Fish endocrinology Flashcards Preview

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Flashcards in Fish endocrinology Deck (58)
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31

In humans, what does isotocin do?

Same hormone co-opted for different function. Receptors are found in mammalian breast tissue and in uterine contraction tissue.

32

What is thyroid hormone implicated in?

1 - Promotes growth but has to work in conjunction with GH and IGF-1
2 - Metamorphosis in flatfish
3 - Salmon migration and metamorphosis

33

What is the role that TH plays in the metamorphosis of flatfish?

Eye migration and change in body shape.

34

What occurs if TH is blocked in flatfish and tadpoles?

Get large baby flatfish
Get really big tadpoles

35

What happens if TH is blocked in general?

May not grow as fast but will block development.

36

What does TH do for salmon migration?

Plays a role in upregulating the salt chloride cells and stimulating the production of a pigment giving the salmon a silvery colour.
May also be involved in homing/imprinting.
- may help olfactory system lock in the smell of natal stream

37

Where is the pineal gland located?

Under the skull

38

The pineal gland releases ________.

melatonin

39

_________ play a role in extraretinal photoreception.

pinealocytes

40

The pineal gland is a small gland sitting at the base of the _____ which can sense ______.

skull
light

41

Pinealocytes are ______-sensitive cells.

light

42

If a fish loses its eyes, how can it tell if it is day or night?

Can sense light levels through photoreceptors in pineal gland

43

What is a major role of melatonin?

Circadian rhythm

44

What does melatonin do?

Melatonin made in pineal gland, feedsback to hypothalamus which allows it to know what time of day it is.

45

If a fish is in complete darkness, will it still make melatonin?

Yes, still roughly 24hr cycle but, exposure to light fine tunes the cycle.

46

What are endocrine disruptors?
Give some examples.

Hormone-mimicking chemicals that alter reproductive cycles.
PCBs, plasticizers, synthetic estrogens

47

The antidepressants that we take affect fish through their ________ system.

endocrine

48

What are PCBs?

Common waste product of industrial activity which can, once broken down, act like fish hormones.

49

What are plasticizers?

Chemical used in water bottles to make them flexible which can have an estrogenic effect when they break down.

50

What is vitellogenin?

Important hormone for egg development, shouldn't be present in male fish

51

What does vitellogenin do to fish?

Skewed sex ratios
Seeing eggs in male fish
Inhibition of spermatogenesis in adult males.

52

Hormones can change _______ through its effect on the hypothalamus.

seasonally

53

What are the 3 environmental controls that affect reproductive controls and behaviour?

Light
Pheromones
Temperature

54

How is light an environmental control?

Life's indicator of seasonality, can tell if summer or winter by how long light is, picked up by retina and pineal.

55

How can temperature function as an indicator of seasonality?

If in shallow water in a thermally changing environment.

56

What is a pheromone?

Natural smell that comes out of animals
These smells are picked up by the olfactory system and have direct effects on the hormone cycle.

57

If there is lots of light, temperature is just right and lots of pheromones, it must be?

Breeding season

58

When its breeding season, lots of pheromones, how is the hypothalamus affected?

(JUST DRAW THE DIAGRAM)
Hypothalamus releases GRN (gonadotropin releasing hormone) which activates the gonads: testies or ovaries.

Male gonadotropin will cause the testes to release testosterone and 11-keto-test (basically the same).
- 11 keto test can act as pheromone when released in fish pee or from the gills

Two things these two do:
1 - Stimulate sperm production in the testes
2 - Stimulate male secondary sexual characteristics production (tubercles or hooknose for example)

Female gonadotropin:
- causes release of 17b-estradiol from ovaries and acts on the liver to cause release of vitellogenin.
17b-estradiol is the main fish estrogen and causes secondary sex characters in female fish
vitellogenin feedbacks to ovary causing egg maturation and finalizes yolk production