A in a study comparing morphological differences in shells of 2 easily confused species, Littorina scutulata and L. plena, is that shell sizes are smaller in both species with increasing wave forces in the habitat. Rugh 1997 Veliger 40: 350.

NOTE for original study see IDENTIFICATION OF LITTORINES RESEARCH STUDY 3

The Littorina species scutulata and plena are morphologically similar, and much attention has been paid to means of separating them visually.  In a study of collections of snails from sites in Puget Sound and the Washington open coast, a researcher investigates ecological differences between the 2 species. The sites differ markedly in degree of wave exposure, but the author is unable to find correlative differences in tenacity in either of the 2 species.  Comparison of foot area against shell height (= length) reveals no significant difference between the species, nor does a comparison of tenacity with foot area.  Hohenlohe 2003 Veliger 46: 162.

NOTE  to measure tenacity, a spring balance is used in conjunction with a means to increase force (see schematic on Right). There are many refinements that can be applied to this basic method, such as what type of lifting force to apply (shear or vertical), what type of substratum to use, number of replicates on the same animal, lab or field, and so on.   However, as long as methods are standardised within a study, then the data should permit comparisons within that study, but not necessarily between studies.  For example, an earlier report on tenacity in L. scutulata of 12-15mm shell length lists stationary tenacity as 1100g ^. cm^-2 and moving tenacity as 500g ^. cm^-2, quite different from the approximately 200g ^. cm^-2 values reported in this study for stationary tenacity in equivalent-sized littorines. For earlier report see Miller 1974 J Exp Mar Biol Ecol 14: 99