[Nhcoll-l] [EXTERN] Re: Best practices for ethanol-fixed specimens

[Dirk Neumann]

Hi Verity,

I would opt for 70%; 95% not only strongly dehydrates the specimens, but also causes a lot of osmotic pressure on tissue membranes, which might effect the usefulness of the specimens for morphological analysis. Tissue subsampling and subsequent storage of tissues in 95% for later molecular investigation might be better.

Hope this helps
Dirk


Am 22.04.2026 um 22:50 schrieb Shoobs, Nate:
Depends on what you want to use them for!
Formalin is not a great long-term preservative, even though it's a great fixative. Since the tissue is fixed already, unless you want to post-fix for some specific purpose like histology, I'd leave them in ethanol.
It's fine to keep things in 95% indefinitely, but if you think they will be used mainly for anatomical study, swapping the 95% for 70-75%  is better for long term storage and will keep the tissues flexible. Some institutions use 80% as a compromise between genetic and anatomical preservation. If you typically voucher frozen material, I'd recommend taking your tissue samples and freezing them before stepping the lot(s) down in concentration. You could even chuck a whole individual in 95% into the freezer.

Personally, I rarely if ever use graded ethanol series for going from high to lower concentration, especially for fresher material, I only bother when going from low-high, but I'm unsure how vertebrates typically handle.
My 2 cents!
-Nate
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[The Ohio State University]
Nathaniel F. Shoobs
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From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu><mailto:nhcoll-l-bounces at mailman.yale.edu> on behalf of Mathis,Verity L <vmathis at flmnh.ufl.edu><mailto:vmathis at flmnh.ufl.edu>
Date: Wednesday, April 22, 2026 at 4:38 PM
To: nhcoll-l at mailman.yale.edu<mailto:nhcoll-l at mailman.yale.edu> <nhcoll-l at mailman.yale.edu><mailto:nhcoll-l at mailman.yale.edu>
Subject: [Nhcoll-l] Best practices for ethanol-fixed specimens

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Hello all
I am hoping to get feedback on the best practices for some recently fixed fluid specimens.  During some recent field work, our lab fixed some rodent fetuses in 95% ethanol while prepping.  I’m hoping for some advice on how best store them long-term now that they are back in the lab/collections.  Do I keep them in 95% ETOH, re-fix them in formalin, or step them down to 70% ETOH for long-term storage?  Or something else altogether?

Thanks for any insight!
Verity
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Stiftung Leibniz-Institut zur Analyse des Biodiversitätswandels
Postanschrift: Adenauerallee 127, 53113 Bonn, Germany

Stiftung des öffentlichen Rechts;
Generaldirektion: Prof. Dr. Bernhard Misof (Generaldirektor), Adrian Grüter (Kaufm. Geschäftsführer)
Sitz der Stiftung: Adenauerallee 160 in Bonn
Vorsitzender des Stiftungsrates: Dr. Michael H. Wappelhorst
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