https://evolutionnews.org/2021/10/s...er-of-engineering-models-for-adaptation/

We know that fishing not only wises up the fish that have been caught, but also their progeny -- even though the DNA remains the same. This article focuses on cichlids, such as tilapia, but the model for adaptive change seems pretty universal among animals. Note that adaptation does not change basic body plan, which seems immutable, but does seem well designed to respond to environmental triggers.

There's a lot to unpack here, especially if this happens within one generational cycle:

"Greater salinity resulted in adult fish displaying shallower bodies and longer jaws.

As a second example, Parsons et al. in a 2016 study fed two separate groups of young juvenile fish different diets. The two groups developed into adults with distinctly different head-jaw structures that were tailored to forage for the available food most effectively. Navon et al. in 2021 reported on a similar experiment that confirmed the Parsons et al. results. The investigators also demonstrated diet-induced adaptive changes to body shape and fin-ray number. The observed dissimilarity between the two diet groups mimicked the differences between distinct cichlid species in the wild."

Thanks for the thoughtful post. Many adaptations are pre- programmed pro-survival design responses to environmental conditions, thus occurring rapidly. There's even a type of seagull that, when blood salinity gets too high, develops an organ to help rid itself of the excess salt. When the same gull goes inland & feeds in fresh water, the organ disappears!

Standard evolutionary theory, slowly bumbling around with random mutations & natural selection, can explain some things but not this. To steal a phrase, life is not only more incredible than we imagine, it's more incredible than we can imagine.

If an adaptation can happen so relatively quick, then I wonder if a fish could adapt to the forage base if it was an 'unnatural' pairing.

For example, if YOY SMB were introduced into a Bluegill only pond, could the SMB adapt to be able to thrive in that ecosystem?

There is another factor beyond adaptation (evolution) which does not involve a permanent change in the genes within the DNA. Certain genes have the ability to be turned on and off (or upregulated or downregulated) based on biochemical modifications like methylation that can occur in response to environmental exposures. This process is called epigenetics and modifications can be passed down to offspring (but often at least partially reset in the next generation). For example, in humans, starvation in a grandparent affects children's, and grandchildren's mortality in males. This control of certain genes is also a product of evolution. Offspring with this flexibility to upregulate or downregulate a gene can adapt to a fluctuating environment such as plentiful or scarce food, and thus are more likely to pass this trait on to their offspring. Cool stuff!

https://www.nature.com/articles/s41467-018-07617-9

Most organisms have far more genetic material than is strictly necessary to "build" that creature.

For example, it was previously estimated that you could make a human with only 2% of our actual genetic code. The rest was "junk" DNA.

Of course, this is ridiculous. I am a firm believer in Chesterton's parable about removing a seemingly pointless gate in the middle of the road. If you can't explain the function of a specific gene, then don't tell me it is useless junk. When you can tell me how and why that gene came to be incorporated in the full genetic code of an organism, then I MIGHT believe you when you tell me exactly what all of the genes do in concert.

One hundred years in the future, people will laugh at what we currently believe is "settled science" about genetics.

The "junk DNA" dogma is a thing of the past. DNA is more than genes, it is also the structure of DNA which impacts the timing and level of gene expression.

https://www.quantamagazine.org/the-complex-truth-about-junk-dna-20210901/

Rod, we used to think that DNA built the creature, but in fact the basic body plan is in the (if I recall correctly) Developmental Gene Regulatory Network, or DGRN. That's kind of mysterious, but appears to be embedded in the membranes of embryonic cells. DNA manufactures the right protein "bricks", then DGRN puts them together to make the tissues & organs that become a chicken, frog, fish, or human being.

Which is the reason why, for all the adaptations & mutations we see, basic body plans are immutable: the DGRN is highly intolerant of change. In fact, major changes are very harmful, usually fatal.

So we aren't gonna change a smallmouth bass into a pike or carp, much less something other than a fish, regardless of how hard we try. But we can explore the built in adaptations designed to help the organism survive changing conditions, like maybe a larger jaw if the only prey is large, or slightly more streamlined form to escape intense predation from, say, muskie or pike. Some adaptations will doubtless be of interest to pondmeisters, such as increased aggression and faster growth. Sunil brought up this idea, and I think he's on to something. Love to see some research into this possibility!

