Jump to content


Photo

Current Theory on Gold Dorsal Spot on Top Minnows?


40 replies to this topic

#1 centrarchid

centrarchid
  • NANFA Member

Posted 07 November 2017 - 08:19 PM

What is the purpose of this structure?  Communication between top minnows or entertainment for predators?  Something else?


Find ways for people not already interested in natives to value them.

#2 Matt DeLaVega

Matt DeLaVega
  • Board of Directors
  • Ohio

Posted 07 November 2017 - 10:00 PM

LOL. Funny that this is the first time I have seen this asked, I have no idea, and honestly surprised that we haven't discussed it.


The member formerly known as Skipjack


#3 mattknepley

mattknepley
  • NANFA Member
  • Smack-dab between the Savannah and the Saluda.

Posted 08 November 2017 - 06:18 AM

They're robofishes and the spots are solar cells for their batteries.

Great question. Like DLV, I'm surprised it hasn't come up before. If they traveled in tighter schools it might have served as a means to confuse predators from above, gold flashes going all different directions when the attack came. Perhaps they do work that way, somehow, like flash markings on certain frogs and other animals. Though why you'd want your defensive surprise on display from the beginning, and that close to your head and spine, I don't know...
Matt Knepley
"No thanks, a third of a gopher would merely arouse my appetite..."

#4 centrarchid

centrarchid
  • NANFA Member

Posted 08 November 2017 - 06:37 AM

I would like to simulate what I bird sees using a fancy camera and filters, just for fun.  I think there is a major surprise hiding.


Find ways for people not already interested in natives to value them.

#5 Chasmodes

Chasmodes
  • NANFA Member
  • Central Maryland

Posted 08 November 2017 - 08:38 AM

I was wondering the same thing... at first, I thought that they might be parasites, LOL.


Kevin Wilson


#6 Matt DeLaVega

Matt DeLaVega
  • Board of Directors
  • Ohio

Posted 08 November 2017 - 08:39 AM

Probably a well developed third or parietal eye that detects movement directly above.

 

They are very obvious on my monitor lizards, and they are also known in some fish species, though I haven't seen Fundulus listed.

 

Would be a good project no matter what it turns out to be.


The member formerly known as Skipjack


#7 gerald

gerald
  • Global Moderator
  • Wake Forest, North Carolina

Posted 08 November 2017 - 01:31 PM

I'm with Matt - the bright spot in the "starhead" group of Fundulus is probably related to the pineal "eye" organ.  But other species such as F. rathbuni have a bright spot just in front of the dorsal fin, not on the head.  Whazzup with that?

 

Another hypothesis:  Maybe the head spot (or back spot) is simply to announce:  "Don't hate me -- I'm NOT a Gambusia!"


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


#8 centrarchid

centrarchid
  • NANFA Member

Posted 08 November 2017 - 02:51 PM

I am betting money it is a signalling structure of some sort.  Either it helps ID conspecifics, confuses predators, or attracts flying eats to water surface.


Find ways for people not already interested in natives to value them.

#9 Matt DeLaVega

Matt DeLaVega
  • Board of Directors
  • Ohio

Posted 08 November 2017 - 04:58 PM

Either way it would be extremely interesting. It certainly could be a target. One that alerts the fish via peripheral vision in time to move from the target, also keeping the(say kingfisher) fixated on the target until that instant burst of power when the topminnow does what it does. Bam! disappears deep, or not, but does so blindingly quick.

 

I hope someone finds the ending to this story. If anyone considers this as a project or any other project, please remember our grant program. It is one of our most important endeavors.


The member formerly known as Skipjack


#10 mattknepley

mattknepley
  • NANFA Member
  • Smack-dab between the Savannah and the Saluda.

Posted 08 November 2017 - 05:09 PM

So you're thinking kind of like an early warning system, Matt? Could be.

What kind of signalling are you thinking, Centrarchid?
Matt Knepley
"No thanks, a third of a gopher would merely arouse my appetite..."

