What important difference between male/female gametes is related to courtship and female choice?

When is this difference important?

What important difference between male/female gametes is related to courtship and female choice?

When is this difference important?

size difference reflects fundamental difference in energy invested in the offspring...

prior to fertilization (but in many species, after fertilization also)

What fundamental mechanism is responsible for male courtship & female choice?

What are the 2 reasons/examples of this?

What fundamental mechanism is responsible for male courtship & female choice?

What are the 2 reasons/examples of this?

- natural selection

- 1) flashy courtship displays & behaviors indicate good genes

2) 'expensive' traits like loud & complex songs put male at greater risk of predation. if he avoids being eaten, he must be really strong.

What are the 3 sexual dimorphisms that reflect the male's needs with regard to courtship?

1) needs brain areas to produce the response or behavior

2) needs motoneurons & muscles to produce the behavior

3) needs activation of the behavior by hormones

What are the 3* sexual dimorphisms that reflect the female's needs with regard to courtship?

1) needs brain areas to detect the male's behavior

2) needs receptors for detection of male's signal

**3) in some cases, she needs hormonal activation of the appropriate behavior and/or sensitivity for the signal produced by the male

What are the 3 examples of courtship behavior we studied?

1) electric fish singing

2) frog singing

3) zebra finch and bird song

What genus is the electric fish?

Where do they live?

Diurnal or nocturnal?

What genus is the electric fish?

Where do they live?

Diurnal or nocturnal?

- Brienomyrus

- incredibly murky water

- nocturnal

What triggers courtship in electric fish?

What is a different courtship trigger that is used by some species?

What do the male and female use to sing?

What triggers courtship in electric fish?

What is a different courtship trigger that is used by some species?

What do the male and female use to sing?

- environmental changes

- when the male detects weak signals from the females

- their electric organ discharge (EOD)

What do elec. fish use EODs to locate?

What 3 things does an EOD communicate?

EODs differ between which 3 groups of elec. fish?

What do elec. fish use EODs to locate?

What 3 things does an EOD communicate about its sender?

EODs differ between which 3 groups of elec. fish?

- conspecifics

- 1) its breeding condition

2) its sex

3) is used to synch spawning (egg laying) & fertilization

- adult males, females, and juveniles

What example demonstrates how powerful the EOD is?

- females will lay eggs in response to a recording of the signal

When can sex differences in EODs be observed?

What type of effects are these known as?

When can sex differences in EODs be observed?

What type of effects are these known as?

- only during the breeding season

- known as transitory hormone effects

What EOD change will change a male pattern to a female pattern?

How can male EOD pattern be changed to female?

How can female be changed to male?

What other type of elec. fish does the female to male treatment work on?

What EOD change will change a male pattern to a female pattern?

How can male EOD pattern be changed to female?

How can female be changed to male?

What other type of elec. fish does the female to male treatment work on?

- shortening of EOD pulse

- castration

- androgen treatment

- androgens to juvenile elec. fish also leads to male EOD pattern

What are the effects of gonadectomy of adult elec. fish on EOD?

Of estradiol administration?

What are the effects of gonadectomy of adult elec. fish on EOD?

Of estradiol administration?

- increase in EOD rate in males

- decrease in EOD rate in females

- estradiol administration --> female EOD pattern

Explain why sexual differences in EODs are only observed sometimes.

Because the fx of hormones on EODS & on electroreceptor sensitivity is purely activational

(and will vanish when hormones return to baseline after the breeding season)

In the specific elec. fish Brienomyrus brachyistius, what is matched in male/female pairs?

Describe the sounds that the male and female each make.

In the specific elec. fish Brienomyrus brachyistius, what is matched in male/female pairs?

Describe the sounds that the male and female each make.

- 'rasp matching'

- the male rasps (high frequency)

&

the female bursts (staccato)

Xenopus is a genus of what kind of animal?

frogs

What 6 things do frog songs reveal?

male-male aggression

size

age

health

species

attractiveness

What does the male frog song advertise?

its reproductive state

Describe how info about each aspect is revealed by frog songs.

Size:

Age:

Health:

Species:

Attractiveness:

Describe how info about each aspect is revealed by frog songs.

Size:  the louder the call, the bigger the frog

Age:  the lower the frequency, the older

Health:  the longer the call, the healthier

Species:  mating w/ wrong species = non-viable offspring

Attractiveness:  the more complex, the more attractive

2 reasons why older is better for frogs?

