Transcript Hormones

大學部 生態學與保育生物學學程 (必選)
2010 年 秋冬
生理分析(二)內分泌
(Physiological analysis)
─動物行為學 (Ethology)
鄭先祐(Ayo)
國立 臺南大學 環境與生態學院
生態科學與技術學系 教授
Ayo NUTN Web: http://myweb.nutn.edu.tw/~hycheng/
Part 1. 動物行為的研究途徑 (個體行為)
 歷史背景 (History of the Study of Animal
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Behavior ).
基因分析 (Genetic Analysis of Behavior ).
天擇 (Natural Selection and Behavior ).
學習與認知 (Learning and Cognition.)
生理分析 (Physiological Analysis)
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(一) 神經細胞 (Nerve Cells and Behavior ).
(二) 內分泌系統 (The Endocrine System).
 發育(The Development of Behavior ).
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6b 生理分析(二) 內分泌
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The endocrine system
How hormones influence behavior
Methods
Organizational and activation effects of
hormones
 The dynamic relationship between
hormones and behavior
 Interaction between hormones,
behavior, and the environment
 A detailed look
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The endocrine system
 Male plainfin midshipman fish display two
reproductive strategies
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Type I males: build nests and hum to court females
Type II males: sneaky cuckolders that don’t build nests or
hum
 Type II males sneak into the type I’s nest and spawn or
lie outside the entrance and deposit sperm there while
fanning water toward the nest’s opening
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They must avoid detection by territorial males
The sperm of the type II male competes with that of the
type I male, who did all the work
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 The midshipman fishes are the genus Porichthys of
toadfishes(蟾魚) .
 Typical midshipman fishes, such as the Plainfin
Midshipman, are nocturnal and bury themselves in
sand or mud of the intertidal zone during the day. At
night they float just above the seabed.
 Some species are armed with venomous dorsal spines
and are capable of inflicting serious injuries if handled.
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More differences between type I and II males
 A type I male is larger and takes longer to sexually mature
Sonic muscles produce the droning hum (雄蜂的嗡嗡聲)
attractive to females
 The specialized brain allows him to hum his courtship song
 He has large motor neurons to the sonic muscles and the
brain center controlling those muscles
 Type II males become sexually mature sooner, but can’t attract
mates
 Sonic muscles are not well developed
 The ratio of testes to body weight is much higher than type
I’s

