Female Reproductive System

1
Female Reproductive System

• Hypothalamus, pituitary, ovary, and liver.
• In all species, oogonia proliferate in the
  ovary, become oocytes, undergo vitellogenesis,
  maturation, and ovulation.
• Endocrine controls of the system begin with
• 1.) hypothalmic responses to environmental cues
• photoperiod and temperature

2
Female Reproductive System

• 2.) hypothalmic responses to proximal cues like
  substrate type, courtship behaviors, and
  pheromones.
• Ultimately these cues influence gonadotropin
  releasing hormone (GnRH) that stimulates GTH-I
  and GTH-II.

3
Role of GTH-I and GTH-II

• Ovarian and testicular function is controlled by
  GTH-I and GTH-II (glycoprotein heterodimers).
• GTH-I/GTH-II contain a common alpha subunit and a
  distinct beta subunit conceived to be FSH-and
  LH-like.
• GTH-I important for vitellogenesis, early
  gonadal development, and elicits the production
  and storage of GTH-II.
• GTH-I secreted during the early phases of
  ovarian development.

4
Role of GTH-II and GnRH

• GTH-II stimulates events leading to final
  oocyte maturation and ovulation in females and
  spermiation in males.
• GTH-IIstimulated by GnRH, NE, and NPY
• inhibited by DA
• In teleosts, multiple GnRH molecules may be
  expressed simultaneously with different
  functions.
• GnRH mRNA levels can be influenced by many
  factors state of sexual maturation,
  photoperiod, and sex steroids.
• Indicates that GnRH is controlled by internal and
  external factors.

5
Delivery of hypothalmic hormones

• How is GnRH delivered to the gonadotrophs in the
  pituitary gland?
• In mammals a hypothalamohypophysial portal system
  is present.
• In cartilaginous, salmonid fishes, and others no
  portal system exists. GnRH delivered by direct
  innervation of all portions of the pituitary.

6
Changes in levels of GTH-I and GTH-II in coho
salmon during reproductive maturation
GTH-II
GTH
GTH-I
M
O
N
A
A
M
S
J
J
Vitellogenesis Ovulation
Adapted from Dickoff and Swanson, 1990
7
Ovary Anatomy

• Teleost ovarian structure is classified into two
  forms gymnovarian and cystovarian
• Gymnovarian ovaries are possessed by most bony
  fishes except (salmonids).
• Lack a true ovarian cavity.
• Characterized by ovigerous folds which lie
  exposed to the peritoneal cavity.
• Oocytes are ovulated into the coelom and moved
  into the oviduct by ciliated epithelium.

8
Ovary Anatomy

• Cystovarian ovaries (salmonids) have a true
  ovarian capsule.
• Oocytes are ovulated into the intraovarian space
  and move down to the cloaca without entering the
  peritoneal cavity by ciliated epithelium or
  smooth muscles.

9
A section through a cystovarian ovary showing
ovigerous folds and location of oocytes
Adapted from Turner, 1983
10
Gymnovarian
Cystovarian
Bilobed
Bilobed
Mesonephric Kidneys
Mesonephric Kidneys
11
Follicle Anatomy

• Ovarian follicle consists of a developing oocyte
  and two surrounding cells layers.
• Innermost layer steroidogenic granulosa cells
  Outer layer thecal layer (fibroblasts, collagen
  fibers, capillaries, and steroidogen special
  theca cells).

12
Diagrammatic representation of the follicle and
oocyte during early vitellogenesis
Nagahama, 1983
13
Oocyte Recruitment

• Three modes of oocyte development in teleosts
• Synchronous- all oocytes develop synchronously
  and ovulate at the same time.
  Ex Pacific Salmon (semelparous)
• Group-synchronous- vitellogenic oocytes are
  divided into groups, which ovulate over the
  course of one breeding season.
• Ex RBT (iteroparous)

14
Oocyte Recruitment

• Three modes of oocyte development in teleosts
• Asynchronous- oocytes at all developmental stages
  are present in the ovary.
• Ex Tropical fish

15
Mechanisms of Sex Determination

• I. Recombination of sex chromosomes at
  fertilization
• a. Chromosomal genotype
• Mammals and most fish Male XY
• FemaleXX
• Birds and some fish MaleZZ
• FemaleZW

16
Sex Determination/Development

• b. H-Y Antigen
• 1. Male specific antigen present on the
  surfaces of cells
• XYH-Y antigen
• Old theory suggested H-Y antigen existed in
  fish--Not true
• 2. Can be used to sex embryos in mammals
• 3. Does not cause male development

17
Sex Determination/Development

• SRY Gene
• Located on the Y chromosome of mammals and NOT
  FISH
• Stimulates male development
• Produces Testis Determining Factor (TDF)
• FISH--Male/female development is regulated by
  genetic and hormonal control

18
Sex Determination/Development

• Development of the gonads, reproductive tract and
  external phenotype
• a. Origin of gonads
• Fish are similar to mammals in that the male and
  female start with an undifferentiated gonad
• Mesonephros (Primative kidney)
• Ovary and testis arise from this undifferentiated
  gonad-PGC migrate from yolk sac to the genital
  ridge--Mechanism is unclear in fish

19
Sex Determination/Development

• b) Origin of reproductive tract
• Two duct system
• Mullerian ducts--female reproductive
  tract-oviducts, uterus, cervix and vagina
• Wolffian ducts--male reproductive
  tract-epididymis, vas deferens, seminal vessicles
• FISH--tubular extension of the gonad

20
Mechanisms of Sex Determination

• II. Temperature-dependent sex determination
• Alligators and turtles have no heteromorphic pair
  of chromosomes-sex is determined by temperature
• Example-Alligators-lays 40-45 eggs (65 days to
  hatch)
• 93oF-All F
• 86oF-All M
• 88oF-Half F and half M

21
Mechanisms of Sex Determination

• III. Behavior sex determination
• Social situations can initiate changes in gonadal
  sex.
• Example-(Marine fish) Sex change is initiated by
  removal or addition of dominant male or female to
  a population.
• Mechanism of action is unclear!
• However, GnRH-cells in the preoptic area of the
  brain increase.

22
Hermaphroditism in Fish

• c. Three forms of hermaphroditism in fish
• 1. Protogynous hermaphroditism-individuals
  develop first into females and turn later into
  males-Ex (Clown Fish)
• 2. Protandrous hermaphroditism- individuals
  develop first into males and turn later into
  females
• -Marine fish

23
Hermaphroditism in Fish

• 3. Synchronous hermaphroditism-Both male and
  female states coexist functionally
• -Sea bass (self fertilization)