Evolution of spicule shape. For each Caenorhabditis species, a drawing of the spicule is shown in right lateral view with the dorsal side to the right (the spicules of C. drosophilae and C. sp. 2 and of C. angaria and C. sp. 12 are identical and are shown for only one species). Three features of the spicule are distinguished, each with two alternative character states: the overall shape (orange boxes), the curvature of the spicule blade (pink boxes) and the shape of the spicule tip (blue boxes). The character states for each species are indicated by filled or empty colored boxes above the images.
Kiontke et al. BMC Evolutionary Biology 2011 11:339 doi:10.1186/1471-2148-11-339