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"Detritivores were predominantly oribatid mites, but other larger forms of generalist-and specialist-feeding arthropods are evidenced by the diverse range of coprolites (fossil poo)" (Slater, Mcloughlin, and Hilton, 2015)
Oribatids did not change much during this period, pretty well carrying on as in the previous - Carboniferous - period. |There were few evolutionary 'events - brown boxes, and no changes in shape or eating - no red/orange arrows.
"Cavities in trunk wood from the Permian...Central Transantarctic Mountains are interpreted to have been produced by oribatid mites (Kellogg and Taylor, 2004). .."the similarity of fungal-induced cavities in Australoxylon to modern white pocket rot suggests that the fungi's relationship to the host plant was primarily saprotrophic." (Slater et al 2012)
The pattern of attack on the trunk wood was attributable to either mites or the overwintering larvae of coleopterans that fed either directly on the wood or on fungi that was in turn feeding upon the wood in a possible 3-way arthropod–fungal-plant symbiotic relationship . (Slater et al 2012)
Oribatids
Oribatids
Terrestrial ecosystems were evolving and diversifying, with the spread of vascular plants and the development of complex forest ecosystems. Oribatid mites are associated with soils and organic debris in these ecosystems, suggesting that their diversification was influenced by the availability of habitats and food sources. They were about in gymnosperm woods (Feng et al 2010). Yet there is little evidence of their diversification in this period and the EPE appears to have had little affect on their branching either. (Schaefer & Caruso 2019)
Put another way
These creatures spread out in the Permian period and survived the great extinction (as few other creatures could) to go on and diversify and drive soil metabolism later.
Deadwood
Deadwood
Talking of mites, what happens with mites and deadwood of conifers? The effects of these micro-arthropods on microbial processes may be most important in robust substrates such as wood.
Remember the oribatids being mentioned in this Period with deadwood now are lower oribatids,
Mites in deadwood
Mites in deadwood
“Spruce deadwood is settled by arich mite fauna. It becomes a more rewarding food resource for mites as they tend to increase with log age, althoughthe maximum density was observed in the last but one decay class. It was both surprising and interesting to find that oribatid mite fauna in deadwood is not depauperated in comparison with forest soil. For oribatid mites’ logs are a separate habitat rather than simply an extension of the forest floor. Some mite species may specialize on deadwood, because 55 species (of 131 in total) were obligate members of the intra-log community.. It was not simply a subset of the soil fauna. Deadwood was richer in species (126) than soil (76),” (Skubala & Maslik 2010 ) However others have noted ‘depauperation’, with less mites in wood than litter and soil.
“Oribatida was the major component of the microarthropod fauna in spruce decaying wood throughout the year. Only in the youngest stages of wood decay, springtails slightly dominated oribatids. Previously, only the macroinvertebrates were considered to be important in early stages of wood decomposition. Oribatid mites may also play some role in decomposition of deadwood, even in the early stages of the decaying process. These mites do affect the structural integrity of the wood, and ultimately wood of final decay class is largely composed of faecal oribatid pellets." (Skubala & Maslik 2010 )
Mites seem to play an important part in dealing with the extremes in soil conditions, prevalent in this period. My supervisor, Dr Madge, looked into how oribatids reacted with moisture. His was the paper that led me to Ghilarov.
David Madge's research
David Madge's research
David Madge examined the reactions and behaviour of four indicator tree living species, Humerobates rostrolamellatus initially chose a dry humidity, but reversed to a moist one after 4-5 days. Belbageniculosa, collected from oak-litter, had an initial moist reaction. Platynothruspeltifer, found in litter and bog moss, had a similar reaction. A species found in permanently damp sphagnum, Fuscozetesfuscipes , showed no marked responses to humidity gradients. He found the higher the temperature, the greater the choice for the higher humidity. H. rostrolamellatus changed its initial dry reaction to a moist one after 5 days desiccation at 15° C when one-third of its original body-weight was lost. B. geniculosa showed a stronger initial moist reaction when starved for one week. The higher the temperature, the faster the speed of movement with all the species of mites. H. rostrolamellatus was more active in moist air than in dry air; B. geniculosa was more active in dry air than in moist; results with F. fuscipes were variable. The humidity receptors are probably located on the forelegs. All of which indicates humidity is important to oribatids, which isn’t very surprising if they are to survive changing soil conditions.
How the soil could be ‘bone’ dry and like concrete, but not long after the rains, it comes back to life. And it is the same with cold temperatures, yet somehow life comes back when there is warmth and water. We know oribatids have a marvellous way to survive – wrap up in a ball of highly durable and strong outer skeleton and wait for the environment to improve. That way it could also withstand possible damage from pressure changes – an increasing hazard as machines get ever bigger so they compact the soils more.
Oribatid evolution
400-360 mya (Late Devon)
330-300mya (Late Carb)
Higher (200-145 mya Jurassic)
Mites (145-66 mya (Cretaceous)
These 'lower' oribatids could chew and poo their way through dead wood, but probably quite confined to this environment. They would also have made small tunnels and create all sorts of shapes and structures to run along. Oribatids withstand dryness and they make the soil come alive, even when it looks very dead. The Oribatids are of vital importance nowadays, but largely ignored. Imagine how important they were long before earthworms arrived. However they were to help transform soils when the earthworms did arrive in the Jurassic and Cretaceous periods. arrive.
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