fly," Washington State University genomics researcher Joanna Kelley, who worked on the project to sequence the midge's genome, said in a statement.


Tough guy

The Antarctic midge (Belgica antarctica) is exciting in more ways than one. It lives most of its life in larval form, frozen in ice. It's the only true insect that lives on the Antarctic continent, and at 0.23 inches (6 millimeters) long, it actually qualifies as the largest terrestrial animal in Antarctica, according to Miami University of Ohio's Laboratory for Ecophysiological Cryobiology. All of Antarctica's other fauna are either smaller (certain ticks and mites) or live in seawater.

Antarctic midge larvae exist in a deep freeze for two winters. They can lose up to 70 percent of the water in their bodies and still survive. As adults, the midges emerge wingless. They then live only seven to 10 days, mating and eating algae and bacteria.



The larvae of the Antarctic midge. The larvae spend two Antarctic winters frozen in ice and can survive losing 70 percent of the water in their bodies.


Antarctic midges fascinate researchers due to the insects' ability to survive massive temperature swings, high exposure to ultraviolet light and other harsh conditions. But upon sequencing the midge's genome, scientists were shocked by the small size.

"It's tiny. That was a huge surprise," Kelley said. "I was very impressed."

With 99 million base pairs, the midge's genome beats out the tiny genome of the body louse, which has 105 million base pairs, and the twisted-wing parasite (in the order Strepsiptera), which lives inside bees, wasps and roaches, and has a genome of 108 million base pairs.


Itty-bitty genome

The research team, which reported the findings today (Aug. 12) in the journal Nature Communications, suspects the mini-genome has to do with the fly's extreme lifestyle.

"It has really taken the genome down to the bare bones and stripped it to a smaller size than was previously thought possible," study researcher David Denlinger, an Ohio State University entomologist, said in a statement. "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 genome lacks "junk DNA," repetitive, non-protein-coding DNA segments once thought to be useless that actually play important roles in regulating genes. The implications of dumping all of this repetitive DNA are not clear, Denlinger said.

Many of the 13,500 functional genes present in the midge genome are involved with development, which makes sense for an animal that spends most of its life in the larval stage. The midge lacks many genes for smell receptors, probably because it doesn't move around or explore very much, something that requires such receptors; without wings, midges stay close to their home turf.

Antarctic midges do have lots of aquaporins, or genes involved in moving water in and out of cells, the researchers found. These aquaporins could be the secret to the midge's survival in extreme dehydration.

"They look like dried-up little raisins, and when we pour water on them they plump up and go on their merry way," Denlinger said. "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."


http://news.yahoo.com/extreme-antarctic-insect-tiniest-genome-152642380.html

[Buster's Uncle]

Few as 'tough' as Antarctic midge
AFP
40 minutes ago



View of Antarctica early in the morning after a snow shower, on March 13, 2014 (AFP Photo/Vanderlei Almeida)



Paris (AFP) - Antarctica's only native insect, a minuscule midge, may rely on a no-frills genome to survive being frozen, dehydrated and blasted with radiation in an ultra-tough environment, scientists said Tuesday.

Slightly bigger than a flea, the wingless bug spends most of its two-year larval stage frozen in the Antarctic ice before emerging for 10 days to mate and lay eggs on the continent's equally hostile surface, and then die.

Apart from resistance to freezing and intense ultraviolet radiation from the Sun, the midge can tolerate losing up to 70 percent of the water in its body cells. Most animals won't survive losing more than 20 percent.

"Few animals can boast of being as tough as the Antarctic midge," said a statement from Washington State University, which took part in a project to sequence the midge's genome.

What the team found surprised them -- the midge's genome was the smallest yet observed in an insect.

"It's tiny," said Joanna Kelley of the university's school of biological sciences and one of the study authors. "That was a huge surprise."

Scientists had previously observed a link between animals living in freezing conditions and large genomes thought to reflect the evolutionary adaptations they had undergone.

But this midge's genome had only 99 million base pairs, compared for example to 105 million for the body louse or 3.2 billion for humans.

"We suspect that it's somehow an adaptation to the extreme environment," said Kelley, though this has not been confirmed.

The midge, known in the scientific community as Belgica antarctica, lacks much of the so-called "junk DNA" -- repetitive sequences and shorter stretches of non-encoding DNA -- that all insects and animals have.

But it has a similar number of functional genes to most flies, about 13,500.

"It has really taken the genome down to the bare bones and stripped it to a smaller size than was previously thought possible," said study co-author David Denlinger of The Ohio State University.

It did, however, have an abundance of genes associated with developmental processes, metabolism and response to external stimuli, "which may reflect adaptations for surviving in this harsh environment."

The midge is the only fully terrestrial animal endemic to Antarctica -- the southernmost continent isolated about 33 million years ago with a cold, inhospitable desert environment.

Belgica antarctica eats bacteria, algae and nitrogen-rich waste produced by penguins, and has no predators.

Denlinger said the findings may have implications for humans in the long term "by revealing how human tissue harvested for transplant could be sustained in cold storage."

The findings were published in the journal Nature Communications.


http://news.yahoo.com/few-tough-antarctic-midge-155707146.html