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					  NEURO AND ENDOCRINE
     CONROL IN FISH
     REPRODUCTION

Great interaction between nervous
and endocrine system
Some neurons display the
combination of both nervous and
hormonal system which is called
neurosecretory or neuroendicrine
ANAOTOMY OF NERVOUS SYSTEM

• Nervous system has two components,
  Central nervous system (CNS) and
  Peripheral nervous system (PNS)
• THE CNS consists of brain and spinal
  cord. The nervous tissue other than
  brain and spinal cord PNS, it
  comprises, nerves, ganglia and
  receptors
NERVOUS SYSTEM

• Nervous system is made of two chief
 cells, the nerve cells and supporting
 cells, nerve cells are neurons and
 they are functional units, conduct
 impulses, receipt and conduction of
 information is impulse, receptor can
 be nerve cell, muscle, gland etc.,
 transmission of message is due
 difference of potential between inside
 and outside of nerve
COMPONENTS OF BRAIN

• Regulating center for all the receptors,
  enclosed in cranium, brain is small
  comparison to body size, gap is filled
  with gelatinous matrix, brain is soft,
  white and coved with extensive network
  of blood vessels, called choroid plexi
• Brain has three main divisions,
  Prosecephalon or fore brain,
  Mesencephalon or mid brain,
  Rhobencephalon or hind brain
PROSENCEPHALON OR FORE BRAIN

• The fore brain consists of two parts,
  Telencephalon and diencephalon
• TELENCEPHALON: most anterior part
  of the brain, responsible for reception
  and conduction of smell impulses, it
  consists of two parts, the anterior
  paired olfactory bulb, and posterior
  two large cerebral hemispheres
 In addition to olfaction /smell, it also
  regulate aggression, sexual activity,
  parental behavior, maintain equilibrium
  to facilitate successful breeding
• Ablation of forebrain in goldfish shows less
  response than normal ones, , tilapia
  neglected young ones, Cyprinidae became
  less cautious to a new situation, spawning
  was suppressed in stick leback, nest
  building behaviour was affected in paradise
  and colour vision in goldfish with the
  extirpation of fore brain
DIENCEPHALON

• It is covered dorsally by the posterior
 bulgings of the cerebral hemispheres.
 It posses cavity inside called third
 ventricle, it has three parts, dorsal
 epithalamus, lateral thalamus and
 ventral hypothalamus. The
 epithalamus contains choroid plexus in
 its roof, the psterior part of the roof
 elevates to form pineal gland or
 epiphysis
• Epithalamus has two ganglionic masses
 called habinulae and also the nerve
 fibres from the telencephalon which
 connects with the thalamus,
 hypothalamus and the olfactory areas
 of the telencephalon
 PINEAL BODY:
 it has two functions, sensory and
 secretory functions. In sensory function
 it acts as chemoreceptor, and in later
 helps in facilitating the olfactory
 response to sex hormones
THALAMUS

• It acts as relay for center for transmitting
  olfactory and strait body impulses to
  thalamomedullar and thalamospinal tract
• Hypothalamus: constitutes the floor of
  diencephalon. Anterior part of the
  hypothalamus contains peptic area. From
  the ventral part of hypothalamus projects a
  pouch like down growth, called
  infundibulun, the tip of the infundibulum
  bears hypophysis or pituitary gland
THE DIENCEPHALON
(FUNCTIONS)
• THALAMUS: Integrating area for sensory
  input, it is also a relay and coordinating
  center between the corpus striatum, cerebral
  cortex and motor columns and contains
  significant portion of reticular system
• EPITHALAMUS: Contains habenular nuclei,
  recevies fibre from olfactory area, transmits
  to motor areas of the brain stem, it receives
  information from light responsive pineal
  which is involoed in the regulation of circadian
  rhythems and reproductive cycles
HYPOTHALAMUS


• Regulation of internal environment, in
  contrast with the somatic sensory and motor
  functions of the tectum, it is visceral sensory
  and motor correlation area and integrates
  basic behavioural pathways requiring
  correlation of autonomic, endocrine and
  somatic functions.
• It contains center for thermoregulation,
  control of water balance,and sleep,
  neurosecretory control of pituitory; Note:
  Fiber tracts in the walls of diencephalon
  connect the thalamic area
MEDULLA

