Dissecting a black widow spider to get its silk glands seems like a task fraught with peril. Luckily, for anyone who dares, now there is video from scientists to show you how it's done.
Research labs do not want the silk glands of these infamous spiders for some kind of bizarre trophies. Spider silks are stronger than steel, and scientists across the globe are racing to develop synthetic fibers mimicking these silks for commercial, military and industrial applications, says biochemist Craig Vierra at the University of the Pacific in Stockton, Calif.
These fearsome arachnids—whose venom is 15 times stronger than a rattlesnake's—were chosen because "female black widow spiders have very large abdomens, making it very easy to isolate the silk-producing glands," researcher Coby La Mattina, also at Pacific, says as she narrates the video. As to why these researchers chose to make the video, "oftentimes the glands rupture during dissection. There are also certain anatomical structures that are difficult to isolate," Pacific researcher Tiffany Tuton-Blasingame says. "Visual demonstration is critical for a good dissection."
The scientists collect western black widows (Latrodectus hesperus) from wood piles, bushes and garages—the spiders' habitat is western North America. "When you knock them off their webs, they'll roll up and play dead, so they're really easy to scoop up," Vierra explained in a phone interview.
The black widows are anesthetized with carbon dioxide gas for 10 minutes. "While attempting this procedure, it's important to wear two pairs of gloves until the spider fangs are removed," Pacific graduate student Yang Hsia says during the video. As deadly as their venom is, their bites are usually not fatal, especially to adults, because they only inject small doses of venom—and like most spiders, black widows prey on insects.
After the researchers knock each spider out, they use scissors to cut the spider in half, snipping off the black widow's abdomen in the five minutes before the anesthesia wears off. (These procedures were approved beforehand by the Institutional Animal Care and Use Committee.)
The scientists then pin the abdomen down on a dissecting dish and use microscissors to cut out an opening. The abdomen is immersed in a special dissecting fluid cocktail of ingredients detailed by the researchers. The exoskeleton is peeled back with forceps, and any fat and eggs are scraped away to expose the seven distinct silk-producing glands. The researchers recommend these glands be removed in a specific order that makes it easier to get all of them out safely. The glands are then flash-frozen in liquid nitrogen and stored at minus 80 degrees Celsius.
The glands in western black widows each produce different kinds of silk: The major and minor ampullate glands manufacture dragline and scaffolding silk; the tubuliform gland synthesizes egg case silk; the aggregate gland makes glue silk; the aciniform gland synthesizes prey wrapping and egg-case threads; the pyriform glands produce silk that sticks onto surfaces; and the flageliform has an unclear function in this species. After scientists extract these glands they can analyze which different genes are expressed or which proteins genes make as well as clone these genes into bacteria and yeast to generate recombinant proteins for artificial silk fiber production, Vierra says.
"After its development this technique paved the way for researchers in the silk biology community," Tuton-Blasingame says in the video. They and others use this method to explore chemical and molecular processes involved in silk-fiber production, assembly and extrusion, she adds. There is still much scientists have learn about spider silk and fabricating versions of it, Vierra notes, so the dissection technique remains highly useful.
"If this technique is completed correctly, it can be accomplished in one and a half to three hours," Tuton-Blasingame says. The scientists detailed their procedure January 11 in the Journal of Visualized Experiments (JoVE). (The journal is not only the world's first scientific video journal, "we are the only scientific video journal at this point, at least to my knowledge," JoVE co-founder Nikita Bernstein said in a phone interview.)
"I wrote long lines for my students and myself to read, and when JoVE came to shoot us, they made me go first, and I kept blowing my lines, which the students thought was funny," Vierra tells Scientific American. "But it was a lot of fun. We all enjoyed making the video."