PRESERVING CHITONS FLAT AS A BOARD

by Richard L. Goldberg

There is nothing more frustrating than being knocked around for 20 minutes in a heavy splash zone while removing a chiton from a rock, only to bring it home and have it curl up like a pill bug! This recounts my first attempt at seriously trying to add a self-collected chiton to my collection. Only after many more failed attempts and, finally, some enlightenment by my friend Frank Robb, then living in San Juan, Puerto Rico, did I realize that these girdled, eight-plated mollusks need to be specially preserved before adding them to one's collection.

I am often asked how I get my preserved chitons to lie flat and natural. My first response is, "Patience.". The steps needed to prepare chitons for a collection have been documented by various chiton specialists (Hanselman, Burghardt, etc.), each approaching the problem using their own tried-and-true preservation techniques.

My own technique is a combination of various methods - and much of my own trial and error. First and foremost, however, before outlining the methods you will need to gather some basic tools to accomplish your goal of preserving a flat, natural-looking chiton.

• Glycerin; alcohol (90% isopropyl alcohol seems to work best)
  
• 1/16" thick plexiglass strips of various sizes
  
• White, multi-strand nylon sewing thread
  
• Low, flat, tupperware-like receptacle, and
  
• Glass jars of various sizes with lids that seal tight

You will also need some field collecting equipment, including

• A dive knife or rust-proof spatula, and
• Plastic bucket which is smooth inside, or wide-mouth plastic jars such as Nalgene jars if you are diving

   Fig. 2 / PATIENCE IS THE KEY - Coaxing a specimen of Chiton tuberculatus onto a spatula.
The most important aspect of the entire process is the field collecting of the chitons. Removing a chiton from a rock is akin to prying a Spondylus from its habitat. If you do it wrong, you've ruined it. Forcing a chiton off a rock with a spatula or dive knife will ultimately cut the foot of the animal, especially chitons inhabiting the crevices of intertidal ironshore rock. This will cause the animal to curl up permanently. I have found collecting at night in the type of habitat to be beneficial, as chitons are out foraging in the dark. Eventually, you will learn how various species of chitons react when coaxed from their substrates. My most successful collecting has been with species that inhabit the undersides of intertidal rocks. Turning rocks and exposing them to sunlight (or a flashlight at night) will cause them to crawl rapidly to the shaded side of the rock. Place your spatula in the path of the chiton (Figure 2), and it will crawl onto the flat surface. Do not rush this process. You may have to hold the spatula still for up to a minute or more while the chiton jockeys around before it trusts the path that it has chosen for its escape. Let the chiton crawl at least half way onto the spatula before quickly lifting it up. You must immediately place the chiton into a bucket or receptacle with fresh, clean sea water from its habitat. Initially, the chiton will curl up, but once comfortable with its temporary habitat, it will attach itself to the inside of the bucket. You should note that chitons will crawl out of your bucket if left unattended. Just slide them back in if they start to escape. It is important to keep the bucket cool and in the shade. You will cook them if you leave them in the hot sun more than a couple of hours. Keeping chitons alive is paramount to properly preserving them.

   Fig. 3 / CHITON HABITAT - Tonicia schrammi hitching a ride on Chiton tuberculatus - La Parguera, Puerto Rico.
Scuba divers are not afforded the time to wait for chitons to crawl off their rocks. Here, you must nudge them off, either with the tip of your dive knife, or sometimes, taking the rocks (if small) to work with back on the boat. Place them in small jars or similar containers. Obviously, chitons under one inch will be easier to remove than those that are two or three inches long. Again, trial and error will be your best guide. Whether shoreline collecting, or scuba diving, make sure to change the sea water and remove dirt and debris from the bucket or jars as the last step before heading back to your home base. Also, make sure you have enough extra clean sea water for the next step.

As you can see, I do not wrap my chitons in the field, a method used by many field collectors. I would rather spend my time covering more ground in the field. Once back at home base, I lay out my "chiton kit" with plexiglass strips, jars, low pan, thread and alcohol (glycerine comes in 24 hours).

   Fig. 4 / STEP 1 - Position the chitons over plexiglass strips immersed in sea water until they relax flat over the strip.
First, place about an inch of the fresh sea water from the chitons' habitat in the low, flat pan. Then take a plexiglass strip, which must be clean of any debris or chemical residue, and place it on the bottom of the water-filled pan. Slide the chiton from its temporary receptacle, and lay it on top of the submerged plexiglass strip. The strip should be large enough for the chiton to fit without the girdle overlapping the edge. The chiton will immediately curl up when placed in the pan. Here is where prior gentle handling will pay off. The chiton will eventually relax and flatten out on the plexiglass. You may have to slide and nudge the chiton so that it sits squarely on the plexiglass strip. Quickly pick up the plexiglass and chiton between your thumb and index finger and hold it in a gentle vice-like grip. Take a 10 to 15 inch length of thread, tuck an end between the plexiglass and foot of the chiton and start to wrap the thread over every other plate of the chiton (five wraps over eight plates); then go back over the skipped plates. Make sure that the thread firmly holds the chiton down from end to end. This alternating wrapping will insure that the chiton will be preserved flat as a board. Also, make sure that both posterior and anterior ends of the chiton's girdle are wrapped down. Tie down the end of the thread, or again, tuck it under between the plexiglass and foot of the chiton. White thread is used because the alcohol will cause the dye from colored thread to bleed on, and stain the chiton's girdle and plates. Chitons with very fleshy girdles, such as Katherina tunicata do not preserve well with thread because the thread leaves a notch, or indentation in the girdle. You will have to use long strips of ¼ to ½ inch wide cloth in place of the thread. In this case, push a straight pin through the cloth wrapping to tie it off at the end, avoiding piercing the chiton's girdle.

