Mesonauta ID

[stiker]

I picked up a group of 10 Mesonauta at the end of last year which came in labelled as “Wild Caught Mesonauta Festivus, Columbia” from the research I’ve done I have found true M. Festivus does not occur in Columbia.

I know they are notoriously hard to ID and the stress/ spawning baring is what helps to identify them.

I have included some photos and a short video of them from the end of January this year.

https://youtube.com/shorts/OJbpFFE_g2A

 

[The Masked Shadow]

duanes

 

[duanes]

duanes

I do not have any real experience with Mesonauta.
When I kept them in the 1960s, they were all simply festivum, all thought of as 1 species.
Although this may be of some hep.
imgres

 

[neutrino]

Trying to ID Mesonauta is a good way to get a headache...

...Especially certain types, even by people typically good at IDs or someone who's kept them before (which I have). A couple of species are distinctive due to their reticulated pattern above the dark lateral bar-- imo with yours some underwater photos might help with that, or they may need to get a little older to let the pattern develop more. In some types the bar pattern is typically much easier to ID in breeding dress.

Confusing internet photos, being misidentified as sold, sometimes the catch location is wrong or apparently mixed types come in labeled from a single location. Color, how distinctively they display their bars, etc. can vary by mood or individual. Good example of the problem is this fishbase entry for egreqius, which talks about ray and scale counts but says they are "usually" this or that. I suspect another thing making them confusing is, similar to A. diadema vs. metae, some of the markers for ID vary by location and can come and go in individual fish according to mood.

That said, there are a couple of people here who might be willing to take a shot at yours.

 

[duanes]

One other rub, back in the time I kept them, and they were known simply as festivum, and may have been unconsciously interbred (like any number of Paratilapia species , or even severumswhen first imported) so there may be hybrid aquarium strains floating around.
If wild caught (as stated in the opening post) this would not be a problem, but in a simple LFS find, that unidentifiable possibility is always there.

 

[ryansmith83]

Mesonauta are tricky. Yours can be narrowed down by the fact that only two described species have the black webbing pattern or black edged scales above the lateral stripe: M. guyanae and M. insignis.

If you knew the true catch location, you might be able to narrow it down. The trouble is that sometimes fish from other countries get sent to exporters in nearby countries for shipment to the US, so a Colombian shipment may also contain Brazilian, Peruvian, or Venezuelan fish, etc.

M. insignis is found in Colombia and Venezuela but they often show a lot of yellow color. M. guyanae are found in Guyana and Brazil. Yours look more like those but then you have to wonder how they came out of Colombia.

Then you have the possibility of it being an undescribed species...

 

[stiker]

Mesonauta are tricky. Yours can be narrowed down by the fact that only two described species have the black webbing pattern or black edged scales above the lateral stripe: M. guyanae and M. insignis.

If you knew the true catch location, you might be able to narrow it down. The trouble is that sometimes fish from other countries get sent to exporters in nearby countries for shipment to the US, so a Colombian shipment may also contain Brazilian, Peruvian, or Venezuelan fish, etc.

M. insignis is found in Colombia and Venezuela but they often show a lot of yellow color. M. guyanae are found in Guyana and Brazil. Yours look more like those but then you have to wonder how they came out of Colombia.

Then you have the possibility of it being an undescribed species...

View attachment 1456585

I had my suspicions that it would either be M. Insignis or M. Guyanae based off the fact they they always show the black pattern above the lateral stripe, even when they have no other barring under the lateral stripe showing. Trying to ID then looking at the baring is not so easy when you try to do it in person haha.

If it is truely out of Columbia I removed M. Egregius and M. Merificus from the options from the beginning due to them not displaying the black pattern above the lateral line.

As you stated though, if they were M. Insignis given they are currently around 4inches for the largest, should I not be expecting to see a lot more yellow colouration

 

[ryansmith83]

I've had two different wild groups of Mesonauta. One was supposedly acora and one was supposedly true festivus. Both groups had a single bright yellow fish and the rest were silver. And then in some groups the females would turn yellow with black bars during spawning, and be silver when not spawning. So either I had a mix of species both times or the yellow color is present in multiple species (but not in every individual).