Landmark-based geometric analysis in describing the shell of the freshwater gastropod Vivipara angularis (Gastropoda: Viviparidae) from Lake Dapao, Pualas, Lanao del Sur, Mindanao, Philippines

This study was conducted to describe the shell shapes of Vivipara angularis collected from four different locations in Lake Dapao, one of the deepest lakes in Mindanao, Philippines. Geometric morphometric tools specifically relative warp (RW) and euclidean distance matrix analysis (EDMA) were used to describe the shapes. Results showed there was no population differentiation in the snail as the shell shapes in all four populations were concentrated towards the means shape revealed by relative warp analysis. A closer look at variations in shell shapes based on the results of EDMA revealed that individual variations were due to differences in selected interlandmark distances observed along the spire, body whorl and aperture of the shell. Observed variations in shell shapes can be argued to be due to ecological factors, developmental differences and/or maybe environmentally induced.