New Angelfish- strange morph...

[tcmfish]

This is a totally off the wall guess to try and explain this and mostly likely has no significance, BUT here goes.

Both dietary and predatory could be related. If the fish has to hunt and forage for food more in the wild it is exposing itself to more predators. The fish could be under stress while hunting or foraging which could cause the ocellus, but in the aquarium it is fed by a human or machine and usually kept in a stress free environment relative to the wild. There are no predators (who feeds juvi bluefaces???). Also it doesn't have to swim much for food which may be less stressful than hunting for food in the wild leading to a loss of an ocellus.

 

[tcmfish]

John is the chemoreception due to a hormone or chemical released by the predator that signals the growth of the thick shell? Correct?

Like in laymen terms... chemical A is given off by crab, detected by receptors in snail and involuntarily triggers growth of thick shell? So the presence or absence of the chemical catabolizes or inhibits the growth of the shell respectively?

 

[copps]

Exactly Tim... and stress induced phenotypic plasticity is also entirely possible as you mention...

 

[jmaneyapanda]

Now were on the same page......but.......I still will have to agree to disagree. I think it is too far a leap of faith to say that these fish are taking some pheremonal indicators from a generalized "predator" to alter their phenotype. In lower class inverts, I would be able to follow, but not for higher end vertebrates, such as teleosts. Perhaps I am 100000% wrong, but until I see some data for it, it seems to "sci-fi", and unnatural.

In regards to the snails, I do understand and accept that, John. We have a difference in understanding to what the "cues" were. Of course animals will develop differently under different physichemical cue, amongst otehr things. I beleive there was a coral reef repopulation effort that ran electrical charge through the artficial reef structure to stimulate growth (if I REALLY havent lost my marbles). However, pheromonal cues to create a metabolic reactions seems a distant step to the forbidding ocelli due to predators being present that is apparent here.

John, in your last post, you indicate "stress" induced plasticity. That kinda takes us back to square one. Stress is not an empirical quality. It is not a chemical presence, a calculated difference from "the norm". It ios a relative condition inflicted on an individual. Would poor water quality, or electrical charge, or darkness, or brightness, or water temp, or whatever else also stimulate such phenotypic plasticity?

 

[jmaneyapanda]

John, this is gonna be us, the next time I see you. You're in red.

 

[copps]

Jeremy, while I cannot see an image, I imagine it's another fight scene... Are you saying you're winning this argument? I disagree... you're practically on my side of the argument now, so we're all good... but you seem to argue for the sake of arguing, even after your original argument fails you morph it into another argument...

You started with...

You are suggesting a permanent developmental alteration based on perception of environment? That is, well....mind blowing. Especially if we are suggesting it to be so in a mere single generation. Darwin is spinning in his grave.

No longer mind blowing... now you agree phenotypic plasticity is possible...

In regards to the snails, I do understand and accept that, John.

... which was just one example I gave... it happens outside of snails too...

I cant fathom what "cue" we'd be talking about (in the scenario suggested) that wouldnt be cognisant.

Now you can fathom a cue doesn't have to be cognisant...

You said this... casting doubt...

John, were not seeing eye to eye here. In your crab reference, what stimulates the snail to "create" the thicker shell? This is where my doubt lies.

And then you say you could see it and you had no more doubt... you lost that argument, but of course you changed the argument again...

In lower class inverts, I would be able to follow, but not for higher end vertebrates, such as teleosts.

Okay, so you're on my side of the argument now, as you originally argued it wasn't possible... now you argue it is, but just not with teleosts... but of course you still have to disagree!

Now were on the same page......but.......I still will have to agree to disagree.

Perhaps I am 100000% wrong, but until I see some data for it, it seems to "sci-fi", and unnatural.

Of course! We're on the same page... my original page... Well, at least you've agreed that your original arguments were wrong, and that it can at least occur in the marine environment outside of teleostean fishes... if I had the time or funds to gather the precise data you're now requiring, in terms of applying it to teleostean fishes, I'd go and buy some peppermint angels...

DISCLAIMER: (I always have to put this in) Jeremy and I are friends and know each other in real life... do not take this as anything more than an argument!

 

[jmaneyapanda]

John, as u, you have FAILED to see my point in this whole issue, which is why it has become so cyclical. I do not doubt that such plasticity is possible (nor ever stated so). I have, and do, doubt the method in whioch you are insinuating it is reached.

Your snail example was a good example, and actually rather disproves your own assertion, in my mind. The snails adapt to a specific pheromonal cue from a predator. It purportedly has been identified. As a metabolic by product, which the snail detect physiologically, and it illicits a metablic reaction (as been adapted of the past million years).

