spiny lobster eggs
From: "Roy Melville-Smith" <rmelville-s@fish.wa.gov.au>
To: <CRUST-L@vims.edu>
Date: 25 Sep 2002
QUESTION:
We are interested in comparing western rock lobster
early stage egg sizes, for different sized animals and different localities.
Distances between the lab and field sampling localities make it impossible
to bring fresh material back to the lab to be measured. Freezing
the eggs for later measurement is a possibility, but some of the samples are
to be collected in localities where even that might be difficult. Last
season we stored samples in 5% buffered formalin, but we found that the size
of eggs was very sensitive to very slight changes in formalin
concentration, so that even the small amount of evaporation from the
sampling containers led to changes in egg sizes.
Obviously we could repeat this again taking more precautions to prevent
evaporation, but I have been wondering whether there is not perhaps a better
solution to the problem.
Is there anyone out there who can offer alternative solutions to what
superficially seems to be a very simple problem. I have no concerns
about eggs shrinking, as long as the shrinkage is consistent through the
samples.
Roy Melville-Smith
Principal Research Scientist
Rock Lobster and Crab Research
Western Australian Marine Research Laboratories
P.O. Box 20, North Beach, WA6020 AUSTRALIA
e-mail: rmsmith@fish.wa.gov.au
Phone: +61 (08) 92468406
Fax +61 (08) 94473062
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COMMENTS 1:
I had the same problem with Panilurus homarus egg
measurements. The only way is to prepare enough buffered formalin with
similar concentration and find a suitable air tight container. You should
also dry the cut eggs with a paper towel, then put in the jar. To keep the
specimens in the same stage, I have measured all of them on the same days
after fixation.
Because the maximum day for measurement in the lab was 14 days, I had to
keep some samples to be measured on day 14. Formalin concentration was not
high (4%) and I did not notice much shrinkage. I hope you will solve the
problem by decreasing fixation days. You could also try 60-70 % alcohol
but sometimes you will get some kind of mucus-like material after fixation
or much change in the egg diameter. It works for a shorter period of
fixation.
Dr. Alireza Sari
Department of Biology,
Faculty of Science,
University of Tehran,
Tehran,
Iran
e-mail:
museum@khayam.ut.ac.ir
***************
COMMENTS
2 :
Have you tried using glycerol in the formalin? I've
used 5 and 10% formalin for a lot of egg work, but I wasn't measuring egg
diameters on fixed eggs.
What about using a glycerol or DMSO modified buffer and freezing in LN2 or a
dry-ice slurry, then into an ultracold?
Jeff Shields