How big could an aquatic creature get?

[Bulldog Psion]

The ridiculously oversized mosasaur in the Jurassic World trailers got me thinking, particularly after watching this clip (https://www.youtube.com/watch?v=R60ElTKJCC4) about it. The guy really needs to improve his delivery, but his point stands -- the marine reptile they show is 667 feet long.

So how long could an aquatic animal potentially be?

Do the largest whales (100-110 feet) represent the actual outer size limit, or could something bigger actually exist, just that it hasn't evolved on Earth?

I suspect that they do, indeed, exist just under some hard limit, but I could be wrong. And it might make an interesting discussion. :smallbiggrin:

[hamishspence]

The ridiculously oversized mosasaur in the Jurassic World trailers got me thinking, particularly after watching this clip (https://www.youtube.com/watch?v=R60ElTKJCC4) about it. The guy really needs to improve his delivery, but his point stands -- the marine reptile they show is 667 feet long.


The first thing I see is "Video is old and contains errors - it is not this large".

This page:

http://jurassiraptor.tumblr.com/post/104208746012/in-defense-of-jurassic-worlds-mosasaur

suggests that it's not an adult shark - and that the length is actually 60 ft - far more reasonable.

[Yora]

I guess it probably could get still a bit bigger than blue whale, but I think it's very unlikely.

Fish have been around for over half a billion years, during which an unimaginable number of mutations have been led to the evolution of huge variations of possible body shapes and sizes. And amazingly, aquatic vertebrates from a time before the first land dwelling animals really don't look much different from what we have today. And there is no reason to assume that aquatic vertebrates had any less mutations to their DNA than those on land. And while all the different species of land animals and bird evolved from fish, the fish themselved barely changed at all in any sinificant way.
Which I take as evidence that fish shaped bodies reached the possible optimum and there just isn't really much room left for any further improvements.

Getting really big has always been a great survival mechanism and there always have been ecological niches for really huge animals. If getting bigger is a viable option, eventually something would evolve to fill that unoccupied space. And the spot now occupied by blue whales had been left empty for almost all of animal history, which to me makes it appear like a niche that really isn't that desireable. And going even bigger would be even more undesirable, so I think there is a good chance that this will actually the biggest animal that will ever exist on Earth. Maybe in the late stages of the Suns life conditions in the oceans will changes in some way that makes even bigger animals a viable option, but I think it's unlikely. (Probably even going to get smaller.)

Possible, yes. But if conditions could exist that would favor the evolution of eve larger animals, they most likely would have been present at some point in the worlds history with some species making use of the opportunity. That it still has not happened makes it seem likely that it won't happen here on Earth at all.

[factotum]

The blue whale is the largest creature that has ever lived on this planet. You have to think that, if it could evolve to be larger than it is, it would have done so! I'm not sure what the limiting factor on a blue whale's size actually is--my guess would be its food source; the larger the creature, the more food needed to keep it going.

[noparlpf]

There are a few obvious limiting factors.

1. Food. Obviously, the bigger a thing is, the more it needs to eat. Even assuming there's just infinite food sitting right in front of an animal, there's probably a point where it physically cannot eat/digest fast enough to get the nutrients to sustain its body.
2. Weight. Even underwater, there's a point where something is so big it starts to crush itself and the bones and connective tissue can't support it.
3. Physiology in general, because I decided I'm too lazy to make this a longer list with separate points. :smalltongue: There are limits to how much blood a heart made of muscle can pump, how big limbs can get before they're too heavy to move themselves, how much oxygen lungs can extract and blood can carry, &c.

[Knaight]

The blue whale is the largest creature that has ever lived on this planet. You have to think that, if it could evolve to be larger than it is, it would have done so! I'm not sure what the limiting factor on a blue whale's size actually is--my guess would be its food source; the larger the creature, the more food needed to keep it going.

This assumes a significant selection force for sheer size, which is far from guaranteed.

[Sith_Happens]

And there is no reason to assume that aquatic vertebrates had any less mutations to their DNA than those on land.

I can think of a reason: Far less exposure to radiation.

[hamishspence]

It's also possible that climate change has made a big difference. For most of history, the poles weren't ice-covered - but a few million years ago, things got a lot colder.

Result - a niche for giant, blubber-covered filter-feeding predators hunting the icy seas.

The more temporate climes have their own filter-feeders (basking sharks, whale sharks) - but they don't need blubber and great size to keep warm - and aren't endothermic - so, don't need to be quite as big.

Teleost fish, had their own giant filter-feeders, in the same size range as those sharks:

http://en.wikipedia.org/wiki/Leedsichthys

[factotum]

This assumes a significant selection force for sheer size, which is far from guaranteed.

