Sober Worms Outpace Intoxicated Counterparts in Chromatography-Inspired Maze Experiment

Researchers at the University of Amsterdam conducted a whimsical yet scientifically rigorous experiment using aquatic worms to explore the principles of active matter separation. Soaked in a dilute ethanol solution, these “drunk worms” were pitted against their sober counterparts in a water-filled obstacle course designed to mimic chromatography systems used in chemistry labs.

The study, published in 2022 in Science Advances, earned its authors the 2024 Ig Nobel Prize in Chemistry “for using chromatography to separate drunk and sober worms.” The research wasn’t about animal intoxication per se, but rather used the worms as living analogs for long-chain polymers to test whether chromatography—a technique for separating mixtures based on differential movement—could sort entities by their level of activity.

Introducing the Worms and Their “Drunken” State

The organisms in question were Tubifex tubifex, slender aquatic worms measuring 10 to 40 millimeters in length, commonly sold as fish food. To alter their activity levels, the team briefly immersed some worms in a 3% to 5% ethanol solution. According to first author Tess Heeremans, the effect was comparable to a human consuming a beer: “4.5% alcohol was enough, about the same amount as a beer.” The intoxication was temporary, with worms regaining full mobility within approximately 10 minutes of returning to plain water.

Co-author Sander Woutersen, who had used these worms as fish food during his childhood, proposed the idea. When pandemic-related lab closures forced Heeremans to relocate the experiment to her dorm room, the maze setup was adapted for the change in environment. The researchers also manipulated activity through temperature variation, testing worms at 5°C, 10°C, and 25°C. Cooler temperatures reduced movement, mimicking the effects of alcohol. To quantify activity, they measured the rate of change in the worms’ body shapes over time—a physical property known as relaxation time.

Design of the Obstacle Course and Chromatography Principles

The experimental maze was a 51-centimeter-long channel containing a hexagonal array of cylindrical pillars, each 6 millimeters in diameter and 15 millimeters tall, spaced 3 millimeters apart. Water flowed through at 0.2 liters per second, and cameras tracked each worm’s progress toward a mesh barrier at the outlet.

In traditional chromatography, molecules migrate through a medium at varying speeds, allowing for their separation based on distinct exit times. The Amsterdam team sought to determine if this principle could apply to “active” polymers—those capable of self-propulsion. Their findings confirmed that transport velocity through the channel was highly dependent on the worms’ activity levels, with more active individuals exiting sooner. Worm length also played a role: at 20°C, travel time increased consistently as worm length grew from 5 to 30 millimeters.

When a 50-50 mixture of sober worms and alcohol-treated worms (dyed blue for identification) was introduced, the first worms reached the exit approximately 50 seconds post-injection. The two groups emerged separated by an average of 40 seconds, demonstrating effective sorting by activity.

Mechanisms Behind the Separation

The disparity in performance stemmed from physical entrapment. Less active worms were more frequently caught on the pillars and remained immobilized for longer durations. In contrast, active worms exhibited dynamic curling, knotting, and wriggling behaviors that facilitated their navigation around obstacles.

This outcome surprised the team, as Woutersen had anticipated that drunk worms would drift passively with the current and exit faster. Co-author Daniel Bonn offered a practical takeaway: “at the pub, somebody needs to stay sober and bring everybody home.”

The University of Amsterdam’s research description highlighted that Heeremans had, for the first time, sorted active matter by activity level. Pillar-array chromatography is already employed to separate DNA strands and synthetic polymers by length; this experiment demonstrated that length remains a factor even when “molecules” are self-moving, while activity introduces an additional separation criterion.

Broader Implications for Living Systems

This research contributes to the field of active matter, which studies systems whose components generate autonomous motion—ranging from bacterial colonies to schools of fish. The methodology could potentially aid in sorting mixtures of active polymers or other self-propelled entities, though such applications remain largely theoretical. No human-health testing was involved in the study.

The experiment illustrated that a foundational chemistry technique can distinguish living organisms based on their motility, bridging laboratory methods with biological variability. Parallel research, such as a 2021 PNAS study on California blackworms forming collective, moisture-retaining blobs, continues to expand our understanding of how living systems organize and adapt under physical constraints.

Key Questions Answered

Were the worms actually drunk?

Yes. A subset of worms was exposed to a 3%–5% ethanol solution to reduce their activity before navigating the obstacle course.

What was the experiment really about?

The study focused on polymer physics. The worms served as living models of long-chain molecules to evaluate whether chromatography could sort objects based on their activity levels.

Which worms finished first?

Sober, more active worms exited sooner. Intoxicated and colder worms were more prone to becoming snagged on the pillars for extended periods.

Did worm length matter?

Yes. Longer worms required more time to traverse the maze, with travel time increasing steadily with length.

Were the worms harmed?

The researchers reported that the alcohol’s effects were temporary, with worms regaining normal behavior within about 10 minutes in plain water.

Source link