1 Small Step for a Squid, 1 Giant Leap for Biological Specimens

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In September, the National Museum of Natural History (NMNH) in Washington, D.C. opened the Sant Ocean Hall. The hall, restored during the largest renovation in the museum's history, is home to 12 exhibits featuring to 674 specimens and models.

squid.jpgPerhaps the most important specimens in the hall are two giant squid. The 24-foot, 330-pound female is the most intact giant squid specimen on display anywhere in the world. She, and a smaller male, were caught by a group of deep-sea fishermen off the coast of northern Spain in 1995 and loaned to the NMNH by Coordinadora para el Estudio y la Protección de las Especies Marinas, a Spanish marine preservation organization.

The organization was keeping the squid in 400 gallons of formalin, a preservative fluid that is considered hazardous cargo and can only be transported commercially in quantities of 16 gallons or less. To get the squid stateside, the museum called the Navy, who accepted the task (dubbed "Operation Calamari") and brought the squid home in a U.S. Air Force C-17 cargo plane (pictured).

The Pickle of Pickling

In hindsight, getting the squid to the museum may have been the easy part. Preserving them posed an even bigger challenge.

There are some 1.5 billion biological specimens stored in institutions around the world (NMNH has about 124 million). "Wet" specimens, those that need to be stored in a preservative fluid, are usually (though not always) first fixed in a fixative solution, most commonly formaldehyde, which prevents the breakdown of proteins by forming chemical bonds and coagulating the contents of the specimen's cells into insoluble substances.

After fixing, a specimen is placed in a preservative fluid, which stabilizes it, prevents cell destruction and acts as its permanent home. The most common preservative fluids are alcohol (usually either ethyl alcohol or isopropyl alcohol), used since the 17th century, and formalin, a solution of formaldehyde diluted in water with some methyl alcohol added to prevent the formaldehyde from forming a solid mass, which was introduced in the 19th century.

Both of these preservatives present problems. Alcohol dehydrates specimens and leaches color from them, causing them to turn brown and then dirty white. Alcohol is also flammable; when Philadelphia's Mütter Museum was collecting specimens, one of the first donors insisted that his collection of fluid-preserved human organs needed be housed in a fireproof building. Formalin is better suited to preserve some specimens because of its fixative properties; it permeates a specimen's tissue and prevents it from decomposing. It's also less flammable than alcohol, but has a strong, unpleasant odor, is toxic and has been linked to certain types of cancer in animal tests.

Neither alcohol nor formalin retains specimens' true textures, and both preservatives allow specimens to move around in their containers, which can lead to breakages.

If you've seen more than a handful of fluid-preserved biological specimens, you know that some look much better than others. Somewhere, someone was doing something that preserved the specimen in excellent condition. Why don't all museums duplicate that technique for their collections? Unfortunately, in fluid preservation, most technique is the result of trial and error and records are rarely kept.

Where No Squid Has Gone Before

In addition to these challenges, Washington, D.C.'s fire marshal has significantly reduced the amount of flammable fluids that are allowed to be kept in public buildings since 9/11. The museum was authorized to use only 10 gallons of alcohol in the entire Sant Ocean Hall, while the female squid alone needed 1,200 gallons of fluid.

Formalin and alcohol were out, so the museum turned to Novec 7100 engineered fluid, developed by 3M, the diversified technology company. Novec, developed in the mid-1990s for cleaning electronics, isn't a preservative fluid, but a storage medium that forms a protective chemical envelope around specimens that have already been fixed in formalin. Novec is nonflammable, nontoxic and ozone-friendly. Its low water solubility keeps it from getting cloudy over time, and it doesn't drain color from specimens.

Novec has its share of problems, though. It evaporates easily, so specially designed jars with an extra-tight seal need to be used to contain specimens and the containers can't sit under lights that produce a lot of heat. Novec is also about 1.5 times denser than water, which means unrestrained specimens float to the top of their container, get exposed to air and decompose. Museum staff had to be careful to keep the squid submerged while also minimizing damage from any restraints they used. The squid are held down by a restraining bracket and reinforced with a metal screen, while broad transparent straps hold down the tentacles and distribute tension across them.

Novec's use in the squid exhibit is an ongoing experiment. For all their flaws, we know alcohol and formalin preserve specimens for a long time. No one knows how the squid will look in 20 or 30 years. Even while they're on display, the museum is taking samples of the squid's tissue and the storage fluid to see if the tissue is going through changes in cellular structure and if any compounds are leaching from the squid into the fluid. The museum is also breaking with preservation tradition by keeping meticulous records, starting with the squid's initial fixative injection in Spain and keeping pace with the tests they perform. The museum has said that every organization that donated specimens for the Sant Ocean Hall is eager to get plenty of data on Novec; if the squid are as intact a few decades down the line as they are now, Novec may become the fluid of choice for preservation. Here's lookin' at you, squid.

December 23, 2008 - 11:00am
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