Why do you think ears
evolved in Butterflies?
a)
b)
c)
d)
To define territory
Predation
Mating
All of the above
Rubina Khan & Connie Goudie
BIO 4420
ENVIRONMENTAL
PHYSIOLOGY
BIOLOGICAL CLOCKS
Light / dark cycle –
environmental cue
seasonal change in L:D
proximate cue for physiological adjustments
reproductive cycle
feeding, metabolism, hibernation onset
ultimate cue for specific activites
hunting, foraging
Circadian rhythms
predictable fluctuations in physiological functions and activities
linked (synchronized) to L:D
persist in constant dark (circa = about, dies = day)
Circadian clocks
suprachiasmatic nucleus (SCN) located in hypothalamus
Suprachiasmatic nucleus
component in a direct neural pathway between retinal input and
CNS
Link between retinal input (light cues), pineal gland and pituitary
SCN communicates circadian signals to other parts of CNS
SCN communicates circadian signals to:
ventromedial nucleus (feeding, appetite)
paraventricular nucleus (ADH, oxytocin)
nuclei, tracts
lesion in SCN-effect?
transplant of SCN neurons-effect?
Melatonin – “night” hormone
Daily rhythm of physiological functions in a human
Subject in a room under controlled
light cycle 16L:8D
Slept at night
12h is noon
0h and 24h is midnight
Rhythm in :
body temperature
plasma growth hormone
plasma cortisol
urinary potassium
Hill et al. 2004 Fig. 10.14
Activity rhythm in nocturnal flying squirrel
activity recorded on a running wheel for 23 days
each line represent one day
12h is noon
24h is midnight
a) Activity pattern is
entrained
under 12L:12D
b) Activity pattern is
free-running
under constant darkness
Hill et al. 2004, Fig. 10.16
Suprachiasmatic nucleus in the hypothalamus is the circadian clock of mammals
Location of SCN in brain
freerunning
rhythm
loss of
freerunning
rhythm
Hill et al. 2004, Fig. 10.17
Reproduction :
physiological function vital for survival of the species
(not the individual)
interest in fish reproduction
aquaculture
maintenance of wild fish stocks
protection of rare species
ecotoxicology – fish as bioindicators
other species?
Steps :
1. Maturation of gametes
2. Partner selection (identification/evaluation)
3. Fertilization of gametes
4. Development of zygote, embryo, larva
5. Survival of juveniles
Coordination and synchronization with and by environmental factors
Great diversity of adaptations
morphological
physiological
behavioural
Important role of the Nervous and Endocrine Systems in reproduction
K-type strategies vs r-type strategies
mammal vs fish
semelparity vs iteroparity
Hypothalamic-pituitary axis
walleye
sockeye salmon
swordtail
cichlid
goldfish
Moyle&Cech, p.123
Pathways for reproductive
stimulation and inhibition
in fishes
Cech&Moyle, p. 132
HORMONES
•BIOLOGICALLY ACTIVE CHEMICALS
•SYNTHESIZED, STORED, AND SECRETED BY:
ENDOCRINE GLANDS
(ductless) e.g. pancreas, thyroid, gonad
NEUROSECRETORY CELLS e.g. supraoptic nuclei of hypothalamus
•SECRETED INTO BLOOD
(free or bound)
•LOW CIRCULATING TITRES (e.g. insulin 5 X 10-12 M)
•SHORT BIOLOGICAL HALF-LIFE
e.g. insulin 5-8 minutes, testosterone 1 hour, FSH 3 hours, thyroxine 6
days
•PLASMA CLEARANCE BY:
TARGET CELL UPTAKE
ENZYMATIC DEGRADATION (liver)
URINARY EXCRETION
STRUCTURAL CLASSIFICATION OF HORMONES
1. PEPTIDES & PROTEINS
peptide hormones
protein hormones
3  >200 a.a.
