[Nhcoll-l] prepping frozen herps

[John E Simmons]

This is really a management issue, the key consideration being the resource
investment in the process vs the usefulness of the specimen that results
from the process. Of course you can make fluid-preserved specimens from
frozen animals, but is it worth the time and chemicals it will take to do
it? Does the specimen quality justify the time and chemicals required?



What I said in *Herpetological Collecting and Collections Management* (3rd
edition, 2015) is that “Once a specimen has been frozen, it is *usually*
not possible to make a satisfactory fluid preserved preparation from it”
due to the rupture of cells from freezing and thawing (thawing usually
causes more damage to tissues than does freezing) which weakens the
structural integrity of the tissues, thus “Frozen specimens are *best
prepared* as skeletons” (emphasis added in both quotations).



I also recommended that if you do need to make a fluid-preserved prep from
a frozen specimen that it should be thawed in a buffered formaldehyde
solution and injected progressively as thawing permits—this step is
important because, as Andy stated, fixatives and preservatives cannot
penetrate frozen tissues. If you fail to inject specimens as they thaw the
outermost tissues become fixed long before the inner tissues, resulting in
an unevenly fixed specimen. For large specimens, you should mark injection
sites on a sketch of the specimen or put pins in the needle punctures to
ensure that the specimen is injected evenly as it thaws.



Andy’s recommendation to stage the specimen from formaldehyde up to the
desired ethanol concentration should also be followed, as this has been
demonstrated to reduce shrinkage, it leaves much less formaldehyde in the
specimen (the trace amounts of formaldehyde will eventually show up in the
alcohol the specimen is in), and overall makes a better specimen.



There are several studies that have looked at the problems of fluid
preservation of frozen specimens, which I summarized in *Fluid
Preservation: A Comprehensive Reference* (2014), and I also reported on
shrinkage and color changes due to freezing. To briefly summarize, freezing
disrupts the arrangement of myofibers, distorts sarcolemmas (connective
tissue sheaths), the time lag between death and when the animal is
thoroughly frozen allows for extensive autolysis and biological
deterioration to take place, and there is a lot of tissue damage and cell
rupture from the formation of ice crystals during both freezing and thawing
cycles.



If you want to take tissues from a frozen specimen, that should be done
before the specimen is preserved, preferably while it is still frozen as
thawing initiates the degradation of DNA, but be warned that tissue from
such specimens will be degraded compared to tissues removed and processed
immediately after the specimen was euthanized. Be sure to label all tissues
removed from frozen specimens as likely to be degraded. Also, add a note in
the catalog record if a fluid-preserved specimen was made from a frozen
specimen—this information will be of use for future research use of the
specimen.



Lastly, about skeletons—given the choice between preparing a good skeleton
or a fair fluid-preserved preparation, why not opt for the good skeleton?
Most herpetological collections are woefully deficient in good skeletal
material. If the specimen is needed as an identification voucher, you can
take digital photographs of the specimen, link them to the specimen record
in the database for confirmation of ID, and still prepare a very useful
skeleton from the specimen.


--John


John E. Simmons
Writer and Museum Consultant
Museologica
*and*
Associate Curator of Collections
Earth and Mineral Science Museum & Art Gallery
Penn State University
*and*
Investigador Asociado, Departamento de Ornitologia
Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima


On Wed, Apr 27, 2022 at 9:24 AM Bentley, Andrew Charles <abentley at ku.edu>
wrote:

> Hi Tonya
>
>
>
> It is true that frozen specimens do not make ideal ethanol specimens as
> the formalin and ethanol do not pervade the tissues as well when frozen an
> thawed.  You can counteract some of that by injecting with formalin into
> all body cavities and leaving it soaking in formalin for a little longer.
> It also helps to step the specimen up through concentrations of ethanol to
> ensure good preservation throughout the specimen.
>
>
>
> Andy
>
>     A  :             A  :             A  :
>  }<(((_°>.,.,.,.}<(((_°>.,.,.,.}<)))_°>
>     V                V                V
> Andy Bentley
> Ichthyology Collection Manager
> University of Kansas
> Biodiversity Institute
>
> Dyche Hall
> 1345 Jayhawk Boulevard
> Lawrence, KS, 66045-7561
> USA
>
> Tel: (785) 864-3863
> Fax: (785) 864-5335
> Email: abentley at ku.edu
>
> ORCID: https://orcid.org/0000-0002-3093-1258
>
> http://ichthyology.biodiversity.ku.edu
>
>     A  :             A  :             A  :
>  }<(((_°>.,.,.,.}<(((_°>.,.,.,.}<)))_°>
>     V                V                V
>
>
>
> *From:* Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu> * On Behalf Of *Haff,
> Tonya (NCMI, Crace)
> *Sent:* Tuesday, April 26, 2022 11:26 PM
> *To:* nhcoll-l at mailman.yale.edu
> *Subject:* [Nhcoll-l] prepping frozen herps
>
>
>
> Hello all,
>
>
>
> I have read (in John Simmon’s book on herpetological collecting, among
> other places) that frozen snake and lizard specimens do not make suitable
> formalin-preserved specimens, and should be instead skeletonised. We have
> quite a few herp specimens in the freezer that we have been planning on
> prepping as ‘pickles’ (fixed in formalin and then stored in ETOH), but  I
> haven’t started yet because of the concern that it may not be worthwhile. I
> wonder if any of you could weigh in on this and tell me what your
> experiences have been, and whether or not you would bother preserving these
> specimens in spirit, or if we should just prep them as skeletons?
>
>
>
> Thanks!
>
>
>
> Tonya
>
>
>
> -------------------------------------------------
>
> Dr. Tonya M. Haff
>
> Collection Manager
>
> Australian National Wildlife Collection
>
> CSIRO
>
>
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