Flashcards in Fish endocrinology - Part 2 Deck (52)
What is a feedback loop, relating to the hypothalamus?
A feedback loop helps to regulate hypothalamic and pituitary activity.
Based on circulating hormones, prevents from making too much.
Where do 17B estradiol and testosterone both feedback to?
Anterior pituitary and hypothalamus, decrease how much is made.
What are the other feedback loops related to?
NTs in the brain.
These 3 can regulate the hypothalamus, up or down regulate.
Mostly behavioural component.
Reproductive physiology is controlled by lots of factors such as: _______ factors/disruptors, _______, _____, ______
Why does reproductive physiology matter?
Matters for aquaculture, ecotoxicology and ties into growth, osmoregulation, nutritional state and can be used for genetic rescue of endangered populations.
Male reproductive anatomy:
Testis hold ______ which exits through the ________ duct (kidney) or through a ________ duct
Female reproductive anatomy:
______ in ovary.
______ goes either directly through ______ to exit or goes into ______ cavity first.
For the most part, sperm and urine exit through a common opening. True or false?
What are the 4 basic spawning types?
1 - Group broadcast spawning
2 - Paired broadcast spawning
3 - Adhesive eggs in nest
4 - Internal fertilization
What is group broadcast spawning?
Fish get together in a group and release sperm and eggs in a large cloud.
What is paired broadcast spawning?
Male and female choose each other but still release eggs and sperm.
What are adhesive eggs in nest?
External fertilization, still have pair
instead of broadcasting, put eggs directly into a nest
What is internal fertilization?
Generally, male adds sperm to female.
Fertilized eggs can be released or stay inside for a period of time.
What are the benefits and costs of group broadcast spawning.
- Less cost for care
- Good chance of fertilization at the group level
- Good chance there was enough fertilization going on so that the species as a whole can continue
- No selection (benefit for less fit fish)
- safe from predators since in group
- No guarantee that genes are passed on - individual
- No guarantee that a fish didn't get outcompeted at the sperm level
- Eggs float away - no idea if they survive
-- predation is a big issue
- No mate choice (bad if fit fish)
- odds of survival of each individual egg is low
What is the compatible gene idea?
Ties in with group-broadcast spawning since there is arguably no selection going on.
So, even though you aren't choosing your mates, sperm and eggs with the most compatible genes are more likely to fertilize.
What are the benefits and costs of paired broadcast spawning?
- More specific - mate choice
-- can lead to enhanced survival
- Low reproductive investment
- offspring still float away - don't know if survive
-- predation is a big issue
- male competition - sneaker males (fertilization rate might be lower)
- less efficient since fewer fish
- eggs are still small since no parental care
What is pelagic larval duration?
Means that as eggs float away, eggs and larvae are pelagic, the longer that they are in the pelagic phase, the lower their survival.
This is because they are floating around, open to predation.
Survival for broadcast spawning can be as low as 1%.
What are the benefits and costs of Adhesive eggs in nest?
- More protection/less predation*
- Mother is spending time investing so get large eggs/embryos (good at the individual level)
- offspring more likely to reach maturity (tend to grow faster)
- Sexual selection*
- Sexual selection*
- More parental care (cost to parent)
- Predation is more devastating*
- Possible sneak fertilization
- all your eggs are in one basket
What are the benefits and costs of internal fertilization?
- Fish will be bigger, hatch our larger and more developed (benefit for offspring)
- offspring may be more fit due to sexual selection
- increased fertilization (sperm and egg not diluted; better chance of meeting)
-Environmental protection (mother can swim to better habitat)
- No sneakers (highest degree of sexual selection
- Mother can choose where to lay eggs
- fewer offspring at a time
- Costs more energy to keep eggs inside
- Space limitation in mother (and possibly dad)
- If mother gets eaten, rip reproductive investment
- male and female have to physically connect - vulnerable to predation during the deed
What is iteroparous?
Multiple spawning events (iterations)
What is semelparous?
Only spawn once
What is oviparous?
Lay external eggs
What is ovoviparous?
Live young but no maternal nourishment
What is viviparous?
Live young with maternal nourishment.
What are the benefits of iteroparous?
- lots of chances to pass on genes
- if conditions werent good the first time, can have another go
- limit on reproductive effort - still need energy to live so, fewer gametes at a time
What are the benefits and costs of semelparous?
- can put all your energy into one spawning event
-- can have more eggs, bigger eggs and lots of gametes
- only one shot
-- if conditions are bad or can't find a mate, no ability to pass on genes
How do semelparous fish quite literally give it all they've got?
Digest muscles and GI tract and send energy to reproductive organs.
When is semelparous a better strategy? When is iteroparous a better strategy?
Semelparous is better when the environment is stable.
Iteroparous is better when the environment is not stable.
Between semelparous and iteroparous, which is more common?