Dorocche t1_iy4pwvx wrote
Well, two things:
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Their colors only stand out compared to other reptiles and mammals. Amphibians and nearly every kind of invertebrate come in just as many spectacular colors. The better question is "why don't mammals have such a spectacular variety of colors compared to other animals?"
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Their variety in shape doesn't really stand out amongst anyone; obviously invertebrates all have enormous variation, but even boring old mammals have everything from tiny/round mice to lanky/springy deer to weird long ferrets to giant stocky rhinos.
It's also worth noting that fish in particular may be so widely varied because they're miscategorized; there's a push among some biologists to split up "fish" into several differently groups because there's so much more variation among "fish" than among equivalent groups.
Mammals don't have as much color variety because our color comes almost exclusively from melanin, which can only do shades of tan/brown/black. Most other animals can synthesize more pigments than that.
But birds in particular do have some other tricks up their sleeves:
Some birds, famously the flamingo but also plenty others, can absorb pigments from their food that their body can't make by itself.
Most green and blue birds actually don't use specc pigments, but their feathers structurally create that color (which is why they're so iridescent).
I don't know if either of those apply to fish.
the_lusankya t1_iy59hrn wrote
It's also worth noting that colourful mating displays aren't useful to mammals because most mammals are colourblind. And since bright colours are expensive, and tan/brown/black/white does a perfectly good job of camouflage, there's no advantage for mammals to have the bright colours.
Megalocerus t1_iy71ozs wrote
A melanin variant can produce an orange shade. Tigers look very bright to us, but not to their prey, which can't make out the redness.
Dorocche t1_iy5dxeg wrote
Also that birds aren't pressured as highly into camouflage because of their ability to fly. But given that they're not unique in their colors, I'm not sure how big of a contributor that actually is.
[deleted] t1_iy7hmm1 wrote
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bradles0 t1_iy90liy wrote
>because most mammals are colourblind
this one has always been weird to me, apes aren't the only mammal that spent a lot of its time finding red berries in a green background, why were we the only ones lucky enough to get trichromatic vision?
Unable-Fox-312 t1_iy54t9g wrote
"There's no such thing as a fish"
LowRepresentative291 t1_iy5jjpk wrote
To put it in perspective: there are species of fish that are more closely related to humans than they are to some other species of fish
Reconvened t1_iy69xug wrote
Which species?
MrSquiddy74 t1_iy77anh wrote
Lungfish and coelocanths are more closely related to us than to other fish
knowledge3754 t1_iy5tlqs wrote
Please elaborate
Unable-Fox-312 t1_iy5wwd6 wrote
We use the big sloppy category "fish" to describe all kinds of creatures under the sea. It's like if we bundled together all the chimps and certain kinds of birds and maybe one mushroom and decided those were all called arbs because they like to live in trees. It's a useful word in the real world, but the category doesn't map cleanly to any evolutionary branch
LowRepresentative291 t1_iy7e36x wrote
All life started in the water. Imagine at some point two species of fish diverged from a common ancestor, species X and species Y. Both became ancestors to many subsequent species. Some descendant species of X (irl: lobe finned fish) eventually came to land, and that's where we descent from. Now, thousands of modern fish species have evolved from species X, and thousands have from species Y. A far descendant from species X might look morphologically similar to a species that evolved from Y (they are both "fish") but it shares a closer common ancestor with humans.
commanderquill t1_iy7ehpi wrote
Life is created, presumably starting from one species. Then there's an explosion of life. Now all kinds of life. Some have fins. Some have feathers. Some have feet.
Some develop into something else, as different to the ones with fins as humans are. But that design fails. Better to have fins. Now they have fins.
Humans come along and see it and go hey, that's a fish.
But this 'fish' maybe used to be a lizard and then became a fish. So it went:
Step 1: ancestor
Step 2: something else
Step 3: something else
Step 4: lizard?
Step 5: fish?
Meanwhile, 'fish' #2 went:
Step 1: ancestor
Step 2: fish?
So you have one fish that came from a lizard and one fish that came from something else entirely. As a result, you have one fish that has a shared common ancestor with humans say maybe one billion years ago and another fish that has a shared common ancestor with humans three billion years ago. That means fish #1 and humans are related by one billion years while fish #1 and fish #2 are related by three billion years.
Conclusion: some fish are more closely related to humans than to other fish, and the category of fish is meaningless.
This is also true of crabs and trees. Mother nature proves to us over and over again that crabs, fish, and trees are the most superior earthly life forms.