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A Type II male resembles a gravid female
 Because of his bulging(腫脹的) gonads
 His coloration is also similar to that of a female
 It is easier for him to lurk around the nests of type I males
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Sneaky cuckoldry：a “fixed” behavioral
strategy
 Type II males will not hold territories or court females
even when both options are offered
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Their morphology prevents behavioral plasticity - the
ability to switch to an alternative behavior
 Type I males cuckold other type I males if given the
chance
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They take advantage of their large size and aggressively
resist ejection by resident type I males
They exhibit aggressive cuckoldry when not humming
(發嗡嗡聲); and defending a nest
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案例：20HE protects female crabs
 A soft-shelled female is extremely vulnerable to predation
By fish, octopus, other crustaceans - including other crabs
 The female releases 20HE (20-hydroxyecdysone) to deter
(嚇住) her mate from eating her
 It is not acting as a hormone (i.e. regulating molting)
 But as a pheromone: a chemical substance that functions
in communication between individuals of the same
species
 20HE may deter feeding in other species of predatory
crustaceans
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Thus, a chemical signal may function
 Within an individual
 i.e. as a molting hormone in arthropods
 Between individuals of the same species
 i.e. as a sex-specific feeding deterrent during mating,
and
 Between individuals of different species
 i.e. as a feeding deterrent
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Mechanism of action of
peptide hormones
 Activates enzymes
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For long-term changes in
protein function
 Examples: luteinizing
hormone (LH) and folliclestimulating hormone (FSH)
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Mechanism of action of
steroid hormones
 Once inside a cell, steroids
combine with receptor molecules
 If binding occurs in the cytoplasm
 This complex moves to the
nucleus
 And attaches to DNA
 Affecting gene expression and
protein synthesis
 Takes hours or days and produces
long-lasting effects on behavior
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How hormones influence behavior
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Hormones modify behavior by affecting
1. Sensory or perceptual mechanisms
2. Development or activity of the central nervous
system, and
3. Muscles important in the execution of behavior
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Effects on sensation and perception
 Hormones influence the ability to detect certain stimuli
And the responses to and preferences for particular stimuli
 In some species, mate choice is based on hormone-mediated
differences in the ability to detect stimuli
 Female domestic pigs are attracted to the boar(雄豬)
pheromone, 16-androsterone, while males are not
 Castrated males given the female hormone estradiol show
female responses to a boar
 Hormones can mediate behavioral responses to stimuli
 Vasotocin: a peptide hormone in non-mammalian
vertebrates similar to the mammalian hormone vasopressin
(血管加壓素 )
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Vastocin influences mate choice in males
 Vasotocin enhances male responsiveness to female
stimuli
 Male newts first rely on visual cues (i.e. size, shape, and
color)
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Then switch to olfactory cues for close-up confirmation of
species, gender, and reproductive state
The male clasps the gravid female for hours in amplexus
The female becomes sexually receptive
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 A newt is an
amphibian of the
Salamandridae
family, although not
all aquatic
salamanders are
considered newts.
 Newts are classified
in the subfamily
Pleurodelinae of the
family
Salamandridae, and
are found in North
America, Europe and
Asia.
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Hormones can cause a change in preference
in animals
 Sex steroids can change social preferences
 Given a choice of social partner, young animals that received
parental care prefer family members
 As they mature, they prefer non-family members
 Hormone-mediated changes in social preference are not limited
to maturing animals
 In winter, adult female meadow voles prefer other females
 During mating season (spring and summer), they prefer
males
 This reversal in preference is caused by higher estrogen
levels, associated with longer days
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Effects on development and activity of the
central nervous system
 Circulating hormones affect behavior by influencing the
central nervous system
 They influence different regions of the brain, including
the
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(1) volume of brain tissue
(2) number of cells in brain tissue
(3) size of cell bodies
(4) extent of dendritic branching
(5) percentage of neurons sensitive to particular
hormones
(6) survival of neurons
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Hormones influence development of
singing behavior in birds
 In the zebra finch, sex differences in the brain
nuclei that control song are established around the
time of hatching
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Soon after hatching, the brain’s hormonal
environment establishes sex differences in adult
singing behavior (males sing and females do not)
The steroid hormones involved in the early
masculinization of the zebra finch brain are
neurosteroids, not gonadal steroids
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Hormones affect muscles and motor neurons
 South African clawed male frogs emit six different calls
 The advertisement call allows females to find males
 Sexually receptive females produce a rapping call
 Unreceptive females tick
 Hormone-induced changes in the muscles of the larynx
results in sex differences in calling behavior
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 Differences in the calling
behavior of male and
female clawed frogs result
from the effects of
hormones on the muscles
of the larynx.
 (a) the male’s call consists
of slow and fast trills
 (b) unreceptive female
emit the ticking call.
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Hormones influence sex differences in muscles
 Most mammals have sexually dimorphic muscles and
motor neurons
 Sex differences in the copulatory movements of adult
rats result from early hormonal influences
 Specialized muscles control copulatory reflexes in male
rats
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These muscles are present in both sexes at birth
But are completely absent in adult females, due to a lack
of androgen at birth
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An exception to the pattern
 Naked mole-rats (裸鼴鼠): cooperatively breeding
rodents living in colonies
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The queen is the only breeding female
Subordinates and males show few sex differences