We should never laugh at the past nor considered science settled. All that we have thus far learned has sprung from some prior misconception and those misconceptions are essential to building new knowledge. They provide the fodder for questions and doubt. Most of what we know is what we now know is false ... the rest is confined to the knowledge of the limits within which our models work well enough to be useful and predictive. At least some of what we think of a successful model are choices we would rather think about them. The model, the math, doesn't need the story we attach to it to work ... at least most of the time. We do the best we can with the difficult task of clarifying the unknown. There is a huge difference between "settled science" and what (good) scientists think about "prominent theory" and "propositional/conjectural ideas". It is only the popular community at large that needs the truth in black and white and that often mistake a proposition/conjecture/conclusion as science. Many are not comfortable with not knowing, they want something solid to believe in. If the future is anything like the past we should expect each 100 years to produce a much different landscape.

jpsdad,

Tone is very difficult to convey over the internet.

You made the exact opposite conclusion than what I intended from my hyperbole in the comment you quoted. (It was an easy conclusion to reach based on my clumsy construction.)

My point was NOT to laugh at our current state of understanding genetics. It was to reinforce how little we actually know at this stage on an incredibly complex topic that has very subtle interactions between an extremely high number of variables.

This topic is certainly more complicated than physical chemistry. We are past the equivalent of the "phlogiston theory of combustion", but IMHO we could still have a knowledge gap almost as large as not yet discovering oxygen.

".... But we can explore the built in adaptations designed to help the organism survive changing conditions, like maybe a larger jaw if the only prey is large,..."


This is the simple thing that I was keying in on.

Could a smallie's physical geometry of jaw change slightly to allow it to eat more bluegill.

My buddy has a newly filled pond, and we've stocked it with (27) adult bluegill from my neighborhood pond. When it comes time for predators, I'd selfishly like him to put SMB in so I can 'reappropriate' some to my neighborhood pond, from time to time.

Exactly. Based on the observational evidence, there are many design hacks in the genome, if not DNA, to help fish & other organisms adapt. We don't know all of them, or what the trigger is in each case, but it would be amazing to research. Mutations are far more limited in what they can do. Besides, they tend to degrade the organism, not help. Very cool stuff!

Actually I didn't form a conclusion. I added to the last comment because it was a conclusion that you made that I think is probably a very accurate prediction. Indeed many may laugh and in the same breath consider the present ideas settled. I was just adding that we shouldn't do that! We should learn from history that we will never stop learning that we were wrong!

Just to be sure you understand Rod. I did not intend to represent your comment as one condoning laughing at the past or considering science settled. It was clear to me you were expressing the irony of it all. It spoke to me and I wanted to expand on it . I think critical of review of one's comfortable thinking ... seeking fault in one's thinking ... and the willingness to change one's mind in the light of evidence are very important qualities/activity of good scientists. Truth has much more subtle meaning in science than it has in popular thought.

Bravo!! I was somewhat reluctant to comment, given that my areas of scientific knowledge are Physical Chemistry (PhD) and Material Science (37 industrial years), but when FishinRod stated

“This topic is certainly more complicated than physical chemistry. “

I had to pipe in. Physical Chemistry and the related Material Sciences are not as cut and dry as you seem to imply. For example, once you get past even 3-body problems, there are no exact solutions. In my field, of particle filled fluids, no real systems can be modeled to sufficient accuracy to predict real world flow (except maybe in mono-modal single component spherical systems), and forget predicting particle induced erosion and attrition. Although we get pockets of engineers that think “the science is settled,” these systems are many years from being fully described.

So, Bravo to all!! We in the sciences should be a bit humble about what we think we know.

Finger Lakes region is beautiful, like most of upstate New York. But I can no longer tolerate, much less enjoy, the long winters the way I did when I was a kid!

I've gradually developed an interest in molecular biology, especially the machinery & information processing systems that make cells go. Not really my field, which is economics & finance, but a torrent of discoveries made possible by modern tech is exciting & challenges old paradigms like the Central Dogma (DNA makes RNA makes proteins makes us) and orthodox neo-Darwinism (random mutations plus natural selection explain biology). From an engineering standpoint, biomimetics is a hot field, as we seek clever solutions inherent in life to various challenges.

All that to say that your expertise is valued here. The more we know, the better pondmeisters we can be!

Thank you for the comments, Anthropic.

Sorry to belabor this. I have one additional comment on Physical Chemistry and ponds. A pond is like a chemical reaction between organic molecules. The outcome is almost never 100% of the desired product but a series of products and side products with their own Gibbs free energy (remember, deltaG=deltaH-TdeltaS - I don’t know how to put in greek characters here)

A+B->C+D x%
->E+F y% etc.

