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The Atlantic tomcod found in New York's Hudson River  (Source: Mark Mattson of Normandeau Associates, Inc.)
Having a variant AHR2 receptor gene has made the tomcod resistant to PCBs in the Hudson River, but it may have harmful effects

Scientists from the Woods Hole Oceanographic Institution (WHOI), the National Oceanic and Atmospheric Administration and New York University have discovered that a certain fish found in New York's Hudson River has lived and flourished through 50 years of extreme pollution. 

Isaac Wirgin, study leader from New York University's Department of Environmental Medicine, along with Mark E. Hahn, senior scientist at WHOI, and Diana Franks, WHOI biologist, have found that the Atlantic tomcod, a common fish found in the Hudson River, has not only survived mass amounts of pollution in this river for a long period of time, but has also thrived in this particular environment. 

It's common to see insects develop resistance to insecticides, or bacteria to antibiotics, but according to Wirgin, this is the first instance where a member of the vertebrate population has developed a resistance to a hostile environment.

The Hudson River has become polluted partially due to two General Electric facilities releasing 1.3 million pounds of polychlorinated biphenyls (PCBs) over a 30-year period. Now, 50 years later, the Atlantic tomcod is alive and better than ever, and researchers have pinned a single genetic receptor as the reason for the vertebrate's resistance. 

Researchers found that a receptor gene called AHR2, which mediates toxicity and controls sensitivity to PCBs, is what made the Atlantic tomcods evolutionary change possible in order to become resistant to PCBs. More specifically, the Hudson River tomcod's AHR2 proteins seem to be missing two of the 1,104 amino acids that are traditionally found in this protein, which weakens the bond between the receptor and the PCBs. Researchers believe this weak bond is what prevents the PCBs from affecting the tomcod in this area. 

With PCB resistance, the tomcod is capable of living in this area and reproducing in the winter. But when summer comes around, the tomcod becomes a prime food source for the striped bass and other fish. This is a problem because despite the tomcod's PCB resistance, the fish still absorb these contaminants and can pass them on to those that eat them. Through this transfer, humans who fish and eat what they catch from the Hudson River can consume the contaminants as well. 

This isn't the only negative aspect of the tomcod's resistance. According to researchers, this genetic change can make these fish more sensitive to other harmful chemicals like polycyclic aromatic hydrocarbons (PAHs) because the tomcod "cannot degrade them properly."

The AHR2 receptor is a normal part of development for the tomcod, but this type of genetic change that has made the tomcod resistant to PCBs in the Hudson River could have long-term harmful effects on the health of this fish. 

"Hudson River tomcod have experienced rapid evolutionary change in the 50 to 100 years since the release of these contaminants," said Wirgin. "Any evolutionary change at this pace is not a good thing."

Cleaning up the river wouldn't be a good thing for the fish either, because the fish would need to adapt to the cleaner environment once again, experiencing more fast-paced evolutionary changes. Researchers are currently unsure as to what these consequences are as far as long-term health goes for the fish during the evolutionary changes. 

Recently, an EPA-mandated cleanup of the Hudson River PCBs has begun, which may be troublesome for the tomcod who have developed a variant AHR2 gene specifically for the toxic substance. 

This study was published in Science.

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By quiksilvr on 2/18/2011 4:32:18 PM , Rating: 3
Oh, the delicious irony.

By GuinnessKMF on 2/18/2011 5:56:34 PM , Rating: 4
What's the big deal, Tomcod exposed to lots of PCB, becomes resistant but filled with PCB, now the Bass that eat it are exposed to lots of PCB ... they'll become resistant to it and be filled with it, then we humans eat the Bass, exposed to lots of PCB, and then ultimately WE become resistant to PCB. It's Win-Win-Win.

I don't see anything that could go wrong.

By vol7ron on 2/18/2011 5:59:18 PM , Rating: 5
because the fish would need to adapt to the cleaner environment once again

adapting to a cleaner environment? what? you mean... they'll live.

The only adaptation they'll need is called "life." It's an ecosystem where they have to eat and not be eaten... i think they'll manage.

By GuinnessKMF on 2/18/2011 9:09:50 PM , Rating: 5
It's like when someone cleans up your room for you, and now you have no idea where your USB memory stick is because they didn't leave it in that pile behind your keyboard.

By RedemptionAD on 2/19/2011 5:49:33 PM , Rating: 2
They are living fine now. Seems they made a genetic trade to stop what was killing them before to a weakness to something that wasn't killing them yet. Not sure what the human bodies resistance to said chemical is but we adapt well and its filtered through another fish if we don't eat the resistant fish directly.
"Life will find a way."- Jurassic Park.

