Expression of sox5 in adult gonads. a–d In adult testes, sox5 fluorescence is restricted to the cells located between the lobules where the germ and Sertoli cells lie. a,b In double transgenic reporter fish, fluorescence of sox5 and dmrt1bY (marking the Sertoli cells) is distinct. c, d The interlobular expression of sox5 co-localizes with 11-β-hydroxylase, a marker of Leydig cells. e–j Expression of sox5 is also detected in another discrete population of cells between but always close to the germinal lobules. h-j Small in size, these sox5-positive cells also express vasa, a specific marker of germ cells. k–n The sox5- and vasa-positive cells do not express dmrt1bY. o–q In adult ovaries, only extremely few sox5 positive cells are detected.