Why? Because we are talking about an ensemble of molecules each with their own kinetic & rotational energy and each bond with its own vibrational energy and each electron in their own excited state - nothing is at rest. The result is often temperature dependent, concentration dependent (think oxygen) and scavenger dependent (eg. free radical scavengers in chain reactions). Yields of the desired product are seldom over 70%. Is this an analogy for a pond?

When it comes to fish food, we see a very similar process. Our desire is for maximum gain of healthy weight, minimal waste product. But even when the fish eat every pellet so none just goes to the bottom & decays, they can only retain so many proteins & nutrients. We're doing well if 100 lb of feed creates more than 50 lb gain of weight. Too much fat can shorten life, as well.

This is much better weight gain than from natural food like insects & small fish, however. Fish must chase them down, using up energy, and besides they are mostly water.

Frank I agree but would like to add a few things. The dry weight energy content of feed is approximately the same as dry weight energy content of anything in the pond that fish will be eating. BUT ... the nutritional quality is different. If we dry BG and form a feed with it the content would be ~ 65% protein. These proteins are better for LMB than say those in Soy. Nutrient profiles are not as beneficial, especially for predators, when the source of the nutrients are feed. There must be a benefit to not having to chase things down because the nutritional profile is not as good for sure. Our member Jim Wetzel once said that the best gains he had witnessed was from dehydrated fish. I find this very easy to entertain. Fish has everything inside it that a fish might need nutritionally.

Makes perfect sense. The best feed contains fish proteins, rather than from, say, feathers. I seem to recall taurine as a vital nutrient fish need.

What I'd love to see researched is whether there is a design hack in some fish to, under the right circumstances, adjust their diets to fit what is available. I don't mean merely eat what is available, like tigerfish in Africa going after low flying birds, but metabolic changes enabling them to benefit more from a diet that would normally be inadequate in key nutrients. Daphnia develop armor, helmets & spears in response to predators, cichlids change jaw size, anolis lizards develop a cecal valve, some seagulls develop an organ to rid themselves of excess salinity, so why not check it out?

Genetics is the fastest changing area of understanding . Much will change over the next 10 years. Our understanding is at an infant level with so much more to learn.

Here is some out of a recent PB issue - Subscribe to the Mag !

Genetics vs adaptation - adaptation works through traits in the genes that may not be evident (turned off until needed). Once turned on those traits can have large scale changes. See below on how fast they can effect fish senses/brain evolution .

THE CUTTING EDGE – SCIENCE REVIEW

By Eric West


Adaptation (environment) vs. Evolution (genetics) in Fish


On The Pond Boss Forum recently there have been discussions on adaptation vs. evolution. This conversation centered around how do fish change, what is the mechanism (environment or genetics) and how long does it take. In Science Class we all learned about Darwin’s theories regarding Evolution. We were taught that Evolution is a slow gradual process. Darwin wrote, "…Natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by short and sure, though slow steps." Parts of Darwin's Theory of Evolution are now a theory in crisis in light of the recent tremendous advances in molecular biology, biochemistry and genetics. Darwin’s prediction was right on a geological scale (Earth’s age) but it has since been shown that evolution of species can happen much faster. In bacteria and insects, single generation change is known to occur. In more advanced species (fish and larger creatures), it was thought that things are more gradual, but still, do occur in sudden bursts.

While evolution was thought to be a slow process adaptation refers to the relatively quick process where through phenotypic plasticity certain groups or individuals change to be better suited to their environment and habitat. The thought is change is needed quickly so that they can survive and maintain normal function. In a prior Cutting Edge issue we discussed this concept described in The Effect of Vegetation Density on Juvenile Bluegill Diet and Growth in the Journal of Freshwater Ecology 2012, 1–11 by Daniel E. Shoup, Michael A. Nannini and David H. Wahl.

In that study environmental conditions during early Bluegill development shaped individuals’ phenotypes so they were more adaptive to the conditions they encountered. Plasticity has been shown to effect sunfish (Lepomis) shape, feeding and behavior in some cases. Here, by the end of the three month experiment, bluegill from the low vegetation ponds were significantly longer – twenty (20%) percent than bluegill from the high vegetation ponds. Were the long bluegill that fed in open water that way because longer fish can swim better in open water and were the shorter bluegill that way because being short allows them to maneuver around the weeds better? In this case a clear finding of adaptation in Bluegill in only three months.

