Friday, October 24, 2008

Suicidal Crickets: Manipulated by Worms

Parasites can manipulate host in varies ways, even causing their host to commit suicide. Hairworm (Nematomorpha) are small aquatic worms that start off as parasitic terrestrial tertrapods in their larval state (known as pre-parasitic) then mature and reproduce in aquatic habitats. Larvae hatch from eggs within 20 days, and penetrate and encyst in aquatic organisms. Cysts within aquatic insects are carried to land when the insect metamorphoses into a fly. Arthropod hosts are infected upon eating a fly containing cysts. Arthropods known to be infected with the parasitic worms are crickets, beetles, mantids, and grasshoppers.

A research study done by multiple scientists which you can find here has concluded the change in behavior of infected crickets and the hairworms technique for its survival. The hosts are infected by two ways, erratic behavior (abnormal behavior in unusual habitats) and suicidal behavior. The scientist who studied the infected crickets set up tanks that mimicked the habitat of crickets. In the tanks were large bowls of water. The analysis was based on 173 infected crickets (only carrying one parasite to avoid any bias) and 158 uninfected crickets. 82% of infected cricket’s committed suicide and only 9% of uninfected crickets committed suicide. It was observed that parasites that induced erratic behavior in their host had a much lower fecundity rate (production of eggs) than those parasites that induced suicidal behavior upon their host.

Approximately a week after a host is infected with the suicidal behavior the crickets would look for a water source and simply jump in the water and drown themselves. The parasite needs their host to jump in the water before it matures. Once in the water, the juvenile is able to mature and reproduce in its aquatic environment and repeat its evolved life cycle.

Posted by Carlos A. Varela (Week 6)


At 3:53 PM, Anonymous Anonymous said...

Woo, that is very interesting and odd behavior, to think how a parasite could evolve to have that much control over its hosts. what i was wondering was if anyone knew how this all went about after the parasite had been ingested, do they reproduce inside of the host, and how they are able to manipulate that, how do they have control over brain activity and function of the body.

Amanda Joyce

At 7:03 PM, Blogger PWH said...

that totally freaks me out it reminds me of the movie the happening where plants were releasing neuro-toxins which cause humans to commit suicide, yeah I know the movie was fiction but could it be that far fetched? Could something like this really happen?

At 7:04 PM, Blogger PWH said...

that totally freaks me out it reminds me of the movie the happening where plants were releasing neuro-toxins which cause humans to commit suicide, yeah I know the movie was fiction but could it be that far fetched? Could something like this really happen?

Jennifer Smith (6)

At 9:32 PM, Blogger PWH said...

This is just crazy, I have never heard of such a thing before! How does the parasites cause the two different behaviors in their host? Also, why would a parasite cause erratic behavior in their host if it is more beneficial for them to cause the suicide behavior? The study was done on crickets, but you mentioned that other arthropods could be infected and my last question is whether those arthropods also commit suicide once infected with the parasite?

-Tara Quist

At 4:25 PM, Anonymous Allison Cornell said...

That's really crazy! How does the parasite make them jump in the water? It must be quite a unique and intricate system. Why do so many non-affected crickets commit suicide? Could the infection be passed on in the eggs? You did say there were more eggs from the suicidal crickets.

Allison Cornell (6)

At 12:09 PM, Anonymous Anonymous said...

This is so interesting! I wonder exactly why the bugs look for a water source even though they cannot survive under water. A little creepy too! Good job.

Ericka Adey

At 3:13 PM, Blogger Dan said...

Very interesting post, hopefully this remains only in the current insects heh. I wonder just exactly how the parasites are able to control their host so well.

~Dan Hong

At 3:35 PM, Anonymous Anonymous said...

In the study it didn't mention anything about predators in the experiment. Maybe if predators were introduced into the experiment fewer crickets would make it to the drowning stage. Erratic behavior in a prey species can sometimes be a huge flag to a predator causing a portion of these infected crickets to get eaten instead of drowning.

Allan Eldridge

At 4:12 PM, Anonymous Anonymous said...

it's so creepy when parasites can control the host's "mind". It reminds me of the cordyceps parasitic fungus I saw on the planet earth documentary. The fungus spores infect ants and take over their brains. When they die, the fungus grows from their body. There's a good video on youtube. I'm really curious about how these parasite relationships evolved.

- Jane de Verges

At 5:40 PM, Anonymous Anonymous said...

Wow, that is very interesting, and actually a little scary. On the note of erratic behavior other than suicide, what kinds of behavior do they perform? I am also curious if there are any other parasites which induce this form of behavior (for example in mammals).

