Figure 2. Geometric model for the calculation of oral sucker area from digitized landmarks in ventral view footage of feeding and climbing by Sicyopterus stimpsoni.

(a) Outline sketch of the mouth of S. stimpsoni in ventral view, with superimposed greyscale shaded geometric shapes defined by labeled digitized landmarks. A, digitized Point 1 (anterior edge of upper lip); B, digitized Point 3 (anterior tip of mandibular symphysis); C, digitized Point 4 (right caudolateral tip of mouth); D, digitized Point 6 (midpoint of mandible on the right side); E, calculated midpoint between points B and C; θ, angle between vectors AB and AC. Note that digitized points are shown as open circles, and calculated points are shown as solid circles. (b) Geometric shapes from (a) separated into three groups (designated X, Y, and Z), with formulae for calculation of their areas. Sucker area was modeled as the sum of these three geometric areas, which assume symmetry between left and right sides.