By interstitial on 2/21/2011 8:47:21 AM , Rating: 2
Unfortunately it doesn't work that way. The effect of being eaten by another fish actually concentrates the pollutant in most cases. That's why mercury concentrations are very low in the ocean but many species of tuna (a high level predator) contain worryingly high levels of it.

By JediJeb on 2/23/2011 6:35:02 PM , Rating: 2
What is rarely ever said though is that most of the toxic chemicals like PCBs collect in the liver and gonadal tissues which humans don't normally eat, unless the processors are just grinding the whole fish up and selling it that way. We had samples in the lab that were supposedly contaminated with PCBs but the meat of the fish had non detectable or barely detectable but not quantifiable levels while the livers did have high levels. If you ground the whole fish up and made the sample that way it was considered high, if you core sampled the meat it was low. It all matters how you look at the sample what you will find.

By YashBudini on 2/18/2011 10:55:53 PM , Rating: 5
It's Win-Win-Win.

Well then you eat them.

By GuinnessKMF on 2/19/2011 10:45:34 AM , Rating: 2
Mmmm, delicious Win.

By Silver2k7 on 2/19/2011 2:49:58 PM , Rating: 2
"GuinnessKMF" wow exactly what I thought :D

By boobo on 2/20/2011 1:16:08 PM , Rating: 2
What could go wrong is that, if the other fish and us hmans aren't missing those 2 AHR2 proteins, we will not be abale to adapt.

If that happens, the other fish and the New York humans will get poisoned and disappear. Then, the negative consequence is that there will be no one left alive near the Hudson to produce contaminants for the Tomcod!

By Kiffberet on 2/21/2011 8:56:05 AM , Rating: 2
I'm assuming there's a bit of sarcasm in there, but with these international posts, it's difficult to tell...

Anyway, the only way the fish 'become resistant' to PCB is because all the fish that weren't resistant died. So the Bass that are resistant will also die, but those that survive will pass on their genes and the next generation will be more resistant. This goes on until humans eat the bass and start getting ill and dying. A few generations down the line and after soaring rates of cancer and other nasty diseases humans will also be resistant.

Not really a win-win-win scenario.

A real WIN scenario would be to hunt down the corporation polluting the river and stopping them!

Granted, they'll probably go set up in but at least the river will be cleaner...

By IGx89 on 2/19/2011 12:30:19 PM , Rating: 2
Sounds more like a de-evolutionary change than anything. It's like aliens all of a sudden attacked us with mind-melting sound waves (ah, Fringe) and the deaf were all who survived :/

RE: Devolution?
By Gzus666 on 2/19/2011 7:54:54 PM , Rating: 2
There is no such thing as "de-evolution", stop making things up. People like you make it hard for science to progress as all the scientists have to waste their time explaining it to dullards like yourself so they can continue to get funding.

RE: Devolution?
By Kurz on 2/20/2011 9:05:13 AM , Rating: 2
Information is always gained when it comes to genetics.

Horrible diet!
By Mumrik on 2/18/2011 7:53:31 PM , Rating: 5
Those poor fish really shouldn't be eating Printed Circuit Boards.

Change or No Change over time?
By JediJeb on 2/21/2011 6:53:15 PM , Rating: 2
"Hudson River tomcod have experienced rapid evolutionary change in the 50 to 100 years since the release of these contaminants," said Wirgin. "Any evolutionary change at this pace is not a good thing."

Is there evidence that this fish had the missing proteins before the pollution was introduced to the environment, or have they been missing them all along? If this fish has been missing the proteins since they came into existence then there was no evolutionary process forced by the pollution. Only if you have proof that the pollution killed off the species before it made a change can you say for sure that there was some form of evolution taking place. I'm not saying evolution doesn't take place, but to assume it is the reason without data to prove this species was not different from other species before the pollution was introduced is flawed science.

Without genetic studies of these fish from 50-100 years ago to compare the current genetics to, how can the conclusion be made?

By Strunf on 2/22/2011 8:14:40 AM , Rating: 2
"this is the first instance where a member of the vertebrate population has developed a resistance to a hostile environment."
And I thought evolution was all about "developing" ways to insure your survival in hostile environments.

"Any evolutionary change at this pace is not a good thing."
I don't see the problem, it's not like in the past earth stood still waiting for us to evolve, evolution again is all about getting the edge and the faster the better. If mammals had take their time after the dinosaurs maybe we would be ruled by birds or insects today.

Thanks GE!
By texbrazos on 2/22/2011 1:04:12 PM , Rating: 2
Thanks GE! They ought to be responsible for cleaning all the PCB's from the water no matter how long it takes.

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