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Current Theory on Gold Dorsal Spot on Top Minnows?


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#21 gerald

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Posted 09 November 2017 - 12:45 PM

Anybody got Gene Helfman's "Diversity of Fishes" ?  That might have some answers.

But of course wild speculation is way more fun.


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#22 centrarchid

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Posted 09 November 2017 - 12:47 PM

I have a parietal eye, as do you.  Some other purpose unless the gold is shielding.


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#23 Matt DeLaVega

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Posted 09 November 2017 - 05:47 PM

Maybe the gold is it? Packed with cells that notice dark and light and detect shadows. I like all theories on this. It is all interesting. Too coincidental to ignore that it falls on the location of parietal eye. Might serve multiple functions. I suspect that no matter the ultimate purpose, that it evolved from a useful parietal eye. Look up studies.There is proof that they do more than influence circadian rhythms in certain species. They pick up shadows and alert to overhead danger. Where it could have gone from there, who knows. I think it would be just as cool if it hypnotizes or confuses predators. 

 

Wish I had a copy of the book Gerald suggests if it could shed some light.


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#24 centrarchid

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Posted 09 November 2017 - 05:54 PM

What about where the gold is on back as well.


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#25 lilyea

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Posted 09 November 2017 - 09:39 PM

Anybody got Gene Helfman's "Diversity of Fishes" ?  That might have some answers.

But of course wild speculation is way more fun.

 

I have the book but from a quick scan of the index and the chapter "fishes as prey" I didn't notice any answers.  With a more thorough scan more relevant info may be present in the Helfman text.

 

Could it be related to there "sun compass"?



#26 Matt DeLaVega

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Posted 10 November 2017 - 08:35 AM

What about where the gold is on back as well.

Not as common on the back as on the head. Once your first question is answered, it would hopefully shed some light on this question.

 

Anyone have the ability to look at one under a microscope?

 

Lilyea- If it is in fact a parietal eye, then "sun compass" is one of they current theories. Why is it so developed in Fundulus though?


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#27 gerald

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Posted 10 November 2017 - 11:17 AM

For navigation around their home range, I'd guess.  They appear to travel a whole lot more than mosquitofish do, from my observations.   And being egg-layers, males might have established spawning sites (maybe several?) that they need to navigate to.  Perhaps they have multiple spawning sites far apart based on sun exposure at different times of day???  Also, Fundulus are remarkably adept at responding quickly to overhead shadows/threats.  I can corrall them with a big seine, but trying to catch them with a dipnet or 4x4 seines rarely works except when they're hiding in vegetation or leaf piles.

 

Lilyea- If it is in fact a parietal eye, then "sun compass" is one of they current theories. Why is it so developed in Fundulus though?


Gerald Pottern
-----------------------
Hangin' on the Neuse
"Taxonomy is the diaper used to organize the mess of evolution into discrete packages" - M.Sandel


#28 Matt DeLaVega

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Posted 10 November 2017 - 03:54 PM

Excellent. I think you have sound theories there. But no matter what, it does make me want to go straight to question 2) why on backs? Centrarchid goes straight to question 2 and you brought it up. Something to it. Possibly it proved functional in other ways, and these fish will be gold all across the dorsal in 100k years. That was just an extreme example. It seems that it must fulfill another purpose as well.

 

This is the coolest topic brought in a bit.


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#29 gerald

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Posted 10 November 2017 - 05:47 PM

Which others have a bright spot on the back, in fornt of dorsal fin?  F. rathbuni is the only one i've seen with a back spot.  Do some of the estuarine species have it too?


Gerald Pottern
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Hangin' on the Neuse
"Taxonomy is the diaper used to organize the mess of evolution into discrete packages" - M.Sandel


#30 centrarchid

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Posted 10 November 2017 - 06:38 PM

Fundulus dispar and Northern Studfish.  Some neotropical species also have the spots that are multiple and / or not over parietal area.


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#31 lilyea

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Posted 10 November 2017 - 08:15 PM

I believe that all five starhead topminnows have the gold dorsal spot and gold head spot:

  • Lined topminnow (F. lineolatus)
  • Southern starhead topminnow (F. notti)
  • Eastern starhead topminnow (F. escambiae)
  • Western starhead topminnow (F. blairae)
  • Northern starhead topminnow (F. dispar)

 

Page and Burr (1991) plate 29



#32 centrarchid

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Posted 10 November 2017 - 08:24 PM

More interesting than I thought.


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#33 Sho Bud

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Posted 10 November 2017 - 10:07 PM

I have kept Northern Studfish in an aquarium for 2 years now, along with 4-5 years of observation in the wild. The tops of their heads look like crystals and they have a gold stripe directly in front of the dorsal. In the wild, they move in fairly large groups of 20 or so fish until they spawn. When spawning, I see them pair up along sandy shorelines. I have never seen them using their pre-dorsal stripes to signal each other,in the wild or in the aquarium. I see them flaring out their throat-pouches,or blackening around their eyes and flexing their bodies and fins to communicate all the time. I have also observed them under UV light and the stripe disappears showing no patterns or anything.

#34 olaf

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Posted 10 November 2017 - 10:14 PM

I have also observed them under UV light and the stripe disappears showing no patterns or anything.

None that you can see, meaning none that give off visible (to humans) light when hit with UV. To eyes that can see UV there may be all sorts of craziness. Or nothing.


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#35 Sho Bud

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Posted 10 November 2017 - 10:21 PM

I'm not an insect. Only they know. The fundulus gold-stripe mystery is still that 😆🐜🐝🐟🐠

#36 centrarchid

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Posted 11 November 2017 - 05:19 AM

Most birds can see in UV.  That is reason birds that appear black to humans are a lot more interesting to a birds eye.


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#37 Sho Bud

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Posted 11 November 2017 - 08:22 AM

Perhaps the scale structure on the head is also for protection from being exposed so much at the surface. Concerning the pre-dorsal stripe, I know some minerals glow or show hidden patterns when exposed to UV light, but the fish did not react in that way. I conclusion, I have discovered that fish don't behave like rocks.🤓😝🙃😅😂

#38 Sho Bud

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Posted 11 November 2017 - 08:43 AM

I have a photo attached.

Attached Images

  • IMG_2396.JPG

Edited by Sho Bud, 11 November 2017 - 08:43 AM.


#39 centrarchid

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Posted 11 November 2017 - 09:07 AM

Looks like we are picking up on a detail not really given much thought.


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#40 Matt DeLaVega

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Posted 11 November 2017 - 09:08 PM

Yep, we are fully "Nerds".


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