Sections of testis from 7 month-old zebrafish.

<p>A) Respresentative haematoxylin-eosin (HE) staining of the mature zebrafish testis; spermatogonia (Sg), spermatocytes (Sc), spermatids (Sd), and spermatozoa (Sp) could all be positively identified. B) <i>in situ</i> hybridization (ISH) of <i>gsdf</i> transcripts in the testis; staining shows strong signal throughout the testis, although it is unclear from which cell type it originates; no staining is visible in spermatocytes or spermatids. Spermatogonia and spermatozoa could not be identified. C) ISH of <i>gdf9</i> transcripts in testis; faint signal was found throughout the testis. It is unclear which cell types the signal is localized to. D) ISH of <i>cd205</i> transcripts in the testis; the signal is strongest in spermatogonia, while it is not visible in spermatocytes or spermatids. Spermatozoa could not be identified. All scalebars represent 100 µm.