BIOLOGY 457/657PHYSIOLOGY OF MARINE & ESTUARINE ANIMALS

May 3, 2004

BIOLOGICAL RHYTHMS

IN THE SEA

Introduction Features of Endogenous, Biological Rhythms

Are pervasive, ubiquitous features of animals (& plants)

Require endogenous mechanisms that have properties like clocks

Vary in strength and persistence:

Exogenous rhythm - requires continuous external cycles

“Hourglass” rhythm - continues for a single cycle in the absence of the external cycle

Endogenous rhythm - persists indefinitely in constant conditions

Evidence for their truly endogenous origin is now certain, including some of the genes that contribute to the periodicity and timing. Experiments have demonstrated that some endogenous rhythms continue in orbiting satellites or at the South Pole!

Periodicities of Biological Rhythms

The diversity of natural cycles in the sea lead to the presence of a number of periodicities in natural rhythms of marine animals.

Tidal rhythm: period is ~12.4 h

Circadian rhythm: period is ~24 h

Lunadian rhythm: period is ~24.8 h

Semilunar rhythm: period is ~14.8 d

Lunar rhythm: period is ~29.5 d

Annual rhythm: period is ~365 d

Properties of Endogenous Rhythms

Require a synchronizer or “zeitgeber”.

In free-running conditions, the period is approximate. Hence the prefix “circa”. A rhythm with a period near 24 h is “circadian”, while one with a period near 12.8 h is “circatidal”.

Organisms may have several rhythms running in parallel, all with different phases.

Are temperature-compensated.

May change period in the presence of some drugs or chemicals (e.g.

D2O).

Examples of Rhythmicity in GonyaulaxIn Presence of External LD Cycle

Examples of Rhythmicity in GonyaulaxThe Glow Rhythm in Constant Conditions

www.mcb.harvard.edu/hastings/ Images/gony.gif

Examples of Rhythmicity in GonyaulaxAll Rhythms in Constant Conditions

Temperature Compensation of Endogenous Rhytnms

Effects of Deuterium Oxide (D2O)

Activity Rhythms in CrabsThe “actograph”

http://www.crayfishworld.com/crab1.htm

Activity Rhythms in CrabsData collected from Sesarma reticulatum

TERMINOLOGY AND ABBREVIATIONS

Types of cycles:LD - alternate light and dark, as in “LD 12:12”LL - constant lightDD - constant darkCC - constant conditions (generally, DD with constant temperature)

Free-run: The expression of an endogenous rhythm in CCPeriods:

T – the period of the zeitgeberτ – the period of the endogenous cycle

Phases:φ – the phase of the biological rhythmΔφ – change in phase of the biological rhythmψ – phase difference between zeitgeber and the biological rhythm

Pacemaker: The biological structure that provides timing; the internal “clock” or oscillator

TYPES OF RHYTHMS IN MARINE ANIMALSShort-Period Rhythms: Circadian & Circatidal

Numerous examples in marine animals – activity, color change, metabolic rate, vertical migration, egg release, visual sensitivity, orientation (see earlier examples in Gonyaulax)

Tidal Rhythms – result from the influences of the sun and moon

Lunar month: 29.5 d

Spring-Neap Cycle: 29.5/2 = 14.8 d (twice a month)

Lunar day: 24 h + 24/29.5 h = 24.81 h

Tidal cycle (semidiurnal): 24.8/2 = 12.4 h

Mixed Circadian and Circatidal Rhythms(Earlier example from Sesarma reticulatum)

CIRCATIDAL RHYTHMS:Example From an Intertidal Organism

Results

www.users.totalise.co.uk/~darrenbarton/ 252b1d30.jpg

CIRCATIDAL RHYTHMS:Alternate Amplitude Reflects Natural Tides

http://kids.msfc.nasa.gov/Shared/News2001/ThermalVent/amphipod.jpg

http://kids.msfc.nasa.gov/Shared/News2001/ThermalVent/amphipod.jpg

CIRCATIDAL & CIRCADIAN RHYTHMS:Frequently are Involved With Reproduction

CIRCATIDAL & CIRCADIAN RHYTHMS:Frequently are Involved With Reproduction

www.hku.hk/ecology/fieldcourse/ hemigrapsus.jpg

SYNCHRONIZATION OF TIDAL RHYTHMS(1) Rhythmic Shaking

SYNCHRONIZATION OF TIDAL RHYTHMS(2) Rhythmic Salinity Cycles

SYNCHRONIZATION OF TIDAL RHYTHMS(3) Rhythmic Pressure Cycles

www.darwin.museum.ru/expos/ floor2/img/krab_b.jpg

SYNCHRONIZATION OF TIDAL RHYTHMS(4) Temperature Shock

VERTICAL MIGRATION RHYTHMSCircadian Examples

VERTICAL MIGRATION RHYTHMSCircatidal Examples

RHYTHMS IN VISUAL FUNCTIONExample 1: Limulus polyphemus

The rhythm in the figure is from the electroretinogram (ERG) in the compound eye.

The rhythmicity may persist for years in constant dark.

The greatest response (& sensitivity) is at night.

soma.npa.uiuc.edu/courses/ physl341/limulus.1.jpg

RHYTHMS IN VISUAL FUNCTIONExample 1: Limulus polyphemus

The rhythm is synchronous is all 5 types of photoreceptor found in Limulus (2 compound eyes, median eye, ventral eye, and caudal photoreceptor).

RHYTHMS IN VISUAL FUNCTIONExample 1: Limulus polyphemus

Synchronization requires efferent output from the brain.

RHYTHMS IN VISUAL FUNCTIONExample 2: Aplysia

Note synchronization in the numbers of action potentials produced in constant darkness (the rhythm peaks during the day, unlike that of Limulus, which reveals the greatest sensitivity at night).

http://www.physiology.wisc.edu/neuro524/learningII02/Slide4.JPG

LONG-PERIOD RHYTHMSLunadian and Spring:Neap Cycles

http://www.crayfishworld.com/crab1.htm

LONG-PERIOD RHYTHMSLunadian and Semilunar Cycles

www.ncl.ac.uk/marine/assets/ photos/midge.JPG

LONG-PERIOD RHYTHMSAn Example of an Annual Cycle

Resting cysts of our old friend, Gonyaulax, were collected in the field and stored at 4 degrees C. Samples were tested for percent germination at intervals throughout the next 3 years.