Explaining Science – vermiform mites

You have heard of mites – minute arachnids that have four pairs of legs when adult, are related to the ticks and live in the soil, though some are parasitic on plants or animals. But what are vermiform mites? Maybe you have heard of vermi-compost, a composting technique that uses worms (like your earthworm in the garden) to decompose organic matter. So vermiform mites are mites with a body shape like a worm:

worm-shaped nematalycid Osperalycus

Why are they shaped like a worm, you may ask – To find out more I interviewed Samuel Bolton, former PhD student in the acarology collection at our museum, now Curator of Mites at the Florida State Collection of Arthropods. Sam’s main research interest is in mites that live on plants and in the soil, especially Endeostigmata, a very ancient group of mites that dates back around 400 million years, before there were any trees or forests. Sam’s PhD research with Dr. Hans Klompen here at OSU, was focused on a small family (only five described species) of worm-like mites, called Nematalycidae.

side note: You may have heard of Sam’s research in 2014 when he discovered a new species of mite, not in a far-away country, but across the road from his work place in the museum.

When Sam started his research it was not clear where these worm-like mites in the family Nematalycidae belong in the tree of life. To find out Sam studied several morphological characters of Nematalycidae and other mites. He focused in particular on the mouth-parts of this group. As he learned more about the mouth-parts of this family, he found evidence that they are closely related to another lineage of worm-like mites, the gall mites (Eriophyoidea). Eriophyoidea have a sheath that wraps up a large bundle of stylets. They use these stylets to pierce plant cells, inject saliva into them and suck cell sap.
Although Nematalycidae don’t have stylets, one genus has a very rudimentary type of sheath that extends around part of the pincer-like structures that have been modified into stylets in Eriophyoidea.

So what did Sam and his co-authors discover?

“.. Not only are gall mites the closest related group to Nematalycidae, but the results of our phylogenetic analysis places them within Nematalycidae. This suggests that gall mites are an unusual group of nematalycids that have adapted to feeding and living on plants. Gall mites use their worm-like body in a completely different way from Nematalycidae, which live in deep soil. But both lineages appear to use their worm-like bodies to move around in confined spaces: gall mites can live in the confined spaces in galls, under the epidermis (skin), and in between densely packed trichomes on the surface of leaves;  Nematalycidae live in the tight spaces between the densely packed mineral particles deep in the soil.”

This research potentially increases the size of Sam’s family of expertise, Nematalycidae, from 5 species to 5,000 species. We have yet to confirm this discovery, but it is highly likely that gall mites are closely related to Nematalycidae, even if they are not descended from Nematalycidae. This is interesting because it shows that the worm-like body form evolved less frequently than we thought. This discovery also provides an interesting clue about how gall mites may have originated to become parasites. They may have started out in deep soil as highly elongated mites. When they began feeding on plants, they may have used their worm-shaped bodies to live underneath the epidermis of plants. As they diversified, many of them became shorter and more compact in body shape.

I wish I could tell you now to go out and look for these oddly shaped mites yourself, but you really need a microscope. Eriophyoid mites are minute, averaging 100 to 500 μm in length. For your reference, an average human hair has a diameter of 100 microns.

eriophyoid Aceria anthocoptes

Reference:

Bolton, S. J., Chetverikov, P. E., & Klompen, H. (2017). Morphological support for a clade comprising two vermiform mite lineages: Eriophyoidea (Acariformes) and Nematalycidae (Acariformes). Systematic and Applied Acarology, 22(8), 1096-1131.

 

About the Authors: Angelika Nelson, curator of the Borror Laboratory of Bioacoustics, interviewed Samuel Bolton, former PhD graduate student in the OSU Acarology lab, now Curator of Mites at the Florida State Collection of Arthropods, in the Florida Department of Agriculture and Consumer Services’ Division of Plant Industry.

 

Ticks in pictures

Some more about ticks.  No, not The Tick comic or the movie Ticks … both may be entertaining, but they feature completely inaccurate depictions of ticks.

