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Acariformes

life science Maturity 7-9 Next article →

Acariformes, also known as the Actinotrichida, are a massive superorder of mites. They represent one of the two main superorders of mites, the other being Parasitiformes. These tiny creatures are incredibly diverse. Scientists have already described over 32,000 different species belonging to 351 families. However, many more likely exist. Experts estimate the total number of species could range from 440,000 to 929,000.

Yellow mite (Tydeidae), Lorryia formosa
Yellow mite (Tydeidae), Lorryia formosa

Modern scientists organize Acariformes into two primary clades, or groups. The first is Sarcoptiformes, and the second is Trombidiformes. There is also a group called Endeostigmata. These are primitive, minute, and soft-bodied mites. They ingest solid food like fungi, algae, and small invertebrates. This group includes organisms like nematodes, rotifers, and tardigrades. While some older views treated Endeostigmata as a separate suborder, modern views often include them within the Sarcoptiformes.

Yellow mite (Tydeidae), Lorryia formosa
Yellow mite (Tydeidae), Lorryia formosa

The Trombidiformes clade is also very complex. Within this group, the Sphaerolichida appear to be the most ancient lineage. There is also a group called the Prostigmata. Scientists struggle to define the exact relationships within the Prostigmata. They divide them into lineages like Anystina, Eleutherengona, and Eupodina. Current computer software often fails to resolve these complicated family trees perfectly. Because of this, researchers often treat these three lineages as distinct.

Yellow mite (Tydeidae), Lorryia formosa
Yellow mite (Tydeidae), Lorryia formosa

Sarcoptiformes mites play many roles in their environments. Most are microherbivores, fungivores, or detritivores that eat solid food. Some groups, called Psoroptidia, live near vertebrates or nest-building insects. This includes well-known species like house dust mites and scab mites. Other types include stored product mites and feather mites. Some Oribatid mites are even vital to other animals. For example, the strawberry poison-dart frog, Oophaga pumilio, eats these mites. The mites provide alkaloids, which are chemical compounds used for poison. Without these mites, the frogs do not develop their famous toxicity.

Yellow mite (Tydeidae), Lorryia formosa
Yellow mite (Tydeidae), Lorryia formosa

Trombidiformes mites are often noted for their impact on agriculture. Many species are significant plant parasites. This includes the spider mites of the family Tetranychidae and the Eriophyidae family. Other members of this group act as predators or animal parasites. Some are even free-living. The velvet mites of the family Trombidiidae are very easy to spot. They are often relatively large and bright red in color.

The history of Acariformes stretches back hundreds of millions of years. The oldest known fossils were found in the Rhynie Chert in Scotland. These fossils date to the early Devonian period, roughly 410 million years ago. We also have records of much larger ancient mites. One fossil species is named Immensmaris chewbaccei from the Cretaceous period. This was the largest fossil acariform mite ever recorded. It was also the largest erythraeoid mite ever found.

Reproduction in Acariformes provides a fascinating look at evolution. Most species evolved from sexual ancestors and use sexual reproduction. However, many species have developed parthenogenesis. This is a way to reproduce without needing a partner. This has occurred numerous times throughout their evolutionary history. Some parthenogenetic groups in the order Oribatida are very old. They likely emerged between 300 and 400 million years ago. In some cases, species using automixis, a form of self-fertilization, have even returned to sexual reproduction.

Yellow mite (Tydeidae), Lorryia formosa
Yellow mite (Tydeidae), Lorryia formosa
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