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Products of Pollution?

Retired Article • Written by Jason Bellows

X-ray of a deformed frog
X-ray of a deformed frog

For decades we’ve heard of the plight of our environment. After years of chemicals toxins making their way to rivers, and seeping into groundwater there is no doubt some unusual and bad things are arising from human interference in nature, but there is some dispute on just how much human affairs have impacted the eons-old ecology.

In a quest to show the ill effects of humanity’s ill-advised pollution, some environmentalists began trying to show specific problems that these uninvited chemicals were causing. In the late 1970’s, one such example began to gain notoriety: deformed frogs. Because of their thin, permeable skin and the amount of time they spend in still water, the frog is a creature highly influenced by small traces of toxic items in their ecosystem. Pictures of frogs with excessive legs, cysts, or other unusual growths have been used to show the masses what our pollution is costing other occupants of Earth. But are these bizarre deformities the result of the intervention of people, or old Mother Nature pulling one of her sneaky tricks making the frog into easy prey?

Ribeiroia is a parasitic flatworm that generally infects birds and snakes in their adulthood, but have a rather complex life cycle that took several years to untangle because of their propensity to pass through several hosts. Most of the time parasites in the Trematoda family lay eggs within their host, and those eggs are expelled in the host’s feces. When the eggs come in contact with fresh water they hatch into free swimming larva which infect a snail. The snail develops a cyst where the larva has infected it, and after an incubation period the larva busts out, now matured into a larger form with a tadpole-like tail to propel it. Most of the time the larva will seek out a mollusk or arthopod to infect, where it will wait for this host to be eaten by the heron or garter snake that it wants as a permanent home.

The ingenious and insidious part is when the larva emerges from its snail-host and cannot find a mollusk that will deliver it to the actual host to which it aspires. If the tadpole-like larva has the opportunity, it will infect a real tadpole. The parasite will burrow into the larger, amphibious tadpole—usually in the buds from which a frog’s legs will eventually form.

It is in Ribeiroia’s best interest to make sure that the frog that it infects will be caught and eaten by the much coveted heron or garter snake, thus it encysts the limb buds. The parasite causes the leg not to grow, or grow deformed. However if the parasite misses its target the leg will grow normally, and the frog might be too elusive to be caught, thus the parasite falls on a backup plan. The parasite causes extra legs to grow that will inevitably make the frog easier pickings for the host-species to which the parasite truly aspires.

And thus the parasite finally reaches the climax of its bizarre and convoluted life-cycle. It turns out the extra legs often spotted on a small amphibian is just another quirk of nature at work, and not the result of humanity's polluting influence.

Article suggested by Millgate.

Article written by Jason Bellows, published on 26 June 2006. Jason is a contributing editor for DamnInteresting.com.

Article design by Alan Bellows. Edited by Alan Bellows.
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51 Comments
xircso
Posted 26 June 2006 at 05:36 pm

Great Jason, now what am I going to rant about? Next you'll say that Blinky was just infected by a parasite that wanted him to be eaten by Mr. Burns. ^0^

Excellent article.


Gadz
Posted 26 June 2006 at 05:56 pm

Excellent writing. One of the best DA articles I've ever read.


tazman
Posted 26 June 2006 at 05:58 pm

Hey

I've been reading articles on this site for about a month now and think i have finally read them all
I want to thank you for a great job you guys have done its been keeping me glued to my computer for ages and not on computer games :)
Well now ive decided to create an account after finally catching up so i can comment.
I once saw one of these deformed things.. A salamander with 5 legs but it was only the bones while i was fishing with my friend so i dont know if it is the same way as with the frogs' parasites or not but pretty damn interesting :)


ke4roh
Posted 26 June 2006 at 06:20 pm

Interesting, but I wouldn't jump to the conclusion in the last sentence. What if pollution is helping Ribeiroia grow, interfering with it finding its mark, making frogs more succeptable to infection, or killing off the intended Ribeiroia hosts? The "Pollution or Parasites" article seems to raise that sort of question.


cornerpocket
Posted 26 June 2006 at 08:15 pm

Seems to me the pond just got muddier. Of course, we don't have to throw out the insinuation with the frog pond...there is still the weird weather, the cancers among humans that are more prevalent in the last 10 years than the previous 30 (discounting the era before detection wasn't as scientific as it has been in the last few decades). All the concerns about the environment won't handle a case-by-case disassembly, but the preponderance surely warns us to take it easy and quit making such major decisions on hunches and quasi-Biblical embracing of end-of-the-world scenarios. Somehow I am prone to distrust Capitalism and the blind belief that if it is good for Exxon (or General Motors) then it is good for America. I'm not even sure America is good for America.


