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What's wrong with the foureye butterfly fish in Visual Explanations?

In the Boston class on 3/14, we were told that there was something wrong with the some of the fish on pages 114-116 of Visual Explanations. I've looked at the pictures quite a bit, but what's wrong is not obvious to me.

One possibility is that the diver on page 115 appears to be pointing with his thumb to a Spotfin butterflyfish instead of a Foureye Butterflyfish. Another is that the Foureye butterflyfish in the drawings on pages 114 and 116 show a black eye band while the eyeband in the pictures on page 115 looks iridescent to me, not black.

Am I on the right track or is the problem something else entirely?

-- Bruce Perry (email)


Response to What's wrong with the fish in Visual Explanations?

On pages 114-116 there are many foureye butterflyfish, nearly all of them very flatlandy in order to show clearly the side of the fish with the real eye and the large false eye. On page 116, I redesign the false eye, again on very flatlandy fish, and then suggest that the false eye is Nature's prank rather then a serious deceptive device.

Later I made a 2-sided cardboard cut-out of the foureye shown on page 116. When moving the cut-out around while it was hanging from a string, I realized that that the predator-view of a retreating foureye might well be 2 big moving flashing apparent eyes waving and weaving near the tail! That is, the 3-dimensional/moving view of a fleeing foureye might well be deceptive and scary to a predator. Fold a piece of paper in half and put big outlined eyes on each side of the fold near the edge and then open and close the paper, flap flap, to create a pair of exciting eyes.

I've been meaning to test this theory by pursuing foureyes with a video camera underwater but have not done so yet. All my earlier foureye butterflyfish images were still photographs usually depicting the flat side of the fish. Normally the way to do stupid underwater photography is to pursue the fish--better usually just to stay and wait for them--but this new foureye study needs to observe the tail of a retreating foureye. Someday I'll make and post a little video here.

The design point here of course is to be real careful about flatland and still-land thinking. Also still-water thinking. And to be careful about making inferences that might be true only in display flatland/still-land and possibily not true in 4-dimensional (3-space and time) life-space.

-- Edward Tufte


Response to What's wrong with the fish in Visual Explanations?

In this clip I found off Google (I ran it thru flash for this example) you can see what appears to be a blatant attempt to keep the eye first visible to a larger group of fishat the bottom right.

Then a fish starts giving it a hard time. Yo ucan then see our foureye blatantly put its false eye directly in view of the offending fish which immediately turns away from the false eye.

Takes a bit to load the first loop:

http://www.pixelplay.org/jeff/foureyefish/

Maybe I am reading to much into the events in the movie, but it does appear to be much more of an active defense system rather than a passive one. Just hoping the enemy will get confused is certainly not as initmidating as presenting some fear in your opponent.

But this clip obviously won't due. Multiple trips to the Bahamas is all that's needed.

-- Jeffrey Berg (email)


Response to What's wrong with the fish in Visual Explanations?

Wow! Thank you!

Theory practically confirmed by Kindly Contributor Jeffrey Berg's video.

I have all too many photo-stills of the the Foureye from behind (back in my naive fish-chasing days of dive photography), but for understanding motion, there is nothing like video (and still-land small multiples as well).

The Foureye Butterflyfish darts around a lot, increasing the flashing eye phenomenon, as can be seen in the video and as those who have chased Foureyes know. But we have to be careful here in producing "Just So" after-the-fact stories of animal behavior (and markings) to fit evolutionary explanations of survival strategies. So for a while it will be helpful to stick close to the visual data and to keep thinking of alternative explanations. For example, why just the Foureye? After all, the non-foureye butterflyfishes, and there are a great many, have also survived to this day. And what is the underlying population of butterflyfish with various markings that started out various times back when? Evolutionary strategies of survival may be the byproduct of all sorts of mutations in a "Hey let's try this" random strategy approach, to be a little sloppy about the language of purpose. It is so easy to drift into the language of purpose here; there is something of a rage-to-conclude in this business. The results seen today of "evolutionary strategies" might well be quite sloppy and random. Maybe someone who actually knows about these matters can contribute some advice concerning the appropriate empirical observations and the scientific logic of analysis.

There's much more to show on this topic and I'll try to put something together in the next week or two.

-- Edward Tufte


Response to What's wrong with the fish in Visual Explanations?

I doubt if I had watched the video without having first read your theory if I might have jumped to such a conclusion for sure.

I think we can also look to nature as a repetative and universal solution finding mechanism. That some solutions appear across environments and continents. In the case of body paint, often body paint such as this is designed as camouflage. Such genetic 'work' is painstakingly spent providing body paint that allows animals to blend with their environment.

But this fish is about as loud as it gets when it comes to visual noise. So I don't think it's trying to blend in with anything. There is body paint such as on birds meant to distinguish sex, and have some affect on mating. But in my own amature experience of watching to many discovery channel shows, it seems these efforts at body paint tend to be shiny, bright, colorful and complex. This is none of that. Although, we can't rule it out without many trips to the Bahamas or finding a Marine Biologist who might already know the answer.

Following genetic examples such as starfish and some octopus, we know body paint can emulate surroundings. So if it is copying something, what in the surroundings could this fish possibly be trying to emulate that could be worth its while in some way?

Here is an option,

Check out the eye on this Carribean Reef Shark:

-- Jeffrey Berg (email)


Response to What's wrong with the fish in Visual Explanations?