• Derived from rhombencephalon, is a reflex
  coordinating center for information received
  from the muscles and joints and fro the
  lateral line organs, its floor contains a large
  part of the reticular formation which
  extends throuout the brain stem, it is a
  network of small many barnched neurons
  that receive and integrate information from
  the cord and many parts of the brain
TECTUM

•   It is a thickened area of gray matter in the
    roof of mesencephalon above the
    aqueduct of sylvius( a canal in the mid
    brain connecting the 3rd and 4th ventricles
    of the brain), it is sensory and motor
    projection area and coordinating center in
    which motor activity is initiated
•   Corpus striatum: A mass of gray matter
    beneath the cortex and in front of the
    thalamus in each cerebral hemisphere
CEREBRAL CORTEX
•   The furrowed outer layer of gray
    matter in the cerebrum of the brain
    associated with the higher brain
    functions as voluntary movement,
    coordination of sensory information,
    learneing and memory
•   Pons: Band of nerve fibres in the
    brain connecting the lobes of mid
    brain, medulla and cerebrum
• Lamina terminalis: Thin sheet of tissues
  which marks rostral
• Anterior commissure: It is a bundle of
  nerve fibres(white matter) connecting
  the two cerebral hemispheres across the
  midline and placed in the front of the
  columns of the fornix(junction between
  posterior eyelid and eye ball)
•   Optic recess: At the junction of the floor and
    anterior wall of the third ventricle, immediate
    above optic chiasma the ventricle presents small
    angular recess or diverticulum(Tubular sac
    branching off from a canal or cavity)
•   Cerebral peduncle: A bundle of myelinated
    neurons joining different parts of the brain
•   Corpus mammillare: Two rounded structures
    under surface of brain that form terminals of the
    fornix
ENDOCRINE GLANDS

• Ductless glands, they release their product
  directly into blood or lymph
• On the basis of organization they can be
  classified as :
• Discrete endocrine glands; pituitory, thyroid
  and pineal
• Organ containg both endocrine and exocrine
  functions, it is kidney, gonads, and intestine,
  kidney contains, heterotrophic thyroid
  follicles, interenal and corpuscles of stanius
Scattered cells with endocrine functions, they
are different neuroendocrines, they are

• Present in digestive tract and are
 called paracrine (eg. Somatostatin),
 they are gastrointestinal peptides,
 hormone or paracrine agent has not
 been cleared
CHEMICAL CLASSIFICATION

• Steroid hormones (testosterone and
  estradiol)
• Protein (peptide hormones), eg.
  Insulin, and those secreted by
  hypophysis, thyroid, interenal tissue
  and pancreatic tissue
• Aminoacid analogues are nor
  epinephrine and epinephrine
PITUITORY OR HYPOPHYSIS

• Same central part in endocrin signalling as in
  mammals, it is ectodermal in origin,
  mesoderm inside which supplies blood to PG
• It is located below the diencephalon
  (hypothalamus), behind the optic chiasma
  and anterior to saccus vasculosus and is
  attached to the diencephalon by a stalk or
  infundibulum, short thick walled hollw
  infundibular stalk contains a lumen which
  continues with the third ventricle
SHAPE AND SIZE

• Oval, compressed dorsoventrally, PG
 has 472.9 micron length, 178 micron
 width, 360 micron depth in mature
 fish and weighs 0.5 gram, it is
 completely surrounded by a delicate
 connective tissue capsule
ANATOMY OF GALAND

• Microscopically it is composed of two
  parts
• Adenohypophysis: glandular part
  originated from oral ectoderm
• Neurohypophysis, nervous part,
  originated from infundibular region of
  the brain, both parts are present in
  close association
GENERAL DIVISION