SparkyTWP
Posted 26 June 2006 at 08:18 pm

I'm always hesitant to blame these deformations on humans. This is because there is usually no systematic accounting until someone thinks they see a problem.

Basically, if you just count up all the deformed frogs you see now, there's no way to compare it to earlier populations, therefore you can't say that the deformed population even changed at all, much less even begin to speculate what caused them to change.


just_dave
Posted 26 June 2006 at 08:35 pm

Oh, come on now; these frogs are just evolving into the next iteration of the species. Just ask your friendly neighborhood evolutionist. ;o)

Actually, I find Ribeiroia to be particularly fascinating. For it to do what it does so that it can be eaten by the critter whose digestive system is most hospitable... I think Darwin would be scratching his head over how that came to be.

Great article!


Iscariot
Posted 26 June 2006 at 10:04 pm

One way or another, it's disgusting. We must exterminate this problem...
Kidding?


ForestGrump
Posted 26 June 2006 at 11:29 pm

Wow, I looked up DI tonight and well...let's say I've been obsessing over frogs for the past hour.

Some noteable things:
1. I recenetly captured 3 tadpoles (of unknown species) from a pond, raised them in my bathroom till they became mature frogs. Very interesting to watch them get their hind legs and become frogs. I set them free yesterday (Sunday) morning back into the pond I got them from. I figured if they're native, they can live out the rest of their life. If they're an invasive species...well...um...there were alot more of them in the pond. And judging from the stuff I'm reading...they were probably pacific tree frogs (i'm in the right area, and they look like it).

2. Noteable stuff I've found.
research notes

Research paper (look at page 3 for pictures)

and deformed frog pictures


sleepwalker
Posted 27 June 2006 at 12:02 am

They eat frogs in China all of the time.
Will there be a chance that Ribeiroia can pass to humans? (chinese in particular).

I just saw a baby with 3 arms in the news.


GMan
Posted 27 June 2006 at 12:37 am

I can already see the next spinoff: Teenage Mutant Ninja Frogs.


Mark
Posted 27 June 2006 at 02:12 am

Parasites are pretty strange, they do all sorts of clever things, I wrote about one which takes over ants' brains on my blog a while back.

Also, did you know that if you put tadpoles in water where there is no iodine, they will just grow into giant tadpoles, and won't change into frogs? It's because they need the iodine to make the hormone that sets off metamorphosis, without it they just get bigger.


mantasj
Posted 27 June 2006 at 02:23 am

I saw this covered in "THE MOST EXTREME" - animal planet channel.

Why is the title so misleading? Why bring up pollution if the parasite is pointed out?
oh I get it... Their NOT products of pollution, instead prey to a microscopic parasite.
I guess I should have read the entire article before jumping to comment on it.


JJ
Posted 27 June 2006 at 03:59 am

Now THAT is Damn Interesing! And the title is a question, not a statement, its a perfectly fitting title. Great work Mr. Bellows


another viewpoint
Posted 27 June 2006 at 05:02 am

So, we see after all this time that there really is an explanation (instead of accusation and insuation) for deformed frogs. Now, can anybody tell me...if DDT was so deadly...WHERE ARE ALL THE BODIES?


AGG
Posted 27 June 2006 at 08:56 am

Awesome! I, too, saw this on Animal Planet. God's creatures are so weird sometimes! Mark, two very interesting tidbits of information, thank you!


LL
Posted 27 June 2006 at 09:48 am

It never ceases to amaze me how living things evolve.

With DDT the bodies were in the thin shelled eggs of many raptors. DDT probably is safe for use in some manner, but the wholesale spraying of crops isn't it.


Ironclaw
Posted 27 June 2006 at 10:20 am

ForestGrump said: "Wow, I looked up DI tonight and well…let's say I've been obsessing over frogs for the past hour.
...

1. I recenetly captured 3 tadpoles (of unknown species) from a pond, raised them in my bathroom till they became mature frogs. "

Wow, frogs that grow that fast must be genertically altered..


SparkyTWP
Posted 27 June 2006 at 10:27 am

DDT kills more people from its absense than its production.