Adaptation (through phenotypic plasticity) is the emergence of new characteristics in order to best suit the changes in the environment or habitat. Adaptation arises at the phenotypic level under the influence of environmental factors on the expression of the existing genes. It has become increasingly clear however, that phenotypic plasticity actually represents a fundamental component of evolutionary change. More questions arise like - what time period is required and what is the mechanism to get from adaptation to genetic change? Now some new thoughts – that genetics can be changed in early development through environmental influences. Similar to what we saw in the above study on Bluegill.
A recent study titled, Using Teleost Fish to Discern Developmental Signatures of Evolutionary Adaptation From Phenotypic Plasticity in Brain Structure by Zachary J. Hall and Vincent Tropepe in Front. Neuroanat. 14:10, 18 March 2020 is illustrative. This study looked at brain development in Teleost fish (ray-finned fishes) like those common in ponds.
In the past the impact of evolution on the brain has been studied by comparing the sizes of brain regions between species or in some cases in the same species. However, more recent work has demonstrated that environmental factors, such as sensory experience, influence brain region sizes intraspecifically (in the same species). This brings into question the distinction between evolution (genetic) and adaptive (environment) sources of brain anatomy variation in fish species.
The authors examined how newer fish research indicates the capacity for the environment to shape brain structure similarly within a species. Some of the first evidence demonstrating the capacity of the environment to shape fish brain structure came from comparisons between related wild-caught and lab-reared fish populations. The noted studies finding Salmon reared in a hatchery exhibit reduced olfactory bulb (smell function) and brain size compared to age-matched wild salmon from the same genetic cohort and also finding that first generation female guppies reared in the laboratory from wild parents exhibited reduced fore-brain and vision processing compared to wild-caught fish. Because the laboratory environment generally lacks much of the sensory stimuli animals would encounter in the wild, these findings suggest that brain development in fish is influenced by sensorimotor experiences. In another study both male guppies collected from regions of high predation and laboratory-reared male guppies exposed to sight and smell predator cues during development have larger brains as adults compared to unexposed males.

Another more recent method of studding fish brain development has been to compare fish populations of the same species inhabiting different environments. These studies revealed habitat-dependent brain size findings similar to studies comparing lab- and wild-bred populations. For example, whole-brain size is larger in sunfish that occupy a littoral shoreline habitat vs. those that live in a pelagic habitat.
The discovery of continuing adult brain neurogenesis in mammals demonstrates that adaptive processes continue to shape the brain well beyond embryonic development. Because fish exhibit extensive neurogenesis in the brain throughout life as compared to mammals it is more likely a life-long process for brain growth in fish. These developments in embryonic and whole life brain development in fish resulting from environmental conditions (adaptation) is proof that adaptive change (through phenotypic plasticity) is quicker , more powerful and far more prevalent than previously thought.

Thanks, Eric. That's a long post, but the subject deserves scrutiny. I fully expect that, in the future, fish hatcheries will develop techniques to make their fish grow faster & be more lure vulnerable than they are today. Not just breeding, aka the slow Darwinian process, but environmental factors that spur on fast development of traits we desire.

And if seagulls can develop organs to reduce salinity in their blood, what if we could do something similar in fish? Perhaps some freshwater species could thrive in brackish water where they do not today. Lots of possibilities, exciting!

Biologists are trained to dismiss living systems that look designed as illusory products of chance. Engineers, on the other hand, have eagerly seized on clever designs to help them develop new technology, a field called biomimetics. I hope to live long enough to see many breakthroughs ahead.

Frank, you may find this interesting ... people have a very broad range of belief with regard to intelligent design and chance. Even so, the distribution of belief is not a normal distribution where the highest frequency occurs somewhere in the middle. So imagine a distribution of belief where one end is completely chance and on the other end is completely intelligence. In the middle, we have those folks who recognize the arguments of those at the extremes giving differing proportions of credence to the opposing arguments. These folks in the middle are what one might call agnostics. Quite simply, they recognize that they do not know and they are at peace with that. At the extremes, where most folks are, are the people who are for the most part cock sure.

Chance is a fundamental belief of atheism.

God is fundamental belief of intelligent design.