Why would the blue whale have got to the size it did if there were *not* such a selection force? Blue whales are filter feeders with no horns, teeth or other weapons they could use to defend themselves--their size *is* their main defence, because they're simply too big for any reasonably-sized predator to have a go at! Therefore, bigger = better as far as these creatures are concerned.

[hamishspence]

Why would the blue whale have got to the size it did if there were *not* such a selection force? Blue whales are filter feeders with no horns, teeth or other weapons they could use to defend themselves--their size *is* their main defence, because they're simply too big for any reasonably-sized predator to have a go at! Therefore, bigger = better as far as these creatures are concerned.

Orcas have no problem with hunting blues in packs - though, like any predator, they will go for the young and weak first.

Wikipedia doesn't say much about "Reasons to evolve great size" but what it does say, seems to be focused on other reasons than "become predator-proof":

http://en.wikipedia.org/wiki/Megafauna


Several reasons for the more rapid evolution of large body size in cetaceans are possible. Fewer biomechanical constraints on increases in body size may be associated with suspension in water as opposed to standing against the force of gravity, and with swimming movements as opposed to terrestrial locomotion. Also, the greater heat capacity and thermal conductivity of water compared to air may increase the thermoregulatory advantage of large body size in marine endotherms, although diminishing returns apply.[5]


C. megalodon would probably have preyed on the blue whale's immediate predecessors, before it went extinct.

[factotum]

That's just generally saying why cetaceans get big, though, it doesn't specifically say why blue whales specifically got *so* big--they're a lot bigger than any other living cetacean, after all (the fin whale, the second largest species, only grows to half the weight of a blue).

[hamishspence]

It's almost as long though. It may be slightly slimmer, to explain the weight difference.

[Ravens_cry]

I wonder if siphonophore (the most famous example is the Portuguese man o' war) could get bigger, though that stretches the definition of single 'creature'.

[cobaltstarfire]

I think Blue whales got so big simply because nothing stopped them. You don't need a selective pressure to evolve in a particular way, you just need whatever trait your species is heading towards to not be a detriment to survival.




I can think of a reason: Far less exposure to radiation.

I remember seeing a study somewhere about why whales don't get skin cancer very often in spite of spending most of their time near the surface. I can't remember what the findings were, but part of the question was "why don't whales get skin cancer?" So I'm not sure less exposure to radiation is the reason for the stability of their cell reproduction.

edit: I think portugese man-o-wars count more as an organism. Sort of like how the biggest organism in the world is that giant fungus network in that forest wherever.

[Tvtyrant]

Why would the blue whale have got to the size it did if there were *not* such a selection force? Blue whales are filter feeders with no horns, teeth or other weapons they could use to defend themselves--their size *is* their main defence, because they're simply too big for any reasonably-sized predator to have a go at! Therefore, bigger = better as far as these creatures are concerned.

What is the largest predator that hunts blue whales? Is the blue whale big enough to avoid being hunted at full size? That is the limit to its size. Being big makes starvation and beaching more likely, so the advantage of it is limited to protection.

Biologists are reasonably certain that North America had faster predators before the Holocene Extinction, because there are prey animals that run much faster than any predator currently in North America.

[valadil]

So how long could an aquatic animal potentially be?


In what context? I vaguely remember reading that pre-asteroid earth had an environment with much more oxygen. Dinosaurs could pump oxygen rich air throughout their bodies, no problem. Current earth doesn't have that same oxygen level and couldn't support dinos. If that's the limiting factor, today's largest animal is smaller than the largest animal on pre-asteroid earth.

[factotum]

If that's the limiting factor, today's largest animal is smaller than the largest animal on pre-asteroid earth.

That's not the case. As I said above, the blue whale is the largest (at least in terms of mass) creature that has ever lived on this planet. If "animal" means "land animal" then yes, there are no living creatures anything like as big as the dinosaurs were, but whether that's down to lack of oxygen or some other factor is something I'm not qualified to judge.

[hamishspence]

What is the largest predator that hunts blue whales? Is the blue whale big enough to avoid being hunted at full size? That is the limit to its size. Being big makes starvation and beaching more likely, so the advantage of it is limited to protection.

The only predator currently that hunts blue whales seems to be the orca (which probably doesn't hunt them at full size). However, I think their immediate predecessors were hunted by the much larger C. megalodon.

[Bulldog Psion]

Yes, I think it's said the adult blue whale is too big for orcas to kill most of the time; they may take a few bites out of it, though.

I seem to remember -- though memory may be serving me poorly -- that whale size only took off following the extinction of C. megalodon. Prior to that, the biggest whales were about the same size, at around 50 to 60 feet.