You are indeed correct about widespread spraying, it's not as effective and can build up in the food chain. Localized small sprays have miniscule effect on the surrounding environment. This assumes the local mosquitos have not developed a resistance to it, such as in India.


ForestGrump
Posted 27 June 2006 at 11:15 am

Ironclaw,

It was over the coruse of 3 weeks...


noway
Posted 27 June 2006 at 11:16 am

cornerpocket said: "Seems to me the pond just got muddier. Of course, we don't have to throw out the insinuation with the frog pond…there is still the weird weather, the cancers among humans that are more prevalent in the last 10 years than the previous 30 (discounting the era before detection wasn't as scientific as it has been in the last few decades). All the concerns about the environment won't handle a case-by-case disassembly, but the preponderance surely warns us to take it easy and quit making such major decisions on hunches and quasi-Biblical embracing of end-of-the-world scenarios. Somehow I am prone to distrust Capitalism and the blind belief that if it is good for Exxon (or General Motors) then it is good for America. I'm not even sure America is good for America."

You're an idiot.


Joshua
Posted 27 June 2006 at 11:19 am

GMan said: "I can already see the next spinoff: Teenage Mutant Ninja Frogs."

I was thinking more along the lines of X-Frogs myself. (Although with deformed and/or missing legs, it would be kind of silly to call their movie The Last Stand.)


Dark Lord Ph8
Posted 27 June 2006 at 11:35 am

cornerpocket said: "Seems to me the pond just got muddier. Of course, we don't have to throw out the insinuation with the frog pond…there is still the weird weather, the cancers among humans that are more prevalent in the last 10 years than the previous 30 (discounting the era before detection wasn't as scientific as it has been in the last few decades). All the concerns about the environment won't handle a case-by-case disassembly, but the preponderance surely warns us to take it easy and quit making such major decisions on hunches and quasi-Biblical embracing of end-of-the-world scenarios. Somehow I am prone to distrust Capitalism and the blind belief that if it is good for Exxon (or General Motors) then it is good for America. I'm not even sure America is good for America."

I can tell you what IS good for America (both North and South). PIE, lots and lots of pie!


LL
Posted 27 June 2006 at 01:34 pm

noway said: "You're an idiot."

You sure know how to make a well thought out argument.


Misfit7707
Posted 27 June 2006 at 02:48 pm

This article is definitely a plus for humanity. We do pollute, and of course pollution is bad. However, I don't think that it's as bad as many people think it is. As for the people who care about nature and the environment, bravo (I enjoy camping, myself), but try not to be so paranoid about it. If someone only goes into an observation to prove something, they'll usually stop once they think they've proven it. Remember the steps of the Scientific Method:

1. Observation and description of a phenomenon or group of phenomena.

2. Formulation of a hypothesis to explain the phenomena. In physics, the hypothesis often takes the form of a causal mechanism or a mathematical relation.

3. Use of the hypothesis to predict the existence of other phenomena, or to predict quantitatively the results of new observations.

4. Performance of experimental tests of the predictions by several independent experimenters and properly formed experiments.

"The scientific method attempts to minimize the influence of the scientist's bias on the outcome of an experiment. That is, when testing an hypothesis or a theory, the scientist may have a preference for one outcome or another, and it is important that this preference not bias the results of their interpretation," ( http://teachers.pas.rochester.edu/phy_labs/AppendixE/AppendixE.html )

No matter how good their intentions were, the environmentalists in this case seem to have either:

Taken it out of order: created a hypothesis first (humanity is ruining everything via pollution), made an observation later (oh these frogs don't look so hot), and reached a conclusion too soon (pollution must be the culprit!)
OR
Simply not kept an open mind: i.e. didn't bother looking for other potential causes or factors, they had the 'results' they wanted.

Fortunately someone remembered to take it in the proper order and perform their own experiments, or at least look further into the situation and keep an open mind about what's causing this. For all you environmentalists out there, I'm all for nature, really I am, but try not to jump to conclusions too soon. Too many people are getting excited about pointing fingers, these days. Fascinating article by the way, Mr. Bellows!

