Hormones and Parental Behaviour Flashcards
what is parental care?
investment in young after fertilisation (direct or indirect)
(Roland & O’Connell, 2015)
1. what did they look at?
2. any pattern across vertebrate taxa?
3. what is the most common parental care in mammals, birds and reptiles?
4. overall?
- parental care in different classes - percentage of species that show parental care and percentage of biparental, female, and male care
- variation across vertebrate taxa
- mammals - 100% species show parental care - majority female (90%) care
birds - >99% species show parental care - majority biparental (90%) care
reptiles - roughly 3% species show parental care - majority female (>95%) care
- lots of variation
little or no parental care
no parental care - e.g. eggs layed and then left
little parental care - Nile Crocodile -> carry offspring to water once hatched then left
Parental care and development of offspring
1. precocial?
2. altricial?
3. what are rat pups born as, and how does this impact parental care?
- precocial = developed
- altricial = underdeveloped
- rat pups born at underdeveloped stage (altricial) - require more parental care than precocial
Oxytocin
1. where is it synthesised?
2. where is it stored and released from?
3. what are the functions?
- synthesised in the hypothalamus
- stored and released from the posterior pituitary
- functions: Uterus contractions during childbirth, stimulation of lactation, pair bonding, orgasm, parental behaviours
oxytocin & lactation
how does oxytocin work in the release of milk from the nipple?
- stimulation of nipple -> brain activity in mother
- The hypothalamus receives sensory information
- Oxytocin released from posterior pituitary
- oxytocin causes cells of mammary glands to contract -> release of milk
positive feedback mechanism
Isotocin
1. what animal uses this instead of oxytocin, with specific example?
2. what does it promote?
- fish - clown fish and other monogamous fish
- promotes paternal care
Prolactin
1. where is it secreted from?
2. functions?
- secreted from the anterior pituitary
- functions: stimulates and maintains milk production in mammals, plays a significant role in BOTH maternal and paternal care across various vertebrate taxa, “Hormone of parenthood”
Hormones & parental care in birds
1. increase in sex steroid hormones (steroids, LH, FSH) coincident with?
2. peak in sex steroid hormones during?
3. high prolactin levels during?
- courtship
- egg-laying
- incubation
Hormones & parental care in birds
Avian maternal behaviour (“broodiness”)
1. broodiness meaning?
2. what hormones are involved?
3. what is this sustained by?
4. what is ovariectomy and what does it eliminate?
5. what restores maternal behaviour?
6. how can prolactin lead to paternal behaviour?
- = a strong desire to have a baby
- progesterone/oestradiol (type of oestrogen)
- sustained by prolactin (ventrum stimulation)
- = removal of one or both ovaries - eliminates incubation behaviour
- treatment with estradiol AND progesterone restores behaviour
- ventrum stimulation leads to secretion of prolactin + high prolactin ensures birds continue to incubate the eggs -> positive feedback loop
Hormones & parental care in birds
avian paternal behaviour
1. examples of behaviours?
2. what hormone is involved in courting?
3. what is independent of hormonal status?
4. what does oxytocin stimulate?
5. what hormone is necessary for incubation behaviour?
- courting (T), nest-building, incubating, feeding
- Testosterone
- maintenance of nest-building independent of hormonal status
- oxytocin stimulates brooding
- testosterone necessary for incubation behaviour
Prolactin & parental care in birds
1. what does the injection of prolactin lead to?
2. what does prolactin stimulate?
3. what is crop milk?
- to an increase of parental care in male and female ring doves
- the production of crop milk
- secretion from lining of the crop, regurgitating to young birds (pigeons, doves, flamingos and some penguins); extremely high in protein and fat; anti-oxidants, antibodies, some bacteria
- in penguin species that produce crop = only male
Prolactin & parental care in birds
1. what happens to prolactin and food consumption post-laying?
2. what happens to crop mixture when prolactin levels fall?
3. how does the content of crop change as time goes on?
- prolactin and food consumption increase post-laying
- crop mixture changes when prolactin levels fall
- content of crop changes to more food and insects as young grow -> decrease in prolactin -> decrease in crop weight -> increase in food intake
Prolactin & parental care in birds
1. Florida scrub jay and helpers?
2. how does prolactin vary between breeding Florida scrub jay males and females and helpers?
