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Aquaculture: Genetics

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

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Aquaculture: Genetics

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  1. Aquaculture:Genetics Dr. Craig Kasper FAS 1012

  2. 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.)

  3. 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

  4. 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

  5. Selective Breeding • Although potential for deleterious results, selective breeding rationalized by: • size • color • shape • better FCR • reproductive capacity • disease resistance

  6. 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.

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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!

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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?

  18. Questions??

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