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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
California grunion (Leuresthes tenuis)
-spawn between 10 pm and 4 am on the night before a full or new moon
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
Dawn Noon Dusk Midnight Dawn
Activity
Crepuscular
Diurnal Nocturnal
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 timesince last singing bout.
Hypothesis 2:Male cricket is cued to sing by the effect of changing lightlevels on some control centre in the brain.
Controls of Rhythms
Calling by Male Crickets
Begin at same time
Shift start time
light dark
light
light dark
Begin at same time
Controls of Rhythms
Calling by Male Cricketslight dark
light
light dark
ENTRAINED
ENTRAINED
FREE-RUNNING
Subesophageal ganglion
Optic lobe
Cricket Calling Rhythm
Rhythm maintained Rhythm lost
separateganglion
In MammalsSuprachiasmatic nucleus
In MammalsSuprachiasmatic nucleus
Remove SCNArrhythmic patterns of locomotion, feeding, hormone secretion
Implant donor SCN tissue
Return rhythmsof donor hamster
In MammalsSuprachiasmatic nucleus
Not the only pacemaker
In Rhesus monkeys
Ablate SCN Loss of activity cycleMaintain body temperature
cycle
Ablate Ventromedial hypothalamus
Loss of body temperaturecycle
General Functioning of Biological Clocks
Environmental cuesSensory receptors
Pace-maker
locomotion
hormone release
feeding
othersClock-settingpathway
Clockmechanism
Observedbehaviour
Gonyaulax – Circadian Bioluminescence
Day
Night
Arrhythmic behaviour
Naked Mole Rat
Day 1
Day 2
Day 3
What is responsible for circadian rhythms in mammals?
Pineal gland Pineal eye
Regulates rhythms based on photoperiod
tim
per
Effector gene
mRNA
mRNA
mRNA
CYCCLK
PROMOTER
PER protein
TIM protein
Effector protein
CIRCADIAN ‘CLOCK’ IN Drosophila
http://www.hhmi.org/biointeractive/clocks/drosophila_clock.html
tim
per
Effector gene
mRNA
mRNA
mRNA
CYCCLK
PROMOTER
PER protein
TIM protein
Effector protein
PER/TIMdimers
dissociate
move to nucleus
CIRCADIAN ‘CLOCK’ IN Drosophila
tim
per
Effector gene
mRNA
mRNA
mRNA
CYCCLK
PROMOTER
PER protein
TIM protein
Effector protein
PER/TIMdimers
tim
per
Effector gene
PROMOTER
dissociate
move to nucleus
GENESTURNED OFF
CIRCADIAN ‘CLOCK’ IN Drosophila
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
cry
per
Effector gene
mRNA
mRNA
mRNA
BMAL1CLK
PROMOTER
PER protein
CRY protein
Effector protein
cry
per
Effector gene
PROMOTER
GENESTURNED OFF
CIRCADIAN ‘CLOCK’ IN MAMMALS
Genetic Control of Daily Cycle - per gene mutationspe
r ge
ne24 hrs
Wild type
Long-period
Arrhythmic
Short-period
After Baylies et al, 1987
Rhythmic Changes in Colour
Uca panacea – fiddler crab
Dark Phase
Light Phase
Darnell. 2012 J.Exp.Mar. Biol. Ecol. 427:39
Rhythmic Changes in Colour
Uca panacea – fiddler crab
Dark Phase
Light Phase
Conflicting demands
Communication
Thermoregulation
Camouflage
Darnell. 2012 J.Exp.Mar. Biol. Ecol. 427:39
Rhythmic Changes in COlour
Uca panacea – fiddler crab
Dark Phase
Light Phase
Darnell. 2012 J.Exp.Mar. Biol. Ecol. 427:39
Black background, low temperatures
White background, high temperatures
Takes precedence
Rhythmic Changes in Colour
Colour changes via melanophores
Rhythmic Changes in Colour
Fully concentrated
Fully dispersed
Light phase Dark phase
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
Steiger et al. 2013. Proc.Roy,Soc.Lond. 280:
Semipalmated sandpiper Pectoral sandpiper
Red phalarope Lapland longspur
Species Mating system
ParentalCare
Sex Arrythmic Entrained Free running
Semipalmated sandpiper
monogamous Biparental Male Pre-incubation
Incubation
Female Pre-incubation
Incubation
Pectoral sandpiper
polygynous Female only Male Entire season
Female Pre-incubation
Incubation
Red phalarope PolyandrousRole reversal
Male only Male Pre-incubation
Incubation
female Entire season
Lapland longspur
Monogamous Biparental (female only incubation
Male Entire season
Female Entire season
Rhythms in Arctic Breeding Birds
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