3. how does prolactin vary between helpers and non-helpers?
- Florida scrub jay - previous offspring help to feed young, look after nest, watch for predators etc.
- Breeding Florida scrub jay males and females have higher prolactin levels than helpers
- higher prolactin in helpers than non-helpers
Hormones & parental care in mammals
1. what is used due to specialised parental behaviour?
2. hormones involved?
- mammary glands
- progesterone, oestrogens, oxytocin, prolactin, cortisol, testosterone, vasopressin, endorphins
(from: Wynne-Edwards & Reburn, 2000, TREE)
how does estradiol (oestrogen) effect maternal behaviour?
rises to peak at parturition (childbirth) then sharply declines following birth. The prepartum rise is important for the onset of maternal behaviour
(from: Wynne-Edwards & Reburn, 2000, TREE)
how does progesterone effect maternal behaviour?
withdrawal before the birth facilitates the onset of maternal behaviour
what occurs at the end of a pregnancy with oestrogen and progesterone?
sharp increase in oestrogen and decrease in progesterone, just before birth
(from: Wynne-Edwards & Reburn, 2000, TREE)
how does prolactin effect maternal behaviour?
production and release are facilitated by other hormones implicated in control of parental care (e.g. estradiol, oxytocin and vasopressin). Hypothalamic administration before the birth facilitates the onset of maternal behaviour
(from: Wynne-Edwards & Reburn, 2000, TREE)
prolactin - measurements in paternal males?
California mouse, Mongolian gerbil, Djungarian hamster, cotton-top tamarin, common marmoset and human
Prolactin & paternal care
1. examples of species that males experience increase in prolactin?
2. what are male prolactin levels compared to female prolactin levels?
3. how do fathers engage in parental care - California mouse?
4. what occurs with marmoset fathers when with infants, compared to nonpregnant females and pregnant females?
- California mouse and marmoset fathers
- fathers have almost as high prolactin levels as mothers
- fathers engage in any aspect of parental care - share care for this species
- Marmoset fathers - when with infants, prolactin levels are increased
Endocrine correlated of human paternal behaviour
1. what does an expectant human father show?
- how do prolactin levels vary between fathers and nonfathers?
- reduced testosterone concentrations - links to decrease in aggression
- reduced cortisol concentrations
- increased estradiol concentrations
- fathers have higher prolactin levels than nonfathers (Gettler et al., 2012)
Endocrine correlates of human paternal behaviour
1. what about oxytocin (OT)?
- little is known about oxytocin in human fatherhood and paternal caregiving
Endocrine correlates of human paternal behaviour
(Grumi et al., 2021)
1. what happens to fathers OT (Oxytocin) levels after childbirth?
2. what is OT significantly correlated with?
3. what is OT not correlated with?
4. what were fathers’ and childrens’ OT levels significantly correlated in?
- increase
- less hostility and with the quality of paternal physical stimulation in play interactions
- not correlated with paternal sensitivity
- father’s and childrens’ OT levels were significantly correlated in a limited subset of studies
Hormones & parental care in fish
what causes:
1. nest building?
2. defense?
3. fanning and brooding?
- nest building: high androgen levels, often together with territoriality and courtship
- defense: high T & 11-keto T during pre-spawning; androgen levels gradually drop following spawning; trade-off between aggression and parental care
- fanning and brooding: e.g. prolactin stimulates fanning in 3-spined sticklebacks and bluegill sunfish; elevated prolactin levels during mouth-brooding in Nile tilapia
Prolactin & parental care in fish
1. what does injection of prolactin lead to in male and female discus ((Symphysodon aequifasciata)?
2. what does prolactin lead to?
- leads to increase of fanning behaviour in male and females
- leads to increase in mucus cell production (“discus milk”) - both male and female produce it
Endocrine Analogies
1. discus fish
2. birds
3. mammals
4. endocrine regulation of endogenously produced…
- discus milk
- crop milk
- mammalian milk
- food for young
milk provisioning in amphibians
(Mailho-Fontana et al., 2024)
1. hormonal regime during parental care?
2. what does female produce?
3. what is the production of “milk” stimulated by?
- unknown - early on in research
- some sort of food - “milk-like substance” - that offspring feed on
- production of “milk” is stimulated by tactile and sound by the offspring
