Fish endocrinology - Part 2

Question 1

What is a feedback loop, relating to the hypothalamus?

Answer 1

A feedback loop helps to regulate hypothalamic and pituitary activity.

Based on circulating hormones, prevents from making too much.

Question 2

Where do 17B estradiol and testosterone both feedback to?

Answer 2

Anterior pituitary and hypothalamus, decrease how much is made.

Question 3

What are the other feedback loops related to?

Answer 3

NTs in the brain.
These 3 can regulate the hypothalamus, up or down regulate.
Mostly behavioural component.

Question 4

Reproductive physiology is controlled by lots of factors such as: _______ factors/disruptors, _______, _____, ______

Answer 4

endocrine
temperature
light
pheromones

Question 5

Why does reproductive physiology matter?

Answer 5

Matters for aquaculture, ecotoxicology and ties into growth, osmoregulation, nutritional state and can be used for genetic rescue of endangered populations.

Question 6

Male reproductive anatomy:

Testis hold ______ which exits through the ________ duct (kidney) or through a ________ duct

Answer 6

sperm
mesonephric
separate

Question 7

Female reproductive anatomy:
______ in ovary.
______ goes either directly through ______ to exit or goes into ______ cavity first.

Answer 7

Eggs
Egg
oviduct
body

Question 8

For the most part, sperm and urine exit through a common opening. True or false?

Answer 8

True

Question 9

What are the 4 basic spawning types?

Answer 9

1 - Group broadcast spawning
2 - Paired broadcast spawning
3 - Adhesive eggs in nest
4 - Internal fertilization

Question 10

What is group broadcast spawning?

Answer 10

Fish get together in a group and release sperm and eggs in a large cloud.

Question 11

What is paired broadcast spawning?

Answer 11

Male and female choose each other but still release eggs and sperm.

Question 12

What are adhesive eggs in nest?

Answer 12

External fertilization, still have pair

instead of broadcasting, put eggs directly into a nest

Question 13

What is internal fertilization?

Answer 13

Generally, male adds sperm to female.

Fertilized eggs can be released or stay inside for a period of time.

Question 14

What are the benefits and costs of group broadcast spawning.

Answer 14

Benefits:

• 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

Cost:

• 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

Question 15

What is the compatible gene idea?

Answer 15

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.

Question 16

What are the benefits and costs of paired broadcast spawning?

Answer 16

Benefits:

• More specific - mate choice
• • can lead to enhanced survival
• Low reproductive investment

Costs:

• 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

Question 17

What is pelagic larval duration?

Answer 17

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%.

Question 18

What are the benefits and costs of Adhesive eggs in nest?

Answer 18

Benefits:

• 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*

Costs:

• Sexual selection*
• More parental care (cost to parent)
• Predation is more devastating*
• Possible sneak fertilization
• all your eggs are in one basket

Question 19

What are the benefits and costs of internal fertilization?

Answer 19

Benefits:

• 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

Costs:

• 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

Question 20

What is iteroparous?

Answer 20

Multiple spawning events (iterations)

Question 21

What is semelparous?

Answer 21

Only spawn once

Question 22

What is oviparous?

Answer 22

Lay external eggs

Question 23

What is ovoviparous?

Answer 23

Live young but no maternal nourishment

Question 24

What is viviparous?

Answer 24

Live young with maternal nourishment.

Question 25

What are the benefits of iteroparous?

Costs?

Answer 25

Benefits:

• lots of chances to pass on genes
• if conditions werent good the first time, can have another go

Costs:
- limit on reproductive effort - still need energy to live so, fewer gametes at a time

Question 26

What are the benefits and costs of semelparous?

Answer 26

Benefits:

• can put all your energy into one spawning event
• • can have more eggs, bigger eggs and lots of gametes

Costs:

• only one shot
• • if conditions are bad or can’t find a mate, no ability to pass on genes

Question 27

How do semelparous fish quite literally give it all they’ve got?

Answer 27

Digest muscles and GI tract and send energy to reproductive organs.

Question 28

When is semelparous a better strategy? When is iteroparous a better strategy?

Answer 28

Semelparous is better when the environment is stable.

