Hormones III

Question 1

When is a photoperiod (circadian rhythms) not a good predictor of breeding success (3 scenarios)?

Answer 1

1. Food
2. Rain
3. Social interactions (drive patterns or modify annual patterns)

Question 2

What is an example of a species where social interactions determine the length of the breeding season? What was an experiment done? What were its results? What is the bottom line of this?

Answer 2

1. Song sparrows
2. Give female estrogen implants (prolong her sexual receptivity for months)
3. Her untreated mate (the male) will also remain in reproductive condition upon seeing she is receptive (testosterone remains high) AND continue to respond to songs just as intensely as early season (control do neither of these)
4. Social cues from the female can modify the annual pattern of the male

Question 3

What is another example of social conditions influencing cycles (not song sparrows)? Elaborate. What is the adaptive advantage of the normal cycle? What are two suggestions about the male that can be made from this pattern?

Answer 3

1. House mice - normally, dominant males mate –> aggressive to pups for three weeks –> protect young for 4 weeks –> back to being infanticidal
2. He will kill young that isn’t his, and protect his own young while they grow
3. Male has an internal clock that regulates his response to offspring, and this pattern is entrained by mating event

Question 4

Think about the house mice example for social cues, and about the pattern that male mice exhibit towards young mice. What are two hypotheses about how this clock could work? What experiment was done to test this? What prediction was made? What was its result? What is the bottom line of this?

Answer 4

1. Clock runs for 7 weeks, or clock is reset every morning and counts days, not overall time
2. 3 sets of males - normal days, slow days (27 hrs) and short days (22 hrs)
3. Prediction - if clock measures real time (weeks, overall time) then infanticidal period = fewer days with long compared to short but still same # hours (all equal # of days if by day)
4. In every cycle, it took 22 days for the males infanticidal rate to drop (meaning that overall time was much longer for 27 days, shorter for 22 days, and that the 7 week clock was not correct)
5. Bottom line = circadian clock, not 7 week clock

Question 5

Think again about the house mice and their pattern of aggression towards young. What hormone regulates this process? What do we already know about this hormone? What was done to test its effect in males and what did this do? What does this show?

Answer 5

1. Progesterone
2. Suppresses parental behavior in female rodents
3. Knockout the receptors so they can’t take it in - males never showed infanticidal behavior
4. Infanticidal tendencies are regulated by levels of progesterone

Question 6

What is a third example of how social conditions effect mating behavior (not sparrow or house mouse)? Elaborate. What hormone is this regulated by? How does this work?

Answer 6

1. Japanese quail –> male will stare at the female and associate with her for hours after mating (make a strong association with that female so that he can copulate with her more and ensure he gets kids).
2. Estrogen
3. Remove gonads = no staring. Estrogen is made by testosterone (must have testosterone to make, but it’s not the final signal).

**Bonus: if you give a male aromatase inhibitor (cannot convert testosterone –> estrogen) then the male won’t stare any more.

Question 7

Think about the ruffs. Remember these are the three types of males (satellite, faeder, independent). Which one of these is hyperaggressive? What is odd about this system? Why is one more aggressive than the others and what causes this?

Answer 7

1. Independent
2. Ind. is hyperaggressive when all three have mating behavior driven by testosterone
3. Faeder and satellite males have a second protein that degrades testosterone in the blood (HSD17B2). This protein is not found in independents, keeping their blood testosterone levels high and causing them to be more aggressive

Question 8

What are the two hormones in humans that drive preferences? How do they effect each sex? What are long-term effects of hormones called? What are activational effects? What is an example of one? Elaborate.

Answer 8

1. Testosterone/estrogen
2. Males - T - development of facial hair/muscle mass (and reduces immune response)

Females - E - development of breasts/hips

3. Organizational effects
4. Short term effects by hormones on behavior or physiology
5. Menstrual cycles in women - estrogen spike –> LH and FSH spike –> progesterone spike

Question 9

How does the birth control pill affect female preference? How does it effect the menstrual cycle?

Answer 9

1. No preference on bill compared to preference for feminine faces for long term relationships normally (more masculine faces for short term relationships under normal circumstances)

**Bonus: In other words, prefers to just mate with masculine, maybe because of testosterone handicap –> higher quality children? (Think about extra pair copulation reasons for female birds)

2. High level of progesterone, baseline levels of FSH and LH

Question 10

What does oxytocin do? How does it act? What was done to test this? What is the obvious conclusion and what did it lead to in human medicine? What was the not-so-obvious dark side?

Answer 10

1. Mother/offspring bonding, maternal behavior, pair bonding after mating
2. Phosphorylation of oxytocin receptors
3. Disrupt phosphorylation in adult rats –> lack of long-term social memory
4. Oxytocin enhances social bonds, so tried treating autism with it (social deficit disorder).
5. Long term effects are counter to short-term effects (kids are less social after long-term treatment and people in general are less open to other cultures)

Question 11

What is another hormone (not oxytocin) that affects social behavior? What does it regulate? What is an example of how vasopressin regulates behavior? What were the fitness levels in each group in this example?

Answer 11

1. Vasopressin
2. Kidneys, sexual motivation, pair bonding, stress response (mothers), spatial memory (males)
3. Prairie voles - males with the receptor (good spatial memory, territorial, good at preventing extra pair in their territory but bad at extra pair paternal care) and males without receptor (poor spatial memory, good at gaining extra pair paternity but bad at preventing extra pair paternity in their territory, less space)
4. They were the same (highly territorial = balance between gain of being territorial and loss from not having affairs) (not much territorial = balance between having lots of affairs happen in their territory and being able to have more affairs himself)