Archive for the ‘Taxonomy’ Category

Mite-y Waist: Correcting a 60-Year Error in Mite Morphology


Much of mite biology is clouded in mystery—even the delineation of their body segments. A new study upends a 60-year-old model for the proper location of mite “waists.” Shown here is a scanning-electron microscope image of a Proteonematalycus wagneri female mite. (Image by Sameul Bolton, Ph.D.)

By Samuel Bolton, Ph.D.

Samuel Bolton, Ph.D.

Most people are surprised to find out that mites live in more places than just inside their mattress or on their pets. But what we acarologists know about mites is, comparatively speaking, not so much more, for there is still a tremendous amount that we have yet to discover about these arthropods.

For example, our knowledge of global mite biodiversity is so meager that estimates of the total number of undescribed species of mites range across nearly two orders of magnitude—from 500,000 to 40 million. And our ignorance extends to some fairly basic aspects of mite biology. There are still competing ideas over the correct body plan for all mites. (See video, below.)

There is even a controversy over where one major body region ends and another begins. This particular controversy interests me because it illustrates how an influential idea can persist long after evidence comes to light that shows it is likely in error. When a bad idea becomes highly influential, often because the originator is influential or because the idea has aesthetic appeal, it can endure for long enough to become entrenched within the culture of a scientific community.

Mites are arachnids, and that means that they have a body that is divided into a prosoma (the limb-bearing region at the front) and opisthosoma (the limbless region at the back). To keep things simple, I will call the border between the prosoma and the opisthosoma the “waist.” This is apt because in most arachnids there is a waist-like constriction between the prosoma and opisthosoma, which makes it very easy to tell where the prosoma ends and the opisthosoma begins. But almost all mites lack such a visible waist.

In 1963, a well-known acarologist, Leendert van der Hammen, published a hypothesis on where the waist is positioned in mites. He proposed that the waist is delineated by a furrow, present in some mites, that runs obliquely from the top of the body to an area just behind the rear pair of legs (see Figure 1, top). However, there are other mites, such as Micropsammus, that have a body with a vertical furrow that looks a lot more like a waist (see Figure 1, bottom). The dorsal part of the vertical furrow is in a different segmental position to that of the oblique furrow. It is therefore not possible that the vertical furrow has reorientated to become the oblique furrow or vice versa, and so only one of these furrows can be the waist.

A model of a mite (top) shows the oblique furrow that Leendert van der Hammen thought was a “waist,” or the division between prosoma (the limb-bearing region at the front) and opisthosoma (the limbless region at the back). The image of a Micropsammus sp. mite (bottom), however, has a vertical furrow that looks a lot like a waist. (Image by Sameul Bolton, Ph.D.)

Most acarologists treat van der Hammen’s oblique furrow as the true waist. However, van der Hammen’s interpretation was based on oribatid mites, which have highly modified morphologies for defense, and so the oblique furrow seems more likely to be the result of a defensive modification than a true waist. Why, then, is his interpretation still widely accepted? One reason is that this is another example of a persistent and influential idea that is long overdue for retirement. Another reason is that almost all species of mites lack visible body segments. The waist is a segmental border that divides the prosoma from the opisthosoma. Without a series of clearly delineated segmental borders, it is difficult to know which of the two furrows is definitely a waist.

There is one mite, however, that does very clearly show its body segments, especially on the part of the body where the waist is. Proteonematalycus wagneri, which has been collected on no more than a handful of occasions, has been examined only very rarely. The description of P. wagneri, which is more than 30 years old, includes drawings of a segmented body that starkly contradicts van der Hammen’s interpretation. Drawings can sometimes be misleading, though. In a paper published in February in PLOS ONE, I analyze new detailed images of P. wagneri, which more clearly illustrate the flaw in van der Hammen’s hypothesis and offer a new model for mite body segmentation.

As seen in this image of a Proteonematalycus wagneri adult female mite, the oblique furrow is absent and so it cannot be the true waist. (Image by Sameul Bolton, Ph.D.)

The image in Figure 2 shows that P. wagneri has a segmental border that is in exactly the correct position and orientation to correspond with the vertical furrow of Micropsammus (Figure 1, bottom). That border is the true waist, not only because it divides the prosoma from the opisthosoma, but also because there is no sign of the oblique furrow. If you can clearly see the body segments but the oblique furrow is nowhere to be seen, that can only mean that the oblique furrow does not correspond with a segmental border, and so van der Hammen was clearly wrong about that furrow being the waist.

But why is it so important to know where the waist is? Well, as I mentioned above, the waist delineates the boundary between two major body regions, the prosoma and opisthosoma. If the oblique furrow were the true waist, it would mark out mites as very unusual compared to other arachnids. In an important way, Proteonematalycus wagneri shows that mites are not quite as weird as we had thought.

In fact, the position of the waist was correctly determined more than a century ago . But over the past half century, countless papers, including my own, have mislabeled characters as opisthosomal when they are prosomal. Almost 60 years of confusion and debate, all caused by one very influential paper that was written by one very influential acarologist. Oh, what a mitey waist.

