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Insects are scared to death of fish - Comments

DavidMcC's Avatar Comment 1 by DavidMcC

I suspect that the reporter has confused "stress" with "fear". Not the same thing. If they were so afraid of fish, they would try to fly away from them. This possibility isn't mentioned.

Fri, 28 Oct 2011 13:57:28 UTC | #884916

glenister_m's Avatar Comment 2 by glenister_m

Extrapolating a bit too far, would this effect be seen with atheists and theists? If so, who is the predator and who is the prey???

(We see a lot of fear when theists ideas are challenged in some countries, but atheists must fear for their lives in others...)

Fri, 28 Oct 2011 14:42:57 UTC | #884935

JuJu's Avatar Comment 3 by JuJu

If larvae are stressed to the point of death prior to metamorphism doesn't that mean they aren't surviving long enough to pass on their genes? So wouldn't that characteristic eventually fade out based on the principles of natural selection? And wouldn't the ones that don't stress out to the point of death, or lack of development, be the ones that survive to breeding age and spread the genes that don't exhibit theses behaviors. Rather wouldn't they spread the genes that allowed them to avoid that fate in order for the species to survive. Wouldn't the genes that code for stressful dying eventually become less prevalent within the population?

Fri, 28 Oct 2011 15:02:38 UTC | #884947

DavidMcC's Avatar Comment 4 by DavidMcC

Comment 2 by glenister_m :

Extrapolating a bit too far, would this effect be seen with atheists and theists? If so, who is the predator and who is the prey??? (We see a lot of fear when theists ideas are challenged in some countries, but atheists must fear for their lives in others...)

It isn't fear, glenister. Insects don't get scared. Even when they fly aawy from something, it's a direct effect. No need for time-consuming enmotions. I think the reporter was just confused about "stress".

Perhaps we can instead extrapolate the poisoning effect! (But, as you say, which one would be the predator? :) )

Fri, 28 Oct 2011 15:03:38 UTC | #884948

davidpercival's Avatar Comment 5 by davidpercival

As the insects were not harmed themselves and didn't see any of the others harmed, they must be born with the fear of fish. It is already known that certain new born geese can identify the shadow of a predator bird from that of a harmless type.

Does this not imply that there is such a thing as "memories" which are inherited within a species by some means we are unaware of that are much more nuanced than simple instinct? It seems far fetched that there are genes that "know" the threat posed by other creatures.

Fri, 28 Oct 2011 15:17:06 UTC | #884957

jbkaffe's Avatar Comment 6 by jbkaffe

Maybe it's just a chemical reaction to big shapes from below. Shouldn't they react the same way in interaction with birds otherwise? ( Or maybe they do? )

DNA memory isn't at all farfetched in my book. The defintion of memory is a bit shady though. I think we need to establish some sort of consensus on the term "memory".

Any bids anyone?

Fri, 28 Oct 2011 15:27:57 UTC | #884966

drumdaddy's Avatar Comment 7 by drumdaddy

Compromised nymphs? Damselflies in distress? What's going on out there? Sounds fishy to me.

Fri, 28 Oct 2011 15:29:24 UTC | #884967

Vorlund's Avatar Comment 8 by Vorlund

I'm not convinced or at least not convinced that stress in this context is 'fear'.

It may be that the dragonfly, aware of the presence of the predator is preoccupied watching its back at the expense of survival activities like catching their own food. In the wild a predator would not be present all the time, when one appears the dragonfly need only fly away and continue its own livelihood.

Fri, 28 Oct 2011 15:49:43 UTC | #884976

Schrodinger's Cat's Avatar Comment 9 by Schrodinger's Cat

Comment 5 by davidpercival

As the insects were not harmed themselves and didn't see any of the others harmed, they must be born with the fear of fish. It is already known that certain new born geese can identify the shadow of a predator bird from that of a harmless type.

Does this not imply that there is such a thing as "memories" which are inherited within a species by some means we are unaware of that are much more nuanced than simple instinct? It seems far fetched that there are genes that "know" the threat posed by other creatures.

Not necessarily. If recognising a particular type of shadow had survival value then what starts out as a vague response to shadows would be honed by natural selection. Those birds more able to recognise a predator shadow would be those more likely to survive and pass on their genes.

A lot of what appears as 'memory' being passed on is probably similar.

Fri, 28 Oct 2011 17:26:24 UTC | #885012

Premiseless's Avatar Comment 10 by Premiseless

Not one area I consider likely to be utilised any time soon for technological advantages.

