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Aquaculture: Genetics. Dr. Craig Kasper FAS 1012 . Genetics: What is it?. Genetics : The science of heredity and variation.

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aquaculture genetics

Aquaculture:Genetics

Dr. Craig Kasper

FAS 1012

genetics what is it
Genetics: What is it?
  • Genetics: The science of heredity and variation.
  • Heredity: transmission from generation to generation (usually through the process of reproduction) factors which cause the offspring to resemble their parents (or not.)
genetics terms
Genetics Terms
  • Selective breeding-the choosing of individuals of a single strain and spp.
  • Hybridization-the crossing of different spp.
  • Crossbreeding-the mating of unrelated strains of the same spp. to avoid inbreeding
selective breeding
Selective Breeding
  • “Artifical selection” as opposed to natural selection, results in reducing genetic variability in a population. Could be considered inbreeding if not closely monitored.
  • If selective breeding involves excessive inbreeding physical abnormalities, metabolic deficiencies, and developmental abnormalities may occur.
  • Inbreeding depression-loss of fitness due to inbreeding
    • more likely to observe occurence of recessive traits
    • Decrease in heterozygosity
selective breeding1
Selective Breeding
  • Although potential for deleterious results, selective breeding rationalized by:
    • size
    • color
    • shape
    • better FCR
    • reproductive capacity
    • disease resistance
hybridization
Hybridization
  • Already looked at hybrid striped bass.

What other examples are out there??

Splake-brook trout/lake trout, Tiger Musky-northern pike/musky

Sunfish hybrids (many combinations)

  • Hopefully achieve “hybrid vigor,” at least in some trait.
  • Most true hybrids are sterile, but not all.
hormones in aquaculture
Hormones in Aquaculture
  • Hormonal cascade (see handout)
  • Importance of Pituitary Gland
    • Hypophysectomy removal of pituitary (under isotonic growing conditions)
    • Pituitary extracts used in some spawning practices
pituitary gland master gland
Pituitary Gland - Master Gland
  • Linked with hypothalamus of brain
  • Produces hormones that affect other endocrine tissues - indirect influence
  • Produces hormones that

affect non-endocrine tissues

directly

pituitary gland
Pituitary Gland
  • Indirect influence
    • ACTH - adrenocorticotrophic hormone
      • stimulates interrenal tissue production of cortisol
    • TH - thyrotrophic hormone
      • stimulate thyroid production of thyroxin (growth, metamorphosis-i.e. flounder)
    • GTH- gonadotrophic hormone
      • stimulates gonads to produce androgens/estrogens
pituitary gland1
Pituitary Gland
  • Effects non-endocrine tissues directly
    • pigmentation - melanophore stimulating hormone (MSH)
      • affects long-term control of color
    • osmoregulation - prolactin, vasotocin
      • controls fresh/saltwater systems
    • growth – somatotrophic hormone
      • stimulates > length, cell multiplication
hormones
Hormones
  • Basic concept-a chemical messenger (intercellular) released by endocrine glands.

Hormones in aquaculture

1) Human Chorionic Gonadotropin (hCG)

-mimics endocrine gonadotropins

-augements serum gonadotropins already present

-induces ovulation

-injected IM (often to get multiple broodfish to synchronize spawning), chorulon (FDA approved)

-dosage 50-2000 IU/kg wet weight

-330 IU’s for striped bass and white bass

hormones1
Hormones

2) Salmon Pituitary Extract (SPE)

-crude acetone dried preparation of whole pituitary

glands

-powder

-natural source of gonadotropins

3) Carp Pituitary Extract (CPE)

*Use extracts which are closest phylogenetically to fish being injected!

hormones2
Hormones

4) Leutinizing hormone-releasing hormone

=Gonodotropin Releasing Hormone

Leutizing Releasing horomone=GnRH

LHRHa=analog (synthetic) (potent)

-triggers pituitary to release gonadotropins

-Intraperitoneal injection (IP)-rapid absoption

hormones3
Hormones

5) Methyltestosterone (MT)-used under strict control

-accelerates growth rate of some fish (no longer used for this purpose)

-tilapia

-sex reversal (apply during sexual differentiation

tilapia, walleye, yellow perch

-can be used to sterilize fish (monosex population)

-can be given orally (food)

6) Estradiol

-all female

gynogenesis
Gynogenesis
  • Development of an ovum without fusion of gametes
    • usually haploid and die
    • sometimes diploid larva develop
      • requires retention of 2nd polar body during meiosis
      • Amazon mollies, cruzian carp do this
  • Induced by:
    • radition, chemical, electrical currents, sperm from related species
sex reversal
Sex reversal
  • Genotypic females turned into phenotypic males (MT)
    • sex-reversed (XX) males cross with normal females yields all female
  • Polyploidy
    • triploid fish (involves retention of 2nd polar body, but fertilized by normal sperm)
    • essentially 2 sets of chromosomes from female, one from male
intersexed fish
Intersexed fish
  • Hermaphrodites-contain ovotestes, can go either way...
    • MT treatment female after sex determination occurs (ovary has already started to develop)
    • intersexed fish must be killed to determine if the process work! Not very good for aquaculture?