(By the way, the preview for this comment looks like I'm not allowed to make more than one new line for typing. I'm relatively new to typing comments here, so if everything in this comment looks packed together, my apologies. If not, and everything looks normal... uhh.... yeah my apologies for writing this concern).


big-jay
Posted 27 June 2006 at 04:29 pm

Am I alone in saying that this article has really freaked me out?


to-be-betrayed
Posted 27 June 2006 at 04:33 pm

remind me not to eat frogs legs....

i must admit, that is pretty amazing that a species has evolved to do that [and please don't flood replies of "i dont believe in evolution....pretty please?]. i wonder just how many species the worm can infect? and it also brings forth the question, are there any other species we dont know about that does something similar?

side note; though i'm probably way off and this probably could never happen [though interesting all the same] i wonder if it'll get to a stage of evolution/symbiosis like with the evolution of eukaryotic cells using other [prokaryotic i think] cells to become organelles? could these worms become beneficial to a species until they are actually taken into the species itself?


EVERYTHINGZEN
Posted 27 June 2006 at 04:54 pm

I will NEVER eat frog legs after reading this...and yes I am among the very freaked out right now.


ballaerina
Posted 27 June 2006 at 07:00 pm

I wanna know what happens when a Ribeiroia infects a human. Anything?

I'm helminthophobic; meaning, I'm afraid of being infested with worms. This article scared the kudknuckles out of me.


Bolens
Posted 27 June 2006 at 08:40 pm

Kudos, Jason.


sulkykid
Posted 27 June 2006 at 08:57 pm

LL said: "You sure know how to make a well thought out argument."

I am adding no arguments, but I wholeheartedly agree with noway.


1c3d0g
Posted 28 June 2006 at 05:33 am

noway said: "You're an idiot."

Why? He's telling the truth, and it hurts, doesn't it? :-/


noway
Posted 28 June 2006 at 08:30 am

LL said: "You sure know how to make a well thought out argument."

No sense in arguing with idiots.

1c3d0g said: "Why? He's telling the truth, and it hurts, doesn't it? :-/"

No.


c. m. edge
Posted 28 June 2006 at 12:07 pm

The lesson here is to get your facts straight.

This reminds me of an occurrence around the student union where I'm currently going to school. There were people protesting abortion, showing pictures of supposedly aborted fetuses and such. Being myself opposed to abortion, I didn't really pay much attention at first. But upon actually bothering to view one of the signs, it had a fetus at two weeks old that looked like a strawberry preserve covered infant about twice the size of a quarter. Despite the fact that it was only supposed to be two weeks into development, it looked fully developed--only small. It had ten fingers and ten toes, a nose, eyes, ears, etc. Considering the fetus shouldn't develop fingers and toes at least for another many weeks and when it is considerably bigger than a a quarter, it was obvious to anyone at least slightly knowledgeable about biology that the sign was a fake.
I was undoubtedly irritated. No matter how good your cause, you need to have a good argument or else you'll more than likely prevent progress and give opposing sides oportunities to declare your entire claim inaccurate.
The same is true with these frogs. I'm all for protecting the environment, but people need to not present incorrect assumptions as facts. Furthermore, in both cases, I'm opposed to using shock value to further a cause anyway. It doesn't demonstrate any understanding in the issue (especially if your information is wrong).
So, argue for good causes logically, and check your facts, especially if you're going to be protesting around a university campus.


c. m. edge
Posted 28 June 2006 at 12:09 pm

noway said: "No sense in arguing with idiots."

No sense in idiots arguing, either.


sulkykid
Posted 28 June 2006 at 12:37 pm

c.m.edge, you are my hero!


whaaat
Posted 28 June 2006 at 12:53 pm

bjbu


Jeremy
Posted 28 June 2006 at 03:30 pm

Frogs with extra legs: deformed victims of genetic mutation...or SUPERFROGS?!


EVERYTHINGZEN
Posted 28 June 2006 at 03:54 pm

Superfreak, superfreak, they're superfreaky....

Why waste your time typing if you guys aren't going to make valid points to your arguments?

Take some time to think over the other's arguments before refuting with spewed crap...then eat some pie and be friends. Frog leg pie, mmmmmmm....


Sparrow
Posted 28 June 2006 at 05:19 pm

The frog never fails to amaze. There are types which can be frozen solid, and revived. Others protect their young by letting the tadpoles develop whilst literally in their parent's back. Also, they're discovering many frogs have antibiotic properties in their "fragile" skin, one of the ways they can live in eternal bacteria-laden wetness. Try hiking in wet boots for a few days and you'll really appreciate that feat.

Remember, just because this article dispels one "frog-mutation due to pollution" theory, that does not mean they are not highly susceptible.

I recall a story from the American Midwest, about a chemical (commonly used on crops – a pesticide I think?) proven harmless in the labs, was turning male frogs into females. Apparently in tiny doses, the chemical enters the body undetected, where it then mimics female hormones. Males produce eggs. However at higher doses, the chemical was detected as the alien it was, and rejected. This is why it passed safety tests.

