What the heck is Epigenetics - complex science

silver creek

Well-known member
Messages
7,204
Reaction score
591
Location
Rothschld, Wisconsin
Most of you have never heard of epigenetics and I don't blame you. It is the type of stuff that MDs and science nerds find interesting. For me it is seriously interesting. It first came up in a discussion about trout UV vision I had with overmywaders, and I thank him for that.

It came up again on another forum when an article about brook trout invasives was introduced.

The original poster thought this was "new" news but how trout change behavior and even body shape has been known for a while. The immediate differences between hatchery trout and native trout can also be traced to epigenetics. So if you are interested genetics including human biology controlled by genetics

Have a read below of the original post and my reply


Interesting article and something to think about. Have a read...

Pervasive Invasive
I have several comments. First, it has been known for some time that animals, including humans modify their behavior when environmental or situational changes occur. This is the result of epigenetics.

It was once thought that the underlying genetic code had to change for morphologic changes such as body shape to occur. That is no longer believed to be true. The underlying genetic code remains the same but how the code is interpreted and manifested through proteins and other transmitters changes to adapt the organism to its environment. So it surprises me not that invasives can change the behavior and even the body shape of the native fish.

Furthermore, these epigenetic traits are inheritable so succeeding generations of animals will show the same behavioral and morphological changes. There is evidence in mice that if a parent is under stress and exhibits stress related behaviors, that the offspring will inherit this epigenetic behavior trait.

Fearful memories haunt mouse descendants

Epigenetic modification is not "new" news. I have a powerpoint presentation on how trout become selective feeders in which I question whether trout who are hatched in a spring creek super selective environment can be selective feeders epigentically before selectivity as a behavior is induced through the environment.

The changes that occur in hatchery raised fish are the result of epigenetics, and 723 changes occured in a single generation! There "were 723 genes differentially expressed between the two groups of offspring."

A single generation of domestication heritably alters the expression of hundreds of genes

Here is a powerpoint on epigenics: https://tinyurl.com/gqntnwm - What is epigenetics and why could it be relevant to recovery and management of protected resources

Here are some references to epigenetics in fish.

Migration-related phenotypic divergence is associated with epigenetic modifications in rainbow trout - Baerwald - 2015 - Molecular Ecology - Wiley Online Library - Migration-related phenotypic divergence is associated with epigenetic modifications in rainbow trout.

https://tinyurl.com/jka52kv - Epigenetics controls social dominance in African fish

https://tinyurl.com/hjzuc65 - The origins of ecotypic variation of rainbow trout: a test of environmental vs. genetically based differences in morphology
 
Last edited:

knotjoe

Well-known member
Messages
379
Reaction score
8
Location
North Central Indiana
Could this be why mermaids are extinct?
They're not extinct, they turned into Rainbow Trout. Something you would know had you read the links and thought deeper into the matter.:p

Seriously though, that is some pretty interesting stuff and almost borders on disbelief and sic-fi. I still freak on the cannibal morph thing Tiger Salamanders do in response to what is said to be population density, possibly drought or stress.

Just doesn't surprise me to see this stuff in fish to some degree. I'd like to hear more about this powerpoint on selective feeding. Maybe a bit on the genetic history of the Rainbow in general and if this might have something to do with it's prominence in studies. Might be a rather odd subject fish in some ways.
 

corn fed fins

Well-known member
Messages
1,376
Reaction score
101
Location
Montrose, CO.
Good reads! Any and all environmental conditions can "change" a species characteristics . This is the basis of evolution. So does a change in behavior or morphology make a different species? No; not at this point in zoology. As selective as behavioral/ morphological traits are they may not be encoded within DNA...but wait.

Still there must be some form of "heritable" mechanism at work. Something that attaches to the DNA, passed through generations, that alters how genes are expressed so the behavior/morphological trait isn't lost with offspring and must be reacquired...OR...there must be receptors that are easily triggered by such environmental stimuli (like humans being predisposed to see and fear snakes). Otherwise, this would not bode well for the species.

