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Tribelos (?) from Mexico

Started by Laci Hamerlik, June 06, 2017, 01:44:07 PM

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Laci Hamerlik

Dear all,

The attached head capsule was found in a cenote (sinkhole) lake in Mexico. My best guess is Tribelos. It has separate clypeus and labral sclerite, but 4 inner teeth on the mandibles and also it seems to me that not only the middle 2 but all 4 median teeth are delineated from rest of mentum. Do you have any idea?
All the best,

Martin Spies

Dear Laci,

May I ask whether this is a subfossil specimen or a Recent, complete one? If the latter, what is the antenna like, especially its configuration of Lauterborn organs?

Can you determine details of the labrum/epipharynx region, e.g. of the labral S I seta, the labral lamella, the pecten epipharyngis, the seta premandibularis (apically simple or divided) and the premandible?

Do the seta interna and the seta subdentalis (SSd) originate on the same side of the mandible or on opposite sides, and does the SSd really arise from a tubercle that projects from the mandibular mola? And just how far distal does the apparently unusually long SSd reach - to the second or even to the first inner tooth?


Martin Spies

Laci Hamerlik

Dear Martin

Unfortunately we are dealing with subfossil specimens, even though they are in a quite good shape.

The antenna is 5 segmented with alternate Lauterborn organs. The premandibules with 2 apical teeth and 1 inner tooth, brush present. Even though the tormal bar is obvious, I dont see the seta premandibularis. The same with S I, labral lamella or pecten epipharyngis.
It seems to me that SSd and seta interna originate at the same side. The SSd really arise from a tubercle that projects from the mandibular mola quite far from the last (4th) inner tooth. And it is very long, reaches the 2nd inner tooth.
Should I take some more pictures of those structures?

Thank you,

Martin Spies

Dear Laci,

Thank you for the additional information and photo. The Lauterborn organ insertions should be opposite each other at the apex of antennal segment 2 rather than "alternate" (on one or two segments); the latter configuration would put the taxon into a completely different branch of Chironomini. If the seta interna and seta subdentalis arise on the same side of the mandible - as one also gets the impression from your photo - then this would seem highly unusual in Chironominae.

Could you possibly bring the specimen to the symposium at Trento? If so, several of the attending colleagues could give you input after direct examination, e.g. during the scheduled taxonomy workshop.


Martin Spies

Laci Hamerlik

Dear Martin,

thank you for you opinion. You are absolutely right, the Lauterborn organs are NOT alternate but placed at the same segment (I confused it). And the SSd and seta submenti: it is very strange but it really looks like that. So I will bring my slide to Trento for further investigation. Thank you for your effort!


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