Reproductive system of scoliodon

Male urino-genital system
Female reproductive system
Yolk sac placenta
Nusrat Perween, AISC Pune 1

Male urinogenital system

 In all the vertebrates the excretory and reproductive
organs are closely related to each other.
 Therefore the two systems together are known as
urinogenital system and the organs as urino-genital
organs.

 In Dogfish (Scoliodon), the sexes are separate and the
sexual dimorphism is conspicuous.
 The male Scoliodon possesses two cylindrical hollow
copulatory organs, the claspers which are
modifications of pelvic fins.
 The claspers are absent in female.

Male Urino-genital Organs:
1. Excretory Organs:
Kidneys
Ureters
Uriogenital sinus
2. Genital organs
Paired testes
Vasa deferentia
Ampullae or Seminal vesicles
Nusrat Perween, AISC Pune
5

kidney
 Brownish red, elongated, flattened ribbon shaped
 Ophisthonephros kidney- anterior part is reduced
and non functional, posterior part is well
developed and functional
 Location- dorsal, deep in trunk region
 Attached to dorsal abdominal wall above
peritoneum
 Extend from base of liver to side of cloaca

 Anterior slender part- genital
kidney
 Posterior thick part- renal
kidney.
 In male- anterior part is
reduced, non excretory and it
convey genital products –
called epididymis
 Posterior part is organ of
excretion
 In female- anterior part –
highly atrophied , no
connection with genital organ
7

Histology of kidney
 Each kidney composed of numerous uriniferous
tubules
 Tubules- bowman’s capsule and glomerulus at blind
end = Malpighian body
 In fishes- glomerulus shows characteristics
mesangial areas –mesangial cells (controls filtration
of plasma in bowman’s capsule
8

9
Scoliodon: Histology of Kidney

 Behind Malpighian body –
coiled renal tubule – neck
(lined with ciliated,
cuboidal epithelial cells ,
proximal segmented distal
segment
 Proximal and distal
segment –coiled – form
parallel arrangement
which helps in effective
reabsorption of elements
 Last part of tubules –
collecting ducts which lead
to ureter
10Nusrat Perween, AISC Pune

Ureter
Receives collecting ducts from kidney
Thin tubules
Open in wide chamber- urinogenital sinus
Female- both ureter (Wolffian ducts) join to open
in sinus while genital ducts open separately
 In male – ureter take over reproductive function
and in continuation of testes
 Therefore accessory urinary duct receives the
collecting tubules from renal corpuscles or
nephrons
 Both accessory urinary ducts joint and open in the
urino-genital sinus

Urinogenital sinus
 Wide chamber –
posterior end and open
in cloaca at the tip of
short urinogenital
papilla
 Urine formation shows
the usual three steps-
ultrafiltration, selective
reabsorption and
tubular secretion
12

Rectal gland – whitish yellow gland situated dorsal
to the intestine. Removes excess NaCl from body
fluids
Gills: they also play a minor role of excreting
sodium and chloride ions through the chloride
cells present on the primary lamellae
13

14
Scoliodon: Male Urino-genital system

Male urinogenital system
1. Paired testes
2. Vasa deferens
3. Ampullae or Seminal vesicles
15

1. Testis
 Present in trunk dorsal to the gut
 Attached to body wall dorsally by a double fold of
peritoneum called the mesorchium
 posteriorly with caecal or rectal gland by a non
glandular tissue.
 Each testis is ribbon like and extend anteriorly
upto the Leydig gland and posteriorly upto the
end of trunk
16

 Arising from each testis anteriorly
there are numerous fine tubules
called vasa efferentia which
traverse through the mesorchium
towards the anterior end of the
large duct called vas deferens
 Each testis can be divided into
anterior two third testis proper
and posterior one third epigonal
or lymphomyeloid organ which
contains abundance granulocytes.
 The mature sperms are carried to
the vas deferens

Histology of testis
 Each testis is enclosed in thin, connective tissue
capsule and is divided internally into small, oval
compartments by connective tissue strands or
trabeculae.
 Inside, there is a region of thin sheets of cells
called the germinal zone from which develop
the spermatocytes.
 The spermatocytes contain the sperms in a
particular stage of development and a few Sertoli
cells.
 The Sertoli cells provide nutrition to the
developing sperms, may engulf the unused
sperms and produce hormonal secretions.

