[Nhcoll-l] Freezing specimens in spirit

[Dirk Neumann]

Hi Tonya,

there are surely a couple of things here:

1. Depending which jars and closures you use in your collection, you 
will have different expansion coefficients. Containers for cryo-storage 
usually consider this (and some even will get properly tight when frozen 
and the lid shrinks under cold temperatures to give a proper fit), but 
jars we normally use in our collections are not designed for such cold 
temperatures. Freezing them, could cause considerable damage to jars 
and/or lids and may lead to high replacement costs in the long run.

2. Lipids, oils, fats and other dissolved components might coagulate. 
For example in insect collections, waxy deposits are commonly observed 
when specimens are frozen (e.g. -25°C). These deposits will not 
disappear when the specimens are thawed again but remain, covering all 
the filigree appendices, antennae, etc. In larger specimens, e.g. fish, 
it could lead to e.g to cholesterol deposits on specimens. So again, you 
surely would introduce more damage when freezing the jars.

3. Changing the temperature regime also influences the chemical 
equilibrium that formed inside specimen jars. Besides lipids and oils, 
lower temperatures usually decrease the capacity of the preservation 
fluid to keep organic compounds in solution. This often triggers 
crystallisation processes, e.g. residual dissolved formaldehyde may form 
paraformaldehyde needles.

Carrying potential pests into your new storage with the jars would only 
be possible if you would move a lot of organic material into your new 
storage area. Some organic material, such as historic big bladder seals, 
are also very vulnerable to low temperatures (shrinkage). So if there 
are no organic deposits on your jars, there wouldn't be much nutrients 
that could be carried. Vice versa, if there would be dust on the jar (as 
we have currently because of major renovation works going on in our 
collection), cleaning jars with a damp cloth should do the job. You 
should be careful with external labels in this case, but usually any 
'dirt' would be on the top. In case of stoppered jars or jars with 
historic seals, you probably would need to be careful with damp cleaning.

Hope this helps,

and good progress with your moving!

With best wishes
Dirk


Am 06.08.2020 um 08:25 schrieb Haff, Tonya (NCMI, Crace):
>
> Hi all,
>
> I have a question for you about freezing whole jars of specimens – 
> what do you think the effect would be, and would you recommend it? My 
> gut says NOOOOOOOO this is a terrible idea, but it has been suggested 
> as a shortcut to kill potential pests before we move the collection 
> into a new building. I personally think that the main thing we don’t 
> want to move into a new EtOH vault is mould, whose spores won’t be 
> killed by freezing anyway. But, I am open to ideas and I wanted to 
> check with other people before loudly stamping down my foot…
>
> Thanks!
>
> Tonya
>
> ---------------------------------------------------------
>
> Dr Tonya Haff
>
> Collections Manager
>
> Australian National Wildlife Collection
>
> National Research Collections Australia, CSIRO
>
> Canberra, Australia
>
> Phone: (+61) 02 6242 1566 (office)
>
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>
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>
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-- 


Dirk Neumann

Tel: 089 / 8107-111
Fax: 089 / 8107-300
neumann(a)snsb.de

Postanschrift:

Staatliche Naturwissenschaftliche Sammlungen Bayerns
Zoologische Staatssammlung München
Dirk Neumann, Sektion Ichthyologie / DNA-Storage
Münchhausenstr. 21
81247 München

Besuchen Sie unsere Sammlung:
http://www.zsm.mwn.de/sektion/ichthyologie-home/

---------

Dirk Neumann

Tel: +49-89-8107-111
Fax: +49-89-8107-300
neumann(a)snsb.de

postal address:

Bavarian Natural History Collections
The Bavarian State Collection of Zoology
Dirk Neumann, Section Ichthyology / DNA-Storage
Muenchhausenstr. 21
81247 Munich (Germany)

Visit our section at:
http://www.zsm.mwn.de/sektion/ichthyologie-home/

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