So it may be that the large size is an adaptation against smaller predators, now that the loss of maneuverability is no longer a disadvantage against a giant shark that is gone from the oceans.

[hamishspence]

I could see it being an adaptation to polar waters - which got a lot colder around the same time as Meg went extinct. However, multiple factors may contribute to the same thing.

C. megalodon wasn't the only giant predator either - Livyatan melvillei may have filled a similar niche:

http://en.wikipedia.org/wiki/Livyatan_melvillei

[Bulldog Psion]

I could see it being an adaptation to polar waters - which got a lot colder around the same time as Meg went extinct. However, Multiple factors may contribute to the same thing.

That's quite true, too. In fact, I think you're probably spot on here -- more than likely, the large size gave a survival advantage for the cold waters with their high density of krill, and the impact of Megalodon's absence was purely passive, i.e. it wasn't around to exert a countervailing selective force.

Edit: yes, I've liked Livyatan basically since its discovery -- though people are more familiar with C. megalodon. Odd that they were contemporaries, as complete competitors cannot coexist. You'd think that two 50 foot to 60 foot marine predators couldn't live at the same time and in the same areas...

[noparlpf]

I could see it being an adaptation to polar waters - which got a lot colder around the same time as Meg went extinct. However, multiple factors may contribute to the same thing.

C. megalodon wasn't the only giant predator either - Livyatan melvillei may have filled a similar niche:

http://en.wikipedia.org/wiki/Livyatan_melvillei

As I scrolled down looking for the size, the first number I spotted was 35 km. That scared me a little. The ocean is only 11 km at the deepest, more like 4 km on average. That would be a big-ass whale.

And then I realised that had nothing to do with its size. :smalltongue:

[cobaltstarfire]

As I scrolled down looking for the size, the first number I spotted was 35 km. That scared me a little. The ocean is only 11 km at the deepest, more like 4 km on average. That would be a big-ass whale.

And then I realised that had nothing to do with its size. :smalltongue:

It's still the size of a sperm whale, and has even more teeth though.

Not nearly as large as a blue, but it's not anything to sneeze at for sure.

[halfeye]

The first thing I see is "Video is old and contains errors - it is not this large".

This page:

http://jurassiraptor.tumblr.com/post/104208746012/in-defense-of-jurassic-worlds-mosasaur

suggests that it's not an adult shark - and that the length is actually 60 ft - far more reasonable.
A six foot Great White is a newborn. That would be unethical, to the point where protests would be generated. If it was a shark of another species? no problem, but no spectacle either.

[hamishspence]

A six foot Great White is a newborn. That would be unethical, to the point where protests would be generated. If it was a shark of another species? no problem, but no spectacle either.

Actually, 3 ft is newborn. 6 ft is juvenile. I recall reading about a person getting bitten by one in waist deep water - shark was small enough that the bite didn't do huge damage.

Some sharks look similar enough to white sharks that at a distance they could be mistaken for them - porbeagles, makos, salmon sharks.

6m Great Whites are extremely rare compared to smaller ones. And very heavy - 2 tons or so.

[halfeye]

Actually, 3 ft is newborn. 6 ft is juvenile.
Wikipedia doesn't give a size at birth, I don't know who these guys are, they give four to five feet long:

http://www.livescience.com/27338-great-white-sharks.html


6m Great Whites are extremely rare compared to smaller ones. And very heavy - 2 tons or so.
Yeah, that sounds about what Wikipedia was saying for big ones.

[hamishspence]

Wikipedia doesn't give a size at birth, I don't know who these guys are, they give four to five feet long:


Another good site, gives 100-150cm:

http://www.elasmo-research.org/education/white_shark/overview.htm

So the smallest newborns will be just a little over 3ft, the largest 5.

Of course, as a parallel universe :smallamused:, sharks may be less protected, and more common, in the JP-verse than the real world.

[Bulldog Psion]

I personally think (though this has nothing to do with the thread, which was inspired by the creature, not about it per se) that's supposed to be a full-sized great white shark.

The "Jurassic" movies are full of clearly ridiculous stuff. My favorite is the original one, where the tyrannosaur paddock is raised slightly above the roadway when the goat is eaten and the t-rex breaks out; seconds later, the paddock is 100 feet below the road so that they can have an "obnoxious kid in danger from a cliff" scene; and then when Dr. Ellie "Endless Terrified Screaming" Sattler looks over the edge, she's able to climb down to the Jeep in 2 seconds without a rope, meaning the paddock has now risen probably 97 feet to be 3 feet below the brink.

These films are Spielberg at his most cynical, and that's saying a lot. He doesn't even bother to try for the appearance of consistency; he just throws all kinds of crazy stuff together to get a "wow" or "eek" factor in, even if it's totally nonsensical, stamps it with his Sacred Super-Director Name, and calls it a day.