#11 centrarchid

centrarchid
  • NANFA Member

Posted 08 November 2017 - 05:30 PM

This problem looks kind of tough to crack.  Testing on birds would be difficult at best.  A tame bird would likely required.  I would like to sit and watch the fish for hours on end to make certain that something easier is not operating before pressing bird option.

 

 

Does anyone have a pet Green Heron I could borrow?


Find ways for people not already interested in natives to value them.

#12 Matt DeLaVega

Matt DeLaVega
  • Board of Directors
  • Ohio

Posted 08 November 2017 - 06:49 PM

Early warning if it is third eye. Or false target if the bird is so zoned in on the gold spot that it stays course even though the fish's peripheral vision has alerted it to overhead movement. Either way I believe it is an early warning to the fish. I can't imagine that it some how confuses birds as the fish starts moving. Heron, kingfisher, have both chosen targets before they move. They don't adjust much once they go for it. I bet it sees movement, or holds a birds attention long enough and strong enough that the fish can move away in an instinctive manner. Instinct says that bird attacks this point on my body, once I see it, I evade it in this manner. Gives the fish a reference point, that it doesn't know exists, but it's instinct recognizes that point. Makes sense to me, but i may be explaining it poorly.


The member formerly known as Skipjack


#13 itsme

itsme
  • NANFA Member

Posted 08 November 2017 - 11:02 PM

I like the attract insect prey hypothesis. Insects are attracted to lights for some reason, which also seems pointless. Anyway these fishes are clearly adapted to feeding on insects at the surface. And the one consistent feature of these spots is that they reflect sunlight. So act like a light emitter. How they would act as any kind of "eye" I cannot fathom.

#14 itsme

itsme
  • NANFA Member

Posted 08 November 2017 - 11:05 PM

They also, like other cryptic pigment patterns, break up the form of the fish's body, making them look like something other than a fish. Maybe so they can sneak up on insects?

#15 Michael Wolfe

Michael Wolfe
  • Board of Directors
  • North Georgia, Oconee River Drainage

Posted 08 November 2017 - 11:07 PM

I wonder if it is camouflage, looks like the glint of sunlight off the water.  Maybe makes the overhead predator think that the water is moving when it is not? 


Either write something worth reading or do something worth writing. - Benjamin Franklin

#16 itsme

itsme
  • NANFA Member

Posted 08 November 2017 - 11:09 PM

Now that I'm thinking on it, I'm wondering more if it serves as camouflage for a fish that lives at the surface, so is always visible, lacking the cover most fishes have of being well below the surface. So having pigments that attract attention away from the shape of the fish's body may be very adaptive from an evading-predators point of view. They're saying hey, I'm not a fish, I'm a little gold spot! Ha!

#17 Doug_Dame

Doug_Dame
  • NANFA Member

Posted 09 November 2017 - 01:19 AM

Fish got bling.

 

(Would be a good Far Side cartoon. Maybe it already was.)


Doug Dame

Floridian now in Cincinnati
 


#18 mattknepley

mattknepley
  • NANFA Member
  • Smack-dab between the Savannah and the Saluda.

Posted 09 November 2017 - 04:57 AM

Dang, Doug nailed it.
Matt Knepley
"No thanks, a third of a gopher would merely arouse my appetite..."

#19 centrarchid

centrarchid
  • NANFA Member

Posted 09 November 2017 - 07:07 AM

Gold spot might serve as a warning or somehow overloads brain trying to process what the fish is.  I think the spot is much more visible to other animals than it is to us.  Our visual system is dumbed down in some ways to take in more information in others.


Find ways for people not already interested in natives to value them.

#20 Matt DeLaVega

Matt DeLaVega
  • Board of Directors
  • Ohio

Posted 09 November 2017 - 12:29 PM

Zebrafish are known to have a parietal eye. Surely there are others.

 

Found this

Looks mosquito fishish

https://www.reddit.c..._aka_a_3rd_eye/


The member formerly known as Skipjack




Reply to this topic



  


0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users