Organization of the male gonad in a protogynous fish, Thalassoma bifasciatum (Teleostei: Labridae)

Abstract

Although the testis in teleosts has been investigated for many years, little attention has been paid to the structure of the outer layers that enclose the testis and to their possible contributions to its organization. The present study in a protogynous male labrid, Thalassoma bifasciatum (bluehead wrasse), describes the arrangement and cytology of these tissues (for convenience, referred to collectively as the outer wall, OW) which include: the outer peritoneal layer and subjacent collagen fibers, myoid cells and diverse other cells and tissues, e.g., fibrocytes, presumptive mesenchyme, macrophages, granulocytes, nerves, and blood vessels. Beneath the OW are two compartments; one is the gamete-laden spermatocysts, the other the interstitium, which is composed of cells and tissues that lie between the spermatocysts. Both OW and interstitium contain similar kinds of tissues and cells. Moreover, the layers of the OW immediately subjacent to the peritoneum are continuous with that in the interstitium. It is suggested that the continuity between these two areas provides opportunities for the exchange of cells that could aid in the maintenance and reorganization of the testis and with the myoid and neural tissue to establish an extensive, coordinated motile system that aids movement of sperm from spermatocysts to the ducts. A recent report on the reexamination of the germinal epithelium concept and its identification in the common snook, Centropomus undecimalis, stimulated us to examine the feasibility of applying this concept to gonad organization and gamete development in T. bifasciatum. In addition, the ultrastructure of the Sertoli cell and formation of spermatocysts are described. Spermatocysts increase in size during the development of gametes. Observations and discussion are presented suggesting how Sertoli cells may accommodate this growth and how new populations of these cells may arise in the mature adult. Finally, ultrastructural characteristics for each stage of spermatogenesis are presented and, using (3H)thymidine and autoradiography, data on the chronology of spermatogonia-sperm cycle are included.

Variation in male reproductive system characters in Corydoradinae (Loricarioidei: Callichthyidae) reflects the occurrence of different lineages in this subfamily

“…Anatomical and histological data obtained in this study reveal that species of Corydoradinae analyzed share, independently of the lineages they belong, the typical testicular structure observed in fishes and shared by other vertebrates (Grier et al, 2016), consisting in the division on germinal and interstitial compartments (Koulish et al, 2002;Quagio-Grassiotto et al, 2013;Grier et al, 2016).…”

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“…The protrusion of tunica albuginea into the testicular parenchyma completely divided it into numerous seminiferous lobules. This is a common pattern found in the family Cyprinidae (Koulish et al, 2002;Schulz et al, 2010;Teji 2010;Montchowui et al, 2012). Anatomical structure of testis in S. denisonii was found to be similar to other cyprinids that have external fertilization (Grier, 1993;Parenti and Grier, 2004).…”

Visão geral sobre reprodução de peixes teleósteos: da anatomia à sinalização molecular

“…Na maioria dos teleósteos, as gônadas de machos e fêmeas são órgãos pares, alongados, envoltos por uma cápsula de tecido conjuntivo fibroso, localizados dorsalmente na cavidade celomática (Koulish et al, 2002). Em algumas espécies, os testículos se fundem em um único órgão (Nagahama, 1983).…”

“…De acordo com Koulish et al (2002), os testículos possuem um compartimento intersticial ou intertubular e um compartimento germinativo ou tubular com funções espermatogênicas ou androgênicas. No compartimento intertubular observa-se os vasos linfáticos e sanguíneos, as células do tecido conjuntivo e nervoso, macrófagos, mastócitos e as células de Leydig.…”

“…A membrana basal e as células peritubulares mióides formam a túnica própria, que reveste o túbulo externamente. As células de Sertoli e as células germinativas formam o epitélio seminífero (Koulish et al, 2002). A estrutura testicular dos teleósteos varia bastante de acordo com a espécie; porém, duas estruturas básicas podem ser definidas de acordo com a diferenciação do compartimento germinativo: lobulares e tubulares (Billard et al, 1982, Schulz et al, 2010.…”