• Proadenohypophysis or Rostral pars
  distalis, lying dorsal to the
  mesoadenohypophysis in the form of
  thin strip
• Mesoadenohypophysis or proximal
  pars distalis, lying almost inbetween
  the rostral pars distalis and pars
  intermedia
• Metadenohypophysis or pars
  intermedia, lying at the dorsal
  tapering end of PG
• On the basis of immunocytochemistry,
  the cells are classified according to the
  hormones released by the
  proadenohypophysis, if they produce
  adrenocorticotrophic hormones, they
  are called ACTH cells, if they secrete
  thyroid stimulatimg hormones they are
  called thyrotrops, if they secrete FSH,
  then called gonado trops
• The teleost hypothalamopituitory is
  unique amongst vertebrates, as there
  is direct innervation of pars distalis by
  neurosecretory neurons of
FUNCTION OF
ADENOHYPOPHYSIS OR PG
• Cells of PG secret hormones, they are
 stored in the form of granules present
 in cytoplasm, the cells can be
 acidophilc, basophilic, or their binding
 affinity with ribonucleoproteins, they
 can be chromphobes if they repel dye
 or chromophilic if they stron affinity to
 dye
PRO ADENOHYPOPHYSIS

•   It contains cells which secrete
    prolactin and corticotropin
    exclusively in addition to other
    hormones
•   MESOADENOHYPOPHYSIS: Proximal
    pars distalis contains cell which
    produce, gonadotropin(GtH) and
    growth hormone(GH), Thyrotropin
    cells may be in either of them
META ADENOHYPOPHYSIS


•   Encompasses more neurohypophysial
    tissue than any other region
•   PINEAL BODY: Roof of diencephalon bears
    pineal body(epiphysis), it secrets
    melatonin, which concentrates the
    pigment of melanophores of fishes,
    inhibits gonadal development and is
    involved in circadian rhythems, an enzyme
    hydroxyindole-o-methyltransferase
    participates in the synthesis of melatonin
NEUROHYPOPHYSIS
•   It comprises connective tissue, neuroglia
    cells (class of cells in brain and spinal cord that form the
    supporting structure for nearons and provide them with
                 loosely tangled network of
    insulation)and
    nerve fibres, these nerve fibres are
    scattered horizontally along the dorsal part
    of the adenohypophysis, interspread with
    granular material, large irregulary shaped
    amorphous masses (having no definite
    shape) and large nuclei, these masses are
    called herring bodies, have intimate relation
    with the diencephalic neurosecretory cells
HORMONES OF PITUITORY
•   7 various hormones, one-cell type-
    one hormone concept
•   Cell secreting hormones not localized
    in a specific region but spread over in
    part of adenohypophysis
•   Hormones secreted by PG are
    proteins or polypeptides
TWO TYPES OF HORMONES

•   I: those regulates the function of
    other endocrine glands, such
    hormones are called tropins or tropic
    hormones e.g.
•   Thyrotropin activates thyroid gland
•   Adrenocorticotropic hormones
    activate adrenal cortex
•   Gonadotropin FSH and LH (Gonads,
    steroids)
• II: which directly regulates the specific
  enzymatic reactions in various body cells
  or tissues, the hormones are melanin
  hormones and melanophore stimulating
  hormone, Thyrotropin hormone is
  secreted from proadenohypophysis and
  stimulates activity of thyroid hormones
GONADOTROPIN

•   Gonadotropin cells are richly found
    in proximal pars distalis, where they
    form solid rim of cells in
    cyprinodonts but in eels and
    salmonids they are present in
    proximal pars ditalis and rostral pars
    distalis, gonadotroph is under the
    control of gonadotropin releasing
    hormone,
•Neurosecretory stimuli may pass along the nerve
fibres piercing the lamina that separates the
neuro from   adenohypophysis and
    penetrating into endocrine
    parenchyma of pars distalis
•   Two types of nerve fibres, A and B,
    Fibres of A type remain in contact
    with hormone producing cells,
    including gonadotrops, b type fibres
    form synaptic contact with a large
    granular vesicle
Adenocorticotropic hormone


•   ACTH is secreted from the cells
    located between rostral pars distalis
    and neurohypophysis, secretion is
    stimulated by hypothalamus
    through cortitropic releasing
    factor,Prolactin, Released from
    proadeno hypophysis, growth
    hormone from
    mesoadenohypophysis, Melanocyte
    stimulating hormone from meta-
    adenohypophysis
USE OF PITUITORY HORMONES IN INDUCED
BREEDING/ REPRODUCTION


• Have practical applications
• Injection or implantation force or stimulate
  spawning of certain fishes of great economic
  value
• Synthesis of sex hormones in gonad is
  controlled by pituitary gonadotropin
• PG extract Containing, GtH taken fro
  sexually mature male or female, hasten
  spawning process, other hormone analogues
  are also used, ovaprim, physex leo(HCG),
  dry PG
REPRODUCTION

