Expression of Rspo1, 2 and 3 in the gonads of medaka analyzed by ISH. Rspo1 and 2 were expressed in both the germ cell and somatic cell in the XX gonads at the early stages (S38 to 10dah) (Rspo1: s, t, a, b; Rspo2: i, j), but they were found in the cytoplasm of oogonia and oocytes after 30dah (Rspo1: c, d; Rspo2: k, l). Rspo3 was faintly expressed in the cytoplasm of oogonia and oocytes of adult female gonads (q). No expression of Rspo1 (e-h), 2 (m-p) and 3 (r) were detected in the male gonads by ISH analysis. (▸ = positive signal in the ovary; ⊳ = position of testis; Oo: oogonia; Oc: oocyte; Po: primary oocyte; CA: cortical-alveolar).