Aquaculture:Aquaculture:GeneticsGenetics

Dr. Craig KasperDr. Craig Kasper

FAS 1012 FAS 1012

Genetics: What is it?Genetics: What is it?

• GeneticsGenetics: The science of heredity and: The science of heredity and variation. variation.

• HeredityHeredity: transmission from generation to : transmission from generation to generation (usually through the process of generation (usually through the process of reproduction) factors which cause the reproduction) factors which cause the offspring to resemble their parents (or not.)offspring to resemble their parents (or not.)

Genetics TermsGenetics Terms

• Selective breedingSelective breeding-the choosing of -the choosing of individuals of a single strain and spp.individuals of a single strain and spp.

• HybridizationHybridization-the crossing of different spp.-the crossing of different spp.

• CrossbreedingCrossbreeding-the mating of unrelated -the mating of unrelated strains of the same spp. to avoid strains of the same spp. to avoid inbreedinginbreeding

Selective BreedingSelective Breeding

• ““Artifical selection” as opposed to natural selection, Artifical selection” as opposed to natural selection, results in reducing genetic variability in a population. results in reducing genetic variability in a population. Could be considered inbreeding if not closely monitored.Could be considered inbreeding if not closely monitored.

• If selective breeding involves excessive inbreeding If selective breeding involves excessive inbreeding physical abnormalities, metabolic deficiencies, and physical abnormalities, metabolic deficiencies, and developmental abnormalities may occur.developmental abnormalities may occur.

• Inbreeding depression-loss of fitness due to inbreedingInbreeding depression-loss of fitness due to inbreeding– more likely to observe occurence of recessive traitsmore likely to observe occurence of recessive traits– Decrease in heterozygosityDecrease in heterozygosity

Selective BreedingSelective Breeding

• Although potential for deleterious results, Although potential for deleterious results, selective breeding rationalized by:selective breeding rationalized by:– size size – colorcolor– shapeshape– better FCRbetter FCR– reproductive capacityreproductive capacity– disease resistancedisease resistance

HybridizationHybridization

• Already looked at hybrid striped bass. Already looked at hybrid striped bass. What other examples are out there??What other examples are out there??

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

Sunfish hybrids (many combinations)Sunfish hybrids (many combinations)

• Hopefully achieve “hybrid vigor,” at least in Hopefully achieve “hybrid vigor,” at least in some trait.some trait.

• Most true hybrids are sterile, but not all.Most true hybrids are sterile, but not all.

Hormones in AquacultureHormones in Aquaculture

• Hormonal cascade (see handout)Hormonal cascade (see handout)

• Importance of Pituitary GlandImportance of Pituitary Gland– Hypophysectomy removal of pituitary (under Hypophysectomy removal of pituitary (under

isotonic growing conditions)isotonic growing conditions)– Pituitary extracts used in some spawning Pituitary extracts used in some spawning

practices (carp)practices (carp)

Pituitary Gland - Master GlandPituitary Gland - Master Gland

• Linked with hypothalamus of brainLinked with hypothalamus of brain

• Produces hormones that affect other Produces hormones that affect other endocrine tissues - indirect influenceendocrine tissues - indirect influence

• Produces hormones that Produces hormones that

affect non-endocrine tissuesaffect non-endocrine tissues

directlydirectly

HormonesHormones

• Basic concept-a chemical messenger (intercellular) Basic concept-a chemical messenger (intercellular) released by endocrine glands.released by endocrine glands.

Hormones in aquacultureHormones in aquaculture

1) Human Chorionic Gonadotropin (HCG)1) Human Chorionic Gonadotropin (HCG)

-induces ovulation-induces ovulation

-injected IM (to get broodfish to synchronize -injected IM (to get broodfish to synchronize spawning), spawning),

ChorulonChorulon (FDA approved) (FDA approved)

-dosage 50-2000 IU/kg wet weight for most fish-dosage 50-2000 IU/kg wet weight for most fish

Others HormonesOthers Hormones

2) Salmon Pituitary Extract (SPE)2) Salmon Pituitary Extract (SPE)

-whole pituitary glands -whole pituitary glands

-sold as a powder-sold as a powder

-natural source of gonadotropins-natural source of gonadotropins

3) Carp Pituitary Extract (CPE)3) Carp Pituitary Extract (CPE)

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

HormonesHormones

4) Leutinizing hormone-releasing hormone4) Leutinizing hormone-releasing hormone

=Gonodotropin Releasing Hormone=Gonodotropin Releasing Hormone

Leutizing Releasing horomone=GnRHLeutizing Releasing horomone=GnRH

LHRHa=analog (synthetic) (potent)LHRHa=analog (synthetic) (potent)

-triggers pituitary to release gonadotropins-triggers pituitary to release gonadotropins

-Intraperitoneal injection (IP)-rapid absoption-Intraperitoneal injection (IP)-rapid absoption

HormonesHormones

5) Methyltestosterone (MT)-used under strict control5) Methyltestosterone (MT)-used under strict control

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

-tilapia (when you need all male populations)-tilapia (when you need all male populations)

-sex reversal (apply during sexual differentiation-sex reversal (apply during sexual differentiation

tilapia, walleye, yellow perchtilapia, walleye, yellow perch

-can be used to sterilize fish (monosex population)-can be used to sterilize fish (monosex population)

-can be given orally (food)-can be given orally (food)

6) Estradiol6) Estradiol

-all female fish possible when used at the right time...-all female fish possible when used at the right time...

GynogenesisGynogenesis

• Development of an ovum without fusion of Development of an ovum without fusion of gametesgametes– usually haploid and dieusually haploid and die– sometimes diploid larva develop sometimes diploid larva develop

• requires retention of 2requires retention of 2ndnd polar body during meiosis polar body during meiosis• Amazon mollies, cruzian carp do thisAmazon mollies, cruzian carp do this

• Induced by:Induced by:– radition, chemical, electrical currents, sperm radition, chemical, electrical currents, sperm

from related speciesfrom related species

Sex reversalSex reversal

• Genotypic females turned into phenotypic Genotypic females turned into phenotypic males (MT)males (MT)– sex-reversed (XX) males cross with normal sex-reversed (XX) males cross with normal

females yields all femalefemales yields all female

• PolyploidyPolyploidy– triploid fish (involves retention of 2triploid fish (involves retention of 2ndnd polar body, polar body,

but fertilized by normal sperm)....WHAT?!?but fertilized by normal sperm)....WHAT?!?• essentially 2 sets of chromosomes from female, one essentially 2 sets of chromosomes from female, one

from malefrom male

Intersexed fishIntersexed fish

• Hermaphrodites-contain ovotestes, can go Hermaphrodites-contain ovotestes, can go either way...either way...– MT treatment female after sex determination MT treatment female after sex determination

occurs (ovary has already started to develop)occurs (ovary has already started to develop)– intersexed fish must be killed to determine if intersexed fish must be killed to determine if

the process work! Not very good for the process work! Not very good for aquaculture?aquaculture?

Questions??