Fig. 6: Reduced eye cell incorporation in cave planarians.

a Similar distribution of EdU incorporation 4 days after delivery in surface and cave planarians (see also Supplemental Fig. 6a, b for additional time points and quantification). Representative images from n = 5 animals for each species. b Newly differentiated eye cells from stem cells in G. dorotocephala and G. multidiverticulata were evaluated using arrestin fluorescent in situ hybridization (FISH) and EdU double labeling. Arrows indicate double-positive EdU⁺; arrestin⁺ photoreceptor neurons (PRNs). Representative images from n = 25 animals for each species. c Newly differentiated brain cells from stem cells in surface and cave planarians were evaluated using ppl-1⁺ and EdU⁺ immunofluorescence double-labeling. Arrows indicate EdU⁺; ppl-1⁺ double positives in one visual plane with magnified examples in the right upper corner. Representative images from n = 20 animals for each species. d During homeostatic replacement of eye cells, PRN incorporation is lower in cave animals (n = 46, 44, 28, from 4, 8, and 12 days respectively) than in surface animals (n = 30, 24, 10, from 4, 8 and 12 days respectively). Intervals were compared with a Student’s two-tailed t-test. e During homeostasis, new brain cell incorporation was similar in the two species (Gm n = 19, 19, 15, for 4, 8, and 12 days respectively; Gd, n = 9, 9, 5, for 4, 8, and 12 days respectively). Intervals were compared with a Student’s two-tailed t-test. f Expression of pkd1l-2 in whole animals (left panels) and one optical plane of newly differentiated ciliated neuronal cells in surface and cave planarians were evaluated using pkd1l-2⁺ and EdU⁺ double labeling (right panels). Arrows indicate EdU⁺; pkd1l-2⁺ double positives with magnified examples in the right upper corners. Representative images from n = 12 animals for each species. g During homeostasis, new ciliated neuronal cell production rate was similar in the two species (Gm n = 12, Gd n = 12, immersed in F-ara-EdU for 48 h and then fixed at 4 days). Intervals were compared with a Student’s two-tailed t-test. For all graphs ****p < 0.0001; ns, not significant. Error bars represent mean ± SD. Scale bars, 50 µm.