Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
Photo#210249
Trichoniscus

Trichoniscus
Houston, Harris County, Texas, USA
August 4, 2008
Size: ~4 mm

Images of this individual: tag all
Trichoniscus Trichoniscus

Moved
Moved from Trichoniscus.

Better Crops?
Hi Graham,

just stumbled on this one while having a browse through the galleries. It's a Trichoniscidae for sure, but I wouldn't be too sure about it being a Trichoniscus - I wouldn't be surprised at all if the animal has eyes made up of a single ocellus. I know these are really tiny, and the images are actually already quite good, better than mine of comparable sized animals, but is there a chance nevertheless that you may be able to come up with a better crop, and/or a slightly more lateral perspective of the head in any of your images of this animal?

Just to leave some notes for further research:

The most fitting I have in terms of distribution data is Jass & Klausmeier's Atlas for Canada, Alaska and the Contiguous United States (2001), but it should be noted that woodlice, especially distribution, are not well researched in the States, especially not "in the field". Jass & Klausmeier's work is basically a summary of the scarce literature published and as such a valuable piece of work, but also quite possibly lacking in comprehensiveness on the species that might actually be found in the field.

Anyway, I had also had a look at the species listed for Louisiana and for the adjacent region of Mexico in Jass & Klausmeier's Atlas for Mexico (2004). Going by that, the following species of Trichoniscidae might be considered:

- Amerigoniscus gipsocolus (Bateman Cave, King Co, Texas)
- Brackenridgia bridgesi (Mexico, Tamaulipas &south)
- Brackenridgia cavernarum
- Brackenridgia palmitensis (Mexico, Nuevo Leon)
- Brackenridgia reddelli
- Cylindroniscus cavicola (Mexico, Nuevo Leon) Cave dweller
- Miktoniscus medcofi (Louisiana)
- "Trichoniscus" orchidicola ??

Edit1: The Brackenridgia supposedly are all eyeless. I've indicated those as red/fail for now.
Edit2: Amerigoniscus gipsocolus is an unpigmented cave dweller, also the granulation would be arranged differently.
Edit3: I have no access to documentation/images for any Cylindroniscus but based on this genus diagnose it should also be a blind cave dweller.
Edit4: The only piece of literature describing "Trichoniscus" orchidicola (note the quotation marks, courtesy of Schmalfuss' catalogue, 2004) supposedly is Mulaik (1960) "Contribución al conocimiento de los isópodos terrestres de Mexico". Schmalfuss lists it as distribution "Mexico". Jass & Klausmeier will have it in Texas too (also based on Mulaik 1960).

The only species in this list that I have a proper idea about is Miktoniscus medcofi and in terms of body granulation, head shape and colour it might have been a candidate, but to the best of my knowledge it should really be much longer/narrower in habitus.

On my part, the others would need some more (literature) research to get even a faint idea of their appearance and then there is, of course, the possibility of other species not yet recorded for the area. Actually, my first hunch - admittedly based on European species - would have been Trichoniscoides albidus (?!)

All that is not very helpful, mostly just "FUD" of course, but hopefully a first step toward fixing an ID anyway. I'll have a look around for better ideas myself later, but figured I'd leave these notes for now and ask for the bigger crops or head details to see what comes up :o)

Also, if you can easily retrieve more of these it could be interesting to collect a batch and send them in for ID. With the current state of woodlice research in the States, changes that you might really help to advance knowledge by recording a new species (for the area or even for the continent) are always lurking in the shadows :o)

That's all for now.
Cheers! Arp

Edit 5 (conclusive?): Considering the range of species documented my best guesstimate would be that this should most probably be a Miktoniscus. I'm currently working on the identification of a Miktoniscus species from a greenhouse in the Netherlands and, based on still incomplete literature, we are still in doubt if those should sort under Miktoniscus medcofi or M. linearis. Both seem to be very similar and one of our doubts is even if the species/genus might be in need of (yet another) revision. But that's all premature. Our specimen however are much "narrower" than this one. All other features, as far as visible seem to be a perfect fit however. As various species of Miktoniscus seem to be native to the region (Texas, Oklahoma, Alabama etc) it seems fair to assume that this might probably be one of those. If so at all, for a proper ID checking a few males under a microscope would be required.

Finally, if at all possible, I myself would be very, very interested in some specimen (preferably life, but even on alcohol would be absolutely fantastic), as it might well help clearing up some misunderstandings we are probably still having about the genus.

Edit 6: Note to self: Wow, look at this one!! (and here also :o)

 
Probably not M. medcofi
Arp,
I too have been doing some research into the diversity of North American terrestrial isopods. In my searches I attempted to acquire some informatiom about the genus Miktoniscus to identify some specimens sent to me by two different people from three locations in Alabama. According to what I found, Miktoniscus as a whole has either one ocellus per eye or is eyeless (depending on the species), has dorsal tubercles/granulations, and have four flagellar articles in antenna 2. The specimens sent to me from Alabama ended up being M. medcofi. I cannot find a description of what the color should be in living specimens the original description by Van Name (1940) says that "The specimens, except very young ones, are strongly pigmented, having the upper surface handsomely variegated with brown or purplish brown pigment on a light background which is whitish or yellowish in the preserved material. There is usually a narrow dark streak across the forehead extending through and behind the eye on each side", but the ones sent to me are apparently without much pigment. I would not expect the unidentified specimens here to be M. medcofi because the species is not known to occur west of the Mississippi valley. I'm not sure that this narrows it down much, but I hope it helps!

Best regards,
Eric

P.S.: Graham, if you'd be interested in sending more specimens to another enthusiast, I would be happy to receive any unidentified isopods you might come across in Texas or elsewhere! ;) I have helped a few people identify some of the small, semi-difficult-to-identify isopods in their area this way, and I get a chance to see, photograph, and culture new species of isopod I would not otherwise get to see.