Next, fill a jar with alcohol and fully submerge the wrapped chitons in the solution. Leave the chitons submerged in the alcohol for 24 hours. Rigor mortis sets in and the chitons will then lay in a permanent flat position. After the 24 hour period, it is time to mix your preserving solution. Glycerin can be expensive, especially if purchased in small amounts at your local pharmacy. If you intend to preserve your own chitons on a regular basis, I would suggest purchasing a larger amount of glycerin from a scientific supply company. Although sold in gallon containers, each batch of preserving solution will cost a fraction of the consumer price. You will need at least one pint of glycerin and alcohol to properly preserve approximately 20, one-inch chitons.

You must decide whether you would like your chitons to be semi-soft and malleable or dry and stiff. A well-mixed solution of 50% glycerin and 50% alcohol yields a chiton that looks natural and slightly malleable. As you reduce the percentage of glycerin, the chiton will become more brittle, and the girdle tends to shrivel up. I would suggest using the 50/50 preserving solution and not skimping on the glycerin. Chitons with hairy girdles preserve nicely in this solution. I would not use less than 25% glycerin. You will end up with a dried out piece of cardboard, so-to-speak!

How long you keep your chitons in the preserving solution depends on their size. A minimum of two weeks will be needed for the solution to permeate a chiton under half an inch in length; four weeks are required for chitons up to four inches long; and as long as six months are necessary for chitons eight inches and larger such as the giant Cryptochiton stelleri (up to 12 inches!).

After 24 hours in alcohol, you must unwrap the chitons before placing them in the preserving solution. This opens up more surface area for the chiton to absorb the glycerin and alcohol.

After the prescribed preserving period, it is time to remove the chitons from the solution and re-wrap them on the plexiglass strip for drying. If you do not re-wrap the chitons, a slight curl, or bend will develop and ruin all of the work you have invested so far. Wrap them in the same fashion you did in the first step of the preserving process (wrapping every other valve in each direction across the chiton). Let the re-wrapped chitons sit on paper towels to absorb the excess runoff in a cool, dry and shaded area for an equal period of time to that which they spent in the preserving solution. You might smell a faint medicinal odor of glycerin from the chiton. This should not be equated with the odoriferous smell of a ripe, rotting gastropod! The chiton is now fully preserved and should last forever is stored away from moisture and humidity.

Store and display your chitons in a dry environment, or they may develop a dreadful case of fungus that will eventually envelop and eat away the glycerin-saturated fleshy portions, as well as pit the calcareous portions of the chiton. If you find signs of fungus developing on your chitons, dip them in alcohol and brush away the fungus with a toothbrush. I have only seen such fungus develop in collections kept in damp, tropical environments, though.

The girdles of certain chiton species such as Tonicia schrammi from the Caribbean will discolor immediately upon being submerged in alcohol - in this case from a beautiful green to a fleshy orange. Unfortunately, there seems to be no way to preserve the green because it is a commensal algae living in the girdle.

The size of your plexiglass strips depends on the area in which you intend to collect. My experiences are limited to the Caribbean and Mediterranean. I usually take a number of 1 ¼" by 2 ½", 1 5/8" by 2 ¾", 2" by 3 ½", and 3" by 4 ½" strips. This covers the gamut of chiton sizes you might run into. West coast chiton collectors (U.S. and Canada) will need additional larger sizes because of the prolific and large species to be found. I bought a 4 by 8 foot sheet of 1/16 inch plexiglass and had the various sizes cut from it. It may take a bit of pre-planning to avoid too much waste.

It should be noted that if you are collecting chitons for scanning electron microscope (SEM) studies of the shell, girdle scales and radula, do not use glycerin. Wrap and keep them wet in alcohol-filled jars until needed. Many museums keep their chiton collections "wet" in alcohol for future study. Chitons preserved in glycerin and alcohol are fine for private collections and for identification purposes in museums, but may not be suitable for scientific study.

One final note regarding the plexiglass strips - do not wash them off with soap and water, because the residue from any chemical will repel a chiton on the next go-round.

This is a quick overview of the method I use to preserve my chitons. It might seem like a lot of effort to go through, but it is certainly worth it when your chitons come out "flat as a board."

Addendum from THATCHERIA, Vol. 26, Number 4, page 8, Fall 1991.

How many times can you re-use the glycerine/alcohol preserving solution? The answer to this depends on the number and type of chitons being soaked. The best guideline is once the solution becomes murky or brownish in color, it is time to replace it. But an even better guideline is not more than two batches of chitons should be preserved in a solution mixture. The solution becomes too infiltrated with foreign particles and body fluids. It is also a good idea to brush off any algae or encrustations found on the plates of some chiton species. Do this after unwrapping the specimen from the alcohol step - when set up in a stiff position, but before the glycerine and alcohol solution step. This will keep the preserving solution viable for a longer period of time.


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