Iteroparous is better when the environment is not stable.

Question 29

Between semelparous and iteroparous, which is more common?

Answer 29

Iteroparous

Question 30

Mammals are ______. (Spawning mode)

Answer 30

viviparous

Question 31

What are the two ways to be viviparous?

Answer 31

Either placental-like connection - direct connection between baby and mother which provides nourishment and removes wastes or;
baby lays fin on ovary wall allowing nutrient exchange

Question 32

What are the benefits of vivparous? What are the costs?

Answer 32

Benefits:
- most chance of individual embryo surviving and developing

Cost:

• most cost per embryo
• fewer embryo

Question 33

What is monogamy?

Answer 33

One male and one female.

Question 34

What is polyandry?

Answer 34

1 female with multiple males

Question 35

What is polgyny?

Answer 35

1 male with multiple females

Question 36

Describe monogamy in fishes?

Answer 36

Can be for just one season - like when nest building in anemonefish.
In some cases, share nest for life until one partner dies.
Can be continued mate choice, breeding season after breeding season

Question 37

Which is rarer? Polyandry or polygyny?

Answer 37

Polyandry

Question 38

When would polyandry be more likely to occur.

Provide an example.

Answer 38

When the female is much larger than the males and when it is difficult to find mates.
This is the case with the deep sea angler fish.
Also occurs with seahorses.
- high cost for male (parental care) but low cost for female

Question 39

Describe polygyny.

Answer 39

One male with multiple females.
Often, male will guard a number of females and restrict access from other males.
Often, male will guard a nest site and only allow access to females.

Question 40

How can a female cheat in polygyny?

Answer 40

Can go from nest to nest.

Question 41

What fish will have satellite males?

Answer 41

Blue gill

Question 42

What fish will have sneaker males?

Answer 42

Salmon

Question 43

Describe satellite males.

Answer 43

Life stage choice in blue gills.
Larger adult males will entice the females so, the younger ones have no chance.
The younger ones might be reproductively mature but cannot compete.
Younger, satellite fish will perform extra-pair copulations.
Younger however, eventually becomes dominant male and will defend a nest.
Life stage choice:
- younger is sneaker, older is not

Question 44

Describe sneaker males in salmon.

Answer 44

Jack vs hooknose in salmon.
Choice between the two occurs relatively early on in life.
Jacks do not have hooks, hooknoses do. (i.e. jacks lack secondary sexual character)
Jacks do not become hooknoses and hooknoses do not become jacks,
When spawning time comes, hooknose defends nest and attracts females, jacks will hide along the edges and will try to fertilize eggs at the same time.
Jacks for the most part tend to die off after spawning but, some evidence they can come back.

Question 45

What are the two types of sequential hermaphrodites?

Answer 45

Protrandrous

Protagynous

Question 46

What is protrandrous?

Answer 46

Male to female

Question 47

What is protagynous?

Answer 47

Female to male

Question 48

Describe how social controls can work for a sequential hermaphrodite species.

Answer 48

One large female fish with other small male fish.
Presence of female keeps the other fish male, peeing out pheromones = social control, keeps the other fish male.

When she dies, lose social control.
Largest male fish, generally, will become female and reestablish the social control.

This only works when 1 fish is dominant with 4/5 subordinates.
More often found in reefs.

Question 49

What is parthenogenesis?

Answer 49

Giving birth without fertilization. (No fish actually does this)

Question 50

What is gynogenesis?

Answer 50

Triploid female fish, lays triploid egg, no normal meiosis.
Sperm from male needed to activate egg, causing it to divide.
All offspring will be triploid females identical to the mother.
No genetic contribution from sperm

Question 51

What is hybridogenesis?

Answer 51

Diploid female lays haploid egg with equal contribution from male and female (thus far).
Egg hatches into a female.
When this female lays an egg, all female, only passes on maternal genome and rejects male genome - segregation during meiosis, throwing away male genome.

Question 52

How can hybridogenesis and gynogenesis persist

Answer 52

Male from a different, related species will mate with the female of that species.
When this occurs, this impresses the female from his own species, leading him to have higher reproductive success while allowing these parthenogenic methods of reproduction to persist.