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Corydoras ln8sc4 identification

Posted: Sun Nov 22, 2020 9:29 am
by snowball
I would like help in identifying these five Corydoras, I believe there are at least two if not more species from ln8sc4, most likely candidates being C. agassizii and C. ambiacus. They were purchased from an online retailer who had them listed as C. punctatus with a stock photo of such, which they are obviously not, and the group of fish I received also included three ln9 Corydoras, probably leucomelas.

Cheers, Andrew

Fish 1
A1_Z62_2216.jpg

Fish 2
A2_NZ7_7002_00001.jpg

Fish 3
A3_Z50_0826.jpg

Fish 4
A4_Z62_2272.jpg

Fish 5
A5_Z62_2260.jpg

Re: Corydoras ln8sc4 identification

Posted: Sun Nov 22, 2020 11:59 am
by Jools
They all look like Corydoras ambiacus to me, some nice young fish in there.

Jools

Re: Corydoras ln8sc4 identification

Posted: Mon Nov 23, 2020 1:42 am
by snowball
Thank you Jools, much appreciated. If you would like higher resolution images of any of these to use in the catelog do not hesitate to ask.

Out of curiosity, what do you consider to be the differentiating characteristic(s) between C. ambiacus and C. agassizii?

Re: Corydoras ln8sc4 identification

Posted: Mon Nov 23, 2020 4:32 am
by bekateen
snowball wrote: Mon Nov 23, 2020 1:42 amOut of curiosity, what do you consider to be the differentiating characteristic(s) between C. ambiacus and C. agassizii?
That's a really difficult question to answer, thus reflecting the possible uncertainty in your original question.

The simple answer is that C. agassizii should have a black mark on the upper body and extending onto the first three dorsal rays, going most or all the way up the fin (FWIW, I wouldn't be surprised if your first photo above is agassizii). By contrast, C. ambiacus has a black mark in a similar area of the body and dorsal fin, but the black will not extend all the way up the fin and it usually covers more than just the first three rays. Both fish are spotted, although often there are predictable differences in the spots. But...
  1. The black mark on the dorsal of the fish may fade and darken with stress and conditions, so C. agassizii may sometimes not show the black going all the way up the fin, and
  2. Both species are variable in their spotting patterns, so it is not reliable (in my opinion) to use the spots as a verdict, and
  3. the number, shape, darkness, and size of the body spots change with age.
Bottom line (for me) is that you may think you have one species for a few weeks or months, but as they settle in, you may doubt your IDs. The variability and similarity present so much uncertainty that some professional taxonomists have talked about reclassifying them as a single species (C. ambiacus, since that name is older), but as far as I know, nobody is working actively on this issue.

Hope that helps.

Cheers, Eric

Re: Corydoras ln8sc4 identification

Posted: Mon Nov 23, 2020 10:18 am
by Jools
Indeed, and there are a couple of synonyms (C. grafi is one, can't remember the other(s)) for that future researcher to consider as well. Reminds me I need to fix a couple of images in the wrong place on the site. I'll do that and also beef up both species' ID information (they do mention this difference, but it could be improved).

Cheers!

Jools

Re: Corydoras ln8sc4 identification

Posted: Tue Nov 24, 2020 12:01 pm
by snowball
Thank you Jools and Eric, I look forward to watching these fish develop in the future, in the meantime I will try to get a better photograph of the first fish which has the black extending further up the dorsal fin.

Re: Corydoras ln8sc4 identification

Posted: Tue Apr 27, 2021 2:19 am
by snowball
Here are some more recent photos of the fish in question, taken since they have settled in and grown a little.

Three of the five have very similar patterning, one has stronger colouration and one has significantly longer pelvic fins.
Z62_6841.JPG
Z62_6844.JPG
Z62_6854.JPG
Z62_6879.JPG
Z62_7001.JPG

Re: Corydoras ln8sc4 identification

Posted: Tue Apr 27, 2021 4:05 am
by bekateen
Besides the Corydoras(ln7) eques, Corydoras(ln9) sterbai and Corydoras(ln8sc4) sp(c102), they look like C. ambiacus to me. And they look terrific!

Cheers, Eric

Re: Corydoras ln8sc4 identification

Posted: Tue Apr 27, 2021 5:07 am
by snowball
I am curious as to why one of them might have developed such long pelvic fins, I've never seen that before. Could it be a form of sexual dimorphism, regional variation or just random? Unfortunately their origin cannot be determined as they came from an online seller selling them as C. punctatus - and three of the eight were C. leucomelas!

btw no C. sterbai in there, but part of a C. brevirostris can be seen in the third photo.

Re: Corydoras ln8sc4 identification

Posted: Tue Apr 27, 2021 6:35 am
by bekateen
Males have pointy pelvic fins. They can appear elongate.
snowball wrote: Tue Apr 27, 2021 5:07 ambtw no C. sterbai in there, but part of a C. brevirostris can be seen in the third photo.
I thought these might be sterbai, but brevirostris is a possibility.

Cheers, Eric