Lengths measurements in microvascular corrosion castings: two-dimensional versus three-dimensional morphometry.

In the present study we compared measurements of vessel lengths from (a) single-digital scanning electron microscope (SEM) images of microvascular corrosion casts (VCCs) of gill filters of tadpoles of Xenopus laevis Daudin by two-dimensional (2-D) morphometry (Optimas 6.5, Optimas Corp., Bothell, Wash., USA; planar measurements) and (b) digital stereopairs by three-dimensional (3-D) morphometry (3D-Morphometry, Minnich and Muska OEG, Salzburg). Depending on the spatial orientation of the vessels measured, we found a maximum difference of 58.84% (100 [3-D]-41.16 [2-D]) in vessel lengths by 3-D morphometry versus 2-D morphometry, which, in multiple (segmental) lengths measurements or when determining space angles, might be even higher. Based on results we consider 3-D morphometry of VCCs to be the method of choice for lengths measurements.