But this really pervades all science and all belief. If one's belief is rigidly that chance is fundamental, then he must believe that everything came from nothing. Though this perspective solves the prime mover conundrum it inadequately addresses fundamental physical law, in particular the conservation of energy. For example, is it not arguable ... by the first law of thermodynamics ... that all the universal energy pre-existed before the initiation of universal expansion? I would just mention that there is a lot of evidence that universe's present state is one of finite age from some event popularly called the big bang. But we are presented with choices. For example, we could imagine a collapse occurred which created the conditions of the big bang thus conserving all the energy in a repeated cycle that could be eternal (having no beginning and having no end). Or, we could imagine a single life of the universe which begins by chance and must die.

The people who tell this story primarily believe in chance and the idea of eternity is very troubling to them. It's too much like believing in God and from their perspective it must be rejected simply because of this reason alone. From my perspective, however, I don't think how the universe works tells us about those things we must take by faith. So if someone on the God end of the spectrum said to me ... "Well then ... if the universe is eternal then this evidence that there is a God." I would say no, we must believe in God by faith alone. Also if someone on the Atheist end said to me ... "Well then ... if the universe dies then this must mean that there is no God". I would say no, because the premise relies on a belief in something one must take by faith. You see we must address the laws of thermodynamics and the first one is that energy can neither be created nor destroyed. So for this law to be fulfilled, the universe must be eternal.

The justifications are rather complex to preserve the notion of chance. Here are some of things we entertain to preserve it.

1. The laws of physics were created by the primordial event (must be taken by faith) and there may well be many other universes with their own laws (must also be taken by faith but is apparently used to strengthen the primary argument that the laws of physics are subject to the creation event ... as opposed to the creation event being subject to the laws of physics)

2. Dark energy. The universe must die if it cannot be recycled and dark energy forces this death. We justify this belief with evidence ... but we should understand that we paint the evidence by choosing what the relationships are. In essence, we paint the evidence with those things we want to take by faith. I would just mention, that faith is very strong whether one believes in God or one believes in chance. I would say there is actually no difference if the belief is rigid. An example of painting is the use of 2nd law of thermodynamics as justification (of chance) but to do so the 1st law must be fixed with the story that the law didn't exist before a primordial event and we must only mention 1/2 of the 2nd law. The entropy of a thermodynamic system must increase or remain the same. You often hear from those who believe in chance that entropy MUST increase and therefore universal death is inevitable. But they don't tell you that a universe that recycles and is eternal does not violate the 2nd law of thermodynamics. You see, any reversible thermodynamic process is isoentropic (entropy remains the same fulfilling the 2nd law).

Make no mistake, beliefs are polarized at each end of the Chance - God spectrum. Enough so that I characterize Atheism a type of religion where that taken as faith is Chance and those things we imagine to support it. To be sure, humans are religious. Atheists merely replace God with Chance and are as immovable in belief as anyone of any other religion. As one who resides between as a minority, the polarity of belief saddens me. It is very difficult to have meaningful collaboration when a litmus is applied to a belief system first. To be sure, I would fear any particular system of belief becoming unanimous. Perhaps, some day, the distribution of belief will look more like a bell curve and there will be a lot more people agreeing to agree and disagree in harmony

It's been a few years, but a member here that had a pond in Florida took saltwater fish and acclimated the ones that he could to live in fresh water, then stocked them in his pond. I'd love to see what his pond is like now.

Yes, I remember the same. Of course, we've seen this in saltwater stripers that were stranded in freshwater impoundments, too.

Good discussion, jpsdad. I'm not real good at taking things on faith. Observational evidence either supports a proposition, or it doesn't. Many things people believe are, in fact, false.
I was trained from childhood to think skeptically, especially at stuff "everyone" knows is true, or because "science" says so.

A brief comment on the Big Bang. Roger Penrose & Stephen Hawking demonstrated that prior to the BB, neither space, time, matter, or energy existed. Thus, whatever caused the BB had to be spaceless, timeless, immaterial. Also immensely powerful, and, given the incredible fine tuned universe for life, intelligent with purpose. Implications are so obvious that the atheistic Soviet Union actually forbade teaching the BB for years.

Back to fish. I recall reading that scientists have discovered that the genetic instructions to build an air breathing animal are found in fish, something like fifty million years prior to land animals appearing. Hard to explain why these utterly useless genes would hang around if they were the mere product of chance.

In my way of thinking observational evidence falsifies a proposition or it doesn't. The difference is not subtle as gives truth while the other logically fallacious. The fallacy is called "Assuming the consequent".

