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#1 LepomisAuritus

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Posted 21 December 2018 - 08:37 PM

I have been snorkeling for a while in my local river in southeastern PA (Delaware drainage), and I often see shield darter (Percina peltata) in the faster current. Last summer I found this specimen amongst some slower water in tree roots and I'm not sure if it is a shield or tessellated darter. Thanks for the help!

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#2 Matt DeLaVega

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Posted 22 December 2018 - 05:50 AM

Are greenside darters a possibility?


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#3 Fleendar the Magnificent

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Posted 22 December 2018 - 01:00 PM

Not a shield darter. They tend to have black spots in a band in their dorsal fin. However, it could be a tessellated or a Johnny darter. Those two seem to be nearly identical in head/body shape, coloration and with the little W or X markings on the sides. I can see that this one in the photo has a little "w" on it's side.



#4 LepomisAuritus

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Posted 22 December 2018 - 07:41 PM

Not a shield darter. They tend to have black spots in a band in their dorsal fin. However, it could be a tessellated or a Johnny darter. Those two seem to be nearly identical in head/body shape, coloration and with the little W or X markings on the sides. I can see that this one in the photo has a little "w" on it's side.

Was leaning toward tessellated, this seems to confirm it. 

Greenside are found in the Susquehanna drainage, but the Delaware watershed streams only have tessellated and shield. Really jealous of the guys in the South and Midwest and their diverse, colorful darters. 



#5 Fleendar the Magnificent

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Posted 23 December 2018 - 12:29 PM

If your watershed doesn't have Johnnies, then it's prolly a tessellated. That said, you don't have rainbows and banded darters in your corner of Pa? I live in Central Ohio and we have quite a few species here. There's 5 species in the river across town from me which is where mine cane from. I have 4 species in my tank which are Johnnies, banded, rainbow and fantail darters. We also have a blue breast darter, but they're scarce. The banded and rainbows are pretty colorful right now even out of breeding season.



#6 LepomisAuritus

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Posted 23 December 2018 - 02:47 PM

If your watershed doesn't have Johnnies, then it's prolly a tessellated. That said, you don't have rainbows and banded darters in your corner of Pa? I live in Central Ohio and we have quite a few species here. There's 5 species in the river across town from me which is where mine cane from. I have 4 species in my tank which are Johnnies, banded, rainbow and fantail darters. We also have a blue breast darter, but they're scarce. The banded and rainbows are pretty colorful right now even out of breeding season.

http://fishmap.org/w...ml?huc=02040203

Just the two species. Neither of which have interesting breeding colors either. I'm at college out in Western PA, so I'm hoping to see some cool darters out there. Probably have very similar species to what you have in Central Ohio. 


Edited by LepomisAuritus, 23 December 2018 - 02:47 PM.


#7 Fleendar the Magnificent

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Posted 24 December 2018 - 01:20 PM

There's a list of darters found in Pennsylvania at:

 

https://www.fishandboat.com

 

 

Look up Pennsylvania's dynamic darters. It's a PDF and most of the way down is a complete list of their  darters, names and protected status. There's 21 species, two of which have been extirpated and no longer exist in that region. We have most of the same species.



#8 Matt DeLaVega

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Posted 24 December 2018 - 04:02 PM

It is almost certainly a tessellated.


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#9 Fleendar the Magnificent

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Posted 25 December 2018 - 07:52 PM

What's the difference between tessellated VS the Johnny darter? They look very much alike.



#10 Matt DeLaVega

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Posted 26 December 2018 - 07:23 AM

DNA, ray count, and distribution . Tesselated are in the Atlantic drainage. Johnny are in Mississippi drainage. They are very similar, so much so that people ID them by location mostly rather than by physical differences. This is a common way to ID many similar species.

 

Read this. Might be of interest. https://books.google...pecies?&f=false


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#11 Fleendar the Magnificent

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Posted 26 December 2018 - 03:03 PM

Thank you Matt. That was an interesting read. From what they said, it seems that the Jonny and tessellated were perhaps at one time one specie and was somehow separated. The tessellated split off and evolving slightly different features than the Johnny. Interesting concept and makes one wonder what cut them off enough for them to evolve into 2 separate species albeit ever so slight of difference?



#12 mattknepley

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Posted 27 December 2018 - 10:16 PM

Funny the geographic variation.  That thing doesn't look a bit like our SC Tessies.  Looks better than most of ours! 