 The queen’s enlarged levator(提肌) ani muscle helps her
deliver enormous numbers of offspring
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 Muscles of the
perineum are sexually
dimorphic in most
mammals, being
larger in males than in
females as a result of
the early effects of
androgens. The
levator ani muscle of
the queen is larger
than that of breeding
males.
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Studying hormone–behavior relationships:
interventional studies
 The experimenter manipulates the hormones of the
animal
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Removes the endocrine gland
Followed by hormone replacement therapy
 For example, testosterone regulates courtship and
copulation in the male green anole
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What happens when the testes are removed?
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 Displays of the male green
anole.
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Removal of testes changes behavior
 Removal led to a sharp decline in sexual behavior in
green anoles
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Administration of testosterone reinstated this
behavior
 Unlike sexual behavior, aggressive behavior only
partially depends on gonadal hormones
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It’s also influenced by social factors such as residence
status
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 Effect of castration and testosterone replacement
therapy on the courtship behavior of the male green
anole.
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Interventional studies have become
sophisticated
 Cannulation techniques(輸管技術) administer tiny
amounts of hormone to specific regions
 Antihormones: drugs that temporarily and reversibly
suppress the actions of specific hormones
 The antihormone RU486 blocks progesterone (黃
體激素) receptors
 Genetic “knockout” mice have a specific gene
inactivated to eliminate the gene product (i.e. a hormone
or hormone receptor)
 Progesterone receptor knockout (PRKO) mice do
not respond to progesterone because they lack the
appropriate receptors
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Male mice respond to hormones
Male laboratory mice are aggressive toward infants and kill them
 Males with progesterone
implants attack pups
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Males given RU486
don’t attack pups
 PRKO male mice do not
respond to progesterone
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Are not aggressive to
infants
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Studying hormone–behavior
relationships: correlational studies
 Researchers look for changes in behavior that parallel
fluctuations in hormone levels
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Not as conclusive as experimental work because there
is no evidence of causation
 One correlational study examined the relationship
between testosterone levels and aggressive behavior
in male song sparrows
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Correlation between behavior and
hormones
 A close correlation exists between male song sparrow
territorial and aggressive behavior and maximum levels of
testosterone
• Testosterone increases
aggressive behavior in
song sparrows - but the
reverse is also true
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Steroid hormones influence behavior through
organizational effects
 In organizational effects, steroids organize neural pathways
responsible for certain patterns of behavior
 Occur early in life - just before or after birth
 Are permanent: the brain or cells change structurally
 i.e. in the responsiveness of neurons to steroid hormones
 organizational effects on nonneural systems
 i.e. changes to the male western mosquitofish fin and its
skeletal supports cause sex differences in mating
behavior
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Activational effects
 Activational effects: occur in adulthood and tend to
be transient
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Lasting only as long as the hormone is present at high
levels
 Involve subtle changes in previously established
connections
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i.e. slight changes in neurotransmitter production or
release along established pathways
Not involved in gross reorganization of neural
pathways
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Organizational & activational effects of steroid
hormones in Norway rats
 Adult male and female rats differ in
their sexual behavior
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Male behaviors: social investigation,
mounting, intromission, and
ejaculation
Female behaviors: associated with
solicitation(誘惑) and
acceptance(接受)
• Differences in adult copulatory behavior are due to differences
in the brains of male and female rats
• Differences are induced by irreversible actions of androgens in
late fetal and early neonatal life
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The organizational effects of gonadal steroids
on sexual behavior
 Development of a “male” brain requires testosterone
around the time of birth
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In the absence of testosterone, a “female” brain
develops
 The effects of perinatal testosterone on adult sexual
behavior are organizational
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Occur early in life and involve permanent structural
changes in the brain
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 Pattern of
sexual
differentiation
in the brain
and behavior
of the Norway
rat.
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Steroid hormones have activational
effects on sexual behavior in rats
 Female rats with high estrogen and progesterone levels
display feminine sexual behaviors when near a
sexually active male
 Removal of the testes in an adult male eliminates
copulatory behavior
 Steroid hormone effects on sexual behavior are
activational
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Estrogen, progesterone and testosterone exert their
effects by activating existing neural pathways.
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Adults vs. juvenile responses to sex
steroids
 Activational hormones: sex steroids in adults have
only a transient activational effect on copulatory
behavior
 By adulthood, the nervous systems of adult males
and females have already differentiated
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The organizational effects of early steroid secretion
have long since occurred
Mature brains are not capable of responding to
hormonal signals of the opposite sex
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Individual differences in the behavior of
male tree lizards
 Individual differences are most pronounced in species
with naturally occurring alternative male phenotypes
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Such as tree lizards
 The tree lizard has alternative male phenotypes that
differ in aggressive behavior and color of the dewlap
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Aggressive males have orange-blue dewlaps
Nonaggressive males have orange dewlaps
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 The Tree lizard or