If A & B yields C then C means A & B are true. Having worked with many models that yield C I have a good understanding as to why C doesn't support that A & B are true. All we can actually say is that A&B are not falsified because we observed C.


Perhaps it is most things. It's really better, for science anyway, to resist the temptation to believe and restrict everything to logical systems where all truth is conditioned to and within the logical system and where all we can know of it is whether an experimental observation falsifies it or not. If an experiment cannot be devised to falsify a theory or proposition, then it isn't science.


Perhaps you could explain what experiment they performed which result depends on assuming there was nothing prior to onset of universal expansion (at least then we would know it wasn't falsified by some predicted experimental result). They could never provide observational evidence of nothing so this would be the next best thing.

Even Penrose and Hawking have faith it would seem.

Interesting. When scientifically trying to explain past phenomena, such as what killed off the dinosaurs, generally abductive logic is employed rather than deductive. That is, since we cannot observe what happened directly, what currently acting cause best explains the observations?

So when we observe a thin layer of ash around the world, above which dinosaur fossils disappear, what best explains their demise? Not a global flood. Not huge earthquakes. Not a terrible Ice Age. Possibly a gigantic bout of vulcanism such that the entire world has an ash layer. Possibly a big asteroid hit which would turn the skies into an oven and throw out searing hot fragments across the planet.

How to decide between volcanoes & asteroid? Well, the ash layer contains unusually high levels of iridium. Meteors & asteroids tend to be rich in iridium, but volcanic ash is not. Thus, our inference to the best explanation is an asteroid impact, though we must keep an open mind if further evidence turns up that runs against that conclusion. Until then, alternative explanations are considered (tentatively) falsified, or at least quite unlikely.

Penrose & Hawking used mathematics to conclude the universe had a beginning, along with space, time, matter & energy. Their findings have been confirmed by physicists & mathematicians. In fact, more recently other astrophysicists found that any universe that is expanding on average must have had a beginning, again by peer-reviewed math. They do indeed have faith in math, as do I, even though Godel showed that math rests upon foundations that cannot be absolutely proven.

I like for a hypothesis to become stronger as time goes by & more evidence comes in. Design in molecular biology is one of those.

Sorry, this sort of thing interests me but we're rather far afield from fishery & pond management. I apologize for getting us off track & will end my comments now.

Is there really any difference in a universe that dies and is consequently reborn and the one they imagine? If the former could Penrose and Hawking tell the difference? It is probably better said that Penrose and Hawking solved the mathematical problems of theory by making up a creation story where all there is ... even the laws that govern all there is ... were created by a god named Nothing.


It may be better said that physicists and mathematicians agree with the analysis and the methods.


But does this really matter when it is what they want to believe already? Ask yourself is there any difference in the evidence that fails to falsify a universe that starts from nothing or one that collapses and expands again? How can they be so cock-sure? I recall Hawking claiming a Theory of Everything was 20 years away and that was close to 40 years ago. Think about it ... a theory of all there is ... so close ... that doesn't leave much room for skeptical thinking.

It's my understanding that bull sharks can survive in fresh water, for some amount of time anyways.

Correct, for a lifetime actually.

It could have been a substantial cannon ball of pure iridium, a dense soft metal, thrown at Earth by ? for the very purpose of terraforming it. Just saying...ha ha ha.

Sounds like you had to deal with chaotic solutions...like, we don't know what it's doing but, with enough experiments, we can mostly bound the possible effects.

I have too many large bluegills, just can't catch enough. A four foot long juvenile tarpon could correct this problem!

Heck, I just learned that a bull shark can survive in freshwater.

A small one of those should work fine for BG.

However, you need to tell your kids and grandkids not to swim in that pond anymore. Now if some winged poachers or two-legged poachers just happen to miss the fine print on your "Bull shark warning sign", then that is just bad luck (for them)!

You can adapt/acclimate a small tarpon to fresh water..... Go for it!!

Yep, create all that iridium dust to fool Earthlings into thinking the dino demise was a natural disaster!

Sorry, can't resist a bit of humor.

A 15 to 20lb FH will take care of your excess BG and wont harm the kids when they are swimming and is some excellent eating when you run low on BG. but it would be kinda cool to have a shark in your pond,, oh the stories.

A trade of humor for humor...always welcome!

