Some Steinkjer Oribatida!

Even though I've worked on oribatids for a whole long time now, I hadn't really had a chance to do proper IDs to species.  But, during December and January, I finally sat down to crack down on some identification fun with a sample I took back in 2023.  The IDs were to supplement some work for a Sabima grant, and the deadline was coming up - so I had to hop to it!

I of course still have a number of species to ID even from this single soil core sample (not to mention the 120ish other soil cores we took for that project), but I thought I'd introduce you to the ones I've met so far!  I submitted the report with 10 species identified, 7 of which were previously unrecorded in Trøndelag.  These 10 were also the first oribatids recorded for Steinkjer Kommune.  Not surprising, since not too many folks bother looking for these guys around here.  For those back in the US, things new for Trøndelag are equivalent to a state record, while things new for Steinkjer Kommune are equivalent to a county record.

Anyway, here is a basic introduction to these 10 species.  I've included at least one photo of each, a screenshot of records for Norway prior to my submissions (taken from Artsdatabanken), and little tidbits of information on each species when I could find anything.

Note:  I include the technical mumbo-jumbo of what I looked at to confirm ID, so just skip over that stuff if you're not in to that part.

Anywho, here y'all go:

Skogsprojektet - Skogen eller bare trær?
Oribatida species accounts

All specimens were taken from Byafjellet in Steinkjer, 08.jun.2023.  Coordinates E011.58128°, N64.05600°.    

Tritegeus bisulcatus

Features checked for determination:
Large lamellae, smooth integument on notogaster, cusp of lamella not dentate laterally, bothroideal seta without distinct head, la posterior to c, closer to 800.

New for Trøndelag: yes
New for Steinkjer: yes

Species information:
Tritegeus bisulcatus the type species for the genus, remains the most widespread species of Tritegeus.  It can be found in the western Palaearctic with its highest concentration in middle Europe.  It has been found in various habitats and seems to prefer forested areas. It’s back is ridiculously smooth compared to the closely related members of Cepheus, making it appear either very young or bald when compared to those species.

“My butt may be smooth, but dang!  Do I have some fancy lamellae or what??”

 

Carabodes labyrinthicus (Michael, 1879)

Features checked for determination:
c2 inserted closer to shoulder, notogastral setae spiniform, interlamellars much like notogastral, dorsosejugal depression narrow, interlamellar region without protuberances or medial depression, bothridial seta directed laterally.    

New for Trøndelag: yes
New for Steinkjer: yes

Species information:

Considered an indicator species of past permafrost conditions.  They are often found in or on lichens or moss, and are in the phycophage/fungivore feeding guild.  With the relatively uneventful sculpturing in the interlamellar region, their face looks a bit like a horse’s. 

“Neeeiigh.”

Look at its cute little butt!

And here you can see some of that fancy labyrinth stuff on it's back!

 

 

Carabodes rugosior Berlese, 1916

Features checked for determination:
Foveae poorly developed on the pordorsal surface (mostly just granulate); interlamellar region well-developed with distinct medial depression but without inverted Y-shaped indentation in center.    

New for Trøndelag: yes
New for Steinkjer: yes

Species information:
Found in moss, leaf litter and rotten wood from forest floor.  The sculpturing on their back is particularly fancy, and can be admired from a distance (unlike C. labyrinthicus, which takes some up-close-and-personal inspection for a real appreciation).

 

“Check out my bumps!”

Raisin or canyonland?  You decide.

Side view.  Check out that smooshed face!

T E X T U R E .

Haha butt!

My attempt at a sketch.

Platynothrus peltifer (C.L. Koch, 1839)

Features checked for determination:
Body usually clean; notogastral setae relatively long, extending to or past insertion of next seta; interlamellar setae do not extend to lamellars; median notogastral carinae well developed and separate anteriorly.   

New for Trøndelag: yes
New for Steinkjer: yes

Species information:
Widespread both geographically and ecologically.  Lives in forest soil and litter, mosses, peatlands, various freshwater habitats, and has even been found in benthic habitats.  They are pretty good at tolerating drought and heat extremes.  This parthenogenic species can carry up to 14 eggs, and probably has a generation time of at least a year (in temperate European forests).  Currently, it is estimated the species has been around for 100 million years, and its current distribution is largely a result of continental drift.  It has good tolerance of metal contamination from smelters.  Not a picky eater, it is happy to eat both fungus and decaying plant material.  They are willing to much on algae in the lab.  Gut content analyses have shown remnants of moss fragments, pine pollen, fungal and arthropod fragments.  They will even eat some nematodes - living or dead, P. peltifer don’t care. 

 

“Trønder rumpe?  Æ e gresskar rumpe!”

 

Nothrus silvestris Nicholet, 1855

Features checked for determination:
Median notogastral setae and h1 relatively long, slightly swollen distally; h2 very long.  Lamellar setae relatively long, as long or longer than distance between insertions.  c2 short and club-like.    

New for Trøndelag: no
New for Steinkjer: yes

Species information:
This species is considered an unspecialized feeder.  It has been successfully reared on lichens, algae, and moss.  One populations was shown to prefer a main course of leaf material (with a side of fungal hyphae, fungal spores or amorphous material).  Gut contents have included plant material, moss fragments, pine pollen, fungal material, arthropod fragments, and protists.  In a cafeteria experiment, they decidedly loved a species of ascomycete that colonizes conifer needles as well as a super common ascomycete that colonizes dead organic matter.   Yum, yum!  And just like P. peltifer, they are happy to eat certain nematodes, living or dead. #teamdontcare.  