However, shift to fish now- what metabolic cue is detected? Stress?! Please. Predators?! C'mon. To me, every "indicator" to the adjusting fish that has been mentioned IS arguably cognitive. Do the fish "know" they are stressed? Can the fish sense a predator? Of course. And to speculate that such consitions would cause a shift in phenotype, ipso facto, soeculates that it is cognitive. I think that is quite failed.

Here is the simple question to be answered that will defeat my stance (and believe me, I invite it. I love being proved wrong in cases such as this!). What is the cue that causes these fish to change their phenotype? Is it the sight of a predator? the smell? Or some subconscious chemcial reaction? This may seem like nit picking, but this is an ENORMNOUS differentiation in how this topic is viewed.

By the way, you know me well. I cant wait for you to see that pic.

 

[myerst2]

The two of you sound like a couple who's been married for 50 years...... Comical b/c you remind me of my cynical and sometimes bitter grandparents.

 

[melanotaenia]

awesome fish, very unique coloration!

 

[LobsterOfJustice]

I think the biggest problem I have with the argument of losing the ocellus due to lack of stress, is so far we've only got one case. Is everyone else who raises a BF from juvie to adult not providing a predator free environment?

It might not have to do with predation at all, just something funky about developing in captivity. Like misbarring in clownfish, emperors not fully developing striping, etc. A lot of male/female changes seem to fall short of 100% stunning as well - male anthias usually look better to me if they've changed in the wild as opposed to captivity, same with wrasses, etc.

 

[tcmfish]

I mentioned that and realize it.

The things you mention are also things that didn't develop not things that were present and lost. The ocellus is also used to deter predators. The emperors striping could be do to the smaller size of our captive fish also.

 

[jmaneyapanda]

I really love the direction this thread is "weaving". And, also, for the record, I am poking a little fun at Copps, and it is ALL tongue in cheek. John is one of the aquarists, and functional scientist and taxonomists for reef fish, that I respect above most others. In fact, I put him above some with the "PhD" moniker in their title. By the way, for those who ahve never met John before, that is an actual picture of him above in the red shirt. He really looks like that. Really.

Now, to the matter at hand- we are opening a pretty big can of worms here. We're almost asking: "why are reef fish colored as they are?" That is a spicy meatball. Before taking a bite, we need to discuss whether were considering long term, or short term points. In other words, are we talking genetic speciation, or just short term adaptation within individuals? Making Im making this into more than it is.

Regarding the ocelli, they are widely believed to be for predator confusion, but this is just the most prominant theory on it. It very well may be for reprioductive purposes (in sexual selection), or other reasons. The biggest question I have for it (which I will ask mother nature, the next time I see her), is why do teh MONSTER adults have it too, when the blue and white juveniles do not? I would argue that the tiny juveniles would need it a million fold more than the adults.

 

[JHemdal]

When I first saw the picture - it struck me that the fish was simply one that had gone through metamorphisis while in captivity. The muted coloration, odd body shape, hint of HLLE around the face, all pointed to a long-term captive to me. Additionally, a friend of mine had grown up one of these back in the late 1960's that looked the spitting image of this fish - all being what I presumed to be captivity-induced artifacts.
Later in the thread I read the fish was fresh from Bali - so I guess my perception was incorrect....

Regarding phenotypic plasticity, the Lake Victorian Haplochromines are a good vertebrate example - their tooth structure changes in fish depending on their diet. Since dentition is one of the main ID factors for this group, that certainly wrecks havoc with out attempts to work out the taxonomy of the group. So - while I don't see the mechanism of ocelli showing or not showing, I can see that changing tooth enamel to meet environmental cues takes more "biological effort" than changing a few melanophores.

Jay

 

[jmaneyapanda]

When I first saw the picture - it struck me that the fish was simply one that had gone through metamorphisis while in captivity. The muted coloration, odd body shape, hint of HLLE around the face, all pointed to a long-term captive to me. Additionally, a friend of mine had grown up one of these back in the late 1960's that looked the spitting image of this fish - all being what I presumed to be captivity-induced artifacts.
Later in the thread I read the fish was fresh from Bali - so I guess my perception was incorrect....

Regarding phenotypic plasticity, the Lake Victorian Haplochromines are a good vertebrate example - their tooth structure changes in fish depending on their diet. Since dentition is one of the main ID factors for this group, that certainly wrecks havoc with out attempts to work out the taxonomy of the group. So - while I don't see the mechanism of ocelli showing or not showing, I can see that changing tooth enamel to meet environmental cues takes more "biological effort" than changing a few melanophores.

