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  Topic: old article of mine, ontogenetic color change in fishes< Next Oldest | Next Newest >  
sir_toejam



Posts: 846
Joined: April 2005

(Permalink) Posted: Mar. 06 2006,18:25   

Well, after years of thinking about it, I finally started encoding all of my old articles digitally.

Here's the very first article i ever published (I did the work as an undergrad at UCSB, and published it when I got to Berzerkely a couple of years later).

It's short, so anybody interested shouldn't get too bored.

http://home.earthlink.net/~tjneal/articles.html

Kudos to anyone who can determine the primary flaw in the experimental design.
(hint: it's a one-word answer, and to get kudos you should be able to get it BEFORE you get to the discussion section.)

The study of ontogentic color change in damselfish was my thesis topic back when i was a grad student.  What was really nice about it was that most damselfish are tropical, so it took me to some rather nice locales like Tahiti, the Carribean, Mexico, etc.

It's still quite an interesting topic to me, especially from an evolutionary standpoint, so feel free to jump in if you find yourself interested in the topic as well.

I also threw in a link to Ken Miller's popular Ohio talk for those that hadn't seen that yet.

cheers

edit (5/17):

hmm, i suddenly realized readers here probably haven't a clue what these guys look like, nor what the color differences are.  I'd post my own pics, but I have as yet not converted them from the old slides to digital, so:

http://www.oceanlight.com/lightbox.php?sp=hypsypops_rubicundus

some good examples there.

  
Alan Fox



Posts: 1391
Joined: Aug. 2005

(Permalink) Posted: Mar. 30 2006,02:50   

Quote
Kudos to anyone who can determine the primary flaw in the experimental design.
(hint: it's a one-word answer, and to get kudos you should be able to get it BEFORE you get to the discussion section.)


I can't spot the answer. Can anyone else or will Sir T. enlighten us? (Cute outfit by the way)

  
Wesley R. Elsberry



Posts: 4807
Joined: May 2002

(Permalink) Posted: Mar. 30 2006,03:38   

The item in the methods section that I saw as a problem was that the group of treatment fish was so small. I see that in the discussion, you note that specific thing as a reason to treat all results as preliminary. But I didn't see a way to state that in one word, so I think you must be referring to something else.

--------------
"You can't teach an old dogma new tricks." - Dorothy Parker

    
stevestory



Posts: 10127
Joined: Oct. 2005

(Permalink) Posted: Mar. 30 2006,03:42   

but how much ontogenetic depth do the damselfish have?

   
sir_toejam



Posts: 846
Joined: April 2005

(Permalink) Posted: May 17 2006,10:51   

Quote (Wesley R. Elsberry @ Mar. 30 2006,09:38)
The item in the methods section that I saw as a problem was that the group of treatment fish was so small. I see that in the discussion, you note that specific thing as a reason to treat all results as preliminary. But I didn't see a way to state that in one word, so I think you must be referring to something else.

ack! sorry for being so long answering the response; I was gone for a while and hadn't seen any responses for at least a couple of weeks prior, so i figured there hadn't been any interest and forgot all about it.

you're red hot, but you must have covered the answer with your foot :)

not just small, but singular!

only one treatment fish of each type was used.

the term I'm sure you recognize for this is:

"pseudoreplication".

for those unfamiliar with the term, it basically refers to an experimental design where there are multiple variables, but one or more of them is insufficiently replicated within the design of the experiment.

for a more in depth discussion of what this is and the prevalence of it in the literature, here's an abstract of a nice little review paper (which i was forced to read by my advisor after i published that paper :) ):

http://www.esajournals.org/esaonli....ge=0187


In this specific case, there are two primary variables we are looking at, the behavior of the adults, and the color of the treatment fish.

to control for randomness (and help control for other potentially competing variables), we replicate, of course, and the adult subjects were replicated (sufficient at least for a non-parametric analysis - ask if you want me to elucidate the difference between non-parametric and parametric), but the treatment fish were not.  This introduces the possibility that the specific treatment fish may have been abberations.

