PlanetCatfish.com

They say "a picture is worth a thousand words". I have Ian's book, Identifying Cordoradinae Catfish and I find it helpful, but even with the pictures, I am not always sure what I should be looking for to differentiate between what to me are similar appearing species. To me, a novice, C. bilineatus, C. napoensis and C126 look the same. Many other pairs and trios look alike to me as well. What am I missing? How can I learn to tell the different species apart?

When I was doing some work in floristics many years ago, I used what's called a "dichotomous key". To use it, you would start at the beginning of the key. There would be a simple descriptive statement about one characteristic of the organism and you would determine whether your specimen did, or did not, fit that description. If it fit the description, you would go to one place in the key and read the next descriptive statement and again determine if your specimen fit; if it didn't fit the description, you would go to another place in the key and read a different descriptive statement. You would keep repeating this process until you came to an end, and that should be the identification of your specimen.

Has anything like this been done for cory cats? Or any other type of key that someone who is comfortable with scientific terminology could use?

Cheri

For these look-a-like species, I think tha place of capture is essential to differentiate them.

When I was doing some work in floristics many years ago, I used what's called a "dichotomous key". To use it, you would start at the beginning of the key. There would be a simple descriptive statement about one characteristic of the organism and you would determine whether your specimen did, or did not, fit that description. If it fit the description, you would go to one place in the key and read the next descriptive statement and again determine if your specimen fit; if it didn't fit the description, you would go to another place in the key and read a different descriptive statement. You would keep repeating this process until you came to an end, and that should be the identification of your specimen.

The same keys abound in ichthyology. The problem with them, from an aquarist's point of view, is that they are often based on bones, muscles, gill rakers, or other features that are not particularly useful to someone trying to identify a living fish.
-Shane

housewren,

There are identification keys, but I am afraid they are of little use in sorting out the look-a-like species. With the species C. napoensis and C. bilineatus there are indeed morphological differences which are published in their respective descriptions, the actual key factor with these two species is their location, C. napoensis from the Rio Napo in northern Peru and the Rio Cochabamba & Rio Beni in Bolivia. These are totally unconnected areas hundreds of kilometres apart. in the case of C126, this is an undescribed species from the Madre de Dios in southern Peru, this species may prove to be close to C. bilineatus, but then we will have to wait for a scientist to verify.

Visually it is impossible to make a positive id between these fish unless you want to preserve and measure all their features and then there is no guarantee you will be right. However if you are able to find out the location where the fish were actually collected from that would be a major pointer.

There are many species that look identical but are totally different species and there may be several reasons for these similarities, which would make a great debate in it's self.

Ian

There are many species that look identical but are totally different species and there may be several reasons for these similarities

ahhh, you have to love convergent evolution

I expect in some cases it's due to isolated populations with a common ancestor.

Is/has anyone been working on the phylogeny of the Corys?

Is/has anyone been working on the phylogeny of the Corys?

http://www.planetcatfish.com/forum/viewtopic.php?t=5004

Thanks, I'll have to get a copy of that paper.

Cheryl

Copy sent via e-mail

Ian

There are many species that look identical but are totally different species

Is there a list of Cory species 'look-alikes' available -- species that can't be distinguished without killing the fish, or knowing the collection location?

I think many aquarists would find such a list quite useful. For example, from my LFS I have purchased many different species labelled as C. punctatus (C. leucomelas, C. agassizi, C. biineatus -- I.D.'s confirmed previously on this list)and have not yet seen the real C. punctatus (I did know they were not the real McCoy). So if I see a fish I like, I bring it home and check out it's I.D. as best I can.

Usually the LFS doesn't provide collection information, so I can't know where they are from. When I have limited the possibilities down to a few species, it would be nice to know if it is likely they can be distinquished without location data.

I am aware that some species have much variability, with some individuals of two species overlapping in appearance--some members of Species A look like some members of Species B, but other members of Species A don't look like any members of Species B (e.g., juvenile C. agassizi and C. ambiacus), so such a list would not necessarily be perfect, but it would be helpful.

Cheryl

Cheryl,

This is what I along with fellow Corydoras enthusiast Hans-Georg Evers published in June 2005 for the sole purpose if identifying all known described species as well as C-mumbered un-described species up to C145.
Cory Identification Book

Ian