 

If you want to go all in for darters, Lep. A, consider joining NANFA and heading to next year's convention in Mississippi.  I think there's almost 30 species in that state!  Don't know all the drainages yet, but you ought to be able to find a few new pretty fish to chase around!


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

#13 Matt DeLaVega

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Posted 27 December 2018 - 11:41 PM

Funny the geographic variation.  That thing doesn't look a bit like our SC Tessies.  Looks better than most of ours! 

 

If you want to go all in for darters, Lep. A, consider joining NANFA and heading to next year's convention in Mississippi.  I think there's almost 30 species in that state!  Don't know all the drainages yet, but you ought to be able to find a few new pretty fish to chase around!

Looked so good that I wondered if it was a greenside. Still looks like it to me, but you know how it goes with photos.


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#14 Fleendar the Magnificent

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Posted 28 December 2018 - 03:47 PM

We have the greensides in the Olentangy, but apparently they're not especially numerous in the area that I am at. We'll see what I next next spring.



#15 gerald

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Posted 28 December 2018 - 04:27 PM

... makes one wonder what cut them off enough for them to evolve into 2 separate species albeit ever so slight of difference?

 

Drainage divides will usually do it.  Headwater fish species get "captured" by a new river basin when one headwater stream erodes upslope into another stream, previously in a different river basin.  Now they're isolated from the parent population, and might change enough over the years to become a new species.  In NC, Waccamaw River basin tesselated darters were isolated yet again in Lake Waccamaw, and have become the Waccamaw darter, and evolutionarily "young" species.  It's odd how some animal groups don't change much after populations get split and isolated, and can remain very wide-ranging species, while others seem to change "quickly" (less than 50,000 yrs) into new species.


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


#16 Fleendar the Magnificent

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Posted 29 December 2018 - 03:45 PM

That does make sense. Rivers erode and when one joins into another leading into another different watershed, that splits the species into an area where they might not have existed before. Wonder how long it took for them to evolutionarily change?



#17 gerald

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Posted 30 December 2018 - 12:46 PM

However long it's been is how long it took.  It's a continuous process; there's no threshold moment at which populations become species, no matter how hard taxonomists wish for or imagine an evolutionary species threshold.


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


#18 Fleendar the Magnificent

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Posted 30 December 2018 - 10:39 PM

True, the process to evolve is a continuous process.

 

Thank you and have a happy 2019!



#19 Doug_Dame

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Posted 31 December 2018 - 09:25 PM

Gerald, I'm not sure I agree ... seems like there IS in fact a knowable, discrete threshold moment for many species nowadays ... it's the moment someone kicks off a maximum likelihood tree analysis on DNA data. Eureka/el voila!!! New species emerge! (Bearing in mind there's a publication bias, in that analyses that don't support new species are presumably less likely to be published.) 

 

This thought re-triggered from a reading a few days ago of a 2015 paper by Allen, Hadiaty, Unmack and Erdman .... yes "our" Unmack ... describing 5 new species of rainbowfish from New Guinea and re-describing two others. (As an amateur, I offer the analogy that this paper does the same type of splitting of the "Goldie River" rainbowfish as was done recently to (with?) the orange-throated darter "complex.")

 

I'm too old to have been in class when it was explained how the statistical analysis of distributions of the DNA sequences in ONE GENE could trump ... or validate ... all the other kinds of information potentially involved in defining "a species." 

 

Disclaimer: This is a semi-tongue-in-check, end-of-year, got-nothing-better-to-do crank rant by an old guy who doesn't really understand modern DNA analysis. But in my youth I wasted a lot of time doing computer simulations of random drift and founder effects in very small populations (N<20), which has probably prejudiced me to this day.

 

:) 

 

And Happy Year to all ! May 2019 be the best year ever.


Doug Dame

Floridian now back in Florida
 


#20 LepomisAuritus

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Posted 01 January 2019 - 02:43 PM

Species definition seems to be a rather contentious issue in biology. Used to be defined morphologically (fin ray counts...etc), but increasingly genetic differences are used. You can also define a species phylogenetically. Biological species definition of reproductive isolation also gets used a lot in textbooks, but seems to be ignored for a lot of fish taxonomy. For instance, a lot of the centarchids interbreed easily enough in the wild, but are considered separate species. 






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