(e.g. TSH-RH)
(e.g. insulin)
2. AMINES
thyroid hormones
catecholamines
tyrosine precursor
(e.g. epinephrine)
small, H20-soluble
3. STEROIDS
adrenal cortical hormones
(e.g. cortisol)
gonadal hormones
(e.g. estrogen, testosterone)
cyclic hydrocarbon derivatives
cholesterol precursor
lipid soluble
4. EICOSENOIDS
(autocrine, paracrine)
prostaglandins
cyclic unsaturated fatty acids
MECHANISM OF ACTION OF
hydrophilic chemical messengers
(e.g. LIPID-INSOLUBLE HORMONES)
peptides and proteins,
catecholamines
•usually not bound to carrier protein
•do not readily diffuse across membrane
•bind to membrane receptor
•H-R complex triggers production of 2nd
messenger
cAMP, cGMP (cyclic nucleotide
monophosphates)
IP3, DAG (inositol phospholipids)
Ca2+ ions
•rapid, short-lived responses; usually
metabolic
Transport of chemical messenger to the target cell
MECHANISM OF ACTION OF
hydrophobic chemical messengers
(e. g. LIPID-SOLUBLE HORMONES
steroid hormones
thyroid hormones
•bound to carrier protein in blood
•readily diffuse across membrane
•bind to cytoplasmic or nuclear receptor
•H-R complex binds to regulatory portions of
DNA
•stimulate (or inhibit) transcription of specific
genes
•and  specific proteins
•effects persist for hours to days
Transport of chemical messenger to the target cell
•Genetic sex in fishes
Some species : F (XX)
M (XY)
Others :
F (ZW)
M (ZZ)
Mammals: F (XX), M(XY)
Birds: F (ZW), M (ZZ)
•Phenotypic sex in fishes
1o sex characteristics : ovary, testes
Great vulnerability, sex change easily inducible
1. Hormonal status (experimental or endogenous)
e.g. treatment with methyltestosterone (F to M)
e.g. treatment with estrone (M to F)
problem of endocrine disrupters and xenoestrogens
2. Environmental or social factors
e.g. temperature
(non-differentiated gonad to M or F/temperature)
e.g. social status/hierarchy
experimental behavioral physiology
Vulnerability of other vertebrates : Effect of temperature on sex determination in
turtles (eggs incubated at low Temp. → Males, high Temp → Females
alligators (high and low temp → Females; intermediate → Males)
External and internal features of an adult fish
Moyle&Cech, p. 120
2o sexual characteristics
•
Specialized anatomical adaptations
Pigmentation, special structures, internal or external fertilization,
reproduction modes (oviparity, ovoviviparity, viviparity)
•
Biochemical adaptations
hormones, pheromones
•
Sexual behaviours
preparation of nets, spawning gravel, nuptial danse,…
Importance of exprimental physiology and endocrinology
approach and methods used
Examples of reproductive modes vis à vis :
sharks, birds, reptiles, …
parental care
internal or external fertilization
Sexual dimorphism in salmon (sockeye salmon)
semelparous vs iteroparous fish
Pacific salmon vs Atlantic salmon
Moyle&Cech, p.123
Phyletic
distribution
of
neurohypophyseal
hormones
Bentley, 1996
NEUROENDOCRINE SYSTEM
The pituitary glands of fishes
diagrammatic representation
of the midsagittal section
Evolution of the pituitary
anatomy/physiology
•Teleostei
e.g. trout, pike, carp
Pituitary gland of a teleost fish
(e.g. eel, Anguilla anguilla)
diagrammatic representation of the midsagittal section
cells that produce hormones in the pars distalis
(part of adenohypophysis) lie in distinct zones
Prolactin cells in pituitary gland of yellow perch, Perca flavescens
x400
Annual reproductive cycles in fishes from temperate zones
(e.g. male rainbow trout, Oncorhynchus mykiss)
Seasonal variation in plasma
levels of steroids
testosterone (x)
11-ketotestosterone (o)
17,20B-dihydroxy-4-pregnen-3-one
(+)
Seasonal variation in
volume of sperm
(open squares)
GSI (circles)
GSI=% gonad wt/body wt
Norris, p. 421
Ovulation cycle in mammals
ESTROUS
vs
MENSTRUAL CYCLES
duration of luteal phase
proliferation of endometrium
vaginal cytology
effect of environment
effect of copulation
sexual receptivity
SPONTANEOUS OVULATORS
(e.g. rat, human)
surge secretion independent of neural inputs
INDUCED/REFLEX OVULATORS
(e.g. cat, rabbit)
surge is triggered by stimulation of vaginal and cervical nerve endings
during copulation
BIO 4420 ENVIRONMENTAL PHYSIOLOGY
Annual reproductive cycles in fishes from temperate zones
(e.g. female rainbow trout, Oncorhynchus mykiss)
Seasonal variation in plasma
levels of steroids
testosterone (solid square)
estradiol (open square)
17,20B-dihydroxy-4-pregnen-3-one
(open triangle
Seasonal variation in
plasma vitellogenin
(solid circles)
GTH (open circles)
Vitellogenesis
Blood-feeding insects
Blood meal initiates JH surge
Then Vtg production
Seasonal variation in ovarian weight (in longjaw mudsucker, Gillichthys mirabilis)
Cycles of ovarian recrudescence and regression
Importance of environmental cues
Moyle&Cech, p.130
•Seasonal reproductive cycles in temperate zone
periods of reproductive activity
periods of rest
Use of proximate environmental cues
photoperiod
temperature
Use of ultimate environmental cues
availability of food, oxygen
mates
spawning habitats,…
•Continual reproduction in tropical zone
Munro et al. 1990, p. 15
Link between retinal input (light cues), pineal gland and pituitary
SCN communicates circadian signals to other parts of CNS
SCN communicates circadian signals to:
ventromedial nucleus (feeding, appetite)
paraventricular nucleus (ADH, oxytocin)
nuclei, tracts
lesion in SCN-effect?
transplant of SCN neurons-effect?
