I am preparing to do a small preliminary study of niche delimitation in a group of fishes, using in part stable isotope analysis. I am completely new to stable isotope analysis, and so I apologize if this is a very basic question.
I have seen several studies which have successfully utilized fin clips or fish scales for this purpose, but I am unsure of how they went about homogenizing the tissue, or if this is even necessary. I have seen other studies, and some core facility recommendations, which (pertaining to fish scales) suggest using the whole scale in the tin capsule with no homogenization needed. Could I do the same for fins, assuming that I could get roughly the same section of fin across all individuals? If homogenization is necessary, what affordable method would you recommend?
Hi Tyler,
You are right there are both ways in literature and both ways have their advantages and disadvantages depends who you ask. (I always felt better if the samples are homogenized because they burn and analyzed in the same way, but this is my point of few)
A opportunity to homogenize the samples is easy with a grinder. like in the attached video with Michelle Gillespie.
there are some automatically devices that can do the job but if your samples are dry enough it only takes a few seconds and you have a homogenized sample. The advantage of this technique is you have always prepared samples if you want to measure samples again.
but first i think the Book of Fry Stable Isotope Ecology give you a lot of Informations to start.
Fry, Brian. 2006. Stable Isotope Ecology. New York: Springer. http://site.ebrary.com/id/10228930.
Just a few infos
best Leon
https://www.youtube.com/watch?v=cuLldtlK2Ic
Thanks for the info and links. I have very small samples, so I was thinking I may do as in the video and dry them out and homogenize manually with small mortar and pestle.
Definitely check out this great and just published paper by Brian Hayden et al. before you start lab work.
Article Small Tails Tell Tall Tales – Intra-Individual Variation in ...
@John Thank you- I think that as per their suggestion I will homogenize, and standardize the section of fin used as much as possible.
As previous respondents have pointed out already, in the interest of repeatability (and reproducibility) when analysing samples in replicates of 3 or 4, homogenization is key. A good way to achieve this without causing thermal stress to samples (which may or may not impact on stable isotope signatures) is to homogenize samples in a freezer mill and to freeze dry the resulting "powder". In this way one obtains data that smooth out any sample heterogeneity resulting from subtle variation in growth rate or (bio)synthesis rate. Obviously, this also means one obtains a time averaged answer.
That being said, depending on the actual sample matrix (and sample amount) it may be possible to obtain chronologically resolved data if it is possible to collect samples across a transect. Depending on size and age of your fish it may be possible to sample and analyze fish scales this way.
If sample availability is not a limiting factor you may even be in a position to do both and see if and how results differ.
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