2. Vas deferens
large, narrow, very much coiled tube and runs along the
entire ventral surface of the anterior kidneys.
Its anterior part is known as the epididymis. It produces
the fluid which nourishes the sperms.
Along with the epididymis is the Leydig’s gland and
both represent the anterior kidney which is associated
with the male genital system.
The spermatophore are formed in the Leydig’s gland
spermatophore - protein capsule containing a mass of
spermatozoa, transferred during mating

3. Ampullae or seminal vesicles
 Posteriorly, the vasa differentia enlarge to form thin
walled opaque ampullae.
 Each ampulla anteriorly gives out a thin walled sac,
the sperm sac.
 Both the sperm sacs unite posteriorly and form the
urinogenital sinus.
 The ampulla store the spermatophores .

Accessory organs :
1. Claspers
2. Siphon
1. Claspers :
 These are paired structures which are the modified
pelvic fins and also called myxoptergium.
 They are the accessory reproductive organs.
 The claspers are erectile, receive sperms and pass
them to the cloaca of female to ensure internal
fertilization .
 In a mature male they measure about 6 cm in
length.

 Each clasper is a tube partially open on the dorsal side
forming a triangular groove due to the infolding of the
dorsal skin.
 The anterior opening of the groove lies near the cloaca
and called the apopyle while the posterior exit is the
hypopyle which opens on a sharp, pointed style.

2. Siphon:
On the ventral side of the body, below the skin, there
is a pair of elongated, glandular and muscular sac, the
siphons
They anteriorly extend upto the posterior region of the
pectoral fin and end blindly.
Posteriorly, they open into the groove of claspers.
They force the sea water into the grooves and help
push the spermatophores in the cloaca of female.

24
Scoliodon: Female reproductive system

Female reproductive system
1. Paired ovaries
2. Oviducts
3. Shell gland
4. uterus

1. Ovaries
 These are large, yellowish,
lobulated bodies.
 They are located in the
abdominal cavity and attached
to the anterior abdominal wall
mid-dorsally by the fold of
peritoneum called
mesovarium,
 The surface shows developing
ova.
 They extend back from the base
of liver and merge into epigonal
organ.

2. Oviduct
 Large tubes extending along
the complete length of the
body
 Also known as Mullerian
ducts
 Open into the coelom by
zigzag slit like aperture called
ostium or oviducal funnel

3. Shell gland
 Both oviducts enlarge
posteriorly and known as
shell gland
 Also known as oviducal or
nidamental gland
 Heart shaped
 Shows a narrow middle
mucus secreting zone and
posterior large shell
secreting zone

4. Uterus
 Behind the shell gland
each oviduct narrows and
finally dilates posteriorly
into wide uterus
 The uteri from both the
sides unites to form a
short vagina
 Vagina opens into the
cloaca by a large aperture

 The vagina is separate from the cloaca by fold of
mucous membrane which functions as a valve and
closes the aperture between vagina and the cloaca
during the development of the embryo
 The mature ova released in the abdominal cavity and
then by the action of the body muscles and beating of
the cilia of the external lining of the visceral organs
 They are carried to the oviducal funnel and ultimately
to the oviducts
 There is no direct connection between ovaries and
oviducts

Fertilization
 Fertilization is internal
 Takes place in the section of
oviduct between the oviducal
funnel and shell gland
32

 During copulation the claspers are inserted into cloaca
of the female.
 The spermatic fluid is transferred through the grooves
of the claspers into the oviducts.
 The siphon sacs force the stored sea water into the
grooves and push the sperms in the body of the female

 Scoliodon is ovoviviparous
 Development of egg occurs
in uteri and give birth to
living youngs
 The fertilized egg or
zygotes descends from the
shell gland into the uterus
 The uteri is divide into
compartments as per
number of embryo
34

 Uteri is filled with uterine fluid which surrounds the
developing embryo and protect them.
 The embryo is enclosed in a thin membrane called egg
case which contains nutritive and protective fluid.

 In early stage of development each embryo is provided
with a tubular yolk-stalk which is connected at one
end with the gut of the embryo and other with the
yolk-sac containing yolk for the nourishment of the
young
36

 In later stage when the yolk is used up, the yolk-sac
becomes greatly folded and embedded in the uterine wall
to form yolk sac placenta
37
Umbilical cord with
Appendicula
Placenta
Uterine attachment
Uterus

 Each embryo develops
villi and fuse with
grooves in yolk-sac this
give rise to simple yolk
sac placenta
 Now the embryo receives
nutrient through the
placenta from the
uterine tissue of the
mother
Scoliodon: Embryo with yolk-sac placenta

 When the embryo is 3 to 4 mm in size, the primary
yolk sac gets elongated and changes to the placental
cord.
 The placental cord produces many finger like
processes called appendicula which absorb the
nutrient from the maternal uterine wall
 Each appendiculum consist of central core of loose
connective tissue and many layers of epithelial cells
around it
 The gestation period is about 6 month and young
Scoliodon are born
 No further parental caring to new born babies

Reproductive system of scoliodon

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