 Three types
 Bisexual,
 Hermaphrodite (Perca, Stizostedion,
  Micropterus)
 Parthenogenic(gynogenesis;
  developemnt of youngones without
  fertilization)(Poecilia formosa)
 Most predominant bisexual
HISTOLOGY
 Ovary contains supporting tissue
  called stroma, which contain oogonia
  and oocytes, oogonium (germ cell)
  after multiplication develops into
  primary oocyte, at early stages of
  development oogonium is large cell
  with a large nucleus, prominent
  nucleolus and chromophobic
  cytoplasm, on multiplication cell size
  reduces and chromosome number is
  halved
HEMOPOIETIC(made of blood)
EPIGONAL(come after) ORGAN(HEO)

 Gonads both testes and ovaries are
  associated with HOE and extend
  back to cloaca
 Female reproductive organ:It
  comprises ovary, oviduct
 Ovaries in relation with oviduct and
  transport of ova can be distinguished
  into three types
THREE TYPES

 Cytovarian type: Lumen of ovary is
  connected with oviduct, both
  oviducts join to open out through
  genital pore, mature oocytes
  released by ovulation into ovarian
  lumen and then pass through the
  oviduct and goes into water through
  genital pore
•In semicytovarian type ,
  oocytes pass through funnel shaped
  transparent groove which opens into
  genital pore, oviduct degenerate
  partially or completely, ova are
  coelomic cavity and then carried
  through the pores or funnel
  (Notopteridae, Osteoglassidae)
 Gymnovarian type not continuous
  with oviduct, oocytes ovulated in
  coelomic or peritoneal cavity and then
  move to oviduct by cilia
STIMULANTS
• External environment:Light, tempertaure,
  rainfall, food , photperiod, salinity affect brain
  by mdifying activities of specific
  neurohormones and neurotransmitters in
  order to regulate secretion rate of
  gonadotropin releasing hormone(GnRH) and
  dopamine from hypothalamus
• Release of PG Gonadotropin(GtH) is under
  dual hypothalamic control, secretion is
  stimulated by GnRH and inhibited by
  dopamine, at the end of hypothalamic-PG-
  gonadal axis, GtH stimulates
  gametogenesis and steroidogenesis
  gonadotropic hormones can be activated by
  hypophysation, PG extracts, gonadotropins
HORMONES OF THE GONADS

• Testes, androgens, testosterone, 11-
  ketotestosterone
• Female produces 2 principal classes of
  hormones, oestrogens which include
  estradiol-17B and oestrone and
• progestagens are 17alpha-20B-
  dihydroprogesterone and 17alpha-
  hydroxyprogesterone
ENZYMES REQUIRED FOR
STEROIDOGENESIS IN THE OVARY

 Glucose-6 phosphate
  dehydrogenase(G-6PDH)
 3 beta-hydroxysteroid
  dehydrogenase(3 beta HSD)
 17 beta hydroxysteroid
  dehydrogenase(17 beta HSD) and
 20 beta hydroxy steroid
  dehydrogenase(20 beta HSD)
VITELLOGENESIS

 Ovary contains numerous oocytes in
  different stags of development and
  degeneration
 Follicular atresia is degenerative
  process by which oocytes at various
  stages are lost even during
  ovulation, they do not synthesize
  steroid hormones and no any
  endocrine function
VITELLOGENESIS
   Degenrating follicles are of two types viz
    corpora lutea (is a temporary endocrine structure in
    mammals, involved in production of estrogen and
    progestogen, which is needed to maintain the
    endometrium) and corpora atretica (being in a
    state of atresia; without an opening)., in
    former the enclosed oocytes are removed
    from follicles by invading granulosa cells
    and ingrowing theca cells
   Egg in the beginning is without yolk but
    vitellogenesis takes place later on (atresia)
VITELLOGENESIS

 In oviparus and ovoviviparus vertebrates,
  blood of mature female contains calcium
  binding lipiphosphoprotein, vitellogenin,
  synthesized in liver under stimulation of
  female sex steroids
 From plasma it passes to oocytes where it
  gives yolk protein lipovitellin and phosvitin
 In Vitellogenesis accummulation of yolk
  substance starts, cytoplasm changes from
  basophilic to acidophilic state
VITELLOGENESIS

