Endocrine Regulation of reproduction

What are the fish internal reproductive organs?

• Testes (Male)

• Ovaries (Female)

What are some examples of external reproductive organs in fish?

• Gonopodium (M)

• Claspers (M) & Cloaca (F) (Sharks)

If a fish has no external reproductive organs, what can be expected?

The fish has an urogenital opening

What is Hermaphroditism?

when both sexes simultaneously, or sequentially switch from one to the other

What are the two types of hermaphroditism

• Protogynous: Start phenotypic female, then turn male

• Protandrous: Start male, turn female (rarer)

What is interesting about the reproduction of seahorses

Male seahorses brood, not the females

What is parthenogenesis?

Asexual reproduction

how many fish species utilize parthenogenesis?

~20

T/F: Parthenogenic species do not usually have sexual reproduction at all

False: They often have both asexual and sexual reproduction

What factors can cause Sex changes?

• Increasing Age

• Increasing Size

• Absence of Males

What are the three young bearing strategies?

• Oviparity

• Ovoviviparity

• Viviparity

What is Oviparity?

External fertilization, develops outside mother

What is Ovoviviparity?

Eggs are fertilized internally, but are not discharged

Viviparity

Internal fertilization, yolked embryo attaches to uterus and changes into yolk sac placenta

What is the tradeoff between development and offspring?

Greater development before release = higher survival rate, but also means fewer offspring and requires more parental resources

What is the phase of gamete development in males, females?

Oogenesis (F), Spermatogenesis (M)

What are the female phases of gamete maturation?

1. Vitellogenesis

2. Final Maturation

What is the male version of gamete maturation?

Spermiogenesis

What occurs after gamete maturation?

Spawning or Resorption

What occurs after spawning or resorption

A recovery period where the fish will either repeat gamete development or return to non-spawning physiology; Death in some species

What are photothermal cues for reproduction?

Gonad development, migration, morphology

What are social cues for reproduction?

synchronized spawning

What is a semelparous spawner’s cycle like?

Fish goes into one major spawning event, then dies

What is the schedule of a total spawner like?

What is a batch spawner’s spawning schedule like?

What is a skip spawner’s spawning schedule like?

What is the difference between synchronous(total) and asynchronous(batch) forms of reproduction in the ovary

Synchronous: In the ovary, all eggs are the same age

Asynchronous: In the ovary, some eggs are more developed than others

T/F: Egg and Fish size greatly impacts the # of eggs produced (Fecundicity)

True

A fish that is 4 times longer will produce roughly __ times as many eggs

10

What is the relationship between substrate size and eggs?

Larger eggs tend to be matched to substrate sizes in mating, fish nestle eggs into substrate for survival

What do small eggs rely on for survival

Dispersal

How do added silt particles from erosion affect mating?

they can damage the mating ground by impacting substrate sizes

What is the somatic index?

The body size % of a tissue or organ

T/F: Gonad somatic index does not relate to fecundity

False, there is a correlation

Female gonad somatic index changes as…

they mature

What can cause gonad somatic index to change over years?

environmental factors

How fast is elasmobranch maturation?

Slow, can take years

How do many sharks get fertilized?

internal fertilization

Sharks exibit what forms of reproduction?

Oviparous, ovoviviparous, viviparous, or parthenogenic viviparous reproduction

How long is an elasmobranch gestation period?

up to 2 years

What is interesting about Sand Tiger sharks ?

They have uterocannibalism:

• 2 Uteruses w/multiple pups

• largest cannibalizes the rest

• only 2 born at a time

Aplacental Viviparity

How was uterocannibalism in Sand Tiger sharks discovered?

Through finding teeth in newly born sharks

What is Aplacental viviparity

There is no placental connection between egg sacs and placenta, there is simply a nutritious uterine fluid embryos consume as well as a small yolk sac

Where to turquoise killifish live?

ephemeral pools that dry up in certain seasons

How do turquoise killifish reproduce in their environment