Biological Rhythms. Biological Rhythms – terms and characteristics Rate of activity Time Amplitude...

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

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


Remove SCNArrhythmic patterns of locomotion, feeding, hormone secretion

Implant donor SCN tissue

Return rhythmsof donor hamster


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

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


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


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



Dark Phase

Light Phase

Conflicting demands

Communication

Thermoregulation

Camouflage


Rhythmic Changes in COlour


Dark Phase

Light Phase


Black background, low temperatures

White background, high temperatures

Takes precedence


Colour changes via melanophores


Fully concentrated

Fully dispersed

Light phase Dark phase


Natural L:D cycle

Reversed L:D cycle

Reversed L:D cycle(+ 3 days)


Rhythms in Arctic Breeding Birds

Steiger et al. 2013. Proc.Roy,Soc.Lond. 280:


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


Biological Rhythms. Biological Rhythms – terms and characteristics Rate of activity Time Amplitude...

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