Ornate Tree Lizard
(Urosaurus ornatus)
is a species of lizard
that is native to the
southwestern United
States and northern
Mexico.
 The species has been used to research the physiological
changes in the body during the fight-or-flight response as
related to stress and aggressive competition. Also, its life
history and costs of reproduction have been documented in
field populations in New Mexico.
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Nonaggressive males (relative plasticity
hypothesis)
 The differences are organized by steroid hormones
during the neonatal period.
 The two types of males have similar hormone profiles in
adulthood.
 Nonaggressive males are flexible in their territorial
behavior, switching between sedentary (定點) and
nomadic(遊走) behavior in response to environmental;
conditions. (developmentally plastic)
 When conditions become stressful, the hormone
corticosterone rises and ultimately reduces site
fidelity(忠誠度), triggering nomadic behavior in
nonaggressive males.
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Developmentally fixed & developmentally
plastic phenotypes
 When phenotypes are developmentally fixed, they can’t
change
 Caused by organizational effects of steroid hormones
in neonates
 Developmentally plastic phenotypes can change
 Behaviors change in response to environmental
conditions
 Changes in adult hormone levels reflect activational
effects
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A reciprocal relationship between
hormones and behavior
• Hormones can activate specific forms of behavior
– And behavioral stimuli can induce rapid changes in
hormone levels
 Sexual stimuli can trigger a rapid increases in
androgen levels
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In the marine toad, androgen levels increase with
time spent in amplexus
Suggesting that mating behavior induced the
hormonal response rather than vice versa
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 Changes in
plasma
androgen in
male marine
toads as a
function of
the time spent
in amplexus.
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 Amplexus (Latin "embrace") is a form of
pseudocopulation in which a male amphibian
grasps a female with his front legs as part of the
mating process. At the same time or with some time
delay, he fertilizes the female eggs with fluid
containing sperm.
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Hormonal suppression of behavior
 Androgens and vasotocin mediate amplexus in newts
Males clasp a female while she becomes sexually
receptive
 What happens if a male in amplexus detects a predator?
 Does he continue with amplexus and “hope for the best?”
 Or terminate the behavior and seek a safe hiding place?
 The hormone corticosterone suppresses amplectic behavior
 Reducing the activity of neurons active during amplexus
 It acts via a receptor in the membrane of neurons, not by
altering gene expression and protein synthesis
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Hormones rapidly change behavior
 The dynamic interactions between hormones, behavior,
and the nervous system allow the behavioral state of
an animal to shift rapidly and adaptively to changing
environmental circumstances.
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Hormones allow an animal to adjust its behavior so that
it is appropriate for the situation at hand
 Hormones, behavior, and the environment interact
to generate adaptive behavior in the long term
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Adjusting to the environment
 Habitats of species provide different mating opportunities
Associations between gonadal hormones and sexual
behavior varies among species
 To allow the greatest number of surviving offspring
 A diversity of reproductive patterns exits in:
 (1) production of gametes
 (2) secretion of sex steroids by the gonads, and
 (3) timing of mating behavior
 Three general patterns of reproduction exist in vertebrates:
associated, dissociated, and constant (but other patterns
exist)
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Associated reproductive pattern
 Some animals (i.e. the
Norway rat) exhibit a close
temporal association
between gonadal activity
and mating
 Gonadal growth and
increased levels of sex
steroids activate mating
behavior
 Found in most vertebrates
studied
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Dissociated reproductive pattern
 Mating behavior is completely uncoupled from gamete
maturation and secretion of sex steroids
 Gonadal activity occurs after all breeding activity has ceased
 Gametes are produced and stored for the next breeding
season
 Gonadal hormones may not play a role in the activation of
sexual behavior
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Species exhibiting an associated
reproductive pattern
 Inhabit harsh environments with a predictable, but
narrow, window of opportunity to breed
 Specific physical or behavioral cue triggers mating
behavior
 Red-sided garter snakes range farther north than any
other reptile in the Western Hemisphere
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The mating opportunity lasts 1 to 4 weeks
 Male courtship behavior is activated by increased
ambient temperature following winter dormancy
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Not by testicular hormones
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 The Garter snake is a Colubrid snake genus common
across North America, ranging from Alaska and
Canada to Central America. It is the single most
widely distributed genus of reptile in North America.
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Hormones do not control red-sided garter
snake courtship
 Testicular activity is minimal in male snakes during the period
between emerging from hibernation and mating
 Five to ten weeks after males have left the den site and no
longer court females
 The testes grow and androgen levels increase
 Sperm produced is stored for use the next spring
 Males use environmental cues, not sex hormones, to determine
mating season
 In females, changes in sexual attractivity and receptivity are
mediated by physiological changes that occur as a
consequence of mating
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Constant (opportunistic) reproductive pattern
 Characteristic of species in
harsh environments (i.e.
deserts)
 Suitable breeding
conditions occur
suddenly and
unpredictably
 In desert-dwelling
animals, reproduction is
initiated by rainfall
 While waiting for breeding conditions
 Species maintain large gonads, mature gametes, and high
circulating levels of sex steroids
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Zebra finches show a constant
reproductive pattern
 Zebra finches live in the deserts of Australia
Droughts last for years, so males and females maintain
their reproductive systems in a constant state of readiness
 Rainfall produces flushes of grass seeds - food for young
 Courtship begins shortly after the rain starts to fall
 Copulation occurs within hours
 Nest building begins the next day
 Breeding readiness also varies with habitat predictability
 Birds in arid rangelands with unpredictable rainfall
patterns keep high levels of reproductive readiness

