BIOLOGICAL RHYTHMS CHRONOBIOLOGY

BIOLOGICAL RHYTHMS
CHRONOBIOLOGY
The imperceptible movement of plants
The bird navigation
The vigil-sleep cycle
At the basis of the life.
A multidisciplinary argument
What is a BIOLOGICAL CLOCK
A molecular / physiological device which
synchronizes activities in the living
organisms
Oscillation CLOCKS
hourglass
time chain of events
BIOLOGICAL CLOCKS OSCILLATING CLOCKS
With an autochthonous pacemaker able to
measure time, to generate and check
automatically the endogenous rhythms
(infradiane, circadiane, ultradiane) also in
absence of environmental messages.
BIOLOGICAL CLOCKS HOURGLASSES
they measure time intervals,
they do not ascillate autonomously,
they need environmental signals
which periodically switch they on
BIOLOGICAL CLOCKS Oscilla0ng Clocks ‐ they define a point in the .me Many Biological Clocks are known with different oscillatory frequencies. They can be classified on the basis of the living organisms where they stay on the basis of • Environmental .me scale (temperature compensated) • Biological .me scale (not temperature compensated) Hourglasses – they define a .me span (e.g. embryo development, pregnancy, etc.) Mul0ple clocks • Mixed oscilla.ng/hourglass [some cellular func.ons] • Mixed periodicity (endogenous/exogenous) INFRADIAN RHYTHMS ANNUAL, SEASONAL, LUNAR, WEEK CYCLES
germination 1 year (plants)
Lethargy : in Citellus lateralis of 324-329 days
Migrations : in Silvidae (Passeriformes)
Menstruation 29.57 days (moon cycle 29.59
days)
CIRCADIAN RHYTHMS About 24 h
Independent from external stimuli
Free runners, when independent from
environmental regulators
Vigil-sleep cycle
Body temperature cycle
ULTRADIAN RHYTHMS From unicellular organisms to mammalians,
from physiological to cognitive processes
Rhythmic phenomenons independent from
the circadian, with which they probaly
interact
Periods of 1.5 – 3 hours are very common
It reflects an economic principle which
avoids to spend energy continuously, with a
rest – recharge cycle.
The spontaneous locomotory activity is a parameter
useful for chronobiology studies.
Each biological clock should have the following features:
• Rhythm persistence
• Period temperature – compensated
• A mechanism conservative among species
Usual techniques used for the study of the circadian
rhythm are not useful, and a spectral analysis is required
(for ex. the Fourier Analysis)
MATHEMATIC – STATISTICAL ANALYSIS TO STUDY BIOLOGICAL RHYTHMS The Fourier analysis derives from the researches of
Jean Baptiste Joseph Fourier (beginning of the XIX
century), who demonstrated that each continuous
function can be the result of a sum of infinite opportune
sinusoidal functions.
The series of simple functions which result from the
decomposition of a complex function is called the
Fourier Series
FOURIER S ANALYSIS 100
90
80
Period 20-24 h
70
60
50
40
30
20
10
0
1
10
1 Day = 24 h = 1440 min
400 min = 6,5 h
200 min = 3,3 h
100
300
480
1000
10000
100
90
80
70
Spectrum power
60
24 h
50
40
12 h
30
8h
20
4h
10
0
1
10
100
300
480
1000
10000
Monitoring of the mouse’s locomotory activity
12 mice were monitored by radar
in their single cages
50
45
LD
40
CIRCADIAN
35
30
25
ULTRADIAN
20
15
DD
10
5
0
1
10
100
1000
10000
100000
___________________________________
A JUMP INTO THE DARK
WHY CAVE ANIMALS Within the true caves the light cycle is absent
Dolichopoda geniculata A trogloxenic species
#A2 - D.g.geniculata (N), Pastena Cave
PRIMI DATI SU
MISIDACEI CAVERNICOLI
Spaeleomysis bo8azzii A troglobiont (stygobiont) species
Each animal interrupts a infrared
beam when it moves into its
aquatic environment
Problems:
- Animal habitat
- Water
- Warming of the apparatus
- De-sinchronization
(acclimatation)
RESULTS Spelaeomysis bottazzii #1
Spectral power #1
10
9
8
7
Power
6
5
4
3
2
1
circadian
0
1
10
100
1000
Time in min (log)
Spelaeomysis bottazzii shows a pattern of activities (the
ACTOGRAM) very similar to that of insects and mammalians
10000
Spelaeomysis bottazzii #1
10
9
8
7
6
5
4
3
2
1
0
1
10
100
1000
10000
Dolichopoda baccettii #10 - Punta degli Stretti
16
14
12
10
8
6
4
2
0
1
10
10 0
10 0 0
10 0 0 0
CONCLUSIONS •  The circadian is not the only rhythm for the mobility ac.vity of animals •  These ultradian components do not depend from the circadian, •  They are not regulated by photoperiod, but when they show higher amplitudes when the circadian is nega.vely affected by photoperiod •  They are temperature compensated •  Tehy stay even in troglobionts as the mysidaceans What about Mysidacea migrating in-out a marine cave?
the Ciolo cave: Hemimysis margalefi & Siriella jaltensis
29-30 / 12 / 2006
12.00
00.30
220 specimens H. margalefi
In lab at 19.5 °C, L 24 h, yeast
20-30
specimens
1 litre aquarium
the aquarium
the light spot
Black room
Uninterrupted
recording for 5
days
the rec. apparatus
the videocam
Every 30 min the recorded image was analyzed.
Each square (of 24) was characterized with the
specimen number it contained.
The sequence (of 30 min intervals) obtained was passed
through the Fourier analyses
Hemimysis margalefi, 38 specimens, 5 days, L 24 h
RESULTS & CONCLUSIONS
Hemimysis margalefi shows an activity cycle of 23 h
It never exits the cave
It is not disturbed by light (24 h)
Siriella jaltensis is absent from the cave during winter.
It arrives in spring
It exits the cave during night
It did not show any acivity during behavioral
experiments (it is disturbed by light)