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14 November 2017 Testicular Histology Reveals a Novel Type of Spermatogenesis in Pseudobranchus axanthus (Caudata: Sirenidae)
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We examined the testicular histology of 32 adult male Pseudobranchus axanthus collected at Rainey Slough (Glades County), Florida, during 1974–76. The process of spermatogenesis was evident throughout all regions of the testes and appeared to occur year-round. The testes contain numerous, spherical-to-oblong testicular lobules that vary greatly in size. Unlike all other salamanders, which exhibit cystic spermatogenesis along with a caudo-cephalic wave of maturing cell types (leading to spatial and temporal segregation of germ cells), spermatogenesis in P. axanthus lacks testicular cysts. Instead, the testicular lobules possess an assortment of different spermatogenic cell stages, all arising from primary spermatogonia through mitotic and meiotic divisions, thus creating a germ cell/Sertoli cell syncytium along the lobular epithelium. Secondary spermatocytes then detach from the lobular epithelium and from their accompanying Sertoli cells and undergo spermiogenesis within the lumen. We propose naming this new type of germ cell development non-cystic lobular spermatogenesis. Upon maturation, sperm travel from the lobular lumen into a longitudinal testicular canal via an intratesticular duct. The testicular canal conveys sperm to about 15 vasa efferentia, which then connect to genital renal capsules. Sperm move through the renal tubules and eventually reach the Wollfian duct. This duct transports sperm to the cloaca.

© 2017 by the American Society of Ichthyologists and Herpetologists
Stanley E. Trauth, Dustin S. Siegel, J. Steve Godley, Zachary C. Adcock, and Roy W. McDiarmid "Testicular Histology Reveals a Novel Type of Spermatogenesis in Pseudobranchus axanthus (Caudata: Sirenidae)," Copeia 105(4), 670-677, (14 November 2017).
Received: 3 May 2017; Accepted: 2 August 2017; Published: 14 November 2017

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