Melatonin – “night” hormone
Gametogenesis in female and male
Normal testes
Chemically-induced
damage to testes
Seminiferous tubule
Hypothalamo-pituitary-gonadal axis in mammals
Ovulation cycle in mammals
Production of oogonia (yellow) and oocytes (red) by
the ovarian germinal epithelium
Mitosis – production of oogonia (diploid 2n)
Meioisis – production of oocytes (haploid n)
Germinal epithelium
Mellinger, p.126
Stages of oogenesis (medaka, Oryzias latipes)
follicular
cells
germinal vesicle
post-ovulatory
follicle
Iwamatsu 1988
vegetative
pole
1
2
1-immature ovary with oogonia
2-recrudescing ovary
(oogonia, vitellogenic oocytes)
3-mature ovary
(large eggs filled with
yolk-vitellus)
3
N.B. different scale
Activation of egg by fertilization
•organization of the peripheral
cytoplasm into blastocyst (embryo)
unfertilized egg
•organization of vitellus yolk
sac (lipoprotein)
fertilized egg
•movement of oil droplets
Mellinger, p.129
Development of embryos and larvae
walleye (Stizostedion vitreum)
Embryo at age 3 days
enclosed in egg membrane
Embryo at 6 days
(removed from egg membrane)
hvv – hepatic vitelline vein
da – dorsal aorta
Embryo at 8 days
after hatching
Larva, 17 days
Moyle&Cech, p.128
Synchronization of
spawning in fish
ovulatory peak of GTH in female
interaction between
•
photoperiod
•
temperature
•
availability of substrate
for egg deposition
•
presence of males
exhibiting sexual
behavior
Stacey et al., 1992
Model of interactions between hormonal factors and pheromones
mediating synchronization of ovulation and spawning in fish
GTH – gonadotropin
PG – prostaglandins
PIP – pheromone induced prostaglandin
17,20P – 17, 20B-dihydroxy-4pregnen-3-one
OVUL - ovulation
Stacey 1994
Endocrine Disruptors :
pollutants that have the potential to disrupt
the endocrine (hormonal) system of animals,
including humans
mechanisms of action:
mimic natural hormones
block action of natural hormones
disruption of synthesis
Induction of egg protein in male fish by sewage chemicals
Jobling et al. 1996, Env.Tox.Chem.
•male trout
•laboratory exposure, 6 wks
•Estrogen (positive control)
Octylphenol
Nonylphenol
•EFFECTS
Vitellogenin in blood
Smaller testes
Intersex in fish downstream from sewage plants
Matthiessen et al. 1998
Normal ovary
Primary
oocytes
Secondary
oocytes
Intersex testis
oocytes
sperm
Animal life cycle
and
developmental
stages
similarities/differences
vertebrates/invertebrates
Life cycle and reproduction in insects
Larva grows, molts, sheds exoskeleton
Last instar – emergence of adult
Two paths of development:
Holometabolous insects
larva - last instar
pupa (+cocoon)
adult
Hemimetabolous insects
larva
nymphs
adult
Juvenile hormone
maintains juvenile stages
Ecdysone (steroid)
important for molting process
Metamorphosis of holometabolous insects – role of juvenile hormone (JH)
relevance/applications/similarities/differences
Hemimetabolism
incomplete metamorphosis
Vitellogenesis
blood-feeding insects
blood meal initiates JH surge
then Vtg production
spermatheca?
other animals?
Oogenesis in silk moth
Parthenogenesis
Homogametic
Female XX
produces
offspring
only
females
reproduction without males
involves divisions of an oocyte
production of diploid individulas, same as the mother
commmon in invertebrates (e.g. insects)
Heterogametic
Female ZW
produces
offspring
only
males
Gametogenesis in female and male
Ovulation
Fertilization
Implantation
Development
Parturition
Ovulation cycle in mammals
Embryonic development
in the uterus of a placental
mammal:
blastocyst binds to uterine wall
trophoblast cells invade
placenta forms
extraembryonic membranes
develop
Other strategies
Sperm storage
delayed fertilization
(…spermatheca…)
Delayed implantation
fertilized ovum develops to
blastocyst stage
(100-400 cells),
but implantation into
uterine wall is delayed
Uterine horns in
pregnant mouse at term
(vom Saal and Dhar, 1992)
Development of mammary glands
Lactation
Role of prolactin
estrogen
oxytocin
TYPES OF GLANDS
Gland = cluster of secretory cells
EXOCRINE GLANDS
secrete fluids through duct onto
epithelial surface
external surface
internal surface
e.g.sweat glands
e.g.gall bladder
mammary glands
salivary glands
ENDOCRINE GLANDS
secrete hormones directly into
circulatory
system
no duct
no distinctive morphological
features
well vascularized
BIO 4420
ENVIRONMENTAL PHYSIOLOGY