        

“They said ‘Join the Club’.  So I grew these setae.” 

Euzetes globulus (Nicholet, 1855)

Features checked for determination:
6 pairs genital setae; epimeral neotrichy on ep. IV; body size around 1200.    

New for Trøndelag: yes
New for Steinkjer: yes

Species information:
Members of this genus live on the soil surface in woods with heavy leaf fall.  Perhaps other litter is okay, as our survey site didn’t have much in the way of proper leaf fall - but there were large moss mats and a healthy layer of evergreen needles.  Adults of E. Globulus have been found in the hair of small mammals, sometimes even in numbers way higher than surrounding habitat, suggesting they use these mammals as public transport.  These mites, being about 1200 micrometers, are certainly larger than species known to use large beetles or giant flies for dispersal, so it makes sense they had to step up their game.  It is worth noting that aside from very rare cases, this species consistently occurs in very low densities.  This could mean they are going to be more susceptible to human disturbance.

“Check out my ovipositor!  Isn’t it long?  Maybe we should call it a longipositor.”

Phthiracarus clavatus Parry, 1979

Features checked for determination:
ad1 and ad2 vestigial (completely reduced to aveoli), seven genital and aggenital setae (anterior corner trio, couple in line with one another in middle, and two longer, more spaced ones leading to posterior edge of plate); sensilli match description for clavatus (feather-like with spoon structure inserted); interlamellars no more than twice the length of lamellars, are not erect and thickened), yellowish-brown color.

New for Trøndelag: no
New for Steinkjer: yes

Species information:
I was unable to find much on the species itself, but phthiracarid mites in general are important decomposers - specifically, with regards to their ability to break down woody material.  They often inhabit unstable habitats such as deadwood, and are key players in the hasty breakdown of woody material, unlocking nutrients that other organisms can’t really digest in that form.  If decomposers with this ability were absent, nutrients would be trapped in woody material for very long periods of time, as it is a slow decomposition process compared to the breaking down of dead leaves and other softer materials.  

“My babies love to eat tunnels through pine needles!  But I’m too old for that now.”

Hypochthonius rufulus C. L. Koch, 1835

Features checked for determination:
c1 reaches insertion of d1.  Notogastral setae long.

New for Trøndelag: yes
New for Steinkjer: yes

Species information:
An omnivore, this species has been found scavenging on dead animals, particularly collembolans, and will eat macerated dead leaves if starving.   Plant, fungal, moss fragments, pine pollen, collembolan and mite remains (and enchytraeid hairs) have been found comprising almost all of their gut content, with collembolan remains seemingly a favorite.  It would be interesting to know if the higher amount of collembolans was due to an actual preference of if it is simply a result of Collembola being freaking everywhere.   H. rufulus will eat nematodes in the lab, so probably also out in the wilds, and high 15N/14N ratios indicate animal material dominates their diet. 

“I’m very good at making babies so you may find a lot of us in a single sample!”

Achipteria coleoptrata (Linnaeus, 1758)

Features checked for determination:
c and la short (same length as other notogastral setae); body less than 700.

New for Trøndelag: no
New for Steinkjer: yes

Species information:
Often found in peatlands.  Gut contents of Alberta specimens was mostly coarse granular material (suggesting dead plant munching), but fungal hyphae and spores are also visible, along with (probably) moss spores.  Stable isotope data points to eating litter.  Also seems to like algae when given the opportunity.  

“Can you see my special pokey shoulder spikes?  I also have some wicked fancy lamellae.”

Tokukobelba compta (Kulczynski, 1902)

Features checked for determination:
genital and anal plates are super close together, 6 pairs of genital setae, 2 pairs anal setae, 3 pair adanal; anal plates have conspicuously thickened carina; no spina adnata; crazy tubercles on edge of epimeral plates, body right about at 500

New for Trøndelag: yes
New for Steinkjer: yes

Species information:
It occurs in montane to alpine habitats, but is not limited to such, and appears to be a cold-adapted species.  It is often found in forested areas, but can also be found in treeless habitat, such as alpine heath or arctic tundra, and is clearly totally fine with acidic environments.  They typically live in the leaf layer or top layer of soil, but like other Damaeidae, are also very happy to live in moss.  They will sometimes be found on lichen, but seem to not have an actual preference for this stuff.  It’s just better than nothing, I guess.  The species loves wet and humid environments, so much so it will be present in moist moss, but absent in adjacent dry habitat such as lichen.  When we took our samples, it was raining a lot, so many of our soil cores were very wet.  But it was interesting that spots more protected by low trees were often powder dry, despite being otherwise similar in vegetation and soil composition.  T. compta’s humidity preference could mean that the species will be absent from areas close to younger tree trunks.  From what we can see, they prefer fungus and algae for dinner.  Like many other mites, it can be found in the nests of birds, suggesting they use birds for dispersal.  A sexual species, available data suggests a 1:1 sex ratio.  

 

Note:  The white ones after the brown mite photos are the protonymphs.  I had two of these and one adult in the sample.

 

“You’re cold?  Pffft.”