Fri, 28 Oct 2011 17:43:54 UTC | #885019

SpEcImEn128's Avatar Comment 11 by SpEcImEn128

Comment 3 by JuJu :

If larvae are stressed to the point of death prior to metamorphism doesn't that mean they aren't surviving long enough to pass on their genes? So wouldn't that characteristic eventually fade out based on the principles of natural selection? And wouldn't the ones that don't stress out to the point of death, or lack of development, be the ones that survive to breeding age and spread the genes that don't exhibit theses behaviors. Rather wouldn't they spread the genes that allowed them to avoid that fate in order for the species to survive. Wouldn't the genes that code for stressful dying eventually become less prevalent within the population?

They are stressed to the point of death in THAT specific environment, not in the wild. Stress is adaptive in natural conditions, it makes them stronger, faster and heal quickly (increased cellular growth) to the expense of their health... It's a tradeoff

Fri, 28 Oct 2011 18:25:57 UTC | #885034

Neodarwinian's Avatar Comment 12 by Neodarwinian

Possibility of over buildup of stress in the artificial conditions of the experiment.

Fri, 28 Oct 2011 19:24:18 UTC | #885055

Stevezar's Avatar Comment 13 by Stevezar

Comment 6 by jbkaffe :

Maybe it's just a chemical reaction to big shapes from below. Shouldn't they react the same way in interaction with birds otherwise? ( Or maybe they do? ) DNA memory isn't at all farfetched in my book.

In my book it is waaaay beyond the pale. There isnt nearly enough bits of encoded information in DNA to provide for a memory.

Sat, 29 Oct 2011 03:28:46 UTC | #885143

Functional Atheist's Avatar Comment 14 by Functional Atheist

I wonder if this is related to the rise of consciousness. Not that the dragonflies or their larvae in this study are consciously aware that they are stressed, but there's something in the gap from purely chemical reactions to stimuli to reactions that are based on purely chemical information that is suggestive.

It reminds me of the experiments where houseflies are subjected to electrical shocks and behave irritably. I'm not saying the shocked houseflies are consciously aware that they are irritated, but they are somewhere along a continuum that begins with purely chemical reactions to stimuli.

Perhaps irritable behavior is the beginning of the capacity to feel irritated, and feeling irritated is the beginning of the capacity to be aware of being irritated, and being aware of being irritated is a form of consciousness.

Insects probably do not have consciousness, but sometimes, as in this study, they seem to be somewhere on the pathway that eventually leads to consciousness.

But perhaps I'm just being irritating. Would somebody please pass me the bong?

Sat, 29 Oct 2011 06:11:11 UTC | #885154

jbkaffe's Avatar Comment 15 by jbkaffe

The magic reality of an irritably buzzed dragonfly: The early years...... bong passed. :-)

In my book it is waaaay beyond the pale. There isnt nearly enough bits of encoded information in DNA to provide for a memory.

Granted, It's a bit out there, but I think you could describe DNA as a sort of memory in itself. Or as precoded bits of information under development.

Edit: Nature's memory I guess...

Sat, 29 Oct 2011 13:17:31 UTC | #885195

Greyman's Avatar Comment 16 by Greyman

Comment 3 by JuJu :

If larvae are stressed to the point of death prior to metamorphism doesn't that mean they aren't surviving long enough to pass on their genes? So wouldn't that characteristic eventually fade out based on the principles of natural selection? And wouldn't the ones that don't stress out to the point of death, or lack of development, be the ones that survive to breeding age and spread the genes that don't exhibit theses behaviors. Rather wouldn't they spread the genes that allowed them to avoid that fate in order for the species to survive. Wouldn't the genes that code for stressful dying eventually become less prevalent within the population?

Not entirely.  Remember that larvae not stressed by predators are more likely to be eaten.

Mutation rates are also increased by stress.  Organisms in hazardous environments are thus more likely to produce offspring with an adaptive mutation if they are stressed by the situation.  It also increases the chance of deleterious mutation, but in situation where offspring survival is threatened anyway it becomes a viable desperation gamble.  Where as the survival of offspring in safe environments is more likely if they maintain the genetic status quo.

Thus there's a selection pressure towards a certain level of stress response.

Sat, 29 Oct 2011 15:32:39 UTC | #885218

DavidMcC's Avatar Comment 17 by DavidMcC

No evidence has been presented here that the smell of fish has a psychological effect on the dragonflies. More likely, it is a directly toxic stress, but the article is ambiguous, so everyone (including the physorg reporter) assumes that it is psychological stress.

Sat, 29 Oct 2011 15:46:51 UTC | #885220

cheesedoff17's Avatar Comment 18 by cheesedoff17

The experiment shows that prolonged stress from which the insect/human cannot escape will have detrimental effects on the health said individual. This can be seen in humans everyday within family or workplace situations. Yes, stress is life threatening.

