Help ID Otocinclus *before* buying

[deco]

Hi all,
new member here
Searched all internet around, till I came to this wonderful site.
Then searched the forums, but no luck finding what I am looking for...

So, this is my question.

I am building a peruvian biotope for some nice Apistogramma Bitaeniata.
In my research I found that the correct Otocinclus for this area should be Otocinclus Macrospilus... but in the aquarium shops scientific names for OTOs are often at random, and indeed I think that the several Otocinclus species are very very similar... too similar, actually, for my unexperienced eye.
So, what are the characteristics i should look for that distinguish one oto from the other one?
For example, Otocinclus Macrospilus and O. Mariae seem (to me) almost the same fish, but the first one come from Upper Amazon Basin of Colombia, Ecuador & Peru, the second one from Lower Amazon, Upper Madeira and Paraguay basins!!

If the shop can say where the fishes came from, there's no problem, but often fishes arrive in Italy passing through specialized importers in Netherlands and Germany... so no real info...

Thank you in advance for the help, and big congrats for the nice site and community!

PS Sorry for my poor english

[Mike_Noren]

The tail spot of a macrospilus is not very big, and divided into a half-moon shaped anterior spot and a triangular posterior spot. The spot also does not extend into the tail fin.

This is a typical macrospilus. The lower one here is another one. Do you see what I mean?

You can safely ignore mariae, it is a Venezuelan fish and if it at all occur in the hobby it's likely very rare - should you ever find one it looks similar to macrospilus but the tail spot extends into the tail fin.

You're far more likely to find fish from the hoppei complex. In theory they have a single large, circular to diamond shaped spot by the tail, in practice it's often difficult to tell them from macrospilus.

[deco]

This is a typical macrospilus. The lower one here is another one. Do you see what I mean?

Yes!! I see it. Cool

So this fish:


Collected by TomC in this trip, the site from where im getting info for my Bitaeniata biotope, is really a Macrospilus, right? Now I can see the "division" in the caudal spot!

Btw, thank you for your superfast response!

[Mike_Noren]

Yeah, remember what I said about the hoppei group species? Typical hoppei are easy to tell from typical macrospilus, but very often one get fish like the ones in that photo, with large circular or diamond shaped spots divided in to two pieces. O. hoppei also occur in Peru (Ucayali) so... I'm not sure what that is. If I had to choose I'd say macrospilus, but it might be hoppei. Then again, perhaps it doesn't matter for your purposes - you're making a habitat from Loreto but Ucayali is next door, and I can pretty much guarantee that no one is ever going to call you on your choice of Otocinclus species.

[The.Dark.One]

Hi Mike

Do you agree these are macrospilus then or hoppei?

http://www.scotcat.com/thedarkone/loric ... spilus.jpg
http://www.scotcat.com/thedarkone/loric ... pilus2.jpg

I identified these as huaorani, do you agree?
http://www.scotcat.com/thedarkone/loric ... aorani.jpg
http://www.scotcat.com/thedarkone/loric ... orani2.jpg

[deco]

Yeah, remember what I said about the hoppei group species? Typical hoppei are easy to tell from typical macrospilus, but very often one get fish like the ones in that photo, with large circular or diamond shaped spots divided in to two pieces. O. hoppei also occur in Peru (Ucayali) so... I'm not sure what that is. If I had to choose I'd say macrospilus, but it might be hoppei. Then again, perhaps it doesn't matter for your purposes - you're making a habitat from Loreto but Ucayali is next door, and I can pretty much guarantee that no one is ever going to call you on your choice of Otocinclus species.

Ok, i see what you mean... it's complicated.
But, anyway, you are right: for what I want to do, if both fishes live in similar environments and can be found in the peru area, that's ok.

By the way, where can I find info like that Hoppei occurs also in Ucayali?
Here on planetcatfish.com i found (if I am looking in the correct place...) that lives in Brazil, and the only other source i found is this Discover Life map (unfortunately with only 2 points...and slow to load), that shows point on central Brazil...

[Mike_Noren]

Hi Mike

Do you agree these are macrospilus then or hoppei?

http://www.scotcat.com/thedarkone/loric ... spilus.jpg
http://www.scotcat.com/thedarkone/loric ... pilus2.jpg

I don't think those two are macrospilus , due to the relatively short dorsal fin; the striped unbranched dorsal fin ray; the number of canal-bearing plates; and the very large caudal pigment spot - so presumably something in the hoppei group. The thing with the hoppei group is that it was revised in 2010 by Lehmann et al., and I've been unable to obtain that article, so I'm not sure how to tell which species this is.

