Dear collegues, I am experimenting with Salamandra larvae, and so far I have been weighing them and measuring their snout-vent lengths (SVL) to monitor their growth, as well as indices for future fitness (size at metamorphosis). Measuring SVL involves relatively large errors since the vent is not clearly visible, and different lengths may result from multiple measurements of the same individual, especially if this is done by more than one person. My question is whether I can use maximal head width instead as a measure of growth that is independent of temporary feeding states. Head width is easier to measure with greater precision, but its variation is smaller than that of SVL. I found data in my lab for ~50 larvae of roughly the same age for whom both heads width and snout-tail lengths (but not SVL) were measured. I found a linear fit between these variables of R^2=0.87 I expect the fit between head width and SVL to be better since tails get bitten short, and also tend to curve during measurements. However, I have never encountered published studies that used head width, while SVL is very popular. Your opinions about this would be much appreciated. Thanks, Asaf University of Haifa