Ideally, in a better design we would replicate the treatment fish as well, in order to control for this.  

The only justification for non-replication of treatment fish in this experiment was that prior to this study, most all similar studies of this type were conducted with painted model fish (again, no replication).  I figured at the time that the general color of the animal was the most likely trigger for variable behavior in the adults (that's what I was testing, after all), but of course in hindsight, there were other possibilities....

any guesses?

and, thanks for expressing interest.  always nice to know someone read it.

cheers

  
sir_toejam



Posts: 846
Joined: April 2005

(Permalink) Posted: May 17 2006,11:00   

Quote (stevestory @ Mar. 30 2006,09:42)
but how much ontogenetic depth do the damselfish have?

well, since it's a made up term by a bunch of confused pseudobiologists...

I'll say it's got a whole lot of "OD".

let me see if i can make up something to justify that (note that the following IS essentially correct and accurate, I'm just playing with the interpretations to smear the innocent >: ) )...

hmm...

OK Pomacentridae (the family that damselfishes belong to), is a highly diverse family with lots of genera and species, that exhibit a wide range of morphology and behavioral "sophistication".

some exhibit parental care, and others even have a limited form of "agriculture" (they selectively farm single algae species within their territories).

If I understand what Nelson was getting at (I rarely do, so please feel free to correct me), the development of such sophisticated behavior would indicate significant ontogentic depth in general within the family.

how's that?

  
BWE



Posts: 1898
Joined: Jan. 2006

(Permalink) Posted: May 17 2006,13:12   

By the way, I am still reading that paper you wrote and I am curious whether you tried to measure any of the wild responses as a control group. i.e. did you watch an event in the wild and then try to recreate it with your fishy in a baggie? And if so, did you set up a categorization system for natural responses that was separate from your experimental response? -(what did you do to control for the effect of the baggie and the observer)

-I appologize if you cover that toward the end, I haven't quite finished yet.

--------------
Who said that ev'ry wish would be heard and answered
When wished on the morning star
Somebody thought of that, and someone believed it
Look what it's done so far

The Daily Wingnut

   
sir_toejam



Posts: 846
Joined: April 2005

(Permalink) Posted: May 17 2006,13:54   

Quote (BWE @ May 17 2006,18:12)
By the way, I am still reading that paper you wrote and I am curious whether you tried to measure any of the wild responses as a control group. i.e. did you watch an event in the wild and then try to recreate it with your fishy in a baggie? And if so, did you set up a categorization system for natural responses that was separate from your experimental response? -(what did you do to control for the effect of the baggie and the observer)

-I appologize if you cover that toward the end, I haven't quite finished yet.

good questions.

In general "wild" observations are only covered in passing, as it was a very short paper.

the entire experimental design was actually based on watching interactions in the wild to begin with.  It was an attempt to control other variables aside from color variation in determining adult response behavior.

typically, juveniles dive into holes too small to follow when adults start chasing them, so you don't get much time to quantify what the actual behavior toward various color patterns is.  However, my personal observations tended to agree with the results of the experiments; adults didn't appear to be any less aggressive toward juveniles (in bags or not) than they were toward other adults that wandered into their territories.

yes, controls were conducted with empty bags; this is mentioned in the methods section.

"seperate from the experimental response"

could I ask you to clarify what you mean here?  thanks.

feel free to fire away; it's always an ego boost to discuss one's own work, even if it was an age ago and full of fun little blunders ;)

on a related note, it would be fun to discuss the evolutionary implications of the preferred "habituation hypothesis" of Thresher at the time I published this work.  I always had some theoretical issues with this.

How on earth would a color pattern that reduces adult aggression evolve to begin with?  what would favor it?

think about it:

in a population of individuals with no likely degree of relatedness, what would be the advantage to an adult to reduce it's level of aggression towards a juvenile?

Moreover, preliminary diet studies indicated that there is overlap in resource utilization between adults and juveniles (not for nest space of course), but at least for food.  There was also some indication that juveniles can be egg thieves from time to time.

It was this hypothesis that i was most deliberately attempting to refute with this design.  

