Early gonad development in zebrafish (Danio rerio)

  • GE Okuthe
  • S Hanrahan
  • BC Fabian


Gonadogenesis in zebrafish goes through an initial ovarian phase then subsequently into either ovarian or testicular phases. How germ cells choose to commit to an oogenic fate and enter meiosis or alternatively not enter meiosis and commit to a spermatogenetic fate remains a key question. This study investigated events of early gonadogenesis in zebrafish with the aim of unraveling the events surrounding the mitotic/meiotic transition in juvenile ovaries. Primordial germ cells were identified at eight days post fertilization (dpf).  Mitotic divisions were apparent at 15 dpf, and meiosis initiated in some gonads after 22 dpf. After 40 dpf, female gonads contained various germ cells including oogonia, post-pachytene and early pre-vitellogenic oocytes, whereas in some gonads, degenerative post-pachytene oocytes and proliferating germ were observed. The occurrence degenerating oocytes as well as a relatively larger proportion of proliferating "gonial" germ cells in the latter gonads was considered the first indication of spermatogenic activity, marking the onset of secondary (testicular) gonadogenesis. It could not be determined here whether primordial germ cells were involved in secondary gonadogenesis. While the mechanisms of this phenomenon in zebrafish ovaries are not well addressed, here it can be seen in the context of an apoptotic regulation.

Keywords: Danio rerio, gonad, mitotic/meiotic transition, development, sex inversion.

African Journal of Biotechnology, Vol 13(31) 3433-3442

Author Biographies

GE Okuthe
Department of Zoology, Walter Sisulu University, P/Bx1 Mthatha, 5117, Mthatha, South Africa
S Hanrahan
School of Animal Plant and Environmental Sciences, University. University of the Witwatersrand, P/BX3 Wits 2050, Johannesburg, South Africa
BC Fabian
School of Molecular and Cell Biology, University of the Witwatersrand, P/BX3 Wits 2050, Johannesburg, South Africa

Journal Identifiers

eISSN: 1684-5315