Oogenesis Flashcards
For what reason is the reproductive energy for female fish high?
Eggs are nutrient and resource rich as must provide the building blocks for developing embryos
Female fish must commit high energy reserves to egg production and start recrudescence well in advance of spawning
draw the Oocyte development of gillhead seabream and zebrafish
Why is salmon “easy” to rear in captivity?
the larvae of salmon can be fed with a commercial diet straight overcoming the problem of feeding zooplankton in most other species
Describe the Ovarian development
How do PGCs migrate?
chemokine signalling
what hormone is important in ovarian development during differentiation
17 estrodiol (E2)
what happens to the ovarian development of XX tilapia and trout when E2 is blocked
trout and tilapia became phenotypic males
How does temperature change affect sex determination in some fish e.g. japanese flounder
XX females at 18°C, XX males at 27 °C the latter can be reversed to females if given E2 (Kitano et al. 2007)
Why are haploid sex cells preferred in breeding fish?
diploid sex cells would result in three sets of chromosomes for the following generation
describe the picture
Oogoniaarranged in nests and proliferate, E2 thought to be important for proliferation
when meiosis begins, becomes a primary oocyte and follicle layer formed
Once the follicle is complete and first meiotic division initiates then becomes the primary oocyte
Main development is formation of organelles and molecules utilised later stages
describe the picture
Cortical alveoli formation
The first obvious sign of gonadal recrudescence
These are used for chorionformation (restructure of egg shell proteins) after fertilisation
The production of cortical alveoli is associated with FSH and an increase in E2
Cortical alveoli formation
Lipid droplets may also be accumulated
How does steroidogenesis work?
enzymes turn cholesterol into testosterone in the theca and then diffuses into the granulosa where the testosterone is turned into estradiol-17B by P450arom (enzyme)
(most important)
what controls Upregulation of steroidogenic enzymes?
GtHs
What is lipoglycophosphoprotein?
where is it produced?
what is it used for?
what is it mediated by?
Vitellogenin
produced in the liver
used as main building block for embryo
mediated by estradiol E2
why are fish embryos developing inside an egg shell?
Egg shell is important in protection from environment and microbial infection as well as guiding sperm at fert via micropyle at animal pole (closes after fert)
Why do Oocytes undergo hydration during final stages of maturation?
to help buffer embryo against osmotic extremes of marine
environment as well a providing bouyancy & dispersal
(Hydration occurs through hydrolysis of yolk proteins into FAAs as well
as accumulation of ions such as K+, Mg2+, Cl-, Ca2+, NH4+)
Describe the process of Atresia
- Gonad regresses at the conclusion of breeding season, therefore resorbs remaining vitellogenic oocytes
- This is primarily coordinated by granulosa cells which phagocytise oocytes and their yolk
- Oocyte nucleus and organelles disintegrate, followed by hypertrophy of follicle cells
