Fig. 2: Eye-body allometry: the cave planarian Girardia multidiverticulata displays fewer photoreceptor cells than surface planarians, but similar brain and pharynx size.
From: Reduced adult stem cell fate specification led to eye reduction in cave planarians
a Schematic representation of eye photoreceptor cells with details of how photoreceptor cells were identified and counted. Simple linear regressions demonstrating cave planarian morphotypes present small numbers of photoreceptor cells that increase more slowly with body size when compared to the steeper slope observed for all three species of surface planarians (Gm, G. multidiverticulata non-discernible eye n = 86; Gm(d), G. multidiverticulata discernible eyes n = 85; Gd, G. dorotocephala n = 58; Dj, Dugesia japonica n = 36; Sm, Schmidtea mediterranea n = 32). Scale bar, 50 µm. b Schematic representation of brain anatomy and the landmarks used for brain length measurements. All planarians (cave and surface species) display similar brain length-body size allometric scaling (Gm non-discernible eyes n = 43; Gm discernible eyes n = 43; Gd n = 29; Dj n = 18; Sm n = 16). c Schematic representation of pharynx length live measurements. Simple linear regressions demonstrating cave and surface planarians have similar pharynx length-body size allometric scaling (Gm n = 43; Gm(d) n = 43; Gd n = 29; Dj n = 18; Sm n = 16). Scale bar, 1 mm. d Both cave morphotypes have a similar number of photoreceptor cells in animals with small (1–5.9 mm in length) and large (6–14 mm in length) body sizes. G. multidiverticulata morphotypes present no differences in eye-body allometric scaling between each other (Gm non-discernible eyes n = 86; Gm discernible eyes n = 85). e ppl-1+ cells in the brains of G. dorotocephala and G. multidiverticulata. f Similar overall number of ppl-1+ cells in the brains of G. dorotocephala (n = 16) and G. multidiverticulata discernible (n = 16) and non-discernible eye (n = 20) morphotypes. Scale bar, 50 µm. For d and f Mean ± SD and one-way ANOVA followed by Tukey’s multiple comparisons test. Mean ± SD. R, coefficient of determination. ns not significant p > 0.01.