Dorocche t1_iy5drqh wrote
Well, be careful with that one, because I usually hear that one in the context of denigrating paraphyly, and paraphyly is a useful and valid method of taxonomic classification as long as there are also equivalent monophyletic words.
Unable-Fox-312 t1_iy5en0l wrote
I was hoping people would search and find my favorite podcast. Obvs there is such a thing as a fish; for the sake of accuracy it's probably better to say for our taxonomy there is no branch that contains all the creatures we commonly call fish while also omitting every creatures we don't call a fish.
Dorocche t1_iy5et4w wrote
No monophyletic branch. But there's a paraphyletic branch, and a definition based on that won't be any less objective or consistent.
I have heard good things about the podcast, though
Unable-Fox-312 t1_iy5j9i5 wrote
I assume paraphyletic is a short way of saying basically the thing I just did: "there is a single fish branch if you're okay with a bunch of non-fish in it"
MrSquiddy74 t1_iy77s15 wrote
Sort of?
Paraphyletic is saying "everything in this evolutionary branch except these things".
Take reptiles for example. In common usage, it excludes birds, even though birds are a subset of dinosaurs, which are a subset of reptiles.
The exclusion of birds from the reptile "group" makes it paraphyletic.
Also fun fact! The most closely related animal group to birds is actually crocodilians (crocodiles, alligators, etc)
Redshift2k5 t1_iy9eyud wrote
it's a sloppy shorthand, fine as a joke but not an explanation
Burstar1 t1_iy5j9vl wrote
I'll piggy back on this to supplement the evolutionary reasons for this.
Mammals, birds, and fish all use sexual selection as a primary basis for their reproductive process. Demonstrating you are an exceptional member of your species is vital to attracting a mate and reproducing successfully. Typically, a Male of a species competes with others for the attentions of the choosy female. To do so they must prove they are stronger, faster, smarter, better fed, and generally more capable of supporting and/or protecting the dependent female than their competitors, or at the very least that his genes are worth the significant female energy investment to bearing offspring.
In the mammalian world, these competitions are best done in a way that is synergistic with survival demands. What better way to prove you can survive better than an opponent than to overcome them in some physical contest: Fight, be bigger, thump louder, etc. often while demonstrating a handicap that accentuates your ability to overcome (think Ginormous antlers that take a lot of food and energy to make and whose weight alone is a hinderance)? Even if you lose this contest you'll survive, learn from the experience, and the innate toughness it required in the first place makes you better to survive in the wild generally speaking.
Birds cannot tolerate the physical stresses of violent competition because the physics they rely on do not allow their skeletons to support it. It would be way to easy for hollow bird bones to break turning a fight lethal 90% of the time. How to compete then? For them, physical indicators are better: bright colourful pigmentation is energy intensive to produce. It will fade if the male is malnourished. It also reveals the presence of disease or parasites. The disadvantage of being so visible proves you are cunning as you're still alive despite it. Coupled with other attributes and performances this allows males to compete with Displays instead of fighting, for a much more survivable experience.
The reasons behind Fish colouration are less clear afaik. Best guesses are that the particular colour pattern of a fish allows them to camouflage in their colourful environment better.
atomfullerene t1_iy60q10 wrote
>It's also worth noting that fish in particular may be so widely varied because they're miscategorized; there's a push among some biologists to split up "fish" into several differently groups because there's so much more variation among "fish" than among equivalent groups.
While this is true, the splits would be jawless fish, sharks and rays, lungfish and kin, and everything else. So a huge chunk of the diversity of fish, and especially the colorful fish, is actually in one group of fish.
Any-Broccoli-3911 t1_iy62m35 wrote
All fishes are one group if you include tetrapodomorpha (amphibian, reptiles including bird, mammals).
https://biologue.plos.org/wp-content/uploads/sites/7/2020/05/Fig1_FToL2-scaled.jpg
If you don't, then fishes are not one group. Not even bony fishes.
atomfullerene t1_iy6544e wrote
> Not even bony fishes.
Sure, but there are 8 living species of bony fish that would not be in the group, so the vast majority of all color and shape diversity in fish is in that one group.
Dorocche t1_iy692fm wrote
And it's far more accurate to say those 8 species aren't "true" fish than to say that fish doesn't exist as a category.
Redshift2k5 t1_iy9e6rx wrote
Fun note with structural colour: our eyes don't have any blue pigment, but we do have blue structural colour.
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