A New Way to See the Wonderfully Strange ‘Water Bear’

tardigrade
A tardigrade, the microscopic animal commonly known as water bear (H. exemplaris). Credit: Bob Goldstein
By Diana Kenney August 26, 2024
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Few animals are as endearingly weird as tardigrades, also known as water bears -- eight-legged, microscopic creatures that have gained somewhat of a cult fan base at the MBL and elsewhere.

Tardigrades are famously resilient, able to survive conditions of extreme temperature, radiation, desiccation, or pressure by shrinking, suspending their metabolism, and entering a death-like state called tun. They can even weather the extremely harsh conditions of outer space.

Students in the 2023 MBL Embryology course got a chance to work with water bears brought to Woods Hole by Bob Goldstein of University of North Carolina, Chapel Hill, whose lab is developing tardigrades as a research organism. Goldstein also brought fluorescent dyes for the students to experiment with imaging of live tardigrades, which are typically imaged in a nonliving, chemically fixed state.

Their explorations have led to a new procedure for live-cell imaging of tardigrades, recently published in STAR Protocols by the Goldstein lab together with nine students and two teaching assistants from the Embryology course.

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A tardigrade (H. exemplaris) as seen with DIC microscopy. Although DIC microscopy enables the visualization of some structures, fluorescence microscopy is more effective in differentiating subcellular structures. Scale bar: 20 microns. Credit: Harry et al, STAR Protocols, 2024

“Many of the students found the adult tardigrades (not just their embryos) beautiful to look at in the microscopes,” Goldstein says. “Many of the fluorescent dyes hadn’t been shown to work for adult tardigrades before, so after the course, a graduate student in my lab (Clayton Harry) worked with a postdoctoral scientist in my lab (Jon Hibshman, who had been a teaching assistant in the Embryology course) to optimize the protocols and get the dyes to work reliably.

“Not many labs work with tardigrades yet, so we try to share methods rapidly with the growing field whenever possible,” says Goldstein, who was a student in the Embryology course himself in 1989.

 

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Effective fluorescent staining of H. exemplaris. Multiple stains can be used simultaneously. This tardigrade has been stained to label lysosomes, mitochondria, and nuclei using LysoTracker Green (green), TMRE (magenta), and NucBlue (blue) respectively. Some anatomical structures are labeled. Scale bar: 30 microns. Credit: Harry et al, STAR Protocols, 2024.

Wasting no time, students in the 2024 Embryology course tried the fluorescent dyes with wild tardigrade species that they collected outside MBL’s Loeb Laboratory, and found they worked well.

“This wasn't surprising -- we were two-for-two with species we'd tried so far,” Goldstein says, “but it was really beautiful to see.”

Citation:

Harry, Clayton J. et al. (2024) Protocol for fluorescent live-cell staining of tardigrades. STAR Protocols, DOI:10.1016/ j.xpro.2024.103232

 

Related Tags
Animals
Embryology Course
Imaging
Microscopy