Date: 5 Feb 1998
From: Brent Newman zool <bnewman@pan.uzulu.ac.za>
To: crust-l@VIMS.EDU
QUESTION:
I am planning several decapod larval rearing experiments (crab larvae
mainly), and wish to examine various aspects of the biochemistry of these larvae. Unfortunately the biochemical analyses cannot be performed at the same institution where the rearing exps will be conducted due to a lack of facilities. In this respect I have several questions which I hope can be addressed:
1. Can the larvae be frozen until the analyses can be performed (about
6-8 months later). If so, what is a suitable freezing temperature? Does
anyone have any comments/suggestions as to in what containers the larvae should be frozen? Should a small volume of water be included along with the larvae?
2. Can biochemical analyses be performed on larvae previously preserved in formalin?
3. Is anyone aware of very recent literature ie very late 1997/1998 which provides new techniques for C,N,H, lipid and protein fractions. I have several of Klaus Angers recent papers and will use similar techniques if there is no additional info.
Lastly, should we be able to freeze the larvae, I presume that eggs can
be treated in the same manner?
Brent Newman
University of Zululand
South Africa
***************
COMMENTS 1:
The larvae should be frozen immediately after sample taking and
homogenized at -25 or -30C . The recipients are preferably glass tubes with screw cap, which can be closed tightly and flushed with nitrogen. No water at all should be added. The samples must be as dry as possible! About sample amounts, e.g. if proximate composition (lipid, protein, water, ash and carbohydrates) on wet samples (tissue) has to be determined, at least 7 g of wet material should be available. If the material is dry (e.g. diets) less is needed. For other analyses, like vitamins, other sample preparations are necessary! (-80C)...
Formalin is not recommended to preserve larvae, as some components might be extracted in the solvent, so you cannot simply remove the solvent. The sample will be too wet.
There exist some very nice new techniques to determine N and C quickly on small sample amounts with very expensive equipment. In our lab we use simple techniques:
for lipids: cold extraction (Folch)
for proteins: Kjeldahl
for ash and water content: ovens
carbohydrates are determined by subtraction.
Eggs should be treated in the same way (as dry as possible).
Karla Van Ryckeghem
Laboratory of Aquaculture & Artemia Reference Center
University of Gent, Rozier 44, B-9000 Gent, Belgium
tel: + (32) 9 264 37 54
fax: + (32) 9 264 41 93
@ : karla.vanryckeghem@UGent.be