Tiny Australian leech named for best-selling author Amy Tan

January 21, 2016
Internal structure of the newly described leech Chtonobdella tanaez, shown from dorsal (A), ventral (B), and lateral (C) angles via micro-computed tomography. Credit: © Tessler et al., 2016

Researchers have named a new leech after best-selling author Amy Tan based on an innovative method for peering inside soft-bodied animals. Chtonobdella tanae, a terrestrial leech from Australia, is the first new species of invertebrate without chitinous or calcified tissues (like a shell or exoskeleton) to be described with computed tomography (CT) scanning. The work was recently published in the journal Zoologica Scripta, and opens possibilities for non-destructively studying soft-bodied organisms, a group of animals ranging from worms to jellyfish that represent a huge part of the tree of life.

"Historically, to get an idea of what the internal structure of a soft-bodied invertebrate looks like, you have to dissect it by hand or painstakingly section the specimen and then reconstruct it in three dimensions," said Michael Tessler, lead author on the paper and a student in the comparative biology doctoral program at the American Museum of Natural History's Richard Gilder Graduate School. "CT imaging is not only more precise than physical dissection, but it also doesn't require us to discard the specimen we're studying."

Like those found in medical offices, CT scanners used for scientific research take thousands of cross-sectional x-ray "slices" of a rotating object to digitally produce a 3D view of its interior. As the x-ray beam passes through the object, different tissues or materials absorb different amounts of x-rays. Detectors on the opposite side pick up the x- rays that travel through the object and create a contrast image based on the density of the internal components. As with all x-ray techniques, dense structures like bone are easily imaged, whereas soft tissues are less able to stop x-rays, making them difficult to image. So while researchers who study things like dinosaur skulls, anthropological artifacts, meteorites, and lizards, among many other specimens, have benefited from CT technology for the last decade or so, those who examine soft-bodied organisms continue to rely principally on traditional dissection techniques to look inside of their specimens.

Chtonobdella tanae shown from the dorsal (A), ventral (B), and lateral (C) sides. The male gonopore (mg) and female gonopore (fg) are shown in view B. Credit: © Tessler et al., 2016

With the goal of making the tissues in soft-bodied animals show more contrast in CT scans, the researchers examined a variety of fixatives, chemicals that preserve biological tissues from decay. They tested the effect of the following fixatives on a common freshwater North American leech, Macrobdella decora: ethanol; glutaraldehyde; a combination of alcohol, formalin, and acetic acid called AFA; and osmium tetroxide. These tests revealed that the best way to enhance contrast in the CT image is to fix the leech in AFA and then refix it in osmium tetroxide, which binds the heavy metal osmium to the internal tissues.

"We were able to resolve the external and internal anatomy at very high resolution," said senior author Mark Siddall, a curator in the Museum's Division of Invertebrate Zoology. "In addition, we were able to see internal structures we might not have otherwise seen because of the disruptive influence of cutting things open."

The researchers then used this fixative combination to CT scan and describe a new species of leech from Queensland, Australia, which, at about 1 centimeter long and 2 millimeters wide, is too small to dissect. The leech was given the name Chtonobdella tanae in recognition of Amy Tan, author of the best-selling novel The Joy Luck Club and other works, who has accompanied Siddall's lab into the field.

This video shows the external and internal structure of the newly described Australian leech Chtonobdella tanae via micro-computed tomography. Credit: © Tessler et al., 2016

"Amy, long a supporter of the work we do here, is someone we knew would consider it an honor, not an insult, to have a leech named for her," said Siddall. "These jungle leeches are mentioned several times in her hilarious novel Saving Fish from Drowning."

"I am thrilled to be immortalized as Chtonobdella tanae," Tan said. "This humble leech has looped across a new scientific threshold—the first microscopic soft-bodied critter to be described inside and out using CT scanning. Imagine the possibilities for identifying legions of tiny organisms that have thus far lived in obscurity. I am now planning my trip to Queensland, Australia, where I hope to take leisurely walks through the jungle, accompanied by a dozen or so of my namesake feeding on my ankles."

As part of this work, the researchers also revised the genus Chtonobdella to include all two-jawed leech species, which were previously distributed in 31 genera.

Explore further: Scientists use biomedical technique to image marine worm

More information: Zoologica Scripta, onlinelibrary.wiley.com/doi/10.1111/zsc.12165/full

Related Stories

Scientists use biomedical technique to image marine worm

May 18, 2010

Scientists have for the first time successfully imaged the internal tissues of a soft bodied marine worm at high resolution using a technique borrowed from biomedical science. The findings are published in the Journal of ...

New X-ray method uses scattering to visualize nanostructures

November 19, 2015

Both in materials science and in biomedical research it is important to be able to view minute nanostructures, for example in carbon-fiber materials and bones. A team from the Technical University of Munich (TUM), the University ...

The new T. rex: A leech with an affinity for noses

April 14, 2010

A new leech species with ferociously large teeth -- recently discovered in noses of children that swam in Peruvian rivers -- is providing insight into the evolutionary relationships among all the leeches that have an affinity ...

Fossil fireworm species named after rock musician

November 19, 2015

A muscly fossil fireworm, discovered by scientists from the University of Bristol and the Natural History Museum, has been named Rollinschaeta myoplena in honour of punk musician and spoken word artist, Henry Rollins.

Recommended for you

The mathematics of golf

August 16, 2017

(Phys.org)—The official Rules of Golf, which are continually being revised and updated as new equipment emerges, have close ties to mathematics. In many cases, math is used to place limitations on golf equipment, such as ...

Study identifies dinosaur 'missing link'

August 15, 2017

A bizarre dinosaur which looked like a raptor but was in fact a vegetarian may be the 'missing link' between plant-eating dinosaurs and theropods, the group that includes carnivores such as Tyrannosaurus rex and Velociraptor.

Unique imaging of a dinosaur's skull tells evolutionary tale

August 15, 2017

Researchers using Los Alamos' unique neutron-imaging and high-energy X-ray capabilities have exposed the inner structures of the fossil skull of a 74-million-year-old tyrannosauroid dinosaur nicknamed the Bisti Beast in the ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Jan 22, 2016
This is music-categorized - it should be in biology

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.