Paleatus vs longipinnis - can someone explain this for me?

[Mike_Noren]

How do you tell

Corydoras paleatus

apart from

Corydoras longipinnis

?

I've had what was sold as paleatus where the males had dorsal fins which were not much higher than the females - was this true paleatus?

Is the presence of elongated dorsal fin a good characteristic for separating longipinnis from paleatus (not counting veilfin type cultivars)?

Is this alleged male paleatus correctly identified?

How can one separate female true paleatus from female longipinnis?

[apistomaster]

In all the common farm raised Corydoras paleatus I have raised and spawned, the older males developed long tall dorsal fins.
I think if visual ID is difficult then you can safely rely on the price. If they are cheap then they are C. paleatus. If they are expensive(10x paleatus price) then C. longipinnis becomes more likely. These are wild fish being imported from the lower Rio Paraguay area which is not a hotbed of collecting activity although more fish are coming in from Uruguay than in many years past.

[Mike_Noren]

Sure, but how do you know that your common farm raised paleatus was actually paleatus, and not longipinnis or a hybrid?

Both species occur in the same area, both have been imported sporadically for a very long time, and both have until last year been sold under the name paleatus. If it's not the fin, what are the actual characters which separate these species?

[apistomaster]

Now I understand your question.
I would think one would need both species then key them out.
Aquarium strains C. paleatus could easily be hybrids. This is the case with aquarium strains of Discus and Angelfish. Unraveling the ancestry of hybrids is much more difficult, especially with fish that have been in the hobby for so long.

[Mike_Noren]

EDIT: I've got hold of the original description of Corydoras longipinnis:
Knaack, J., 2007 Beiträge zur Kenntnis der Callichthyidae (Teleostei: Siluriformes). III. Corydoras longipinnis sp. n. - ein neuer Panzerwels aus dem río Dulce in Argentinien (Teleostei: Siluriformes: Callichthyidae). Vertebr. Zool. 57(1):35-55.

It's obviously German-language, but I'll provide a summary of key points here once I've read it.

[Mike_Noren]

Here's select points from the paper; my comments in brackets. Apologies in advance for any mistakes made.

* Elongated dorsal and pectoral fins of males; the dorsal is so long it reaches the base of the caudal, which is unique among the Corydoradinae. Female longipinnis have "normal" dorsal and pectoral fin lengths. In long-finned cultivars of paleatus both females and males have elongated fins.
* Short and rounded snout, more so than in paleatus.
* Slender; ripe female longipinnis are said to have half the mass of ripe equal-length female paleatus. Males bigger and heavier than females.
* The shape and spotted or cross-barred pigmentation of pectoral and ventral fins are unique to this species (paleatus has unpatterned pectoral and ventral fins).


My reflections based on the discussion and pictures:

* Both sexes have 3-6 dark cross-bars in the dorsal fin. I think this, along with the patterned pectoral and ventral fins, might be a good character for separating this species from paleatus. However, one pictured fish appear to lack cross-bars in the dorsal.

* One female pictured in the paper has significantly different pigmentation: she's not got the typical large dark lateral spots, but has an even sprinkling of small dark spots, looking very similar to Corydoras sp. C7. It appears from the text as if that is not typical, although it is also stated that fish killed with MS-222 change pigmentation from small spots into something more similar to paleatus-style blotches.

* As far as I can tell the authors mention but do not supply any characters for separating Corydoras longipinnis from Corydoras sp. "C7" or another undescribed species found "between the southern border of the distribution range of Scleromystax macropterus and the north-easternmost locality of C. longipinnis". Pictures of C7 and the other undescribed species in the appendix show fish which seem very similar to Corydoras longipinnis.


Finally, In the discussion the authors make the rather surprising statement that the species is not morphologically stable: Within 4-7 generations of captive breeding the resulting fish are so dissimilar to the wild-type fish that they no longer can be confidently assigned to species. My personal reflection is that kind of morphological instability would make me, personally, suspicious that longipinnis might be a naturally occurring hybrid.

Well, an interesting read, but it left many questions unanswered.

[kim m]

I think C7 is a considerably smaller species than C. longipinnis.

[Mike_Noren]

The authors discuss this. They obtained C7's from a pet shop, let them grow to full size, and measured them: females were 53-55 mm SL, and males 39-44 mm, suggesting that although longipinnis does grow slightly larger, the difference is only a few millimeters.
The main difference they find between longipinnis and C7 is that C7 has a stockier body shape than longipinnis.

[Coryman]

I have been keeping and breeding C7 for about 10 years and they are definitely different in appearance from both C. longipinnis and C. paleatus. They do not have any of the large body blotches that the other two species do. There is also another species in the mix C114, yet another C. paleatus looking species and may just prove to be a form of C. paleatus.

Ian

C007 male


C114 male


C. longipinnis male


C. paleatus female

All images courtesy of Ian Fuller & Corydorasworld.com

[Mike_Noren]

Two questions:
1) that female paleatus... Is it from wild stock? I think it's the first paleatus I've seen with striped dorsal, and which lack the five dark saddle-spots along the dorsal side?
2) do you know what this "morphological instability" the authors talk of might be? Your (presumably captive-bred?) longipinnis doesn't look impossible to identify to me.
3) would you happen to know if wild paleatus males have elongated dorsal fins too?

(OK, that was three questions.)

[Bas Pels]

3) would you happen to know if wild paleatus males have elongated dorsal fins too?

Two years ago, I brought 2 bags with Corydoras home. 1 from Lago Durant, near the town Treinta y Tres, Uruguay, 1 from a mall arroyo in the region Canelones (Aya aquas blancas)

The first have males with elongated fins - so when C longipinnis was described, I assumed them to be C longipinnes. The latter have no elongated fins

So I can confirm wild paleatus males do not nescisarily have elongated fins

[Coryman]

"1) that female paleatus... Is it from wild stock? I think it's the first paleatus I've seen with striped dorsal, and which lack the five dark saddle-spots along the dorsal side?"
All the fish in the pictures are wild forms.

"2) do you know what this "morphological instability" the authors talk of might be? Your (presumably captive-bred?) longipinnis doesn't look impossible to identify to me."
If I understand the term correctly, I would say that when the morphological data was taken it was found that some or all of the measurement variability was greater than would be expected, i.e. the head length may vary by 5% in the majority of Corydoras, but in this case it may have been 10% or more and therefore outside of the considered normal expected differential. Of course I may be totally wrong and in that case would ask for those with scientific training to explain.

3) would you happen to know if wild paleatus males have elongated dorsal fins too?
My male specimens of wild C. paleatus did have slightly longer more pointed dorsal fins than the females. but not to the extent that dorsal or pectoral fins in C. longipinnis do.

Ian

[Mike_Noren]

Thank you.

I kept Corydoras paleatus some years ago, and although I had the fish for several years the males never developed strikingly elongated dorsal fins, but I was unsure if this was natural or a result of degeneration in captivity.

The reason I started this thread was a discussion on another board about the sex of this fish:
http://smg.photobucket.com/albums/v181/ ... armal1.jpg
I said that I believed it to be a male of a cultivar of paleatus, but as I didn't know how to separate paleatus from longipinnis or the several similar undescribed species, I wasn't sure, and promised I'd try to find out.

I am now reasonably confident I can tell longipinnis from paleatus, I am satisfied that normal-finned paleatus occur in the wild, but I am still unsure whether high-finned paleatus, such as the one in the photo, occur in the wild or is a entirely a cultivar.