Fig. 3. Distribution of NKCC during the ontogeny of Dicentrarchus labrax. of (A) Embryo; (B) 1-day-old prelarva; (C,C',D) 3-day-old prelarvae. (A) Transverse section showing apical staining in the cells lining the digestive tract (DT) and basolateral staining in the tegumentary ionocytes (TI). (B) Transverse section of the developing branchial chamber, showing immunostained chloride cells (CC) are already present on the opercular membrane (O) and the branchial slits (BS). (C) Longitudinal and (C') transverse sections of prelarvae with intense staining of the intestinal brush-border. Note the immunopositive tegumentary ionocytes. (D) Transverse section showing weak apical staining of the renal collecting ducts (CD) and apical staining of the digestive tract. M, muscle; NC, notochord. Scale bars, 10 µm (A,C'), 20 µm (B,C,D).