The testes of fish are paired elongated organs that are attached to the dorsal wall of the body cavity. Within the testes are seminiferous tubules containing germ cells that undergo spermatogenesis to produce sperm, and Leydig cells that produce testosterone. Teleost fish have either lobular or tubular testes organized into lobules or tubules. Elasmobranch testes do not contain seminiferous tubules and can be diametric, radial, or compound in morphology. Knowledge of fish testes morphology provides insight into fish reproduction and conservation.

1. Topic Name:
Morphology of Fish
Testes

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).
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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
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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
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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.
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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.
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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
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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:
(i) 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
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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.
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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.
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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
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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.
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Function

16. Functional
Morphology of Teleost
Testes
Testes in Teleost 2 types:
1.Lobular
2.Tubular
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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, the 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).
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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.
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21. Morphological
Types
Morphologically there
are three different types
of testes in elasmobranch.
 Diametric
 Radial
 Compound
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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)
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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
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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
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