Calbindin-D32k in the Echinoderm Nervous System Figure 4. Anti-calbindin 1, anti-parvalbumin, and anti-calbindin 2 immunoreactivity in the podial nervous system of Holothuria glaberrima (Holothuroidea). Longitudinal and transverse sections through the tube feet showing immunoreactivity to anti-calbindin 1 (A,D,G,M), anti-parvalbumin (B,E,I,N), and anti-calbindin 2 (C,F,K,O) in the different subdivisions of the podial nervous system. (A–F) Immunoreactivity was observed with all markers in the podial nerve (arrows) and in the podial cylindrical fenestrated sheath (arrowheads). (G–L) Co-labeling of anti- calbindin 1 (G) and RN1 (H), anti-parvalbumin (I) and RN1 (J), and anti-calbindin 2 (K) and RN1 (L) was observed in fibers and cells (arrows) of the PLoS ONE | www.plosone.org 7 March 2012 | Volume 7 | Issue 3 | e32689