This is some great science! And if you think that tailwater fish behave differently.....you're right.:D
 

roadkill1948

Well-known member
Messages
179
Reaction score
1
Location
Southern Indiana
Clownfish, wrasses, moray eels, gobies and other fish species are known to change sex, including reproductive functions. A school of clownfish is always built into a hierarchy with a female fish at the top. When she dies, the most dominant male changes sex and takes her place. (I haven't verified the fact of this)
 

corn fed fins

Well-known member
Messages
1,376
Reaction score
101
Location
Montrose, CO.
Clownfish, wrasses, moray eels, gobies and other fish species are known to change sex, including reproductive functions. A school of clownfish is always built into a hierarchy with a female fish at the top. When she dies, the most dominant male changes sex and takes her place. (I haven't verified the fact of this)
Don't tell Nemo!
I could have so much fun with this but I'd end up being banned. Lol

Sent from my VS986 using Tapatalk
 

throssing

Well-known member
Messages
325
Reaction score
1
Location
Lyons, CO
Most of you have never heard of epigenetics and I don't blame you. It is the type of stuff that MDs and science nerds find interesting. For me it is seriously interesting. It first came up in a discussion about trout UV vision I had with overmywaders, and I thank him for that.

I have several comments. First, it has been known for some time that animals, including humans modify their behavior when environmental or situational changes occur. This is the result of epigenetics.

It was once thought that the underlying genetic code had to change for morphologic changes such as body shape to occur. That is no longer believed to be true. The underlying genetic code remains the same but how the code is interpreted and manifested through proteins and other transmitters changes to adapt the organism to its environment. So it surprises me not that invasives can change the behavior and even the body shape of the native fish.

Furthermore, these epigenetic traits are inheritable so succeeding generations of animals will show the same behavioral and morphological changes. There is evidence in mice that if a parent is under stress and exhibits stress related behaviors, that the offspring will inherit this epigenetic behavior trait.





I find this interesting and provocative. I must disagree with this statement, however: "Furthermore, these epigenetic traits are inheritable so succeeding generations of animals will show the same behavioral and morphological changes."

This is a restatement of Lamarck's theory of evolution, a competing theory to Darwin's theory of evolution, which is now accepted by the scientific community. Here is how Webster defines Lamarck's discredited theory:

Lamarckism : a theory of organic evolution asserting that environmental changes cause structural changes in animals and plants that are transmitted to offspring.



There is no doubt that the underlying genetic code determines the structure of animals. The expression of the code can be influenced by the environment, but the offspring will inherit the original genetic code, which will be once again be subject to environmental influences.
 

knotjoe

Well-known member
Messages
379
Reaction score
8
Location
North Central Indiana
There is no doubt that the underlying genetic code determines the structure of animals. The expression of the code can be influenced by the environment, but the offspring will inherit the original genetic code, which will be once again be subject to environmental influences.
Sounds about right, at least with respect to the Tiger Salamanders I mentioned above. The data has probably been refined since I first saw anything on it, but the potential of individuals within a brood to turn into carnivorous "dragons" as they're called was a small percent. Something like 12%. Interesting thing is, when those dragons breed and produce offspring in a challenging year, the number of potential dragons is roughly same in the next brood.

The species stays the same, as does the genetic variation/potential in succeeding generations. You probably know much more than I do about this, the words phenotype and genotype come to mind and I'll leave it to you to say yay or nay. Is it 12% (slightly) different genotypes and the "dragon" is resultant phenotype? That's a big assumption, there could certainly be other factors which account for the percent and maybe they all can, I haven't scrounged much lately for such research.

I'd like to hear more from anyone about the potential for permanence if it exists.
 

corn fed fins

Well-known member
Messages
1,376
Reaction score
101
Location
Montrose, CO.
I find this interesting and provocative. I must disagree with this statement, however: "Furthermore, these epigenetic traits are inheritable so succeeding generations of animals will show the same behavioral and morphological changes."