 Three essential yolk substances, yolk vesicles, yolk
  globules and oil droplets
 Yolk vesicles contain glycoprotein, later become
  cortical alveoli and take part in perivitelline space (a
   space between the oocyte and the zona pellucida) Outer most
   layer
 Yolk globules are made of mainly lipoprotein with
  some carbohydrates and other substances
 Oil droplets contain glycerides and small amount of
  cholesterol
 On completion of vitellogenesis, movement of
  germinal vesicle, fusion of yolk granules and grouping
  of oil droplets occur
•Chromosomes

 Becomes thread like in
  nucleus(leptotene stage), zygotene,
  pachytene, diplotene, and finally
  diaknesis
a At this stage of development
  oogonium is surrounded by a single
  layer of follicle cells which in turn are
  surrounded by stromal cells, other
  layers are
MATURE OOCYTE

 Components; Theca cell layer,
  interspersed with blood vessels,
  basement membrane, layer of
  granulosa cells, , then zona radiata
  layer which encloses germinal
  vesicle
TYPES OF EGGS

 Unfertlized eggs are opaque and
  heavier than water, they can be
  floating and non floating, adhesive or
  non adhesive
 Eggs of Common carp are adhesive
  and non floating, while those of
  Catla(light red), Labeo
  rohita(reddish), Labeo
  calbasu(bluish), Cirrhinus
  mrigala(brownish) are non floating
  and non adhesive
Eggs of Clarias batrachus and Heteroneustes
fossilis are adhesive, non filamentous and green
in colour

 Eggs of Notopterous notopterous
  and Notopterous chitala are
  yellowish
 Eggs of Channa punctatus and
  Channa striatus are floating and
  amber in colour
MALE REPRODUCTIVE ORGANS
   Paired structures, situated on either side,
    below the kidney, Have two major
    functions; production of spermatozoa
    (spermatogenesis) and production of
    sterods(steroidogenesis)
   Size of testis becomes enormous during
    breeding season
   Testis may be sac like or lobulated,
    rounded or triangular, nevertheless they
    are suspended from the dorsal body wall by
    mesentery call mesorchia, they are well
    vascularized and contain nerve fibres
HISTOLOGY

 Each testis is enclosed in connective
  tissue sheath, tunica propria of
  connective tissue priject into the
  lumen forming tubes
 Blind end is site of primary
  spermatocytes
 Tubular structure consists of two
  parts, interstitial and lobular
 Former consists of interstitial cells,
  fibroblasts, blood and lymph vessels
Later is distinguished into germ and somatic
cells, somatic cells analogue to Leydig cells
are positive for lipid and cholesterol and
produces steroid hormones

•   Another type of cells in interstitium are
    sertoli cells(cyst cells) around
    spermatogonic cells, they supply
    nutrients to to the germinal cells
STAGES OF SPERMATOGENESIS
   Stage I:Presence of only large
    spermatogonia, immature stage
   Stage II:spermatogonia multiply in testis by
    mitosis until many are present, then
    spermatogenesis starts,Spermatogonia
    increases in size to become a primary
    spermatocyte(2n)(PS)
   Stage III:rapid enlargement of testis
    volume. PS goes under Ist Meiotic
    division(2n to n) and gives 2 secondary
    spermatocytes(SS) (each with n
    chromosomes but duplicated)
•Sex cells are at all stages of spermatogenesis. SS in
turn divide(IInd meiotic division), Spermatids (n)



   Following II nd meiotic division each
    matures to spermatozoa at the end of this
    stage
   Much of cytoplasm is lost and nucleus
    compacts to small head with haploid DNA
    and acrosome with lysins (enzymes),
    behind the head is a midpiece which
    includes two centrioles and tightly coiled
    mitochondria which supply energy for newly
    formed flagellar tail that provides motility
 Stage IV:End of spermatogenesis process,
  some gonad channels are filled up with
  mature spermatozoa, in others
  spermatogenesis is continued
 Stage V:Spread of mature spermatozoa
 Stage VI: Resorption of remaining
  spermatozoa

				
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