Topic 5 & 6 Flashcards
(20 cards)
What is CRISPR?
- Clustered Regularly Interspaced Short Palindromic Repeats
- Family of DNA sequences found in prokaryotes
How does CRISPR work?
- Cas9 –> CRISPR-associated proteins –> nucleases that cuts DNA
- CRISPR is a collection of DNA sequences
- CRISPR tells Cas9 where to cut
- Cas9 is an enzyme that cuts DNA
- Involves changing the sequences which changes the messages –> exhibit new property/characteristic
- Microinjection of CRISPR/Cas9 embryos
Function of CRISPR
- Genome editing –> fix alleles at existing trait loci, create new alleles/introduce alleles from other strains/species
- Enhance dz resistance in fish
- ↑ biomass/growth rate
- Achieve 100% sterility to prevent interbreeding w wild species (if escape)
Ethical implications of genome editing/manipulation (Environment)
- Ecological risks if escaped
- Bioengineered organisms may have intraspecific/interspecific interactions w env/other org.
- Need to evaluate environmental risks in relation to pollution, energy, land use –> Environmental Impact Assessment (EIA)
Drawbacks of genome-based biotechnologies (environmental issues)
- Similar to impacts of exotic/invasive species
- Fishes in open aquaculture system can interact w wild indivs. –> transfer of pathogen/diseases
- Escaped viable culture indivs –> ecological hazards
1. Alteration of predation
2. Resource competition
3. Change in fitness of novel genotypes in the wild due to interbreeding –> breed w wild animals = affect genotype - Genetically-engineered infertile aquatic species can reach maturity but X reproduce –> upset demography in small natural populations –> possible risk of local extinction
Why is Broodstock nutrition important?
- Nutrition (quality + quantity of diet) has profound effect on gonadal growth & fecundity –> affects broodstock reproductive success, spawning, hatching ability of eggs & survival rate of offspring
- Quality nutrition = Maintenance & reproduction for commercially important fish species = ↑ production success (esp in less desirable culture practices) = ↑ income
What does suboptimal nutrition/food restriction affect?
Reproductive potential
- Time of first maturity (delayed)
- No. of eggs produced (fecundity)
- Egg size
- Egg quality (measured by chemical composition)
- Delayed spawning
- Hatchability
- Larval quality
Energy Partitioning
Partitioned b/w
- Maintenance
- Growth
- Reproduction
Maintenance requirements met then excess energy divided into growth & reproduction
Essential nutrients in reproduction
- Lipid + Fatty acids: HUFA affects fish maturation, (in some species:) ↑ fecundity, fertilization & egg quality; ↑ essential fatty acids = ↑ fecundity + hatchability
- Vitamin E
- Vitamin C
- Amino acids
- Trace minerals
Lack Vitamin E
- Immature gonads + low reproductive performance
- Lower hatching rate & survival of offspring
- ↑ % of abnormal eggs
- ↓ fecundity in gilthead seabream
Lack Vitamin C
- ↓ prod. of steroid
- Poor yolk formation
- Reduced sperm concentration
Lack amino acids
- Indivs spawn at smaller size
- eggs w low hatchability & deformities
Lack tace minerals
- lower % of both eyed & viable eggs
Broodstock diet
- Broodstock conditioning diet: optimized growout diet (high load of fatty acids)
- Reproduction diet: before/during spawning –> meet needs for max reproductive performance (spawning success, fecundity, gamete quality) & vertical transfer of nutrients & biologically active substances to offspring
- Recovery/maintenance diet: assist recovery from repro. exhaustion + recondition for next repro cycle
What does stress in broodstock cause?
- Affect egg & larvae quality
- Impair fitness of progeny
- More difficult to rear small larvae
What causes broodstock stress?
- Cannot acclimate in captivity
- Stocking density
- Water quality
- System design
- Handling processes: grading, sampling, tpt
HPI axis
Hypothalamic-Pituitary-Interrenal Axis
- Stress causes the hypothalamus to secrete Adrenocorticotropic hormone (ACTH) stimulating hormone
- ACTH Stimulating hormone signals the pituitary gland to secrete ACTH
- ACTH acts on the interrenal cells
- Causes the interrenal cells to secrete cortisol
- Cortisol acts on body cells –> loss of appetite, ↓ed mucus production, ↓ed resistance
Stress indicators
Glucocorticoids (cortisol & corticosteroid) –> biomarker for stress quantification
- Consistently high cortisol level = inability to restore homeostasis
Results in
1. Chronic stress
2. Prolonged physiological response (from secretion of cortisol)
3. Detrimental effects of glucocorticoid mediated actions: ↓ed growth, ↓ reproduction, immune suppression, ↑ed mortality
4. Fish performance & welfare affected
Stress & reproduction
Vertical transfer of maternal hormones (mother to egg)
- Developmental hormones (e.g. thyroxine)
- Reproductive hormones (e.g. testosterone)
- Metabolic hormones (e.g. cortisol)
Cortisol
- indirectly influence by altering allocation of vitellogenin (egg yolk precursor) & levels of developmental hormones during gametogenesis
- directly influences larval morphology: -ve correlation b/w level of cortisol in ovaries of breeding females & size of larvae produced (↑ed cortisol = smaller larvae)
Stressed broodstock = eggs w high level of cortisol = poor quality larvae
Stress-free broodstock
- High quality eggs
- Larvae of greater fitness
- Reduced larval mortalities
- Stronger juveniles & healthier fish
Success in closing reproductive cycle of fish = no stress