This is a restatement of Lamarck's theory of evolution, a competing theory to Darwin's theory of evolution, which is now accepted by the scientific community. Here is how Webster defines Lamarck's discredited theory:

Lamarckism : a theory of organic evolution asserting that environmental changes cause structural changes in animals and plants that are transmitted to offspring.



There is no doubt that the underlying genetic code determines the structure of animals. The expression of the code can be influenced by the environment, but the offspring will inherit the original genetic code, which will be once again be subject to environmental influences.

Epigenetics studies the mechanisms by which DNA code is asserted, not to changes in the DNA itself. These mechanisms are heritable traits, not encoded in the DNA but attached to the DNA. Been a while since I've read this stuff but I think methylation(sp?) is another process by which DNA expression can be altered without changing the DNA code? Heritable factors does support part of Lamarck's theory but not the theory as a whole.

If the stimulus that triggered how the DNA code was expressed was removed, would the species shed that particular induced characteristic now that it is no longer needed for survival? Maybe...maybe not? How about a steelhead? Behavioral and morphological modification through gene expression. IMO, I think Darwin and Lamarck would both miss this one. These steelhead traits could be referred to as being unnecessary for the survival of the species and "reducible" complexity.

Even Darwin's Theory of Evolution is becoming more scrutinized because of the advancements in the field of genetics. I will have to agree with Darwin's statement, "To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree."
 
Last edited:

corn fed fins

Well-known member
Messages
1,376
Reaction score
101
Location
Montrose, CO.
I believe that the answer to this question is "Yes."
Okay. Specific example: Steelhead desmoltification can take place in young fish due to obstructions in their migration. So smoltification does not favor river/lake bound fish. So why would steelhead continue to exhibit such a distinct behavioral difference when their anadromous behavior creates more obstacles in the pursuit of reproduction, making it less likely to be successful? In time, will smoltification be a lost epigenetic effect? What environmental conditions call for this phenotype? If it's all about inherited genes, then the massive rainbow inbreeding should hasten the loss of the phenotype I would guess, but this does not appear to be the case.
 

throssing

Well-known member
Messages
325
Reaction score
1
Location
Lyons, CO
Okay. Specific example: Steelhead desmoltification can take place in young fish due to obstructions in their migration. So smoltification does not favor river/lake bound fish. So why would steelhead continue to exhibit such a distinct behavioral difference when their anadromous behavior creates more obstacles in the pursuit of reproduction, making it less likely to be successful? In time, will smoltification be a lost epigenetic effect? What environmental conditions call for this phenotype? If it's all about inherited genes, then the massive rainbow inbreeding should hasten the loss of the phenotype I would guess, but this does not appear to be the case.

I do not understand the example that you have posed, so I can't give a reasoned response.
 

corn fed fins

Well-known member
Messages
1,376
Reaction score
101
Location
Montrose, CO.
I do not understand the example that you have posed, so I can't give a reasoned response.
No, you are spot on with "yes" as to losing the characteristics. My whole point was why do they continue when it's unnecessarily complex. That's what I was getting at.

Sent from my VS986 using Tapatalk
 

silver creek

Well-known member
Messages
7,204
Reaction score
591
Location
Rothschld, Wisconsin
April Volkey has 2 podcasts with John McMillan, who is now the project head of the TU Wild Steelhead Project. It is really a great interview and gets into Steelhead biology including why some rainbows become steelhead and migrate to the ocean and some from the SAME redd with the same parents become stream rainbow trout. I've listened to most of the first podcasts and there are 2, so give it a go. It really is fascinating.

John McMillan - Steelhead Biology (Part 1) | Anchored with April Vokey Podcast on acast

John McMillan - Steelhead Behaviour (Part 2) | Anchored with April Vokey Podcast on acast

In this blog post, John McMillan clarifies his comments about hatcheries.

