Macrofauna separation technologies + Sandgerdi course

Petersen, Mary Elizabeth MEPetersen at zmuc.ku.dk
Fri Jul 27 18:31:01 EST 2001


Friday, 27 July 2001

Dear Les,

For those of us who are less informed, how does Ludox work? What does it do
to the specimens? Do they become oily or greasy or otherwise messy to work
with?

Most of the material in shell gravels can be cleanly - if not very easily -
separated from the heavy fraction by elutriation, where one takes a small
portion of the sediment (+ seawater [live material], water [material fixed
in formalin but not yet rinsed] or alcohol [unsorted fixed and rinsed
specimens]) in a bucket and swirls it around until the animals are in
suspension. The suspension is then poured through a fine sieve and the
liquid that goes through the sieve can be reused until it becomes too dirty.

Heavier objects such as molluscs, echinoderms and some crustaceans, plus
things attached to shells (which will not come up when swirled), need to be
picked out by hand. The sieve should be emptied after each round to prevent
damage to the specimens. The method is one I learned when I was working as
an assistant to John H. Day at the Duke Marine Laboratory, -and I will be
forever grateful to him for showing me the method. It is wonderful for small
things. When working with live material, specimens able to "glue" themselves
to bits of shell or gravel, such as Pisione spp., will probably not come up,
but at least for most polychaetes (but not those in heavy tubes), the method
is great. I used it on a number of the Sandgerdi samples (see below) with
very satisfying results.

Feedback on Sandgerdi:

The Cladistics Course in Sandgerdi, Iceland (taught by Fredrik Pleijel and
Greg Rouse, with lectures also by Kirk Fitzhugh, Kristian Fauchald and
Sabine Cochrane), was excellent. In addition to learning the basic and some
of the finer theoretical and practical aspects of cladistics, intertidal
collecting and collections by divers taking part in the course made it
possible to see number of live Icelandic worms, many of which were
photographed by Greg. For interested persons who didn't make this one, I can
decidedly recommend trying to get on the one that will probably be held
before the Madrid conference.

Greetings from a hot (c. 29-30(C) Copenhagen,

Mary

Mary E. Petersen
Tel +45-35 32 10 67 - Fax +45-35 32 10 10
E-mail: mepetersen at zmuc.ku.dk
>ooooooooo))))):>

 -----Original Message-----
From: 	Les Watling [mailto:watling at maine.edu] 
Sent:	26 juli 2001 23:39
To:	annelida at net.bio.net
Subject:	Macrofauna separation technologies

As most or all users of this list are undoubtedly aware, chemicals such as
Ludox have been used for years to separate meiofauna from marine and
estuarine sediments.  In fact, I found a dozen or so references wherein
Ludox was used to extract nematodes and small crustaceans from forest soils.
I would like to know whether anyone has used Ludox or similar silicate sols
to extract larger, i.e., small macrofauna-sized, worms from sands and
gravel.  In an early version of Holme and McIntyre's book on methods for the
study of marine benthos there is also a reference to the use of
trichloroethylene.  Has anyone tried that or similar compounds? Ideas on
this subject would be greatly appreciated.  I have a small project where we
will be sampling with a grab sampler in sand and gravelly sand sediment.  

Best,
Les.


Les Watling
Professor of Oceanography and
Pew Fellow in Marine Conservation
Darling Marine Center
University of Maine
Walpole, ME 04573

Phone 207-563-3146 x248
Fax  207-563-3119
<watling at maine.edu>


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