Let’s talk about real ticks:  Ticks are rather large mites. To demonstrate this, here is a family portrait:

family portrait of Ixodes pacificus, California Dept. of Public Health

Family portrait of Ixodes pacificus, California Dept. of Public Health [public domain]

From left to right, larva (6 legs), nymph (8 legs), male and female of Ixodes pacificus, the Western black-legged tick, from the west coast (you can see them with the naked eye, therefore they are big).

All members of the family feed on host blood using highly modified mouthparts, but only larvae, nymphs, and females engorge (feed to the point where their body truly swells up).

close-up of mouth parts of Amblyomma extraoculatum, U.S. National Tick Collection (USNMENT00956315)

Close-up of mouth parts of Amblyomma extraoculatum, U.S. National Tick Collection (USNMENT00956315)

Here are some nice examples of engorged females.  Keep in mind that while engorged ticks are easy to find, they are often difficult to identify.

Most of the ticks we encounter in Ohio have females that feed only once.  They engorge, convert all that host blood into a single mass of hundreds to thousands of eggs, and die.

tick with eggs (c) Univ. Nebraska, Dept. Entomology

Tick with eggs, Univ. Nebraska, Dept. Entomology

Ticks in general get really bad press.  Kind of sad, because ticks are very good at quite a few things, like surviving (some can survive hours under water or years without food), or manipulating your immune system (using a dizzying array of chemicals often found only in ticks). On second thought, that may not strike most people as positive, so let me end with a few pictures of beautiful creatures. I already introduced Amblyomma americanum, which occurs in Ohio, the others are African, A. chabaudi on tortoises in Madagascar, A. variegatum usually on cattle. Amblyomma variegatum is the main vector of heartwater, a disease making cattle herding impossible in parts of Africa, but still, very pretty.

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See some more of these specimens close-up, but at a safe distance through microscopes at our Annual Open House, April 22, 2017.

 

Dr. Hans Klompen, Professor EEOBiology at OSUAbout the Author: Dr. Hans Klompen is professor in the department of Evolution, Ecology and Organismal Biology and director of the Ohio State University Acarology Collection.

*** Which of these ticks is your “favorite”? Let us know on Facebook ***

 

Know your ticks: Ohio

Daffodils are in bloom, students walk around in shorts and T-shirts, so it must be the beginning of tick season.  And indeed, the first ticks are out and questing (= searching for a host). This might be a good time to talk about ticks in Ohio.  Ohio is not a major center for tick diversity, but it has some diversity.  Most people only know the three main people biters, Dermacentor variabilis (American dog tick), Amblyomma americanum (lone star tick), and Ixodes scapularis (deer tick), so let’s start with these:

Dermacentor variabilis is perhaps the most widespread and common tick in Ohio.  Immatures feed on rodents and other small animals, but adults feed on medium (opossums, raccoons, dogs) to large (humans) mammals.  Of the “big three” this species is the most tolerant of drying out, and the most likely to be encountered in open areas.  The main activity period for adults is mid-April – mid-July.  D. variabilis is the vector of, among others, Rocky Mountain Spotted Fever (RMSF) and tularemia.  Columbus used to be a focal area for RMSF, but the disease is less common now.  D. variabilis may also cause tick paralysis, although less frequently than the related D. andersoni from the Rocky Mountains region.

American dog tick

Dermacentor variabilis American dog tick

Amblyomma americanum used to be uncommon in southern Ohio, but has increased in numbers and range over the last decades.  This is part of a general trend.  In the eastern U.S., this species is rapidly expanding its range northwards.  All instars, larva, nymph, and adult feed on mid-size to large animals, incl. humans.  Like D. variabilis, females can deposit very large clutches of eggs, but in this case the resulting larvae often stay together.  If you are unlucky and step close to a mass of these “seed ticks”, you may be attacked by hundreds of ticks simultaneously.  These ticks are active in all warm months of the year.  Unlike D. variabilis, “Lone stars” are not common in open areas, preferring more shady and humid sites.  For a long time A. americanum was listed as vectoring few human diseases, but it has now been identified as vector of human monocytic ehrlichiosis and STARI, and possibly tularemia and Q-fever.