As far as i know, this was the very first study to attempt to actually quantify and test adult aggression towards juveniles in this fashion, such as it was.

  
sir_toejam



Posts: 846
Joined: April 2005

(Permalink) Posted: May 17 2006,16:03   

i added a link to some pics of these guys in the original post.

  
BWE



Posts: 1898
Joined: Jan. 2006

(Permalink) Posted: May 18 2006,05:48   

The only serious tropical diving I have done is around the florida keys and I was way more interested in the barraccuda than the various reef fish but one thing occurred to me on my last trip there. I was diving with a guy who had been diving the area for a long time (He was a little older than me), who said that color in general of the various reef fish changed with the health of the reef. Especially with the prevalence of large fish. He didn't have any data to back up the assertion but he has been diving the area for a long time so I assume that there is some sort of phenomena he has observed. He claims that brighter reds tend to give way to muted oranges and yellows tend to give way to yellow blotches as a reef loses health. (same fish, different colors)

Your piece got me thinking. What do the adults see? Not that there is an answer to the advantages but maybe the adults have a harder time recognizing the juveniles as fast. You could design an experiment to determine response times for adults to react to different colored juveniles.

I guess that would fall under the same heading that other reef biologists have been studying for some time -"why the color?"-

IIRC, A guy in Australia analyzes the spectrums that different fish see and concluded that the damsel types and other, smaller fish see more UV than larger fish. Maybe it changes with age too?

-Funny aside, the fist time I went there, I brought my 6mm wetsuit and hood. Why, I don't know. But it gave me a chuckle every time I came back to the hotel and saw it lying there.

--------------
Who said that ev'ry wish would be heard and answered
When wished on the morning star
Somebody thought of that, and someone believed it
Look what it's done so far

The Daily Wingnut

   
sir_toejam



Posts: 846
Joined: April 2005

(Permalink) Posted: May 18 2006,09:41   

Quote
What do the adults see?


indeed.  not just the adults, what about predators?

colors that look like bright blue spots to us, might look black to a predator, or neutral gray.

think leopard spots, tiger stripes, etc.

I tend to lean towards more simple explanations of camouflage these days to explain OCC; but it's VERY hard to gather evidence to attempt to refute this to begin with.

example:

how would you gather conclusive evidence to refute the idea that a leopard's spots help to camouflage it from its prey (or potential predators - yes, lions will kill leopards, for that matter)?

you'd have to know something about the way the common prey animals process their surrounding visually, and maybe even paint a few leopard's spots out to see if it has a direct effect.

not easy.

John Endler has been doing a lot of excellent work on this question lately in fish.  I've half thought about getting another degree and apply to his lab.

money is always the issue, tho.  It's really hard to get money to study this kind of thing, interesting tho it might be to some.

as to reef fish changing color...

many fish can radically alter their coloration on short time scales.

if you ever get the chance, try doing a night dive and a day dive in the same area and you will see great differences in not only the species assemblage, but also the colors of many of the individuals that are present at both times.

parrotfish, for example, can look like a totally different species when they are "sleeping".  

diet can also have an effect on fish color.  in reefs that are shifting away from live coral and more towards dead coral with algae (common in the tropics these days), this will result in some shifts in diet which can affect color.

note that these issues are entirely different than OCC, just to be clear.

Quote
I brought my 6mm wetsuit and hood.


lol.

a full 6 mm?  that would be a bit toasty.

I often wear a full 3 mm suit in the tropics if I'm doing a lot of diving.  around 30 feet plus, the water ain't THAT warm.  Even at 80 f, your body is still losing heat pretty fast without a suit on.

I did some snorkelling off the keys last year (near key West and a bit south of Largo); is that where you were?

  
BWE



Posts: 1898
Joined: Jan. 2006

(Permalink) Posted: May 18 2006,12:05   

Key Largo, coral reef state park. I have relatives in Jupiter (West Palm Beach) and that's where we go. It's closer.

To select for OCC, spectrum is my best guess. Imagine a creature that can see infra-red and babies that develop exceptionally good insulation. Wouldn't matter where the babies ended up.

