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Soil mites are essential for soil health, and their critical role in plant health is getting increasing attention from the scientific community.
Soil mites can live for up to seven years and have developed a way to travel miles in a single day. Their life cycle is imperfect. The largest soil mite subclass (Oribatid) reproduces asexually – no males.
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Soil Mites
Soil mites abound in almost every soil type, from your garden to tropical rainforests, temperate forests, and grasslands to bogs, caves, and salt marshes. Their extreme diversity is evidence of their specialization, reproductive abilities, and adaptability.
Acarology (the study of mites and ticks) is a relatively new branch of zoology. It offers vast fields that still need exploration in species identification, behavior traits, and their impact on the ecosystem.
What is known is that acarid arachnids (mites) consist of tens of thousands of species, many of which are disease vectors. This is unfortunate because the four soil-borne soil mite classes do no harm and are, in fact, irreplaceably significant to soil and plant health.
Soil Mites and the Relationship Between Micro- and Mesofauna
Soil is a living system, and increasingly scientists are discovering that, rather than being a localized system, soil systems are interconnected, and some have been found to cover huge areas. Fungi mycelium forms a symbiotic relationship with the roots of seed plants, called mycorrhiza.
If that is impressive, fungi are only a part of the soil food web. Essentially, the soil food web is like a food chain, but a web better represents predator/prey relationships. Every part of the soil food web is essential.
Think of a mechanical clock made of springs or weights driving cogs connected to hands on the clock face. If you remove one of the cogs, the clock will no longer work, and the hours, minutes and second hands will come to a standstill.
Soil mites are an essential ‘cog’ in the soil food web.
Microfauna
Microfauna (microscopic animals) are classified as non-plants smaller than 0.1 mm (four-thousandth of an inch (0.00393701 inches)). The soil food web includes bacteria, fungi, actinomycetes, algae, and protozoa microorganisms,
They are responsible for converting organic matter to bioavailable compounds, easily absorbed by the plant roots. Microorganism populations are enormous, and a teaspoon of soil may contain as many as 8 billion soil biota.
These microorganisms eat carbon and use nitrogen for cell development. Nitrogen is the most abundant component of the atmosphere and is highly volatile in soils. Microorganisms capture the nitrogen and are a source of plant nitrogen when they die.
The next tier of the soil food web, mesofauna, releases nitrogen near roots when they eat the microorganisms.
Mesofauna and Macrofauna
Working our way up the soil food web, the soil engineers, population controllers, and plant litter transformers are anthropods and earthworms.
Arthropod species form a significant part of the soil’s meso- and macrofauna. The five main soil-borne arthropods include
- Acari (mesofauna) – mites – the most populous
- Isopoda (macrofauna) – woodlouse, sowbug, roly-poly, pill bugs
- Myriapoda (macrofauna) – millipedes, centipedes
- Insecta (macrofauna) – insect larvae, ants, beetles
- Collembola (mesofauna) – springtails
Acari is the most diverse and numerous of the group. Arthropods are ecosystem engineers, plant litter transformers, and population controllers, functioning across the three tiers of an effective soil food web.
You may wonder where earthworms fit in. Pot worms and earthworms are non-arthropodal organisms. They are also essential to the soil food web as they help with aeration, improving soil tilth and drainage.
The Soil Mite’s Metamorphasis (Life Cycle)
Mites are not insects and are more closely related to ticks but also to spiders and scorpions, all of the Archinid class in the Arthropod phylum.
Complete Metamorphosis
You’ve heard it said that a leopard doesn’t change its spots, and a mite also doesn’t change much as it grows. Complete metamorphosis happens when an organism goes through distinctly different forms as it matures.
A butterfly, for instance, lays its eggs that hatch into a larva and transforms into pupae, from which an adult butterfly emerges.
The Soil Mite’s Incomplete Metamorphosis
The soil mite changes only incrementally, from an egg to a larva, through three iterations as a nymph, before becoming an adult soil mite.
The egg hatches into a larval stage (only has three pairs of legs), which molts to the first nymphal stage, called a protonymph. After losing an additional second (duetonymph) or third (trionymph) time, the nymph matures into an adult soil mite.
Mites, like ticks, have three pairs of legs as larvae and four pairs of legs as nymphs (and adults). The grasshopper metamorphosis is incomplete, incrementally morphing through several skin moltings until adulthood. Reproductive abilities mark maturity in soil mites, but more on this later.
Soil Mite Mobility
Soil mites can hold on to beetles and other insects as they fly. Whether in the wings or the heads, soil mites can cling to the flying insects and will only disembark in environments better suited to their needs.
Phoretic mites have fascinated scientists for centuries, and it remains unclear how they know when to disembark from their ‘taxi.’
Getting Rid of Soil Mites In Vermicompost Bins
Mites don’t only use flying insects for their phoretic expeditions. Worm or bug farmers and even vermicomposting may notice tiny clusters of almost translucent mites on their worms.
Beetle Breeding Daniel Ambuehl’s YouTube videos demonstrate what to do with infected larvae or earthworms. It’s a bit long, so skip through part one and see the outcome in part two.
He uses the principle to provide the soil mites with an alternative, i.e., remove the need for emigration. The soil mites hitch a ride to escape an environment poorly serving their purposes.
As soon as the environment improves, i.e., when the need for emigration is removed, the soil mites disembark. You can add several things to your vermicomposting bin to encourage your soil mites to get off the worms or larvae.
Soil mites primarily feed on organic matter. The soil mites disembark when the ‘infected’ worm’s environment has more organic matter. Unlike bacteria and fungi, they don’t need much nitrogen; even sawdust or dry leaves will see them leaving the ‘bus’ to feed.
I have also heard that watermelon or pumpkin rind works, but I haven’t tried it,
Soil mites do not feed on their transport, so your worms are safe. Still, I don’t imagine it’s the best for the worm’s general well-being, as demonstrated by the beetle video shared in the section above.
Soil Mite Reproduction
Soil mites include many sexual and parthenogenetic (thelytokous) species. Soil-borne organisms, in general, have four ways of reproducing:
- Sexually – male and female, egg and sperm, ensures genetic diversity. The way some soil mites reproduce.
- Binary Fission – the way bacteria, fungi, and actinomycetes reproduce. These single-cell organisms grow until they can divide, duplicating the DNA.
- Hermaphroditism – the way earthworms reproduce. All earthworms are hermaphrodites (having both male and female reproductive organs) but still need an exchange of both eggs and sperm from another worm.
- Parthenogenesis – the way most oribatid soil mite species reproduce. In parthenogenesis, the whole population is females that lay unfertilized eggs that hatch into larvae and grow into nymph clone daughters.
Frequently Asked Questions
In Summary
The soil mesofauna includes springtails and soil mites, mainly oribatid mites. These organisms are ubiquitous and vital to the soil food web.
They shred dead organic matter, making the nutrients available to other organisms, including bacteria, fungi, and actinomyces. As scavengers, soil mites also feed on nitrogen-rich microorganisms, making the nutrient more available to plants.
For millions of years, many soil mite populations have only included females. They can lay eggs unfertilized by males, so they do not require sex to reproduce.
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