Biological Rhythms
Biological Rhythms – terms and characteristics
Rate of
activity
Time
Amplitude – magnitude of change in the activity
Period – time required to complete an entire cycle
Phase – any recognizable part of the cycle (e.g. active phase)
Biological Rhythms – terms and characteristics
1. Rhythms are temperature-compensated.
2. Unaffected by metabolic poisons or inhibitors
3. Occur with approximately the same frequency as
some environmental feature
4. Self-sustaining – maintain cyclicity in absence of cues
5. Can be entrained by environmental cues
Types of Rhythms
i) Epicycles (Ultradian) Rhythms
- cycles of repeated activity that are less than 24 hours
Arenicola marina - feed on surface every 6 -8 mins
Types of Rhythms
i) Epicycles (Ultradian) Rhythms
Types of Rhythms
ii) Tidal Rhythms
- cycles of repeated activity that are synchronized with tidal flow
-fiddler crab - times activity cycles to
match tidal flow
High tide
Foraging area
Types of Rhythms
ii) Tidal Rhythms
Types of Rhythms
ii) Tidal Rhythms
Types of Rhythms
iii) Lunar Rhythms
- cycles of repeated activity that are synchronized with lunar cycles
Clunio marinus
Emergence is geared to lowest tide
Types of Rhythms
iii) Lunar Rhythms
- cycles of repeated activity that are synchronized with lunar cycles
-spawn between 10 pm and 4 am
on the night before a full or new
moon
California grunion (Leuresthes tenuis)
Types of Rhythms
iv) Circadian Rhythms
- cycles of activity that are repeated approximately every 24 hours
Types of Rhythms
iv) Circadian Rhythms
- cycles of activity that are repeated approximately every 24 hours
Crepuscular
A
c
t
i
v
i
t
y
Nocturnal
Diurnal
Dawn
Noon
Dusk
Midnight
Dawn
Types of Rhythms
v) Circannual Rhythms
-rhythms that are approximately 1 year long
- hibernation
Year 2
Year 3
Year 4
Controls of Rhythms
Calling by Male Crickets
Hypothesis 1:
Male cricket possesses an internal timer that measures time
since last singing bout.
Hypothesis 2:
Male cricket is cued to sing by the effect of changing light
levels on some control centre in the brain.
Controls of Rhythms
Calling by Male Crickets
light
dark
Begin at same time
light
Shift start time
light
Begin at same time
dark
Controls of Rhythms
Calling by Male Crickets
light
dark
ENTRAINED
light
FREE-RUNNING
light
ENTRAINED
dark
Cricket Calling Rhythm
Optic lobe
Subesophageal
ganglion
Rhythm maintained
Rhythm lost
separate
ganglion
In Mammals
Suprachiasmatic nucleus
In Mammals
Suprachiasmatic nucleus
Remove SCN
Arrhythmic patterns of
locomotion, feeding,
hormone secretion
Implant donor
SCN tissue
Return rhythms
of donor hamster
In Mammals
Suprachiasmatic nucleus
Not the only pacemaker
In Rhesus monkeys
Ablate SCN
Loss of activity cycle
Maintain body temperature
cycle
Ablate
Ventromedial
hypothalamus
Loss of body temperature
cycle
General Functioning of Biological Clocks
locomotion
Environmental cues
Sensory
receptors
Clock-setting
pathway
Pacemaker
hormone release
feeding
Clock
mechanism
others
Observed
behaviour
Gonyaulax – Circadian Bioluminescence
Night
Day
Arrhythmic behaviour
Day 1
Day 2
Day 3
Naked Mole Rat
What is responsible for circadian rhythms in mammals?
Pineal gland
Pineal eye
Regulates rhythms based on photoperiod
CIRCADIAN ‘CLOCK’ IN Drosophila
CLK
CYC
per
mRNA
PER protein
tim
mRNA
TIM protein
Effector
gene
mRNA
Effector
protein
PROMOTER
http://www.hhmi.org/biointeractive/clocks/drosophila_clock.html
CIRCADIAN ‘CLOCK’ IN Drosophila
CLK
CYC
per
mRNA
PER protein
tim
mRNA
TIM protein
Effector
gene
mRNA
Effector
protein
PROMOTER
PER/TIM
dimers
move to nucleus
dissociate
CIRCADIAN ‘CLOCK’ IN Drosophila
CLK
CYC
per
mRNA
PER protein
tim
mRNA
TIM protein
Effector
gene
mRNA
Effector
protein
PROMOTER
PER/TIM
dimers
move to nucleus
dissociate
per
tim
Effector
gene
PROMOTER
GENES
TURNED
OFF
Setting the Clock
Light (blue) absorbed by cryptochromes
Allosteric change
Can bind PER and TIM
Breakdown of PER and TIM
End of inhibition of transcription
CIRCADIAN ‘CLOCK’ IN MAMMALS
CLK
BMAL1
per
mRNA
PER protein
cry
mRNA
CRY protein
Effector
gene
mRNA
Effector
protein
PROMOTER
per
cry
Effector
gene
PROMOTER
GENES
TURNED
OFF
Genetic Control of Daily Cycle - per gene mutations
24 hrs
Wild type
per gene
Long-period
Arrhythmic
Short-period
After Baylies et al, 1987
Rhythmic Changes in Colour
Uca panacea – fiddler crab
Light Phase
Dark Phase
Darnell. 2012 J.Exp.Mar. Biol. Ecol. 427:39
Rhythmic Changes in Colour
Uca panacea – fiddler crab
Light Phase
Conflicting demands
Dark Phase
Thermoregulation
Camouflage
Communication
Darnell. 2012 J.Exp.Mar. Biol. Ecol. 427:39
Rhythmic Changes in COlour
Uca panacea – fiddler crab
Dark Phase
Black background, low temperatures
Takes precedence
Light Phase
White background, high temperatures
Darnell. 2012 J.Exp.Mar. Biol. Ecol. 427:39
Rhythmic Changes in Colour
Colour changes via melanophores
Rhythmic Changes in Colour
Light phase
Fully
concentrated
Dark phase
Fully
dispersed
Darnell. 2012 J.Exp.Mar. Biol. Ecol. 427:39
Rhythmic Changes in Colour
Darnell. 2012 J.Exp.Mar. Biol. Ecol. 427:39
Natural L:D cycle
Reversed L:D cycle
Reversed L:D cycle
(+ 3 days)
Darnell. 2012 J.Exp.Mar. Biol. Ecol. 427:39
Rhythms in Arctic Breeding Birds
Steiger et al. 2013. Proc.Roy,Soc.Lond. 280:
Rhythms in Arctic Breeding Birds
Semipalmated sandpiper
Red phalarope
Pectoral sandpiper
Lapland longspur
Steiger et al. 2013. Proc.Roy,Soc.Lond. 280:
Rhythms in Arctic Breeding Birds
Species
Semipalmated
sandpiper
Pectoral
sandpiper
Red phalarope
Lapland longspur
Mating
system
monogamous
polygynous
Polyandrous
Role reversal
Monogamous
Parental
Care
Biparental
Female only
Male only
Biparental
(female only
incubation
Sex
Arrythmic
Entrained
Free
running
Male
Preincubation
Incubation
Female
Preincubation
Incubation
Male
Entire season
Female
Preincubation
Incubation
Male
Preincubation
Incubation
female
Entire season
Male
Entire season
Female
Entire season
