Bending of long slender organisms (or other structures) can be an important 
practical problem. Changes due to bending could dominate the results. 
Separating sets of landmarks into more rigid sublets can help as long as the 
endpoints of the subsets are homologous and not arbitrary or dependent on the 
bending of a particular specimen. The tpsUtil program has an "unending" option 
if one has a subset of points that one knows should be in a straight line. That 
would be difficult for larvae.

Note: I see you are using ver. 2.30 of tpsDig. Version 2.31 is current. I do 
try to keep fixing bugs so It can be useful to stay current.

____________________________________________
F. James Rohlf, Distinguished Professor, Emeritus. Ecology & Evolution
Research Professor, Anthropology
Stony Brook University

-----Original Message-----
From: Avi Koplovich [mailto:netbird.porta...@gmail.com] 
Sent: Tuesday, February 27, 2018 3:09 AM
To: MORPHMET <morphmet@morphometrics.org>
Subject: [MORPHMET] Digitizing landmarks on live larvae

Hi,
I've started a new project and came to the point of marking fixed and semi 
landmarks.
Not all pictures are satisfying, mostly because of the posture of the larvae 
during photographing (sometimes raising it's tail). So in order to reduce the 
noise by the animal posture, I thought it would be helpful to separate head and 
tail as was done in Levis et. al. 2016, Biol. J. Linn. Soc.
I'm using the landmarks 1, 20 and 48 as fixed landmarks, and all the rest are 
semi landmarks. I'm not sure of using 20 and 48 as fixed landmarks, and I 
wonder if I can use landmark 40 as fixed landmark since it is restricted by 
both x (side line) and y (dorsal connection of the tail fin). Can/Should I use 
the eye as a fixed landmark for the head (i.e. can it interfere with 
interpreting the head contour)?
Here is an example to show what I mean:
https://drive.google.com/file/d/1iO7lCN3ZCtV7DF9vsczkb_EYoSli1Orr/view?usp=sharing
I'll be happy if you can advise on that.
Thank you,
Avi

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