Morphology of Fish Testes

The Morphology of teleost and elasmobranch fish testes

1. Topic Name: Morphology of Fish Testes Welcome to My Presentation

2. Introduction The testes of fish is generally a paired elongated organ. Testis is attached to the dorsal wall of the body (in both side) by a mesorchium which is vascularized and contain nerve fibres . The testis has two major functions, the production of spermatozoa (spermatogenesis) and another function is the production of steroids ( Steroidogenesis ). 2

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4. Phases of Testes The testes change morphologically during the annual reproductive cycle, passing through 5 phases: Regressed, Early Maturation, Mid Maturation, Late Maturation, and Regression 4

5. Morphological examination of bony fishes testes shows that these organs are composed of both germinal as well as interstitial compartments that are always separated by a basement membrane; therefore, the cells in one compartment do not intermix with the cells of the other compartment. Morphology of Teleost Testes 5

6. Germinal Compartment The germinal compartment is composed of the seminiferous tubules, being formed by 2 cell types: germ cells and somatic epithelial cells, the latter being Sertoli cells. 6

7. Seminiferous Tubules Seminiferous tubules are  located within the testes , and are the specific location of meiosis, and the subsequent creation of male gametes, namely spermatozoa. 7

8. Germ Cell Male germ cells  are the main actors of spermatogenesis, the complex biological process of cellular division and transformation resulting in a male haploid gamete from diploid spermatogonial  germ cells. Germ cells include all the stages of differentiation of the spermatogenic cells. Spermatogonia Spermatocyte Spermatid Spermatozoa 8

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10. Sertoli Cell A  Sertoli cell is a "nurse“ cell of the testicles that is part of a seminiferous tubule. Function: Provides the support of germ cell (ii) Transfers metabolites or hormones towards germ cells (iii) Helps in the phagocytosis of residual content (iv) Helps in increasing testosterone concentration in seminiferous tubules 10

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12. Interstitial Compartments The interstitial compartment is composed of connective tissue and Leydig cells. The connective tissue contains fibroblasts, immunological cells, blood vessels and nerve fibers. The steroidogenic Leydig cells are located especially near the blood vessels and produce testosterone. 12

13. Leydig Cell Leydig cells are interstitial cells located adjacent to the seminiferous tubules in the testes. The best-established function of Leydig cells is to produce the testosterone. 13

14. The vas deferens, or  ductus deferens, is part of the male reproductive system  of many vertebrate. In fishes sperm duct leads from each testis to a urogenital opening behind the vent or anus.  Sperm Duct 14

15. Seminal Vesicle Seminal vesicles are glandular outgrowths of the common sperm duct in certain fish species. The SV epithelial cells secrete a mucopolysaccharide -protein-lipid-rich fluid (seminal vesicular fluid, SVF). The seminal vesicle fluid mobilizes the sperm cells. 15 Function

16. Functional Morphology of Teleost Testes Testes in Teleost 2 types: 1.Lobular 2.Tubular 16

17. Lobular Testes Tubular Testes Lobular testes are composed of numerous tubules which are separated from each other by a thin layer of fibrous connective tissue The tubules are regularly oriented between the external tunica propria (blind end) and a central cavity into which the spermatozoa are released Within the lobules, primary spermatogonia goes under numerous mitotic division to produce cysts containing spermatogonial cell Primary spermatogonia are located only at the blind end of the tubule. As spermatogenesis and spermiogenesis proceed, t he germinal cyst move centrally within the testes toward the vas efferens (efferent duct) Example: Common Snook, Centropomus undecimalis ( Centropomidae ), the Cobia, Rachycentron canadum ( Rachycentridae ); Tilapia, Oreochromis mossambicus etc. Example: Gar, Lepisosteus platyrhinchus ( Lepisosteidae ), Black Tetra, Gimno-corhymbus conirostris ( Pimelodidae ), the Rainbow Trout, Oncorhynchus mykiss ( Salmonidae ), and the Tarpon , Megalops atlanticus ( Elopidae ). 17

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19. Morphology of Elasmobranch Testes The testes are paired, elongated organs suspended from the dorsal wall at the anterior end of the body cavity. The main difference between teleost and elasmobranch testes is that elasmobranch testes do not have seminiferous tubules. 19

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21. Morphological Types Morphologically there are three different types of testes in elasmobranch. Diametric Radial Compound 21

22. Diametric Radial Compound In diametric testes, the germ cells are located in a strip on one side of the testis. Example: Blue shark ( Prionace glauca ), bronze whaler ( Carcharhinus brachyurus ), Port Jackson shark ( Heterodontus portusjacksoni ), piked dogfish ( Squalus acanthias ) and draughtboard shark ( Cephaloscyllium laticeps ) In radial testes, the germinal zone is located at the centre of multiple lobular structures in the testis that are separated by a duct system. Example: Short-fin mako ( Isurus oxyrinchus ), white shark ( Carcharodon carcharias ) and thresher shark ( Alopias vulpinus ) The germinal zone is located at the centre of each lobule Compound testes are a combination of both radial and diametric types. Example: Atlantic stingray ( Dasyatis sabina ), freshwater stingray ( Himantura signifer ), little skate ( Raja erinacea ), and smooth butterfly ray ( Gymnura micrura ) 22

23. The testes are the organs that make sperm and testosterone which act as the basis for reproduction. The knowledge of fish testes morphology will help us in future to analyze different perspective of fish reproduction. Not only this, the study will provide us a pathway to bring back extinct or critically endangered fish species. Knowledge of the normal reproductive biology of fish is of a great importance not only for better understanding of the theory of fish development, but also to be used as a baseline for understanding the pathological changes results form exposure to harmful toxicants.  Epilogue 23

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25. Thank You for Your Kind Attention  “We know that when we protect our oceans we’re protecting our future.” — President Bill Clinton “We are using resources as if we had two planets, not one. There can be no 'plan B' because there is no 'planet B’.”— Ban Ki-moon 25