Fig. 3From: Non-invasive imaging techniques combined with morphometry: a case study from Spirula Illustration of the ontogenetic development of the Spirula spirula shell. a Whorl height (wh). b Whorl width (ww). c Whorl width index (WWI). d Whorl height expansion rate (WHER). e Whorl width expansion rate (WWER). f Conch width index (CWI). g Conch height index (CHI). h Whorl interspace (wi). Diameter is plotted on the x axisBack to article page