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 DawnNoonDuskMidnightDawn ActivityActivity 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 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 Begin at same time Shift start time lightdark light dark Begin at same time

Controls of Rhythms Calling by Male Crickets lightdark light dark ENTRAINED FREE-RUNNING

Subesophageal ganglion Optic lobe Cricket Calling Rhythm Rhythm maintainedRhythm 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 Environmental cues Sensory receptors Pace- maker locomotion hormone release feeding others Clock-setting pathway Clock mechanism Observed behaviour

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 glandPineal eye Regulates rhythms based on photoperiod

tim per Effector gene mRNA CYCCLK PROMOTER PER protein TIM protein Effector protein CIRCADIAN ‘CLOCK’ IN Drosophila

tim per Effector gene mRNA CYCCLK PROMOTER PER protein TIM protein Effector protein PER/TIM dimers dissociate move to nucleus CIRCADIAN ‘CLOCK’ IN Drosophila

tim per Effector gene mRNA CYCCLK PROMOTER PER protein TIM protein Effector protein PER/TIM dimers tim per Effector gene PROMOTER dissociate move to nucleus GENES TURNED 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 BMAL1CLK PROMOTER PER protein CRY protein Effector protein cry per Effector gene PROMOTER GENES TURNED OFF CIRCADIAN ‘CLOCK’ IN MAMMALS

Genetic Control of Daily Cycle - per gene mutations per gene 24 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 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 J.Exp.Mar. Biol. Ecol. 427:39

Rhythmic Changes in COlour Uca panacea – fiddler crab Dark Phase Light Phase Darnell 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 phaseDark phase Darnell J.Exp.Mar. Biol. Ecol. 427:39

Rhythmic Changes in Colour Darnell J.Exp.Mar. Biol. Ecol. 427:39

Natural L:D cycle Reversed L:D cycle (+ 3 days) Darnell J.Exp.Mar. Biol. Ecol. 427:39

Rhythms in Arctic Breeding Birds Steiger et al Proc.Roy,Soc.Lond. 280:

Rhythms in Arctic Breeding Birds Steiger et al Proc.Roy,Soc.Lond. 280: Semipalmated sandpiperPectoral sandpiper Red phalaropeLapland longspur

SpeciesMating system Parental Care SexArrythmicEntrainedFree running Semipalmated sandpiper monogamousBiparentalMalePre- incubation Incubation FemalePre- incubation Incubation Pectoral sandpiper polygynousFemale onlyMaleEntire season FemalePre- incubation Incubation Red phalaropePolyandrous Role reversal Male onlyMalePre- incubation Incubation femaleEntire season Lapland longspurMonogamousBiparental (female only incubation MaleEntire season FemaleEntire season Rhythms in Arctic Breeding Birds