lone star tick

Amblyoma americanum lone star tick

Ixodes scapularis appears to be an even more recent resident.  This species was rare or absent in Ohio before 2010, but has now been found in a majority of Ohio counties.  The reason for this sudden expansion is unclear.  This is a relatively small species.  Larvae can be found in summer, nymphs late summer, and adults in fall and early spring.  Immatures tend to feed on smaller sized hosts, e.g. rodents, small birds, while adults prefer larger hosts, such as deer.  However, all instars may attach to humans.  Nymphs are considered the most problematic: they are small (thus often undetected), and can be infected with e.g. Lyme disease (unlike the even smaller larvae).  Like A. americanum, this species prefers shady, humid environments.  New subdivisions build in forests, resulting in large amounts of forest edges with lots of deer, have been a very good habitat for this tick in New England.  Ixodes scapularis has become famous as the vector for, among others, Lyme disease, human granulocytic anaplasmosis, and babesiosis.  Co-infection is common in New England and appears to result in increased pathology.

deer tick

Ixodes scapularis deer tick

So much for the common people biters.  It is important to note that most species of tick rarely if ever bite people.  They prefer different, usually smaller, hosts.  For example, Rhipicephalus sanguineus, the brown dog tick prefers feeding on dogs.  It is one of the few species that may occur indoors in dog kennels etc.  Haemaphylis leporispalustris appears to be specialized on hares and rabbits.  Several Ixodes species, I. cookei, I. dentatus, I. kingi, I. marxi, can be found on small to medium sized mammals, often associated with nests or burrows.  Finally, the so-called soft ticks, family Argasidae, are represented by only a single species in Ohio, Carios kelleyi, primarily found in bat colonies.

Find out more about the ticks’ life cycles and their diseases.

Dr. Hans Klompen, Professor EEOBiology at OSUAbout the Author: Dr. Hans Klompen is professor in the department of Evolution, Ecology and Organismal Biology and director of the Ohio State University Acarology Collection.

 

*** Have you found a tick yet this spring? send us a photo of your specimen on Facebook! ***

 

Everyday Life at the Museum-part 1

Visitors to our Annual Open House – by the way, the next Open House is coming up soon on Saturday April 22, 2017 – often wonder what everyday life in our museum collections looks like. During the Open House we showcase specimens in fabulous displays but how do we accession and maintain specimens throughout the year? To find out I took a walk through our building on a weekday morning and stopped by each collection to get a snapshot of our students’ and staff’ workdays. Watch the short videos below to get some behind the scenes insights and see how important the help of OSU undergraduate students is for our collections.

In the Borror Laboratory of Bioacoustics Evolution and Ecology major Morgan VanDeCarr digitizes recordings of House Finches Haemorhous mexicanus. The song of these birds was recorded onto a reel-to-reel tape by researcher Erik Bitterbaum at Occidental College in 1976.

In the Triplehorn insect collection Art major Katherine Beigel takes images of tiny insect specimens under a microscope and stacks them into one composite image using special software. Here she shows us a Coleoptera, beetle specimen.

In the Acarology collection Dr. Hans Klompen, Professor in the OSU department of Evolution, Ecology & Organismal Biology, talks to a student. The tick and mite specimens are neatly shelved and ready for the next Acarology Summer Program (June 19 – July 7).

In the Tetrapods collection Evolution and Ecology major Chelsea Hothem updates location information in the computer database. To get accurate data she often goes back to the specimens and reads information on the tags.

We will look behind the scenes in the herbarium, the mollusc and the fish collection on Friday!

 

About the Author: Angelika Nelson is curator of the Borror Laboratory of Bioacoustics and the museum’s social media and outreach manager.

 

*** Do you have any questions? We would be happy to answer them ***