Sat, 29 Oct 2011 18:14:22 UTC | #885244

JuJu's Avatar Comment 19 by JuJu

Comment 16 by Greyman

Not entirely. Remember that larvae not stressed by predators are more likely to be eaten.

Being stressed to the point of fleeing or doing something else that doesn't get you killed is quit different from dying right on the spot or not developing at all because of stress. Dying of stress doesn't pass on any more successful genes than getting eaten.

Mutation rates are also increased by stress. Organisms in hazardous environments are thus more likely to produce offspring with an adaptive mutation if they are stressed by the situation.

Ones that die prior to having offspring because they were stressed to death don't have offspring. Is there any evidence that an organism in a stressful environment will have an increased mutation rate? Won't the rate of mutation and variation remain the same? Its the ones that don't stress to the point of death, the ones that have what it takes to avoid that scenario who survive and at least have a chance at having offspring.

Being in an environment where predators are close by will give an organism who just happens to have a genetic make up capable of avoiding death prior to having offspring a better chance at survival. That's just natural selection 101.

Being in an environment where predators are close by causing the death of an organism prior to having offspring will cause something like one of these scenarios:

  1. None of the organism have a variation or mutation that allows them to survive past this fatal stress period, so the ones with that genetic make up die off. And the fatal stress genes will become less and less common.

                                           -or-
    
  2. A few of the organisms are lucky enough to have a variation or mutation that allows them to survive and it gives them a way to avoid the fatal stress period, so they survive and have offspring that also have this genetic trait. And the genetic trait that causes fatal stress will become less and less common among the population.

Either scenario will cause the fatal stress characteristic to become less and less common.

Sun, 30 Oct 2011 00:30:46 UTC | #885322

JuJu's Avatar Comment 20 by JuJu

This being an experiment that places the insect in an artificially created scenario that the insect might not often find itself in nature is the best explanation for this behavior. This experiment shows us nothing about natural selection, its just an interesting observation that has been relayed to us.

Sun, 30 Oct 2011 00:43:01 UTC | #885323

DavidMcC's Avatar Comment 21 by DavidMcC

The nature of the "stress" might be bettter understood by a combination of determining whether it is the sight or smell of the predator that affects the insect's life. My bet is that it is the smell, because that could be toxic. I doubt that it is mere sight, because insects probably don't have enough neurons to get worried about things. Repeating the experiment with the fish hidden from view, but not from smell, would help. Of course, even if it is only smell that matters, any direct toxicity effect has to be determined, because the smell alone might be enough to "worry" the insect, if it is capable of getting worried.

Sun, 30 Oct 2011 08:44:49 UTC | #885348

Itseasyifyoutry's Avatar Comment 22 by Itseasyifyoutry

Comment 5 by davidpercival :

As the insects were not harmed themselves and didn't see any of the others harmed, they must be born with the fear of fish. It is already known that certain new born geese can identify the shadow of a predator bird from that of a harmless type. Does this not imply that there is such a thing as "memories" which are inherited within a species by some means we are unaware of that are much more nuanced than simple instinct? It seems far fetched that there are genes that "know" the threat posed by other creatures.

The occipital lobe is part of the cerebral cortex. Something like a visually triggered reaction to the complex image of say a common predator's shadow or sharp teeth might indicate the potential for a kind of inherited conscious visual memory. One of the cardinal evolutionary purposes of the cerebral cortex was to store extragenetic information gained following birth and passed on to the next generation during the course of a human life. However, there are clearly other prewired complex functions of consciousness which we are born with. It's a very interesting subject.

Tue, 01 Nov 2011 05:59:09 UTC | #885875

Jessiperite's Avatar Comment 23 by Jessiperite

I doubt the smell is toxic. That's fairly silly.

I'd say the result of this experiment is fairly easily explained.

This is an unnatural situation for the insect.

Evolution doesn't deal well with usually novel situations immediately. It takes generations to adapt.

Essentially the insect evolved to detect predator signs and to "become stressed" to get the hell outta there and watch itself.

But since this situation is forcing the insect to be continually stressed (it probably eats up more energy and forces whatever the insect has that mimics adrenaline to be constantly released)

Like overstressing a car motor pulling a trailer it was not designed to pull, for long distances.