Makes you wonder about the fertility of the local men in that area.


Emmy
Posted 28 June 2006 at 07:12 pm

I learned about frogs today, Grandpa!!!


Melon Head
Posted 28 June 2006 at 08:10 pm

EVERYTHINGZEN said: "I will NEVER eat frog legs after reading this…and yes I am among the very freaked out right now."

On the contrary, frog breeders can get a higher meat yield. Now it's 3or 4 legs per frog...KAAAAAAAAACHING!!!!!


ballaerina
Posted 28 June 2006 at 08:24 pm

Melon Head said: "On the contrary, frog breeders can get a higher meat yield. Now it's 3or 4 legs per frog…KAAAAAAAAACHING!!!!!"

Ew.


paalexan
Posted 29 June 2006 at 08:52 pm

The basic argument of this article, that leg deformities in frogs are caused by a parasite and therefore not caused by pollution, is unsound on the face of it--it presumes a single cause, but we know perfectly well that this can't be assumed. The more we know about interspecies interactions, ecological and developmental complexity, etc., the more we know that single causes for observed phenomena are extraordinarily rare, perhaps nonexistent.

A related case that illustrates the problems in this reasoning is that of schistosomiasis along the Nile; incidence of the disease in humans increased drastically when the Aswan low dam was built, because this caused severe habitat alteration (no floods!) that led to rapid population growth in the parasite's intermediates hosts, snails. Here we know full well that the activities of a parasite were determined in part by anthropogenic change.

SparkyTWP wrote:
"Basically, if you just count up all the deformed frogs you see now, there's no way to compare it to earlier populations, therefore you can't say that the deformed population even changed at all, much less even begin to speculate what caused them to change."

Absolute numbers offer a poor comparator, sure. We also know occurrence rates, though, and those we can compare across localities, across times, etc., and see if parasite incidence is correlated with pesticide use... as a matter of fact, that's exactly what various researchers have already done! And, yup, there's a positive correlation between frog deformity rates & pesticide concentration. If Ribeiroia is an intermediate link in that correlation... well, there's still the correlation, and we still have to explain it!

Patrick Alexander


elgatitoandaluz
Posted 30 June 2006 at 03:14 am

This is just an extract of the whole world of parasites,
recomended reading:
Parasite Rex : Inside the Bizarre World of Nature's Most Dangerous Creatures
by Carl Zimmer

PS: not recommended reading at lunch time :D i sooooooo enjoyed this book!


HGirl
Posted 30 June 2006 at 06:09 am

Poor little frogs... Imagine that it was human that had to live into that water.


Tink
Posted 07 October 2006 at 11:49 pm

ballaerina said: "Ew."

I second that,eeewwww,eeeewww! Did you see the pictures? EeeeeeWWWWWWWeeee!!!! LOL


Tink
Posted 07 October 2006 at 11:51 pm

HGirl said: "Poor little frogs… Imagine that it was human that had to live into that water."

Naw, we don't have to live in it, we just drink it. :)
Oh and fish pee in it too.


Mirage_GSM
Posted 14 July 2008 at 12:21 am

To everyone wondering if those things could infect humans:
I seriously doubt this parasite would survive boiling or whatever way frogs legs are cooked by whoever is inclined to eat them, so I think it should be pretty safe.
That's not to say it's not gross...


atonyt
Posted 23 January 2009 at 12:02 pm

I have always been terrified of frogs, as far back as I can remember. If I see one while walking up to it, I am OK, and just make sure I keep my distance. However, if I am walking and one moves right beside, I tend to scream or throw my wife in front of me: nothing makes you feel more like a man than screaming and running behind your wife.

I hate frogs. Good creepy article.


DumbGuy
Posted 07 May 2009 at 06:19 am

This article was not-so-damn-interesting to me. Frogs are cool, they hop and chow insects, dead ones become insect food...life goes on.

I found more enjoyment reading people's reactions to the article. i'm just a bit disgusted by the tit-for-tat squabbling. what's with the idiot talk, and while we're taking about the effects of pollution on the planet, how does negativity in the news pollute human behavior toward each other? Maybe if they had a mandatory 'GOOD NEWS" day every week where everything was positive and uplifting, people wouldn't have the tendency to fly at each other over something they disagree with.

Play nice people :-)


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