1) have successfully survived environmental hazards that the offspring will be facing, so must have good genes

2) singing costs a lot of energy, so only very fit & healthy frogs can keep up singing for long (thus attracting potential mates)

What are the acoustic signals generated by frogs called?   How are they generated?

- clicks

- laryngeal muscles contract and relax the vocal organ, the larynx

The motoneurons innervating the laryngeal muscles have been traced to where?

they have been traced within the laryngeal nerve to cell bodies in the hindbrain

Explain why female frogs can't emit the male response call.

The male larynx contains more muscle fibers & their fibers can contract & relax very rapidly (100/sec).

The female vocal organ cannot contract/relax fast enough bcz has fewer fibers & they are slower; 40/sec.

Also, the female brain lacks certain connections so cannot generate the mate call pattern.

What is DTAM?  How do male frogs differ from females with regard to the DTAM?

 - it is a pattern generating nucleus for vocalizations

- females lack the connection between the DTAM and the neurons/motoneurons that operate the larynx.

What is shown on the slide depicting successful frog mating?  For rejection?

- rapping and the male's response

- ticking and the male's response

Masculinization of the frog brain:  what happens during development?

Androgens organize the larynx and the brain circuitry underlying mate calling.

Testosterone saves the cells -- similar to SNB in spinal cord

Describe the role of hormones in the adult male frog brain.

T and DHT during adulthood are necessary to activate the mating calls (even if organization took place successfully during development).  Castrated males will resume calling if treated with T or DHT.

Describe the role of hormones in the adult female frog brain.

Activational:  E is required in adulthood in order to be able to respond to male calls (by rapping)

What are the 2 types of songbirds we studied?

1) age limited learners

2) open ended learners

What is the definition of a song? (for songbirds)

a series of syllables that last for seconds to minutes

What about a song is unique to each species?

its structure

Describe the degree to which diversity exists between species of songbirds.

some species can only produce a single song but others can produce over 100 different song types

Do male or female songbirds sing?

in some species only the male sings, in some it is mixed

What 2 reasons do males sing?

1) establishment or defense of a territory

2) courtship - females get to choose mates & individual song characteristics will often be the deciding factor

What makes a bird an age-limited learner?

they learn to sing only if exposed to song during a critical period early in life

(for swamp sparrow, within 10-60 days of hatching)

What are the 3 stages of song learning in age-limited learners?

subsong

plastic song

crystallized song

What does song-learning in age-limited learners depend on? (besides exposure during critical period)

the bird being able to hear himself

What/when is the subsong?

~8 months,

starts to emit sounds w/ remote resemblance to actual song

What/when is plastic song?

~10 months,

the song is more polished but the syllables are out of order

What/when is crystallized song?

by 12 months,

song has a well-defined, invariant structure

Describe T and E levels during song learning in age limited learner.

During the critical period (exposure to adult song) between day 10 and day 60, E levels rise slightly, afterward decline but not back to pre-CP level; while T level rises more dramatically than E but returns to pre-CP level.

- during plastic song phase T starts rising, plateaus just before crystallized song phase begins -- CRUCIAL for crystallization

What defines an open-ended learner? Give an example of an open-ended learner.

can learn new songs throughout their lives

ex: canary

3 stages of song learning in open-ended learners?

subsong

plastic song

stereotyped, adult song

When does subsong begin in open-ended learners?

Plastic song?

Stereotyped, adult song?

When does subsong begin in open-ended learners?

Plastic song?

Stereotyped, adult song?

subsong - around 40 days after hatching

plastic - at about 60 days

stereotyped adult song - by 8 months

Describe the stereotyped, adult song of an open-ended learner during and after the breeding season.

- relatively stable in structure during the breeding season

- after breeding season, syllables are modified, dropped, or added

What does HVC stand for in the bird brain?

high vocal center

What results from estrogen treatment in newly hatched female zebra finches?

What about additional treatment with androgens in adulthood?

What results from estrogen treatment in newly hatched female zebra finches?

What about additional treatment with androgens in adulthood?

- greater neurogenesis in HVC and area X

- male song

What results from anti-androgen treatment / 5-alpha reductase inhibitor treatment in juvenile male zebra finches?

smaller lMAN, area X, RA

What is the result of castration & anti-androgen treatment of young male zebra finches?

song does not become crystallized

Describe the activational effects of testosterone on adult song in zebra finches.

castration markedly reduces song production;

partially restored with testosterone propionate;

reduced again after TP withdrawal

Describe song production, plasticity (canary), testosterone level, and song nuclei size during breeding season.

production, T level, and song nuclei size are all higher during breeding season while plasticity (canary) is lower.