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The mystery of cubic wombat poop and plants that send emails

by Alex Scott
February 28, 2021 | A version of this story appeared in Volume 99, Issue 7


Much ado about cubic poo

Scientists in the US and Australia got to the bottom of the mystery of how wombats generate poop that is cube shaped. Their findings could change the way that certain products with edges are manufactured as well as provide clues to illness in humans.

Cartoon image of wombat with cubed poop.
Credit: Yang H. Ku/C&EN/Shutterstock
Intestinal impressions: Scientists solve the mystery of wombats' cube-shaped poop.

As marsupials, wombats have pouches to carry their young, but they don’t have any obvious external attributes that would produce cube-shaped poop. Various theories abound to explain the square scat, including the idea that wombats do a little postpoop sculpting to create poop they can use to mark their territory without its rolling away.

In 2018, scientists found that wombats’ intestinal features were responsible for the fecal phenomenon. In January, the same group reported that wombat poop has an unusually slow passage through the animal’s intestine and that variable stiffness along the final 17% of the intestine is responsible for creating the cube shape (Soft Matter 2021, DOI: 10.1039/D0SM01230K). The discovery has implications for the diagnosis of cancer in humans because cancer that affects the stiffness of the colon at a certain point may be associated with feces of a certain shape. Also, engineers could copy the way wombats shape poop to develop novel techniques for shaping soft materials, such as plastics or food, into geometric shapes.

“I don’t know if people will be interested in cubic sausages in future, but this could change the way we shape soft matter, or how we can manipulate soft robots,” Patricia J. Yang, the study’s first author and currently a postdoctoral fellow at Stanford University, says in a press release.

Although the wombat mystery has been squared away, the Newscripts team understands that dung beetles continue to be furious with wombats.


Emails from the field

Scientists at the Massachusetts Institute of Technology have developed bionic spinach, rice, and a species of fern that can all send an alert via a smartphone in the event that the plants absorb high levels of arsenic from soil. The presence of arsenic in food crops is a major source of ill health for people in a number of countries.

Cartoon image of a spinach plant using a phone.
Credit: Yang H. Ku/C&EN/Shutterstock
Plants in peril: Spinach equipped with special sensors can send email alerts when they detect arsenic, pests, or explosive chemicals.

The scientists created the connected plants by embedding near-infrared fluorescent sensors—in the form of single-walled carbon nanotubes—into plant leaves; this process had no detrimental effects. The sensors fluoresce when exposed to molecules of arsenite, a common form of arsenic in soils. This reaction in the leaves of the bionic plants is picked up by a camera in the field coupled with an inexpensive portable computer, programmed to send an alert email when fluorescence occurs (Adv. Mater. 2020, DOI: 10.1002/adma.202005683).

The novel approach has the potential to be far cheaper, faster, and more convenient than current methods for testing the presence of arsenic, which include regular field sampling and analysis of plant tissues using spectrometry.

“This novel sensor could be a game-changer, as it is not only more time-efficient, but also more accurate and easier to deploy than older methods,” Michael S. Strano, the MIT professor who led the study, says in a press statement.

Strano and his colleagues have also developed sensors that will send an email when there are other threats to plants, such as leaf-eating caterpillars. In 2016, they used a similar approach to make spinach that can detect the presence of land mines via the mines’ release of nitroaromatic compounds into soil.

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