By the teeth of their skin, cavefish find their way

Figure 1. Mechanosensory skin denticles (MSDs). (A) Astroblepus pholeter. Scale 1 cm. (B) Scanning EM of MSDs; on the head (asterisk marks the eye, scale 1 mm). (C) A club-like MSD protruding from a socket (scale 100 μm). (D) Histological cross-section of base and innervation (arrowhead) of MSD (scale 100 μm). (E) Pseudocolored TEM of MSD socket (yellow: neuron, red: muscle, blue: dentine; scale 10 μm). (F) MicroMRI scan of head (oblique dorsal view) showing brain and dorsal nerves (arrow). (G) Histological section (scale 100 μm) shows dorsal nerve (arrow), cerebellum (Cb) and anterior lateral line nucleus in brainstem (LLa; arrowheads). (H) Tract tracing section at similar level showing nerve branches under LLa (DiI, 100 μm thick, scale 100 μm). (I) Electrophysiological responses recorded extracellularly in dorsal nerve while mechanical stimuli (arrows) were applied to ipsilateral dorsal trunk MSDs. Each stimulus is followed by a burst of action potentials. These responses are abolished (bottom), when MSDs have been scraped (scale 2 seconds). Gal Haspel1, Adina Schwartz2, Amy Streets2, Daniel Escobar Camacho3, and Daphne Soares2,*