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<p>The ultrastructure of spermatogenesis and spermatozoon of <i>Ophiotaenia tessellata</i> Gamil and Fouad 2023; a proteocephalidean cestode infecting <i>Natrix tessellata</i>, was studied using transmission electron microscopy. Spermatogenesis has several stages; the last one is spermiogenesis. It follows a rosette type, with detailed examination of spermatogonia, primary and secondary spermatocytes, and finally spermatids are formed. Spermiogenesis begins with the formation of a differentiation zone at the periphery of each spermatid, surrounded by arching membranes and an apical electron-dense material. This zone is supported by cortical microtubules and contains two interconnected centrioles, from which free flagella develop. Each centriole is associated to a striated rootlet. The differentiation zone protrudes into a conical projection, evolving into a median cytoplasmic process. After rotation, the flagella fuse with the cytoplasmic process, followed by nucleus migration. Later the young spermatozoon is detached from the residual cytoplasm. The mature spermatozoon of <i>O. tessellata</i> is filiform, tapered at both extremities and lacks mitochondria. It contains two axonemes of unequal length with the 9 + “1” pattern typical of <i>Trepaxonemata</i> and has a single crested body, a nucleus and cortical microtubules. Thus, it corresponds to type II spermatozoon, described in almost all Proteocephalidea. Four distinct regions with varying ultrastructural features are observed. The spermatozoon structure of <i>Ophiotaenia tessellata</i> is compared to other proteocephalidean cestodes.</p>

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First report on spermatogenesis and spermatozoon ultrastructure of the Proteocephalidean cestode Ophiotaenia tessellata Gamil & Fouad, 2023, an intestinal cestode of colubrid snake Natrix tessellata (Laurenti, 1768) from Egypt

  • 期刊论文

  • 发表日期：

    2026年3月3日

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  • Irene S. Gamil,
  • Reda M. Mansour

摘要

The ultrastructure of spermatogenesis and spermatozoon of Ophiotaenia tessellata Gamil and Fouad 2023; a proteocephalidean cestode infecting Natrix tessellata, was studied using transmission electron microscopy. Spermatogenesis has several stages; the last one is spermiogenesis. It follows a rosette type, with detailed examination of spermatogonia, primary and secondary spermatocytes, and finally spermatids are formed. Spermiogenesis begins with the formation of a differentiation zone at the periphery of each spermatid, surrounded by arching membranes and an apical electron-dense material. This zone is supported by cortical microtubules and contains two interconnected centrioles, from which free flagella develop. Each centriole is associated to a striated rootlet. The differentiation zone protrudes into a conical projection, evolving into a median cytoplasmic process. After rotation, the flagella fuse with the cytoplasmic process, followed by nucleus migration. Later the young spermatozoon is detached from the residual cytoplasm. The mature spermatozoon of O. tessellata is filiform, tapered at both extremities and lacks mitochondria. It contains two axonemes of unequal length with the 9 + “1” pattern typical of Trepaxonemata and has a single crested body, a nucleus and cortical microtubules. Thus, it corresponds to type II spermatozoon, described in almost all Proteocephalidea. Four distinct regions with varying ultrastructural features are observed. The spermatozoon structure of Ophiotaenia tessellata is compared to other proteocephalidean cestodes.