Alex Jackson

At 5:43 PM, Anonymous Anonymous said...

I've heard about parasites causing their hosts to have some harmful behavior. Do you know what exactly the parasite does to alter the host behavior? Is it some sort of chemical imbalance?

-Cecelia Hunt

At 6:12 PM, Anonymous Anonymous said...

This is kind of freaky. How exactly does the parasite do this? I'm sure that the crickets aren't committing suicide the way we think of it, making a concious decision to end one's life. Does the parasite take over the host's nervous system somehow? Or maybe somehow the parasitical instinct to find water overrides the cricket's own survival instinct?

-Corinne Delisle

At 7:50 PM, Blogger PWH said...

This article is an interesting find. Parasites in general are very fascinating. They seem to have developed some of the most interesting survival techniques. I know for example many g.i. parasites such as roundworms can stay in their egg form for years and be protected by a special shell even in harsh environmental conditions. They can then emerge when they are ingested and complete their lifecycle. I wonder what exactly the worms affect in their host that causes them to seek water? Is it so much that the crickets committed suicide or that they were drawn towards the water and then could not get out? I wonder if these hairworms are something I should be concerned about? Where in the world can you find these worms?

Posted by: Lindsay Goodyear

At 8:51 PM, Anonymous Anonymous said...

This is very different and interesting! How can such a parasite control a host in such ways? Also, why did not affected crickets commit suicide? Why don't other animals, like you mentioned beetles, act in these ways? Good post!

-Alyson Paige

At 9:38 PM, Anonymous Anonymous said...

Are you trying to say that the hairworm has changed its technique for survival by increasingly inducing suicidal behavior upon their host instead of erratic behavior?

Can the hairworms choose between erratic and suicidal behavior based on the situation? Does this have to do with their behavior affected by their genes for a certain behavior?


At 10:19 PM, Anonymous Anonymous said...

very interesting. i wonder how it is able to make it find a water source. i wonder if it makes it unable to quench its thirst or something similar. however to the parasite it is perfect for it to propagate.

Matthew Sousa

At 10:46 PM, Blogger PWH said...

it seems strange that the cricket would have to kill themselves, it would seem possible for them to just jump into the water and for the parasites to mature in the water without having their hosts die. I would think that the parasites would move to different environments more efficiently then if they just stayed in the same body of water.

-Joe Alonzo

At 11:12 PM, Anonymous Anonymous said...

I've watched a lot of sci fi films and turning another organism into your own robot is in a bunch of them. What kind of aquatic orginisms do they generally infest? Do they only infect animals or can they also attach themselves to plant matter to wait to be eaten? How do they reproduce, asexually or sexually?

Ada Marie Flores

At 11:47 PM, Blogger PWH said...

Wow. What do you think makes the cricket want to find a water source? Is the desire to find water directed caused by the parasite? If so, what may be the mechanism? I think it's really interesting that the parasite can completely use the host in order for it to survive. I wonder how these parasites might affect humans? Anything we need to be worried about? Thanks for the post.

-Amanda Sceusa

At 11:55 PM, Anonymous Jen Kodela said...

When the larvae is in the fly, is it detrimental at all? Or does it only hurt the arthropods that eat the fly?

At 1:24 AM, Blogger PWH said...

does the article say how the worm affects the cricket and force it to commit suicide? these worms should be pretty small, do you know their rough size?
interesting article!

Hessom Minaei

At 1:58 PM, Blogger PWH said...

This is incredibly odd and different. I did not think a tiny parasite could have that much power on their host. Do you know how a parasite makes a cricket kill itself? How it works?

So Jin Lee

At 3:18 PM, Anonymous Anonymous said...

Thats pretty cool- there's one thing I find missing though.
What causes the parasite to become active and induce that reaction? Is it a certain change in the carriers' environment? is it automatic once they mature?

Noam Pelleg

At 11:43 PM, Blogger PWH said...


The hairworm will not try to manipulate any large host. If the worm is ingested by a large mammal it would try to find a way out and seek for a smaller host. The worm would most likely die. Therefore, humans are safe from being manipulated by these parasitic worms. Small insects are perfect niches for the hairworm.

The crickets and hairworms researched in this specific study were collected in native forest in southern France. However, these worms are found worldwide in many varies species. Not all species completely manipulate their host but they all change the behavior in their host.

Unfortunately, researchers have still not discovered how this parasite manipulates the brain activity in its host. (It would be a great research project)

Carlos A. Varela (Week 6)

At 11:48 PM, Blogger PWH said...

There is a cool video on youtube named "worm suicide" of the cricket jumping into water and the worm coming out of the cricket once in the water.


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