[NHCOLL-L:1705] RE: Fish hydration

[Simmons, John E]

I have tried numerous rehydration techniques for amphibians and reptiles,
and non have been successful.  My current policy is that when a specimen
dries out beyond the point of being able to simply refill the container to
restore it, I leave it dry.  If and when researcher needs to rehydrate the
specimen, we use a procedure at that time.  The section below from an
upcoming publication of mine explains the reasoning in more detail.

 

This is a fairly common problem in collections of fluid preserved specimens.
If anyone has any experience (either good or bad) with these or any other
techniques, please post a note to the list.  

 

Also, please note that although rehydration may appear to be successful in
the short term (e.g., the time it takes an author to get a note into print)
in the long term, the useful life of the specimen is usually shortened
considerably.

 

**********************************

REHYDRATION OF SPECIMENS

After years of unhappy experiences, I have concluded that once a
fluid-preserved specimen has become dehydrated, it should probably be
maintained in that state unless it is absolutely necessary to rehydrate it
in order to use it.  Dehydration is very damaging to fluid-preserved
specimens; rehydration will cause even more damage.  Rehydration efforts are
rarely successful, and will shorten the life of a specimen.  In the event
that it is absolutely necessary to rehydrate a dehydrated specimen, the
techniques listed in Table 9 have been suggested.  It is best to experiment
on a junk specimen before attempting to rehydate a valuable specimen.
Although various rates of success have been claimed, none of the published
reports includes an analysis of the long-term preservation status of the
treated specimens.

 

Table 9.  Rehydration techniques.


Technique

Reference

Comments


30% ammonia and warm water

Traditional technique

Poor results; ammonia damages proteinaceous tissues


2:1 solution of hydrogen peroxide and water

Traditional technique

Poor results; hydrogen peroxide damages tissues


3:1 isopropyl alcohol and water

Traditional technique

May initially soften specimen but results in further dehydration of the
tissues over time


Surfactant (detergent) in water

Banks and Williams 1972

Generally poor results on badly dehydrated specimens; chemicals in the
detergent will contaminate specimen for future chemical analysis


0.25 to 0.50% solution of commercial grade trisodium phosphate in water

van Cleave and Ross 1947

Usually unsatisfactory; trisodium phosphate is potentially damaging to
tissues


0.5% trisodium phosphate and water for 24 hr

Marhue 1983

Usually unsatisfactory; trisodium phosphate is potentially damaging to
tissues


Stage through solutions of 10%, 5% and 0.5% acetic acid, followed by
trisodium phosphate solution

Vogt 1991

Arguably the most successful system, but acetic acid and trisodium phosphate
will damage protein


50% propylene glycol or ethylene glycol solution

Marhue 1983

Unknown effects on specimen; glycols are unsatisfactory as preservatives


10% solution of enzymatic drain cleaner (e.g. Drano(tm), Liquid Plumber(tm))
for 3 weeks

Vogt 1998

Very damaging to specimen tissues; never subject specimens to exposure to
proprietary products of uncertain composition

 

Banks, H.J. and D.J. Williams.  1972.  Use of surfactant Decon 90 in the
preparation of coccids and other insects for microscopy.  J. Australian
Entomol. Soc. 11:347-348.

 

Marhue, L.  1983.  Techniques to restore dried-up invertebrate specimens.
Pp. 175-177 in Faber, D.J. (ed.).  Proceedings of the 1981 Workshop on the
Care and Maintenance of Natural History Collections.  Syllogeus 44:1-196.

 

van Cleave, H.J. and J.A. Ross.  1947.  A method for reclaiming dried
zoological specimens.  Science 105(2725):318

 

Vogt, K.D.  1991.  Reconstituting dehydrated museum specimens.  Curator
34(2):125-131

 

Vogt, K.D.  1998.  The reconstitution of dehydrated museum specimens II.
The Biology Curator 16:6.

 

 

John E. Simmons

Collection Manager, Natural History Museum & Biodiversity Research Center

and

Coordinator, Museum Studies Program

University of Kansas

1345 Jayhawk Boulevard

Lawrence, Kansas 66045-7561

Telephone 785-864-4508

FAX 785-864-5335

jsimmons at ku.edu

www.ku.edu/~museumst/

 

-----Original Message-----
From: V.Mthombeni at ru.ac.za [mailto:V.Mthombeni at ru.ac.za] 
Sent: Wednesday, September 18, 2002 7:49 AM
To: NHCOLL-L at lists.yale.edu
Subject: [NHCOLL-L:1704] Fish hydration

 

Dear list members,

 

I am also keen to know the standard procedures for hydrating fish which have


completely dried out (previously stored in alcohol). I would appreciate if
any 

unswers given to Timothy can also reach me.

 

Thank you for your co-operation.

 

Regards

Vusi Mthombeni

 

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