An aside, to be sure, just tangentially germaine to this thread: the U.S. Air Force did some experiments in the mid '80s by painting the underside of F-16s to simulate the markings and features of the upper side in hopes of seeing if this would give their pilots an advantage in dogfights. The thinking was that the duplicate markings would confuse an opponent's sense of the speed, direction and distance of the U.S. fighter, at least for a split second. Don't know the results but fighter jets are not currently painted this way in production.

-- Steve Sprague (email)


Response to What's wrong with the fish in Visual Explanations?

You can also look back further to the use of body paint as a method of confusion, decoy, and fear on a weapon.

For example:



The lack of this camouflage today may have more to do with the abilities of human preception and intelligence than anything else. Without cognitive front brain activity that allows us to make value judgements on our perceptions, such camouflage might have been more successful against a reactionary brain with less cogntition.

An interesting modern approach to note is the work in Optical Camouflage. Here is a group of students at the University of Tokyo who were working on some rudimentary Optical Camouflage with off the shelf equipment.

-- Jeffrey Berg (email)


Response to What's wrong with the fish in Visual Explanations?

As an evolutionary biologist, I'll take a stab at answering ET's query about testing hypotheses of adaptation. Such hypotheses may be suggested by obvious intuition (e.g. that eyespots imitate eyes), or may be very difficult to come by (e.g., it took centuries to figure out what the lateral lines of fish do [they are sense organs]). In evaluating such hypotheses, it is important to keep in mind various alternative explanations: that the supposed adaptation is merely fortuitous, that it is the correlated effect of some other feature of the organism (e.g. the red color of blood is a side effect of the presence of iron in hemoglobin), that it is merely an ancestral trait (e.g., skull sutures in mammals are NOT an adaptation to passage though the birth canal: our egg-laying reptilian ancestors also had them), that it is adaptive to something else, etc. Having come up with a suggested function, there are several ways to evaluate it. Among the first considerations are the morphological/behavioral complexity and genetic basis of the feature-- the simpler the trait, the more plausible is the alternative that the feature is fortuitous (by a mechanism known as "genetic drift"). Another early consideration is how the feature fits into the context of the ancestral condition-- the feature may an inheritance, rather than an evolved adaptation (as in the mammalian skull sutures above). Actual testing of the function can take several forms. One approach may be called the engineering approach. For example, based on hydrodynamics, a number of features of fish/dolphin/icthyosaur shape can be shown to be functional. The method of correlation seeks a correspondence between the feature and and the environmental circumstance it is supposed to be an adaptation to. For example, even if you knew nothing about hydrodynamics, the presence of flippers evolved independently in sea turtles, icthyosaurs, plesiosaurs, mosasaurs, marine crocodiles, seals, whales, sea otters, and manatees supports the idea that flippers are an adaptation to living in water. The method of variants is the most direct way of testing the effect of the feature. Sometimes, the feature varies naturally. For example, you can see if birds avoid eating red salamanders more than black salamanders. The feature can also be varied experimentally. For example, you can obscure a supposed warning coloration on a poisonous animal, or add a warning coloration to a delicious animal.

This just scratches the surface of a subject on which there is a long literature. For the butterfly-fish, I highly recommend Hugh Cott's classic "Adaptive Coloration in Animals" (Methuen, 1940), which includes a detailed discussion of concealment, advertisement, and disguise. The emphasis is on color, but behavior is also considered in relation to its use in making coloration effective. Prior to Cott's analysis, work on adaptive coloration swung between the most ridiculous just-so stories (e.g. flamingos are pink so as to blend in with sunsets when crocodiles look at them from the water's surface in the evening from the east) to arguments that the most detailed mimetic resemblances (e.g. of many insects to leaves and twigs) were merely chance resemblances that had no consequences for the organism. ET may also appreciate the use of line figures, tables, graphs and plates (one in color, the frontispiece, is a nice small multiple of sorts) in Cott's book.

For a look at the general principles involved in the study of adaptation, the starting point for contemporary discussions is George Williams' "Adaptation and Natural Selection" (Princeton University Press, 1966), where he takes the view that adaptation is an "onerous concept", and should only be invoked when necessary. Williams also has some later books on the subject ("Natural Selection", Oxford U. Press, 1992; "The Pony Fish's Glow", Basic Books, 1997). Not everyone would agree with all that Williams writes, but he has been very influential in determining what the issues are, and what alternative points of view imply. For a brief introduction, try the appropriate sections of Douglas Futuyma's "Evolutionary Biology" (Sinauer Assoc., 1997) or Scott Freeman and Jon Herron's "Evolutionary Analysis" (Prentice Hall, 2003); these are both current, comprehensive textbooks.

And the reason that fighter planes are dark above and light below is countershading, one of the oldest known of all principles of camouflage: it makes them harder to see from above and below (think of a fish seen from the bottom and the surface). The Air Force must have chosen concealment over advertisement

-- Greory C. Mayer (email)


This thread may be dead but...

An important notion to consider with fish and vision is that they often have a blind spot aft; therefore, if a fish has something behind it it needs to view, it must turn to one side or the other. This blind spot may explain some of the behaviour described in the video (which I was unable to view).

Further, it is a theory of reef fish coloration that they can take advantage of color to communicate because it is easy to hide from predators on a reef. Most other fish do not have this luxury and therefore must be muted in color, except for countershading.

-- Mike P (email)




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