John McMillan Podcast Clarification - April Vokey

In it he writes:

”4. The question that I think was most confusing on my end was: How can hatchery fish be different from the wild fish if they come from the same stock? Here I can clear up some of what I was trying to explain.

Let me step back, and reiterate that the hatchery rearing environment can change a number of aspects of the fish, including brain size, body shape, fin size, and otolith/lateral line makeup. But, those are phenotypic changes that are induced by the environment of the hatchery and they are not necessarily passed along to offspring. For instance, in my wolf-boy analogy a young man was raised with wolves and did not know how to communicate with humans. He did not speak and it would be likely that modern technology would find differences in his brain wiring compared to normal humans that have a long history of interacting with one another. It would be the same as having a different region of the brain can take over other functions after injuries. Those types of changes are phenotypic because wolf-boy’s offspring would have all the capabilities of being a normal human. In other words, it was his upbringing that changed him. His genetics did not change. And this gets into nurture v. nature. The bottom line is that things like small brain size are due to lack of stimuli in the hatchery, meaning that how the fish is nurtured instills changes, but the changes can be reversed in the next generation.

The phenotypic change is not the issue as much as the genetic change. Because if the changes in hatcheries were only phenotypic, then they would revert back to wild fish after spawning and rearing in nature. But, that is not what research is seeing for steelhead. For example, after first generation hatchery steelhead from wild stock spawned in the wild, their offspring also survived poorly (in Hood River studies). This suggests that the hatchery rearing affects genetics that are passed on generation-to-generation. Indeed, a follow up study found that those first generation hatchery steelhead differed genetically from wild steelhead in traits like immune system function and metabolism.”


The Hood River studies he refers to above is the study I pointed to in my original post

The changes that occur in hatchery raised fish are the result of epigenetics, and 723 changes occurred in a single generation! There "were 723 genes differentially expressed between the two groups of offspring."

A single generation of domestication heritably alters the expression of hundreds of genes
For those of you that have not or will not listen to April Volkey's podcast with John McMillan might think it odd that Johns specifically mentions that those first generation fish differ in metabolism from wild steelhead. Metabolism is not a visible trait. This is important for two reasons. First that fish may look identical as we may think that they are identical. Secondly, McMillan in his first podcast explained that steelhead metabolism is what drives the rainbow trout to go out to the ocean and become steelhead. Fish with a fast metabolism need more food to survive and these are the rainbows that will go out to the ocean because it has more food than most rivers.

Hatchery fish are raised in an environment that has relatively slow flows compared to wild rivers. Secondly they do not need to hunt for food or escape from predators. This changes their brains and their metabolism. Specifically, they have smaller brains on average and slower metabolism. Few hatchery raised steelhead go out to the ocean after they are raised. So although they came from wild Hood River Steehead eggs, they revert back to resident rainbow trout. And these epigenetic traits are passed on to future generations.

You may have noticed that McMillan does not say that these traits are epigenetic. I think that is because he simplified the genetics for the purposes of the podcast. But clearly, by referring to the Hood River study, these are epigenetic changes. The underlying genetic DNA sequence cannot change to this degree in a single generation.

Therefore, the changes in hatchery fish continue after they are released in wild AND they can be imparted to future generations of steelhead and THAT is the reason you DO NOT WANT hatchery fish mating with wild fish. The Hood River study says that they are epigenetic. And I think these epigenetic changes are passed on. Does it really matter whether these are "genetic" or "epigenetic" changes? Epigenetic changes have the potential to revert and that is the difference. The second difference is that if these are really genetic changes, Darwin's theory that evolution is gradual over millions of years is clearly wrong and I am not willing to take that step into that abyss.

So the question is do all the epigenetic changes revert? Not necessarily. In my original post I posted this research that showed epigenetic behaviors were inherited by a future generation of mice.

Fearful memories haunt mouse descendants

There is other research that shows similar inherited behaviors in other animals including humans.

Epigenetics & Inheritance
Transgenerational Epigenetic Inheritance
 
Last edited:
Top