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Fish Reproduction Brian Peterson, M.S. Objectives. Aquaculture and its role in the U.S. and Idaho Female reproductive system -Ovary and follicle anatomy Sex determination and hermaphorditism Alligator production in Idaho Research at the U of I. 1999 Census Catches ~ $1 Billion in Sales.

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objectives
Objectives
  • Aquaculture and its role in the U.S. and Idaho
  • Female reproductive system

-Ovary and follicle anatomy

  • Sex determination and hermaphorditism
  • Alligator production in Idaho
  • Research at the U of I
1999 census catches 1 billion in sales
1999 Census Catches ~ $1 Billion in Sales

Aquacrop Value ($)

Catfish 488,000,000

Trout 77,000,000

Salmon 100,000,000

Ornamental 69,000,000

Source: Economic Research Service, USDA

fish farming vs cattle ranching
Fish Farming vs Cattle Ranching
  • Fish farming is the fastest growing sector of the world food economy.

-Growing ~ 11%/year

-13 million tons produced in 1990 to 34.4 million tons in 1999.

  • Cattle ranching hit high of 53 million tons in 1990.

-Surpass cattle ranching as a food source by the end of this decade.

Source: World Catch News

rainbow trout production 1999
Rainbow Trout Production 1999
  • Idaho currently ranks # 1 in the nation in RBT production- 48 % of total sales
    • 76 % of market size fish

#2)North Carolina 4.5 million lbs

#3)California 2.3 million lbs

  • 1999 Idaho produced ~ 47.5 million fish which equates to ~ 46 million lbs
  • 1999 total sales of RBT- ~ $37 million

Source: Economic Research Service, USDA

terms to know
Terms to Know
  • Teleost—Fish that exclude jawless fish, cartilaginous fish, lobe-finned fish, and sturgeon.
  • Vitellogenin—Glycolipoprotein produced in the liver and accumulated in the oocyte as yolk.
  • Vitellogenesis—Process of yolk formation.
female reproductive system
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

female reproductive system1
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.

role of gth i and gth ii
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.
role of gth ii and gnrh
Role of GTH-II and GnRH
  • GTH-II: stimulates events leading to final oocyte maturation and ovulation in females and spermiation in males.
  • GTH-II—stimulated 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.
delivery of hypothalmic hormones
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.
slide13
Changes in levels of GTH-I and GTH-II in coho salmon during reproductive maturation

GTH-II

GTH

GTH-I

M

A

M

J

J

A

S

O

N

Vitellogenesis Ovulation

Adapted from Dickoff and Swanson, 1990

ovary anatomy
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.
ovary anatomy1
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.
slide16
A section through a cystovarian ovary showing ovigerous folds and location of oocytes

Adapted from Turner, 1983

slide17
Gymnovarian

Cystovarian

Bilobed

Bilobed

Mesonephric Kidneys

Mesonephric Kidneys

follicle anatomy
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).
slide19
Diagrammatic representation of the follicle and oocyte during early vitellogenesis

Nagahama, 1983

oocyte recruitment
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)

oocyte recruitment1
Oocyte Recruitment

Three modes of oocyte development in teleosts

  • Asynchronous- oocytes at all developmental stages are present in the ovary.

Ex: Tropical fish

mechanisms of sex determination
Mechanisms of Sex Determination

I. Recombination of sex chromosomes at fertilization

a. Chromosomal genotype

Mammals and most fish: Male= XY

Female=XX

Birds and some fish: Male=ZZ

Female=ZW

sex determination development
Sex Determination/Development

b. H-Y Antigen

1. Male specific antigen present on the surfaces of cells

XY=H-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

sex determination development1
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
sex determination development2
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 genitalridge--Mechanism is unclear in fish

sex determination development3
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

mechanisms of sex determination1
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

alligator production
Alligator Production
  • Alligators are being grown in southern ID

Young alligators are grown in tanks at 85-90oF year- around-grow at a rate of 2 inches per month

Alligators are harvested at 3 yrs old (~5 feet long)

Skins sold for ~$30/ft

Meat sold for~$10-20/lb

mechanisms of sex determination2
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.

hermaphroditism in fish
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

hermaphroditism in fish1
Hermaphroditism in Fish

3. Synchronous hermaphroditism-Both male and female states coexist functionally

-Sea bass (self fertilization)

research at university of idaho
Research at University of Idaho

Hypothalamus

SS (-)

GHRH (+)

Anterior Pituitary

GH

my research
My Research
  • Release patterns of GH in fish.
  • Somatostatin role in GH release.
  • Passive immunization against SS

Immunize another animal (rabbit, sheep, cow)

  • Active immunization against SS

Immunize animal of interest

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