Peter
Your student has a real problem here. However: 'The best is the enemy
of the good' (you know how Julian just loves quotations), and she'll
just have to do the best she can.
I agree completely with what Richard B said. Microhardness will at
least give you something, and microhardness is loosely correlated with
abrasion resistance via Archard's law (it's on the web!). Microhardness
testers are pretty common in engineering departments and reasonably easy
to use. Nanohardness is an order of magnitude more difficult, and
expensive, and not to be recommended except in extremis.
Definitely don't try to treat in bulk.
Freezing in sea water is I think a good idea. Most mineralised tissues
are reasonably forgiving of having been frozen and then thawed.
Preservation in alcohol or formol definitely not a good idea.
Strength of the whole structures of things like copepods could be tested
using small testing equipment, but normalising to compare like with like
would be v. difficult. Fish larvae and salps of course are not amenable
to testing in any sensible way, and hardness is meaningless in their
case, though Julian could probably come up with an ingenious way of
testing their TOUGHNESS.
I read VERY recently of a report, but I'm damned if I can remember
where, of people who had been testing diatom strength using a glass rod
as a load 'cell' They found quite nice relationships, as I remember,
between edibility and various mechanical properties. But all these
kinds of methods will only make sense on hard tissues, not sloppy salps!
A question that occurred to me is whether these prey will have been
partially digested already. If they have, that's an added problem, of
course.
Good luck
John
Professor John Currey
Department of Biology
Area 9
PO Box 373
University of York
York YO10 5YW. UK
email [log in to unmask]
tel +44 (0)1904 328589
fax +44 (0)1904 328505
|