I fully expect that mosasaur to change size as needed. When they show it in some scenes, it'll probably be the correct size. Then, when he wants a "wow" reaction from the audience, it'll suddenly dilate to 667 feet so it can chow down on a full-sized great white shark. Then it'll shrink for the next shot, I'll bet dollars to donuts.

Because that's how Mr. Spielberg rolls. And that's why his movies make me uncomfortable, because I'm fully aware that he has even less artistic integrity than usual, and he uses cheap, lazy, blatantly obvious tricks to play on the emotions of his audience like a cheap violin. And yet, I line up to pay my ticket money and sit there watching the manipulative, cobbled-together, contemptuously thin tripe he puts out.

The man's like P.T. Barnum on steroids, yet, even knowing that he's laughing inwardly at me and everyone else as the suckers born every minute for him to take, I still shell out my money to him. And it makes me feel dirty inside, but I can't resist the bribe of frickin' dinosaurs. :smallbiggrin:

EDIT: I see this isn't Spielberg this time around, but the franchise has apparently been infected with his spirit, so the point still stands as far as I'm concerned.

DOUBLE EDIT: ah, he's an executive producer. So my point REALLY stands. I'm now imagining him saying "just have the mosa-whatsit get real big for the feeding scene, big enough to eat a great white shark whole. So what if everyone sees it changes size? This is a part-Spielberg movie, for Cthulhu's sake, people will like it if I tell them to! Ia, ia, Ph'nglui Mglw'nafh Multi-Millions H'ollywood wgah'nagl fhtagn!"

[erikun]

I can think of a reason: Far less exposure to radiation.
Radiation is generally not a major factor in mutation or evolution. For the most part, radiation tends to be highly destructive to living cells in major quantities; this is no more productive to mutations and to just standard living conditions. Plus, mutations and genetic drift tend to work just fine in "radiation-free" environments; they tend to be more based on breeding generations and some sort of natural selection, if anything.

The only real way that radiation would affect mutation/evolution is if a creature would mutate to survive or thrive in a radiation-heavy environment. (See: radiation-eating fungi (http://en.wikipedia.org/wiki/Radiotrophic_fungus))

[Bulldog Psion]

Radiation is generally not a major factor in mutation or evolution. For the most part, radiation tends to be highly destructive to living cells in major quantities; this is no more productive to mutations and to just standard living conditions. Plus, mutations and genetic drift tend to work just fine in "radiation-free" environments; they tend to be more based on breeding generations and some sort of natural selection, if anything.

From what I understand, mutations are mostly just accidental coding errors, in effect? The result of imperfect biological processes attempting to copy something precisely and botching it? :smallwink:

[erikun]

From what I understand, mutations are mostly just accidental coding errors, in effect? The result of imperfect biological processes attempting to copy something precisely and botching it? :smallwink:
Basically, yes.

Radiation doesn't generally cause genetic coding errors, though. It tends to cause functioning errors. As in, it tends to damage a cell so that it can't function or functions incorrectly. This effect tends to be called cancer and clearly isn't something that gets passed along to a child. :smalltongue:

[hamishspence]

I fully expect that mosasaur to change size as needed. When they show it in some scenes, it'll probably be the correct size. Then, when he wants a "wow" reaction from the audience, it'll suddenly dilate to 667 feet so it can chow down on a full-sized great white shark. Then it'll shrink for the next shot, I'll bet dollars to donuts.
Even the 20 ft white shark only produced a 177 ft mosasaur, using scaling.

'Zilla in the Matthew Broderick movie does change size noticeably though - it's possible that, despite an "official" 60 ft mosasaur size, the scenes won't stick to it.

[cobaltstarfire]

Basically, yes.

Radiation doesn't generally cause genetic coding errors, though. It tends to cause functioning errors. As in, it tends to damage a cell so that it can't function or functions incorrectly. This effect tends to be called cancer and clearly isn't something that gets passed along to a child. :smalltongue:

Also something that whales are freakishly unlikely to develop.

Though you can have a genetic predisposition towards cancer, which can be passed on to a child.

[No brains]

For creature size, are we limiting ourselves to just animals, or can we use cheater colonies like fungi, aspen trees, and other lifeforms?

I wonder how hard a blue whale has to thrash in order for it to give itself a joint injury? If we had some data on that, we could get a figure on what kind of force it takes to make even massive blocks of tissue fail.

[LibraryOgre]

For creature size, are we limiting ourselves to just animals, or can we use cheater colonies like fungi, aspen trees, and other lifeforms?


We want to go with cheater colonies, we might as well point to LUCA.