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Onlookers(旁觀者) in the social environment
 Male Siamese fighting fish are spectacularly colorful
They build mucus-covered bubble nests at the water
surface
 Nests attract females and are home for eggs and hatched
fry
 Males defend territories centered on their nest
 Social environment (presence/absence of an audience) and
territory status (presence/absence of a nest) (onlookers)
 Influence aggressive behavior and hormone levels in
males

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泰國鬥魚 (Siamese fighting fish)
 泰國鬥魚原產於泰國，別名
五彩搏魚，屬絲足鱸科，搏
魚屬。飼養鬥魚的歷史比較
早，這是比較容易飼養的觀
賞魚之一。
 在某些地區，以牠善鬥的特
性，作為娛樂的工具。
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Evidence of hormone-mediated aggression
 Aggressive behavior and levels of 11KT (an androgen
in fish that mediates aggressive behavior) in male
Siamese fighting fish were influenced by male territory
status and audience
 Males without a nest were less aggressive

And had lower 11KT levels, when a female audience or
no audience was present
 In the presence of another male, males were less
aggressive

And had lower 11KT hormone levels, when both had
nests
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Male Siamese fighting fish behavior
 Experimental
setup for testing
the response of
male Siamese
fighting fish to
presence and
type of
audience.
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Male Siamese fighting fish behavior
 In males, 11KT levels
are influenced by the
presence of a nest and
an audience
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The hormonal basis of helping at the nest
 Helpers: nonbreeding animals that assist the breeding pair
in rearing young

Providing food and protecting the young
 The evolutionary causes of helping: helpers get some of
their genes into the population even though they don’t
breed
 Florida scrub jays live in small groups in south central
Florida scrub oaks

Helpers: offspring of the breeding pair from a previous year
who remain on the territory and help raise siblings
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Florida Scrub-Jay
 The Florida Scrub-Jay
(Aphelocoma coerulescens)
is one of the species of
scrub-jay native to North
America.
 It is the only species of
bird endemic to the U.S.
state of Florida.
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The physiological basis of helping behavior
 Helpers are physiologically capable of reproduction
 Their testes and ovaries produce hormones
 They can gather enough food to breed successfully
 Levels of the stress hormone corticosterone (suppresses
production of reproductive hormones) equal breeders’
 Prolactin levels increase through the breeding season,
initiating parental care



