In situ hybridization (probed with fluoroscein isothiocyanate-oligo-γ-tubulin probe) of different stages of zebrafish oocytes and embryos. (A) and (G) Fully grown, immature oocytes. (B) and (H) Mature oocytes or eggs) and embryos. (C) and (I) 32-cell embryos. (D) and (J) 256-cell embryos. (E) and (K) Approximately 30% epiboly gastrula. (F) and (L) pharyngula). The top panels in (A) through (F) show the "with probe" treatments, and the lower panels in (G) through (L) show the corresponding "without probe" treatments. The primordial blastodisc (b) that forms at the animal pole of the egg during oocyte meiotic maturation labeled intensely with the probe (B) Inset: Immature oocyte probed after hemisection showing cortical label. Anti-FITC secondary antibody conjugated to alkaline phosphatase and the substrate 3,3'-diaminobenzidine were used to develop color. The specimens were dehydrated in 100% MeOH and placed in clearing media containing benzyl benzoate and benzyl alcohol (2:1 dilution) prior to being mounted on slides. Scale bar = 250 μm. Reprinted with permission .