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Yesterday I`ve purchased four Otocinclus in a local shop. I think three of them are the same species, but the 4th i think it´s a O. vittatus, because of the different tail patern.

Here´s the "vittatus".





And here is one of the unidentified (maybe O. mariae or macrospilus...)



What do you think?

Looks like you're correct about the O. vittatus, but I think the other is neither O. mariae or O. macrospilus.

but I think the other is neither O. mariae or O. macrospilus.

Then?

This seems to be the one identified as Otocinclus “Rio Ucayali” in the Evers & Seidel Catfish Atlas.

If you follow Evers & Seidel, then the top fish looks to be O. vestitus, as do most of the specimens in the cat-elog under O. vittatus.

O. vittatus should have a clear vertical black bar at the base of the caudal fin. Other than that I see nothing to distinguish the two species.

O. vittatus should have a clear vertical black bar at the base of the caudal fin

You mean the vertical bar in the middle of the tail or at the base?

http://www.planetcatfish.com/catelog/im ... ge_id=3923

racoll wrote:If you follow Evers & Seidel, then the top fish looks to be O. vestitus, as do most of the specimens in the cat-elog under O. vittatus.

There isn't supposed to be any difference in pigmentation between vittatus and vestitus, the only difference is that vestitus lacks lateral line canal pores on the posterior half of the body. Unfortunately that character is both very difficult to see and one of the first in Schaeffers key, so pretty much everything gets identified as vestitus.

This is vittatus (after Schaeffer 1997)
http://213.112.199.139/temp/idify/vitta ... aeffer.jpg

This is vestitus (after Schaeffer 1997)
http://213.112.199.139/temp/idify/vesti ... aeffer.jpg

There is no described species of Otocinclus which is supposed to have the pigmentation of the fish in the third photo, meaning that it's either an undescribed species, or an aberrant individual.

Mike Noren wrote:the only difference is that vestitus lacks lateral line canal pores on the posterior half of the body

I will try to take a macro pic, maybe this way would be possible to see the pores...

Mike Noren wrote:There is no described species of Otocinclus which is supposed to have the pigmentation of the fish in the third photo, meaning that it's either an undescribed species, or an aberrant individual.

I think it´s more probable to be an aberrant individual (three aberrants in fact...).

Thanks guys for the answers!

There isn't supposed to be any difference in pigmentation between vittatus and vestitus, the only difference is that vestitus lacks lateral line canal pores on the posterior half of the body. Unfortunately that character is both very difficult to see and one of the first in Schaeffers key, so pretty much everything gets identified as vestitus.

Thanks Mike. I'll have to track down that key.

Given the similarity between the two, it makes me wonder why Evers & Seidel stated for O. vittatus, "The typical design of the caudal fin is readily apparent on the photographs, facilitating in great measure an unequivocal identification by the aquarist".

I think it´s more probable to be an aberrant individual

No, there are many undescribed Otocinclus .