Jay

Jay, there is no HLLE on this fish, I can see how the photo suggests this, but as observed in life, it isnt there. There is a lot of bubbles and debris floating past in the photos, so maybe thats whats making it look so.

Regarding the Victorian fish, what "cue" determines the plasticity? Is it known, or speculated? Does it change in the lifespan of a singular fish, and can it revert if the stimulus is removed?

Curiosity is killing this cat.

 

[cas]

This discussion is out of my league, but from my reading of this thread it appears that this fish never had an ocellus.

If that is correct could this just be an individual fish showing the traits of a recessive gene? i.e no ocellus meant the fish was more likely to be eaten, the gene would be less likely to be passed on. There are many recessive genes in humans that are passed on and do not cause an issue unless both parents pass it on, i.e hemophilia.

 

[JHemdal]

The cue in the cichlid's teeth is their diet. The fish of some species require certain dentition to extract snails from their shells. When kept in captivity, the individual's tooth morphology changes to suit the changed diet. Feeding the fish live snails will change it back. It doesn't seem to simply be a mechanical change - the teeth get shorter when fed soft aquarium foods, and get longer if the fish "needs" them to extract snails from their shells.
Like I said, if it wasn't that we need to use teeth structure as a meristics to tell the species apart, it wouldn't be that big of a deal.
These fish are even more plastic in their phenotype when you go from generation to generation....evidence supports the idea that over 400 species of these cichlid evolved in Lake Victoria since the lake mostly dried up about 14,000 years ago. However, now half are extinct, and many more endangered because people transplanted the predatory Nile perch to the lake: http://microcosmaqx.typepad.com/jay...hromine-cichlids-of-lake-victoria-africa.html

I gues they aren't plastic enough to counter the Nile perch's predation of them!


Jay

 

[jmaneyapanda]

So, the fish will "grow" longer teeth in the presence of snails? Can it occur if housed in the same water column, but not exposed (ie- does the fish need to eat the snail)? What species is this? I'd like to read more about this. I am very curious as to the metabolic mechanism of this event. If the sight or smell of these snails causes an anatomical adjustment, I am amazed. If it is consumption, I would like to se if anyone has looked into other potential effects or causes (ie- excessive calcium or fatty liver deposits, or similar).

 

[jmaneyapanda]

On a totally unrelated note, I recently watched a documnetary on lake Victoria (based more on the politics and socioeconomic issues thatn the wildlife), and they showed people eating the entire nile perch- skeleton and all. Yeck.

 

[copps]

This discussion is out of my league, but from my reading of this thread it appears that this fish never had an ocellus.

If that is correct could this just be an individual fish showing the traits of a recessive gene? i.e no ocellus meant the fish was more likely to be eaten, the gene would be less likely to be passed on. There are many recessive genes in humans that are passed on and do not cause an issue unless both parents pass it on, i.e hemophilia.

I think this is something plastic based on the fact that many of these things seem to be driven by the environment, not randomly as you would expect with genetics...

Jeremy, you seem to find it hard to believe that environmental changes can have an effect on the plasticity of these things... what causes protogynous (like angelfish) and protandrous hermaphrodites (like clownfish) to change sex in a matter of days? What caused my juvenile emperor to undergo a fast change to adulthood as soon as he was not under the dominance of the other adult I had? Do you agree with the commonly held notion that juvenile Pomacanthus coloration allows them to live within the territory of an adult, and that the change is designated not by size of the fish but by the sociodynamics of the territory the fish lives in?

 

[jmaneyapanda]

I think this is something plastic based on the fact that many of these things seem to be driven by the environment, not randomly as you would expect with genetics...

Jeremy, you seem to find it hard to believe that environmental changes can have an effect on the plasticity of these things... what causes protogynous (like angelfish) and protandrous hermaphrodites (like clownfish) to change sex in a matter of days? What caused my juvenile emperor to undergo a fast change to adulthood as soon as he was not under the dominance of the other adult I had? Do you agree with the commonly held notion that juvenile Pomacanthus coloration allows them to live within the territory of an adult, and that the change is designated not by size of the fish but by the sociodynamics of the territory the fish lives in?

John, this is hormonal drive and is directly involved in sexual selection. The sight of the other fish is not what causes the change, but the hormonal variation trigger by the other fishes presence. That is the cue, not the visual indication. This is my point. Bring it full circle back to the original fish in question, if stress from predation is the visual cue, what is the actual mechanism for lack of production of the lenin to make the spot? Is it hormonal? And if so, what hormone would only be produced by the appearance of a generalized "predator"? In the angelfish and clownfish comparison, the social interaction stimuliates an redorductive endocrine response, which causes the morphologic alteration.