I identified these as huaorani, do you agree?
http://www.scotcat.com/thedarkone/loric ... aorani.jpg
http://www.scotcat.com/thedarkone/loric ... orani2.jpg

I tried using the key in Schaeffer and got huaorani, but the meristics and coloration doesn't fit: huaorani's dorsal fin should reach to the middle of the anal fin, and in these two it at best reaches the anterior third; huaorani doesn't have saddlemarks between the dorsal fin and the caudal fin, and these fish do (BUT the drawing of huaorani doesn't match the text description well).
Pigmentation and meristics are very similar to Schaefers description of caxarari, but as far as I can tell from the photo there's only two non-canal-bearing plates, instead of caxarari's 6-11 non-canal-bearing plates.
It's not macrospilus , as that has an even bigger dorsal fin than huaorani and 4-8 non-canal-bearing plates.

In short yes, Schaefer's key and the number of non-canal-bearing plates suggest it's huaorani.

Disclaimer: I must point out that I am not in any way an expert on Otocinclus, just an interested hobbyist, and I think I in the past may have suggested different ID's for fish which looked much like these. The buggers are difficult, and I am increasingly skeptical about the validity and diagnoses of a couple of the species of Otocinclus.

By the way, where can I find info like that Hoppei occurs also in Ucayali?

Well, I got it from the book The Neotropical Cascudinhos: Systematics and biogeography of the Otocinclus catfishes by S. A. Schaefer, but in general a good source for information is Fishbase. Just don't, uhm, trust the photos. There also used to be a German site with a lot of good info on otos but it seems to have disappeared.

[The.Dark.One]

Thanks Mike

Perhaps we could try and get hold of the Lehmann paper? Anyone on PC have it or have access to it?

Is it this one?

Lehmann A., P. , F. Mayer, and R. E. Reis 2010
A new species of Otocinclus (Siluriformes: Loricariidae) from the Rio Madeira drainage, Brazil. Copeia 2010 (no. 4): 635-639.

[deco]

Well, I got it from the book The Neotropical Cascudinhos: Systematics and biogeography of the Otocinclus catfishes by S. A. Schaefer, but in general a good source for information is Fishbase. Just don't, uhm, trust the photos. There also used to be a German site with a lot of good info on otos but it seems to have disappeared.

Ok, thank you very much for all the excellent info! Maybe you are an hobbyist, but you know really a lot on these little fishes
Unfortunately i dont think that here in Italy i could find a copy in a Public Library of the "Proceedings of the Academy of... Philadelphia", but i saw that it's possibile to buy an electronic version of it...

Does that article contain also some info on the biotope/environment? I know that otos live usually in clearwater large rivers, but do you know if they can be found also in blackwater creeks/ponds/submerged forest? I am going to use peat in my tank and was wandering if this is ok (although not very common) for the otos or not. I know I am going a bit offtopic, if you prefer I can open a specific topic in "South American Catfishes".

[deco]

The thing with the hoppei group is that it was revised in 2010 by Lehmann et al., and I've been unable to obtain that article, so I'm not sure how to tell which species this is.

If this is the paper:

Re-validation of Otocinclus arnoldi Regan and reappraisal of
Otocinclus phylogeny (Siluriformes: Loricariidae)

by

Pablo Lehmann A., Fernanda Mayer and Roberto E. Reis

there is a freely available copy here (pdf color format)

Hope it helps

[racoll]

If this is the paper: Re-validation of Otocinclus arnoldi Regan and reappraisal of Otocinclus phylogeny (Siluriformes: Loricariidae) by Pablo Lehmann A., Fernanda Mayer and Roberto E. Reis there is a freely available

That one is in Neotropical Ichthyology. The one the guys are talking about is in Copeia. I have access to this article. PM me if anyone wants it.

Perhaps we could try and get hold of the Lehmann paper? Anyone on PC have it or have access to it?

The thing with the hoppei group is that it was revised in 2010 by Lehmann et al., and I've been unable to obtain that article, so I'm not sure how to tell which species this is.

[Mike_Noren]

I have now obtained and read the Lehmann et al. paper. In it they describe the species Otocinclus mangaba from the Madeira basin, which can be separated from O. macrospilus and O. hoppei by the lack of a ventral series of plates (if you look at the belly of most otos you find three "rows" of plates, mangaba lacks the center row); this should be possible to see on a macro photo of the ventral side of the fish. It also has slightly different pigmentation in the caudal fin, but this is probably a weaker identifying character.

Unfortunately the paper does not go in to any depth discussing O. hoppei and O. macrospilus, which to me appear to be endpoints on a continuum with numerous intermediate forms. All proposed diagnostic characters separating the species are overlapping and it is common to find individuals which can not confidently be identified as either hoppei or macrospilus.