Gonad formation and pre-meiotic proliferation of gonocytes in the Japanese willow minnow <I>Gnathopogon caerulescens</I>

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  • Kobayashi Toru
    Laboratory for Aquatic Biology, Graduate School of Agriculture, Kindai University
  • Ashida Hiroshi
    Laboratory for Aquatic Biology, Graduate School of Agriculture, Kindai University Present address: Okinawa Churaumi Aquarium

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Other Title
  • ホンモロコにおける生殖巣の形成および減数分裂前の生殖細胞の増殖
  • Gonad formation and pre-meiotic proliferation of gonocytes in the Japanese willow minnow Gnathopogon caerulescens

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Abstract

This study histologically examined gonadal formation and sex differentiation in the Japanese willow minnow Gnathopogon caerulescens. Larvae and juveniles reared at 20°C were collected in batches at different timepoints [every 5 d from 0 to 20 d post-hatching (dph) and every 10 d from 30 to 50 dph]. In newly hatched larvae, primordial germ cells (PGCs) had migrated to the gonadal anlagen near the dorsal hepatopancreas under the peritoneum, before genital ridge development. At 5 dph, stromal cells accumulated near PGCs, and by 15 dph, they proliferated around the PGCs and formed gonadal primordia. The germ cell number remained constant in all fish at 15-20 cells until 20 dph; thereafter, in approximately 50% of them, active gonocyte proliferation commenced and underwent meiosis. By 40 dph, the germ cell number in some fish increased beyond 1200, and by 50 dph, ovarian cavities were evident. The remaining fish that did not undergo these differentiation steps developed sperm duct structures at approximately 30 dph and maintained 60-80 germ cells up to 40 dph.

Journal

  • Aquaculture Science

    Aquaculture Science 67 (1), 9-17, 2019

    Japanese Society for Aquaculture Science

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