Females produce more prolactin than males
Cues from the nest, eggs, and nestlings stimulate production
Helpers have low prolactin levels because breeders won’t
allow them near the nest until the young have hatched
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Prolactin levels are lower in helpers
 There is a relationship
between a helper’s level of
prolactin and the feeding
score (a measure of how
much a bird fed the nestlings)


Feeding score = 0: helpers
didn’t help
Prolactin levels of the
helpers that did help are
much higher
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Scent-marking
 Scent-marking: the act of strategically placing a
chemical mark in the environment


Many mammals apply urine, feces, or secretions from
special scent glands on the digits, legs, chest, belly,
head, or in the anal canal
Many mammals have scent glands at multiple locations
 Scent marks convey information about individual
identification, age, and reproductive state

Establish and maintain territories and breeding
relationship
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Urine-marking by domestic dogs
 Urinary behavior is sexually dimorphic
 Adult males urinate more frequently than adult females
 And are more likely to urine-mark
 Urinary posture is sexually dimorphic: males lift a leg to
urinate, females squat
 Sex differences in urinary posture are organized by sex
steroids (testosterone) around the time of birth


But testosterone is not needed for the leg-lifting posture
A neutered male still lifts his leg to urinate
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Urine marking in female dogs
 Urine marking is more common
than previously described for
female dogs
 The propensity to mark with urine
varies across the estrous cycle


Most common just before and
during estrus
Conveys information about her
reproductive state
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Hormones affect salmon migration
 Adult Atlantic salmon leave the ocean and return to their
natal stream to spawn in the fall



Laying thousands of large, fertilized eggs in a gravel
depression called a redd
Parr: very young salmon, 5 cm long, with vertical marks on
their sides for camouflage
Smolt: 15 cm long fish that undergoes smoltification, which
prepares them for migration to the ocean
 Dramatic changes in physiology, morphology, and
behavior occur during changes from parr to smolt

To prepare for migration
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Atlantic salmon
 Salmon is the common name for several species of the
family Salmonidae.
 Several other fish in the family are called trout; the
difference is often said to be that salmon migrate and
trout are resident, a distinction that holds true for the
Salmo genus.
 Salmon live along the coasts of both the North Atlantic
(one migratory species Salmo salar) and Pacific Oceans
(approximately a dozen species of the genus
Oncorhynchus), as well as having been introduced into the
Great Lakes of North America.
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Young salmon change dramatically
 Parr marks are replaced by silver in smolt to evade (躲
避) predators
 Young salmon change their position in the current


Parr face into the current (positive rheotaxis) to see food
coming
Smolts face downstream (negative rheotaxis) for their
impending migration to the sea
 Social behavior also changes
 Parr aggressively defend individual feeding territories
 Smolts exhibit decreased territorial and agonistic behavior
and eventually form schools
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Environmental factors initiate and
hormones mediate changes
 Environmental factors (i.e. high water flow and
increasing photoperiod and temperature) prompt
smoltification
 Hormones mediate physiological and morphological
changes




Prolactin decreases during smoltification
Growth hormone increases and increases tolerance for
saltwater
Cortisol promotes acclimation to a particular environment
Thyroid hormones replace parr marks with silver
coloration
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Summary
 Transfer of internal information by the endocrine system
occurs slowly, with general, long-lasting effects
 Communication occurs through hormones and
neurohormones that produce changes at the cellular level
 That ultimately influence behavior
 Two types of hormones are peptide and steroid hormones
 Hormones influence behavior by affecting: sensation, the
central nervous system, or muscles responsible for the
execution of behavior
 Effects of steroid hormones on behavior have been divided
into organizational and activational effects
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Summary
 Hormonal effects on behavior can be studied by
interventional studies or correlational studies
 Hormones initiate changes in behavior

And behavior can causes changes in levels of hormones
 Interactions between hormones and behavior are
sensitive to the physical and social environment
 Behaviors mediated by hormones include

Aggression, courtship, mating, caring for young, scentmarking, and migrating
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問題與討論
[email protected]
 Ayo 台南 NUTN 站
http://myweb.nutn.edu.tw/~hycheng/
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