Scientists discover a sexually transmitted virus in crickets, which effectively castrates its hosts, but encourages sexual activity like an aphrodisiac

Scientists discover a sexually transmitted virus in crickets, which effectively castrates its hosts, but encourages sexual activity like an aphrodisiac

In a patch of grass along the Gulf Coast, a Texas field cricket rubs his wings together to produce his characteristic « chirp. » He’s playing a courting song to attract the attention of a nearby female. His advances work and she approaches. After brushing each other with their antennae, the pair get down to business. The female mounts the male to receive a packet of sperm that he has released onto his abdomen, and that will pump sperm into her for the next half hour.

It all seems perfectly normal — for bug sex, anyway — but there’s actually something amiss here. Our six-legged Romeo is sterile, and his partner will soon be infertile. Her innards will become swollen and blue, and she won’t produce any eggs from their tryst. There’s no bouncing baby crickets on the way, and no happy ending to this romance. Except, that is, for a particular virus that has encouraged these star-crossed lovers to mate.

The virus, known as IIV-6/CrIV, benefits from the cricket’s copulation because it spreads through sexual contact. And what’s more, the virus promoted that contact in the first place, according to a new study.

It’s a brilliant bit of behavior modification, similar to strategies employed by other viruses and parasites that can only flourish if their hosts do certain things. Rabies makes its hosts more aggressive so the virus can be spread by bites. Hairworms turn their grasshopper hosts into suicide jumpers so they can get to water. Some wasps force spiders to build weird webs to support their cocoons. All of this is done via chemical warfare waged on the host’s central nervous system. A little venom here, or a tweak in hormone levels there, and the brain and body are hijacked for the parasite’s own ends.

Biologist Shelley Adamo came across it in her lab at Dalhousie University in Nova Scotia when some of the crickets she kept there stopped laying eggs. She dissected some of the crickets and found that their fat bodies — an organ that stores fats and produces proteins for the immune system — were bloated and had turned blue. A peek through a microscope revealed that the organs were full of hexagonal viral particles that had packed themselves into a crystalline shape, which gave the fat body an eerie blue sheen.

The fat body is the perfect headquarters for interfering with communication between the immune system and the nervous system, and for altering its host’s behavior and physiology.

And that’s just what the virus did. The infected crickets could forget any chance of being parents. Adamo found that the females all had fewer than ten eggs inside them, while some had none. In contrast, a healthy cricket can usually hold more than a hundred. The males still produced sperm, but the cells were either severely crippled or entirely immobile. This kind of « parasitic castration » can help viruses and parasites secure more of the host’s bodily resources for themselves without killing the host or hurting its ability to attract mates.

Despite their reproductive shortcomings, the crickets still wanted to mate. In fact, the males seemed more eager to get it on than usual. When Adamo and her team paired the crickets up, healthy, uninfected males waited around 10 minutes before they started serenading a female. Ones that were sick with a bacterial infection waited around 13 minutes — they were clearly not in the mood. Males that were infected with IIV-6/CrIV, on the other hand, didn’t slow down at all. They actually started the mating game faster, taking only about three minutes to get courting. Meanwhile, the females, whether they had the virus or not, all mounted the males and took their broken sperm in the same amount of time.

The researchers think that the accelerated mating is a behavioral change forced by the virus so that it can be transmitted from cricket to cricket. About half of the infected-uninfected pairings led to the virus being spread. In some cases, the virus didn’t even need the crickets to have sex, and hopped host-to-host while the insects nuzzled antennae during courtship.

The virus has another trick up its sleeve. Mucking with the crickets’ immune system not only speeds up their courtship, but also keeps them in good enough shape to attract a mate. Animals that are sick usually won’t put much, or any, effort into mating. They’ll also often stop eating and lose weight while their immune systems fight off the infection. Other animals will pick up on these signs and avoid mating with sick suitors. That would be a dead end for a sexually transmitted infection, but the crickets with IIV-6/CrIV didn’t show any of these « sickness behaviors » and were still attractive enough get other crickets to mate. They maintained their weight and went about their day as normal, the researchers think, because the virus keeps their fat bodies from producing the immune signals that tell them to do otherwise.

Adamo and her team aren’t sure how IIV-6/CrIV does any of this, but they think it is at least partly attributable to a reduction in the host’s overall protein content and the activity of virucidal enzymes. That would explain the lack of sickness behaviors, but not the males’ speedy courting. Researchers will need to observe some more poor crickets mating futilely to fully understand the virus’ exploitation of cricket sex.

Source

Related posts

CERN frees LHC data

CERN frees LHC data

Anyone can access collision data from the Large Hadron Collider through the new CERN Open Data Portal. Today CERN launched its Open Data Portal, which makes data from real collision events produced by LHC experiments available to the public for the first time. “Data from the LHC program are...

Dark matter could be spotted in GPS time glitches

Dark matter could be spotted in GPS time glitches

GPS has a new job. It does a great job of telling us our location, but the network of hyper-accurate clocks in space could get a fix on something far more elusive: dark matter. Dark matter makes up 80 per cent of the universe's matter but scarcely interacts with ordinary matter. A novel...

Scientists Made Synthetic Life Using Genetic Material Whipped Up in a Lab

Scientists Made Synthetic Life Using Genetic Material Whipped Up in a Lab

In every 8th grade science class, you learn the five nucleic acids that make up the base pairs in DNA and RNA: A,C,T,G, and U. These and these alone, we're taught, are the building blocks of life. Not anymore. Researchers have astoundingly created two new completely, unnatural base pairs and...

« Date Rape » Drug Is Now Detectable By a Fluorescent Sensor

"Date Rape" Drug Is Now Detectable By a Fluorescent Sensor

Scientists in Singapore have developed a simple and brightly colored method to see if someone has tampered with your drink with GHB, commonly known along with Rohypnol as a date rape drug Scientists have created a new, brightly colored way to detect if a drink has GHB, commonly known along with...

Eating vegetables reduces your risk of death up to 42 percent

Eating vegetables reduces your risk of death up to 42 percent

A diet filled with fresh produce is good for your health, and now a large study suggests that eating plenty of fruits and vegetables may substantially cut your risk of death. Researchers analyzed the eating habits of more than 65,000 people in England between 2001 and 2013. They found that...

Leave a comment