Rehydrating invertebrate specimens

In Conservation DistList, Instance: 11:39, October 23, 1997 I wrote
Kathy Hall <kathyhall<-a t->mail< . >utexas< . >edu>

>I'm an objects conservator at Texas Memorial Museum. One of our
>curators just asked me about what would be the best way to
>rehydrate specimens from a collection of cave invertebrates
>which unfortunately dried out. I understand that these types of
>specimen are difficult to rehydrate due to the chitinaceous
>exterior.

This is the summary posted to nhcoll. Thanks everyone! A summary of
the replies on this question:

Extra References:

    Marhue, L. 1983. Techniques to restore dried-up invertebrate
    specimens. In: Proc. of the 1981 Workshop on the Care and
    Maintenance of Natural History Collections, edited by D.J.Faber,
    Syllogeus no.44: 175-177.

        Gives concentrations and soaking times for two different
        treatments;- the propylene glycol technique (50% solution
        for 24 hours, recommends not using ethylene glycol due to
        toxicity), and trisodium phosphate (0.5% overnight). Both
        found to be effective, no conclusions drawn as to best
        method. Also discusses using a few drops of surfactant in
        water (not tried but also said to be a successful method).

    Vogt, K.D. 1991. Reconstituting Dehydrated Museum Specimens.
    Curator 34:125-131.

        A response to problems with the trisodium phosphate (TSP)
        method with larger vertebrate specimens which can't be
        boiled and which would need impractically long soaking
        times. Describes a method which involves first soaking in a
        weak solution of acetic acid (to aid in disruption of the
        cell membrane and water transport across it), and then in
        TSP. The acetic acid will also act to inhibit microbial
        growth. This reduces soaking times. Probably not useful for
        calcareous invert. specimens, though.

Also:

    Thompson, Thompson and Drummond. 1966., Crustaceana 10, p109.
    Also discusses the ethylene glycol technique.

    Holm, Ake. 1978. Om Carl Clerk Spindelsamling. Fauna och Flora,
    73(5):201-205. On reclaiming the oldest spider collection in the
    world (thanks to James Cokendolpher for the translation)
    -specimens were first wet with drops of ethylacetate and then
    50% alcohol added, after a few days this replaced with 80%. [I
    assume this works in the same way as using acetic acid].

In addition:

Several people said they had used the TSP method, and were happy
with the results, one person recommended leaving the specimens as
they are (dry), one person mentioned contacting the SPNHC Fluid
Assessment Subcommittee, and one person had tried rehydrating fish
larvae using ethanol or 3% formalin with mixed results (no change in
ethanol, some specimens absorbed some fluid in formalin but were
still mis-shapen).

Also mentioned was the possibility of using a 75:25 mix of isopropyl
alcohol in distilled water and heating in a microwave. (I would
think that using a microwave is not a good heating technique as it
is so very uncontrolled).

One person also recommended adding glycerin to the final ethanol
solution -so that specimens will remain flexible if they dry out.
Levi*, however, does not recommend this, saying that it is messy and
will encourage mould growth if they dry out again ("The Care of
Alcoholic Collections of Small Invertebrates", Herbert W. Levi,
Systematic Zoology, vol 15, #3, September 26, 1966).

So..  I guess that we will try using TSP or a surfactant on a small
batch of test specimens, at as low concentrations and for as short a
time as possible, soaking to remove residue, refixing, and then
taking them up to 70% ethanol in steps. Hopefully this will give
some idea on the best way to treat the rest of the specimens.

Kathy Hall

                                  ***
                  Conservation DistList Instance 11:45
                 Distributed: Monday, November 17, 1997
                       Message Id: cdl-11-45-006
                                  ***