Many years ago, seven juvenile tarpon were found in an irrigation canal that feeds Medina Lake water to farms south in the Medina valley. About 150 miles from the Gulf of Mex. And about twenty years after tarpon disappeared from the central Texas coast (Corpus Christi)...meanwhile, it seems they are coming back, I saw a small one in a coastal pass.

Well, saltwater stripers managed to adapt when they were inadvertently cut off from the sea by freshwater impoundments. So maybe this would be possible, too. If so, I'll bet it will be a rapid adaptation of new function already inherent in the genome.

I haven’t looked at this in a few months but wish to add a comment. As far as science goes, it is never really settled. Big Bang or Big Bounce. I have a fondness for quantum mechanics and cut my scientific teeth on it in the 80’s (J. Phys. Chem. 1983, 87, 1438ff.), plus I find distasteful a singularity of energy at zero volume, and indeterminate physical laws left fully to Chance. With the quantom view, there is no initial singularity, and the universe expands from a finite volume where general relativity and the small scale physical laws are pre-existant. Even some stucture, such as massive black holes this early in the universe, might be explained. In addition, Big Bounce ekpyrotic (https://en.wikipedia.org/wiki/Ekpyrotic_universe) and cyclic models do not produce a multiverse, and while the random physical properties in a Big Bang expansion yields a universe truly left to Chance with the very properties of the universe determined by random Chance, this is not true with a Big Bounce. The uncertainty principle prevents an entirely predictive universe structure, but the laws of physics are invariant.

I find this much more appealing, not fully left to Chance. In any case, one still has to come to grips with the origin of a cyclic universe.

The prime mover problem.

But then the beauty of the cyclical universe in its reliance on the eternal immutability of the laws of physics. Given this assumption, I am not sure it makes sense to describe an origin. The assumption of immutable laws of physics seems to imply that there can be no initial creation event ... that would break the laws of physics and would require a supernatural event. So it's plausible that if laws of physics cannot be broken ... a cyclical universe can have no beginning.

The question of creation is a question that cannot be answered by science. It is something that will always require faith in a fabricated story. I am comfortable with the idea that the universe could be cycling eternally and that we will never understand how it was created.

Observations of the fine tuning in the initial conditions, constants, and laws of physics necessary for life have rather decisively shown that our universe is indeed miraculously unlikely, unless there are infinite other universes or bounces out there. The multiverse is unobservable, and even if it were true wouldn't get rid of fine tuning, this time at the level of the universe generating mechanism. Bouncing universes suffer from the problem of the energy required to keep bouncing.

Neither multiverse nor cyclical models escape the need to explain the origin of such an incredibly fine tuned universe. As in molecular biology, the more we know the harder it is to deny design as a superior explanation to chance, in my opinion. Follow the evidence wherever it leads.

Since this thread has veered away from fish adaptation, I would like to say this. I believe Talladega Nights is a documentary.

Frank, I guess just think of is this way. The universe is. It exists. I don't need multiverses and fine tuning arguments to understand that it exists. In my way of thinking, these are merely stories imagined to support a foregone conclusion that someone really wants to believe in. I say this because these ideas aren't supported by evidence. Rather these are stories woven with evidence through association. Evidence has no opinion. Opinions, most often already formed, drive our inference of what evidence means.

Unlikely universe? Then why are we and the universe here? Maybe it had to be and always has been. For all I know and all you know our universe is all there is and it doesn't need any help being the universe.

For me, the real questions lie in what it is and how it works. Understanding the laws governing the universe. I don't think there is anything special about our time in the universe (though indeed it may be special to each of us as thinking organisms) but in the end and I don't think it a miracle. It's just a physical system governed by the physics of the universe (not yet fully understood).

There are laws at play that inspire me to think the universe may be cyclical. But most prescient is the first law of thermodynamics. I am not aware of any evidence that suggests that energy or matter can be created from nothing. As far as I know, the law has never been observed to be broken. I have no reason to presume that something supernatural usurps the law. It is just much easier to imagine that all the energy existing at the onset of expansion was conserved in a collapse (thus preserving the law).

To be sure, we don't understand what could collapse the universe. We know it isn't gravity. Something in addition to gravity would have bind the universe if it were to collapse. Universal processes must be isoentropic in order to collapse the universe. This would require the universe to be self contained. These are things we already know (or suspect) are required in such a universe. What gives us pause is what this could mean for other ideas we presently consider to be true. In other words, there is much vested in the stories we have told and we might look foolish if we have to admit many of the things we had come to believe are actually false.