That is the luxury of grad school: You are ok with being crushingly poor.

And in Puget sound and the Pacific off Oregon Washington, 6mm feels pretty thin.

--------------
Who said that ev'ry wish would be heard and answered
When wished on the morning star
Somebody thought of that, and someone believed it
Look what it's done so far

The Daily Wingnut

   
sir_toejam



Posts: 846
Joined: April 2005

(Permalink) Posted: May 18 2006,12:24   

meh, still takes money to do research.  Most of my research grants were just big enough to pay my food and lodging expenses; well short of funding my research needs.

Even at Berkeley, the school had little money left to fund the basic research of its grad students ( I think MAYBE i got about 400.00 year for basic research from Berkeley as a grad student there - and even that was competetive).

NSF found my proposal to fund research in OCC worthy of merit (it won some kind of award that i can't recall now), but not enough to warrant any significant monies.

OCC is the kind of research that could occur in an already well-funded lab (like Endler's), or if one was independently wealthy already (tried that too, btw - ask if you want to know that sad story)

I've since become more interested in trophic interactions within specific ecosystems, and models for fisheries management.  More money for that, but I never did lose my interest in OCC.  I suppose I'll get back to it someday (heh, reminds me of exactly the words Ron Thresher used when i first spoke with him 15 years ago).

responses to thoughts:

infrared would be pretty useless underwater; it gets absorbed quite rapidly, but i get where you are going with the idea, and yes, spectral analysis and pattern analysis is where folks in this area are going these days.

cold in puget sound?  you don't have to tell me :)

It's even cold in Monterey (average around 50 f).  I have a 7 mm full suit with johns and coat for Monterey.  Is a 6 mm enough for Puget Sound?

I'd be thinking dry suit at that point.

ever get hit by one of those fire sponges when you were in FLA?

####, i hate those things!

  
BWE



Posts: 1898
Joined: Jan. 2006

(Permalink) Posted: May 18 2006,12:39   

I have a dry suit. I brought the 6mm because the dry suit would be too HOT! hahahaha. I do use the wetsuit sometimes though. There is a marine park off Muckelteo where some of the giant octupi hang and Puget Sound warms considerably in the late summer. (I'm thinking ~55F?)

I was thinking terrestrial with infrared. Just that I couldn't think of what you might see with UV.

I chose my thesis to ride on someone else's grant money because I was lazy and because it was fun and because I was quite poor. I had seven 80 gallon tanks to tend! Only a few boat trips even necessary.

No fire sponges but I got a small nick from a stingray and owww owwww owww they hurt. I felt like achilles. Lots of Barraccuda down there. I don't know how people ever get used to that. Now you see em, now you don't.

--------------
Who said that ev'ry wish would be heard and answered
When wished on the morning star
Somebody thought of that, and someone believed it
Look what it's done so far

The Daily Wingnut

   
sir_toejam



Posts: 846
Joined: April 2005

(Permalink) Posted: May 18 2006,12:56   

55? why that's positively balmy! don't see why you'd even need a wetsuit ;)

speaking of UV, I'm sure you have at some point seen one or more of those nature proggies on TV that show how a bee "sees" by using a computer enhanced image showing UV reflections from flowers, etc?

When i was in grad school, it was thought that UV was, like infrared, essentially not utilized underwater because of rapid absorption.  However, since then it's become clearer that not only does UV penetrate further than previously thought, but there are now documented visual pigments indicating utilization of UV in several marine animals.

er, that's a long-winded way of saying, yeah, UV might be important.

as to grad school; yeah my life would have been MUCH easier had i chosen to work on cichlid behavior with my major prof.

I only have my own ego to blame :)

hmm, i think i have some pics i took of barracuda when i was in the carribean; impressive critters, no doubt.

I'll see if i can dig one up.

...

ahh, here we go:

http://home.earthlink.net/~tjneal/barracuda-1b10x7.jpg

I took this in Cozumel, but it's the same species as the ones in FLA.

  
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