The insect is not smart enough to figure out it is not in danger, just as a bee hive can overreact to be touched. It just reacts, like a little robot, to an unnatural situation. (CONSTANT predator stress, in nature, the insect would naturally either escape, or be eaten, not the constant middle ground)

Tue, 01 Nov 2011 06:49:12 UTC | #885880

DavidMcC's Avatar Comment 24 by DavidMcC

Comment 23 by Jessiperite

I doubt the smell is toxic. That's fairly silly.

Only as "silly" as the smell of burning rubber (when caused by actual burning rubber) being toxic to humans. My point was that the word "fear" was put in by the physorg journalist, not by the actual researchers, who only used the word "stress". The word "stress" does not necessarily mean what the journalist evidently thought it meant. Poisons in the environment are a "stress", and the emissions of the fish could be poisonous to the insect, as an alternative to causing it to "worry". It has never been shown that insects "worry" about stuff, but it is known that they can be poisoned. Therefore, both possibilities should be investigated, as I have suggested above.

Tue, 01 Nov 2011 09:15:44 UTC | #885895

DavidMcC's Avatar Comment 25 by DavidMcC

Here's an article that explains the confusion as being the result of applying the word "stress" to mean both "eustress" and "distress": Selye: eustress and distress

Tue, 01 Nov 2011 10:30:52 UTC | #885908

DavidMcC's Avatar Comment 26 by DavidMcC

An example of the difference between eustress and distress from my own childhood: When I was a kid, I sometimes messed around in the backyard, occasionally doing stupid things like burning plastic. When I did that, I was subjecting myself to "eustress", but did not suffer "distress", because I didn't know that I was slowly poisoning myself. Thus, the dragonfly might well suffer "eustress" from the "smells" emitted by the fish, and have a shorter life as a result, if they happened to be toxic, but it is not clear whether it was even capable of suffering "distress", which was not demonstrated merely by the shortened lifespan.

Tue, 01 Nov 2011 10:43:02 UTC | #885910

DavidMcC's Avatar Comment 27 by DavidMcC

... One final point: there is no mention in the article of the flies even trying to fly away from the predator. This suggests to me that they were not distressed. This only leaves eustress as the cause of the shorter lifespan, unless there's something we're not being told about the insects' behaviour.

Tue, 01 Nov 2011 13:57:52 UTC | #885961

Alan4discussion's Avatar Comment 28 by Alan4discussion

@OP - In a second experiment, 11 per cent of larvae exposed to fish died as they attempted to metamorphose into their adult stage, compared to only two per cent of those growing in a fish-free environment. "We allowed the juvenile dragonflies to go through metamorphosis to become adult dragonflies, and found those that had grown up around predators were more likely to fail to complete metamorphosis successfully, more often dying in the process," says Rowe.

..

Comment 27 by DavidMcC

... One final point: there is no mention in the article of the flies even trying to fly away from the predator. This suggests to me that they were not distressed. This only leaves eustress as the cause of the shorter lifespan, unless there's something we're not being told about the insects' behaviour.

The point being missed, is that - The young nymphs develop under water, and the adults fly above it. - http://www.naturegrid.org.uk/biodiversity/invert/dragnfly.html, so the issue of nymphs flying away does not arise. They are aquatic and cannot fly. They only emerge in metamorphosis to the flying adult form ( with some dying in the process).

I think the points made @23 by Jessiperite are valid. In their immature aquatic stage the nymphs would be hard wired to flee and hide from large predators, so if kept in view of, or near predatory fish without the chance to flee and hide (under rocks), they would be stressed or distracted from feeding and growing normally.

They eat: other animals. Both dragonfly adults and nymphs are carnivorous.

The nymphs eat lesser water boatmen, pond snail eggs, water fleas, bloodworms and even newt larvae and small fish. Dragonfly nymphs, have a special hooked "mask" which can be shot forward to catch their prey.

As active predators themselves they would be evolved to identify prey and avoid predators which would threaten them. Size would be a major issue with fish! The nymphs have to hunt or ambush prey to feed.

Sat, 12 Nov 2011 23:23:28 UTC | #889725

DavidMcC's Avatar Comment 29 by DavidMcC

Alan, sorry I was fooled by the picture of an adult dragonfly in the OP! As a result of the picture, I didn't notice that the text said they were using nymphs, which you rightly say are aquatic. Therefore, the problem remains one of the inherent ambiguity of the term "stress". AFAIK, it is still not known whether insects suffer from too much worry, or whether predatory fish poison their prey slightly.

Mon, 14 Nov 2011 15:00:09 UTC | #890071

DavidMcC's Avatar Comment 30 by DavidMcC

... OK, maybe the nymphs rely entirely on camourflage to protect themselves from predatory fish, but that was not stated either.

Mon, 14 Nov 2011 15:21:32 UTC | #890079