[Nhcoll-l] Preservative for invertebrates

[Simon Moore]

Hi Harim,

I am sure that you will get many replies to this in time.
70% ethanol, is the preferred preservative (over formalin) for most animal tissue these days due to its low toxicity and non-carcenogenicity despite its flammability and propensity for evaporation.  In other words it is preferred largely due to health & safety reasons, also for its ability to preserve DNA.
However it does alter many pigments chemically and one of the classics is the the blue lobster changing to red as alcohol will 'unbind' the more complex crustacyanin molecule to produce its component astaxanthin which is the red lobster colour.  Tetrapyrroles as found in plants (chlorophyll) are rapiy 'unbound' by alcohol giving plants a bleached/washed-out appearance in alcohol. 
Alcohol (70%) will also auto-dilute over time - the pure alcohol evaporates (romantically known as the angels' share)  so the remaining alcohol became increasingly diluted.  As the alcohol auto dilutes, the rate of evaporation will gradually become slower.
There are those who find that 50% alcohol is less flammable and volatile but will (just manage to) maintain the state of preservation to an adequate level.  There may be other reasons that will soon become apparent but that is the situation as I presently understand it.

I hope that this is useful.

With all good wishes, Simon. 

Simon Moore MIScT, RSci, FLS, ACR
Conservator of Natural Sciences and Cutlery Historian,
www.natural-history-conservation.com 

  ----- Original Message ----- 
  From: Harim Cha 
  To: nhcoll-l at mailman.yale.edu 
  Sent: Monday, May 13, 2013 8:28 PM
  Subject: [Nhcoll-l] Preservative for invertebrates


  Hi all,

  I am looking for help/advice on finding references on preservative of invertebrates.

  If anyone knows/has references mentioning

  1) reasons for using 70% ethanol as a standard long term preservative of marine invertebrates

  2) effects (pros/cons) on using lower concentration (50%) of ethanol as a long term preservative of marine invertebrates

  could you please contact Harim, a collection manager at SIO, at hacha at ucsd.edu



  Any advice or comments on using lower concentration of ethanol as a long term preservative would be really appreciative. 



  Thanks,

  Harim

  -- 
  Harim Cha

  Benthic Invertebrate Collection
  Scripps Institution of Oceanography
  University of California, San Diego 0244
  9500 Gilman Drive, La Jolla, CA 92093-0244, U.S.A.
  Phone: 858-822-2818

  Courier delivery (FedEx/UPS) address:
  8675 Discovery Way
  138/ 141 Vaughan Hall
  La Jolla, CA   92037



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