Read More

Proteonematalycus wagneri Kethley reveals where the opisthosoma begins in acariform mites


Samuel Bolton, Ph.D., is curator of Acari at the Florida State Collection of Arthropods, in the Florida Department of Agriculture and Consumer Services’ Division of Plant Industry. Email: samuel.bolton@fdacs.gov.

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Museum digitises five millionth specimen to unlock secrets of collection

By James AshworthFirst published 18 January 202218

A naturally bright green stonefly has signalled full speed ahead for the Museum’s digitisation project, as it releases its five millionth specimen online.

As well as making the Museum’s specimens available online for anyone to access, the digitisation of these collections could contribute billions of pounds to the global economy.

The digitisation of the Museum’s five millionth specimen is unlocking information that could save species from extinction and boost the global economy.

A stonefly found in New Zealand, called Stenoperla prasina, achieved the landmark figure after it was digitised as part of an ongoing project to unlock the Museum’s collections and make them freely available on the web. 

Stoneflies, along with the related mayflies and caddisflies, are vital indicators of the health of an ecosystem, and are one of the reasons why a study published in Research Ideas and Outcomes estimated that digitising the Museum’s entire collections could be worth over £2 billion.

Helen Hardy, who leads the Museum’s digitisation programme, says, ‘This is a huge landmark for us and the combined effort of many digitisers, curators, researchers, data managers and others. Sharing data from our collections can transform scientific research and help find solutions for nature and from nature. 

‘Our digitised collections have helped establish the baseline plant biodiversity in the Amazon, found wheat crops that are more resilient to climate change, and support research into the potential zoonotic origins of COVID-19. 

‘The research that comes from sharing our specimens has immense potential to transform our world and help both people and planet thrive.’ 

A stonefly is held with tweezers in front of a computer
Stenoperla prasina is green in life, and fades to brown after death. Image © The Trustees of the Natural History Museum, London  

Learning the lessons of the past

On the death of Sir Hans Sloane in 1753, the UK Parliament purchased the 71,000 objects that Sloane had collected over his life. This collection formed the basis of what would become the Museum, the British Library and the British Museum. 

Since those early days, the Museum’s collections have expanded significantly to include some 80 million objects from around, and even beyond, the world. From meteorites to marmosets, and mahogany to manuscripts, these specimens touch upon every domain of life and continent on Earth.

Information from the collections spans hundreds of years and is still vital for research today, telling scientists about how humans have altered the planet and preserving species that have become extinct as a result of our actions. 

All this information is recorded on labels, notes and within the specimen itself, but this means it is often only accessible to those who can physically access the Museum. In 2014, the digitisation of the collections began to make the wealth of specimens in the Museum collection freely available online.

‘To digitise a specimen, we release the data about the specimen, where it was collected, what species it was and who collected it available online so that researchers know what we have in our collection,’ says Jennifer Pullar, Digital Collections Communications Manager.

‘In addition to this basic record, we might also take photographs of the specimen and its labels, as well as providing extended specimen information such as genomic and chemical analyses.

‘We are passionate about providing free and open access so that anyone around the world can use this data for their own research.’

So far 1.7 million insects, 900,000 plants and 500,000 fossils have been digitised and published onto the Museum’s Data Portal.

To date, 30 billion records have been downloaded as people from around the world make use of the digitised specimens, while more than 1500 research papers have cited data from the portal.

The information can be used in many ways that can boost the global economy, including medicine discovery, tackling invasive species, and preserving biodiversity

A computer, the ALICE set-up and a tray of pinned insects
ALICE equipment (centre) uses multiple cameras to capture a specimen from all angles. Image © The Trustees of the Natural History Museum, London  

Protecting the future

The Museum’s collection is incredible varied, from nannofossils that are barely visible to the human eye to the largest animal on Earth, the blue whale. To work with this variety of specimens, the digitisation team have developed different ways of working each specimen type.

Each comes with its own challenges, such as accessing the labels on insects when the specimen and its details are all attached to the same pin. To tackle this challenge, ALICE, or Angled Label Image Capture and Extraction equipment, allows a specimen to be photographed from a variety of angles to capture its body and its labels simultaneously.

This has increased the number of pinned insect specimens that can be digitised by one person in a day from around 250 to 900, while also reducing the physical handling of delicate specimens so that they can be preserved for future generations.

The five millionth specimen to go through this process was the stonefly S. prasina. Stoneflies are found around the world and are a mostly herbivorous group of insects which spend much of their lives as underwater nymphs, though S. prasina is a predator on other insects.

The stoneflies’ dependence on fresh water and short life span makes the insects useful to scientists for assessing how healthy an ecosystem is by the presence and size of their populations. 

The Museum is digitising its 89,000 specimens of stoneflies, mayflies and caddisflies as part of a project to improve our knowledge of these insects. This will allow better assessments of their vulnerability to extinction to be made by the International Union for the Conservation of Nature (IUCN), who compile the Red List of Threatened Species

Hopefully this will help better protect not only the insects themselves, but the freshwater habitats in which they live. In turn, this can have knock-on effects that help to benefit people who live within and rely on these environments. 

This is just one of the ways in which digitising natural history collections can help to benefit the natural world and in turn the global economy.

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