reproduction 3

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Slide1: 

1. Feminization 2. Masculinization 3. Triploidization 4. Cryopreservation 5. Broodstock management

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Monosex culture - advantages Higher growth rate of one sex Prevention of energy diversions Reduces aggressive interactions Greater uniformity of size at harvest Avoids reduction in product quality Reduces unfavorable EI through escapees

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1. Feminization Two strategies: Hormone therapy Gynogenesis

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Hormone therapy Hormonal feminization is employed by industry – salmonid culture Two methods employed: 1. Direct feminization 2. Indirect feminization

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1. Direct feminization Sexually undifferentiated fish All-female stocks Estrogen treatment

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1. Direct feminization Applicable to any species Employs estradiol-17b Treatment during early stages of differentiation Most widely used method No treatment-based mortality Public perception disadvantages Females when mated will produce 50:50 ratio

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2. Indirect feminization – female homogamety

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2. Indirect feminization – female homogamety Females must be homogametic sex Masculinization of females More than 1 generation to complete Sex specific probes allow separation of XX neomales Market fish not treated with steroids Used with chinook salmon and trout commercially

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Gynogenesis Egg stimulated to divide by genetically inactivated spermatozoon Spermatozoon inactivated by UV Induced diploidization by pressure shock

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Gynogenesis Low survival ~ 50% Abnormal ovaries May produce variable sex ratios Use of females for monosex production

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Lability

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Oestrogen and Oncorhynchus sp.

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2. Masculinization - methods Sorting Hormonal sex reversal Interspecific hybridization Androgenesis Supermales Triploidy Transgenesis?

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Interspecific hybridization Oreochromis niloticus x O. aureus O. mossambicus x O. aureus O. Mossambicus x O. hornorum O. spilurus niger x O. macrochir O. spilurus niger x O. hornorum O. aureus x O. hornorum Tilapia zillii x O. andersonii All progenies monosex

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3. Triploidization Produces sterile animals Subject eggs to an environmental shock: 1. heat 2. pressure 3. cold 4. chemical 5. electric

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4. Cryopreservation Long-term storage of living cells using liquid nitrogen as a coolant Stored material can be maintained for centuries Important to conserve genetic material Embryo storage only reported with hard clam and oyster

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5. Broodstock management Nutrition - vit. E; HUFA; a-tocopherol Stress Vertical transmission of diseases viral bacterial fungal