Lecture 21: Reproduction III Flashcards
timing
- reproduction requires energy
- young produced during peak food abundance
capital breeders
use endogenous resources (stored nutrients) to fuel reproduction
examples of capital breeding:
emperor penguins, baleen whales, some seals
income breeders
use exogenous resources (taking in new food materials) to fuel reproduction
examples of income breeders
some seals, bats, and some copepods
induced ovulators
ovulation occurs due to external stimulus, such as mating
examples of induced ovulators:
- some carnivores, rodents, rabbits
- dromadery, alpaga, shrew, rhino
spontaneous ovulation species
sow, cow, ewe, mouse, macaque, dog
signaling ovulation
???
concealed ovulation
- promote male paternal care
- confuse paternity
example of concealed ovulation:
hanuman langurs
delayed fertilization
- sperm stored over winter hibernation
example of delayed fertilization
bats
delayed implantation
- reproductive strategy where a fertilized egg pauses its development and remains in a dormant state, delaying implantation in the uterus until conditions are favorable for the embryo’s survival
examples of delayed implantation:
cats, rodents, seals, armadillos, bears
embryonic diapause
temporary, reversible pause in embryonic development, specifically at the blastocyst stage, allowing for delayed implantation and birth when conditions are optimal
example of embryonic diapause
kangaroo
sequences of reproductive events of monkey:
- ovulation
- copulation
- fertilization
- implantation
- gestation
- parturition
- lactation
concealed ovulation
sequences of reproductive events of lynx:
- copulation
- ovulation
- fertilization
- implantation
- gestation
- parturition
- lactation
induced ovulation
sequence of reproductive events of bat:
- copulation
- delay
- ovulation
- fertilization
- implantation
- gestation
- parturition
- lactation
sperm storage/delayed fertilization
sequence of reproductive events of bear:
- ovulation
- copulation
- fertilization
- delay
- implantation
- gestation
- parturition
- lactation
delayed implantation
sequence of reproductive events of kangaroo:
- ovulation
- copulation
- fertilization
- delay
- implantation
- gestation
- parturition
- lactation
embryonic diapause
FSH and LH
come from pituitary gland, induce ovulation
estrogen
coming from developing follicle, leads to development of uterine wall
chorionic gonadotropin
comes from uterine wall, sends signal to corpus luteum that implantation has taken place
progesterone
produced by corpus luteum, often regarded as the “pregnancy hormone” (at 3 months gestation, the placenta takes over secretion of progesterone)
image from slides
hormonal fluctuation
- LH and FSH spikes trigger ovulation
- estrogen and progesterone levels fluctuate, influencing uterine lining
ovarian changes
- the follicle matures, leading to ovulation
- after ovulation, the corpus luteum forms and secretes progesterone
- if fertilization occurs, Chorionic Gonadotropin (CG) maintains progesterone production
uterine lining (endometrium) changes
- menstrual phase: shedding uterine lining
- proliferative phase: thickening of the lining due to estrogen
- secretory phase: further development, supported by progesterone
sexual selection
- selection arising through preference by one sex for certain characteristics in individuals of the other sex
example of sexual selection
peacock
male signals
- tend to signal male quality (health, vigor)
- energetically expensive (to serve as honest signal)
- tradeoffs with high testosterone
“weapons”
- traits, often elaborate and diverse, that evolved through male-male competition for access to mates or resources that attract females
examples of “weapons”
horns, antlers, large body size, or aggressive behaviors
- seen in moose, elk
“charms”
- conspicuous traits that evolve through enhancing an individual’s ability to attract a mate or compete for mating opportunities
examples of “charms”
bright plumage, large horns, or elaborate displays
- seen in types of monkeys
Lekking
- congregation of males displaying for females
- a small number of males do a majority of the mating
- hot shot hypothesis
- hotspot hypothesis
hotshot hypothesis
hotspot hypothesis
testosterone
increases male competitiveness, decreases parental care, also somewhat involved in female reproduction
testosterone drive male sexual phenotypes
looking at house sparrows:
- they have patch on throat called badge
- larger badge size = higher testosterone
- females choose based on badge
trade off with testosterone: basal metabolic rate
- higher testosterone = higher BMR
- increased energetic costs due to increased metabolism
trade off with testosterone: immune response and oxidative stress
- higher testosterone = decreased immune function and decreased resistance to oxidative stress
trade off with testosterone: prenatal care
- unmanipulated males (“normal” levels of testosterone) = all incubating young
- control males = all incubating young
- implanted/manipulated males = some incubating young (30%), but most did so sporadically (50%) and a good amount completely deserted their young (20%)
extrapair mating
- females will often build parental bond with a low-T male (higher prenatal care)
- females will often seek out extra-pair copulations with high-T males (to increase fitness of offspring)
differences in sexual selection between males and females
- males compete for mates, females often compete for access to resources
- sexual selection in females may be more constrained if development of traits depresses reproduction
spotted hyena
- gregarious carnivores
- female dominated hierarchy- inherited
- pseudo-penis (enlarged clitoris) that can sometimes result in suffocation during birth
hyenas have female-dominated social hierarchies that are inherited
- social rank is inherited from mom to baby
- higher social rank = produce larger # of offspring, higher level of offspring more survival, higher level of androgens in fecal matter (so higher testosterone levels)
- more maternal fecal androgens = more cub aggression
why does all that stuff happen in hyenas?
- no correct answer at this point
- possible reasoning includes sperm competition and side effect of high testosterone
male choice based on female traits: olive baboons
- promiscuous during estrus
- anal swelling increases body by 14%, constitutes an extra load as well as constrains locomotion and sitting
- parasite prone skin
- often thought to be important as a sexual signal
does swelling size correlate with reproductive output?
- males prefer females with larger swellings
prenatal care
nest building, guarding, carrying
parental care often extended
providing food and nursing
parental care is expensive
lactation is the most energetically demanding period for a female mammal
prolactin
induce parental care behaviors
prolactin: males vs females
prolactin is more abundant in females than males
- seen during behaviors like prelaying, incubation, brooding, shading, rearing, post-fledging
brood parasitism
a strategy where one species relies on another to incubate its eggs and raise its young
- ex: catfish lay eggs among cichlid eggs
