Reproduction

Question 1

What does the BPG-axis stand for?

Answer 1

Brain-Pituitary-Gonad axis – it controls reproduction via hormonal signaling.

Question 2

What hormones does GnRH stimulate the pituitary to release?

Answer 2

Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH).

Question 3

What neurotransmitter inhibits GnRH release?

Answer 3

Dopamine.

Question 4

What is the main role of LH in fish reproduction?

Answer 4

Stimulates steroid hormone production.

Question 5

What is the main role of FSH in fish reproduction?

Answer 5

Stimulates gametogenesis and gonadal growth.

Question 6

What hormone triggers final oocyte maturation in females?

Answer 6

17α-20β dihydroxy progesterone (17,20-P4).

Question 7

What hormone is critical for vitellogenesis in fish?

Answer 7

Estradiol (17β-oestradiol).

Question 8

What is 11-ketotestosterone (11-KT) responsible for in males?

Answer 8

Stimulates spermatogenesis and spermiation.

Question 9

What is the Gonadosomatic Index (GSI)?

Answer 9

(Gonad weight / Body weight) × 100.

Question 10

What is the difference between semelparous and iteroparous species?

Answer 10

Semelparous breed once and die; iteroparous can breed multiple times.

Question 11

What environmental factors affect the timing of fish reproduction?

Answer 11

Temperature, daylight, food availability, flooding.

Question 12

What are the three main types of reproductive strategies based on spawning site?

Answer 12

Non-guarders, Guarders, Bearers.

Question 13

What is batch fecundity?

Answer 13

The number of eggs produced per spawning event.

Question 14

What is the trade-off between egg size and fecundity?

Answer 14

Larger eggs = fewer, more viable offspring; Smaller eggs = more, less viable offspring.

Question 15

How does food availability impact reproduction?

Answer 15

Higher food availability increases growth, fecundity, and spawning frequency.

Question 16

What reproductive hormone is used to induce spawning in aquaculture?

Answer 16

Gonadotropin-Releasing Hormone (GnRH) analogs with dopamine antagonists.

Question 17

Which gland produces melatonin, influencing seasonal reproduction?

Answer 17

The pineal gland.

Question 18

How does melatonin influence fish reproduction?

Answer 18

It slows down dopamine breakdown, helping synchronize reproduction with daylight changes.

Question 19

What are the two cell types involved in female fish steroidogenesis?

Answer 19

Theca cells and granulosa cells.

Question 20

What happens in theca and granulosa cells during vitellogenesis?

Answer 20

Theca cells produce testosterone, granulosa cells convert it to estradiol.

Question 21

What triggers the switch to producing 17,20-P4 in granulosa cells?

Answer 21

Increased gonadotropin stimulation as ovulation approaches.

Question 22

Which hormone helps stimulate prostaglandin production for ovulation?

Answer 22

17,20-P4.

Question 23

What is vitellogenin, and where is it produced?

Answer 23

It’s a yolk protein produced by the liver under estradiol stimulation.

Question 24

What is spermiation?

Answer 24

The release of sperm into the ducts for ejaculation.

Question 25

What environmental changes can accelerate sexual maturity in fish?

Answer 25

Increased food availability or reduced competition.

Question 26

What reproductive life-history strategy involves only one breeding event before death?

Answer 26

Semelparity.

Question 27

What strategy involves repeated breeding across multiple seasons?

Answer 27

Iteroparity.

Question 28

In what seasons do salmon typically spawn?

Answer 28

Autumn to early winter.

Question 29

What triggers spawning in floodplain tropical rivers?

Answer 29

Rising floodwaters.

Question 30

Name two types of brooders among fish.

Answer 30

Mouthbrooders (e.g., Tilapia) and pouch bearers (e.g., Seahorses).

Question 31

What are pelagic eggs?

Answer 31

Eggs that float and develop in open water.

Question 32

What are demersal eggs?

Answer 32

Eggs that sink and develop on or near the substrate.

Question 33

What happens to fecundity if food availability improves mid-season for batch spawners?

Answer 33

Fecundity can increase by recruiting more oocytes.

Question 34

What is determinate fecundity?

Answer 34

Fecundity is fixed before the spawning season begins.

Question 35

What is indeterminate fecundity?

Answer 35

New oocytes continue to be recruited during the spawning season.

Question 36

What is the major ecological advantage of large eggs?

Answer 36

Larger larvae have better survival chances due to larger prey range and resistance to starvation.

Question 37

In fish ecology, what is the main cost of producing large eggs?

Answer 37

Lower overall fecundity (fewer eggs).

Question 38

What external factor besides food can socially control maturity timing in some fish?

Answer 38

Presence of larger, dominant males.

Question 39

How does ration size affect reproductive performance in threespine sticklebacks?

Answer 39

Higher ration ➔ more frequent spawnings with shorter intervals.

Question 40

Which hormone combination is commonly used in aquaculture to induce ovulation?

Answer 40

LHRH-a (GnRH analogue) + pimozide (dopamine antagonist).