False Corydoras trilineatus

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niederle
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False Corydoras trilineatus

Post by niederle » Fri Nov 24, 2006 3:25 pm

Image
Type specimen of Corydoras trilineatus is high and has the eye below the extension of the scutes junction zigzag
and on the line connecting snout tip and dorsal spine root. Head is not arched above snout, but before dorsal fin.
The following image from PlanetCatfish shows a fish with the eye above the lines and head arched above snout.
Image
Image
I would like to know if this variation has been studied, if it occurs within populations or only between populations and if the population from the type locality has been studied.
Last edited by niederle on Thu Apr 12, 2007 12:41 pm, edited 4 times in total.

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MatsP
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Post by MatsP » Fri Nov 24, 2006 3:54 pm

I moved these posts to the "bugs" forum, as that's where they belong (as you're not a member of the Cat-eLog team, so you can't post in the Cat-eLog forum, which is the other place where incorrect information can be discussed).

The link to a czech university web-site that you're using doesn't appear to work. Any chance you can put it somewhere more reliable?

Also, do you have any idea what the fishes are, if they are not C. trilineatus?

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Post by niederle » Mon Nov 27, 2006 10:47 am

withdrawn
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MatsP
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Post by MatsP » Mon Nov 27, 2006 11:54 am

Well, I have no place to host the picture, so we really need to find a place where it can be hosted that works...

If it's a copyrighted picture, you'd also need to have the copyright owners permission to publish it on a web-site...

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Post by niederle » Mon Nov 27, 2006 1:57 pm

withdrawn
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MatsP
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Post by MatsP » Mon Nov 27, 2006 2:10 pm

And it's working right now - I also managed to get to the site a while back.

Since it's your own drawing, you could perhaps post it on a more reliable place, such as photobucket.com or imageshack.com. Both have easy to use interfaces to add pictures and link to them in other places.

I'm not a specialist on Corydoras, so I can't discuss the correctness of your statements - but are you saying that the original description by Cope, 1872, states that the species is defined by having those features, or are you just stating that those features are in the type specimen and thus the below fish are different from the type specimen?

And could you please add to your location in your profile (top right of the screen) so that you have a country as well, just so that it's more clear where you're from - it is part of the forum rules...

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Post by Silurus » Mon Nov 27, 2006 2:37 pm

The ACSI Imagebase also has photographs of the lectotype of Corydoras trilineatus.

http://acsi.acnatsci.org/base/image_lis ... rilineatus
Image

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Post by MatsP » Mon Nov 27, 2006 2:58 pm

Those pictures show, indeed, that the extended line of the mid-lateral zig-zag is above the eye. But that's not to say that other specimens are not different from this. For example, the type specimen seems to be fairly bulky -> possibly female. Does that mean that juveniles and males are exactly the same? Probably not.

I'm still not expert enough to say if it's right or wrong, just discussing it on my limited capabilities and knowledge.

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Post by niederle » Mon Nov 27, 2006 3:40 pm

withdrawn
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Post by Coryman » Fri Dec 01, 2006 2:20 pm

niederle,

It is almost impossible to validate your argument about C. episcopi from the pictures you are showing. In the C. episcopi picture the fish is being viewed from a high oblique angle and does not show a true profile.

Besides this fact, have you tried taking pictures of mature sibling males and females, especially when the females are in breeding condition. I am certain you will find that the formula you are using will be completely floored. The drawing on which you demonstrate the alignment is also in my opinion not a good reference, because it shows the body in an unnatural position, the caudal fin is raised and therefore creates a distorted view of the body scute intersection points.

C. trilineatus is found in several river systems in northern Peru, Ecuador and Colombia. The Rio Yavari; Rio Huytoyacu; Rio Nanay and Rio Yasuniand, and in line with the biotopes in these rivers they have evolved slight variations in colour pattern and to a degree body shape. Whether or not these differences constitute different species is not for me to say, but where does one draw the line between species, one spot or two. The fact that all these forms will readily interbreed and the resulting fry patterns all develop in the same manner, tells me that they are the same species.

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False Corydoras trilineatus

Post by niederle » Tue Jan 02, 2007 2:04 pm

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Post by Coryman » Wed Jan 03, 2007 10:00 pm

I think instead of stating that the fish we see in the hobby are not the same as the drawing of the type specimen, which I may add is 135 years old. You should be checking morphological data of the variants available in the hobby now against those of the type material. Line drawings are not necessarily obliged to be accurate.

If you are trying to validate the existence of C. episcopi then it needs to be done with type material from type localities and not inaccurate drawings.

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Post by niederle » Thu Jan 04, 2007 11:15 am

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Post by kim m » Thu Jan 04, 2007 12:06 pm

Perhaps we should call them Corydoras Epilineatus or Corydoras Trilioscopei :wink:

I think it's just variations within the species...my humble opinion.
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Post by niederle » Thu Jan 04, 2007 12:39 pm

kim m wrote:Perhaps we should call them Corydoras Epilineatus or Corydoras Trilioscopei :wink:

I think it's just variations within the species...my humble opinion.
You may be right, but I expected that experts are able to give exact answer. You can see that I hesitated to present my opinion, I simply presented my observations. I am not an expert and my query was intended for experts.

Josef

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Post by kim m » Thu Jan 04, 2007 1:07 pm

Perhaps you should contact an Ichthyologist...is that spelled right?

I think they're more into bone structure and such.
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Post by Coryman » Thu Jan 04, 2007 2:06 pm

As Kim has said if it is an explanation from experts then for the observations that you are stating your discussions should be with taxonomists and not so much hobbyists. We too make observations public, well some of us do but we are in no position to state whether your observations hold any scientific weight, all we can do is offer what we find to science and let the Ichthyologists decipher it.

Where is the line drawn between two species? is it 1% or 10% morphological variation, or somewhere in-between. Science has the rules already set out.

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Post by niederle » Mon Feb 12, 2007 1:54 pm


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