The Effect of Lactic Acid on the
Thermoregulatory Behavior of Gravid Female
Red-sided Garter Snakes
Chris R. Friesen
Mentors: Dr. Robert T. Mason
Deborah Lutterschmidt
Howard Hughes Medical Institute Undergraduate Research Program
Department of Zoology, Oregon State University
Red-sided Garter Snake
(Thamnophis sirtalis parietalis)
Our Beautiful Model Organism
Terms:
Gravid, Gravidity:
Pregnant
(Being Madonna is not a necessary
condition for gravidity)
<http://images.usatoday.com/life/gallery/madonna-life/pregnant.jpg>
Terms:
Viviparity:
Live bearing
Oviparity:
Egg laying
Red-sided
San Francisco*
Giant*
Our Model Organism
Species (T.sirtalis)
Genus (Thamnophis)
•San Francisco Garter Snake
(Thamnophis sirtalis tetrataenia)
Lake Erie Water snake*
•Giant Garter Snake
(Thamnophis gigas)
•Lake Erie Water Snake
(Nerodia sipedon insularum)
*<http://www.californiaherps.com/snakes/images/tstetrataeniacu.jpg>
*<http://www.carolinian.org/images/LakeErieWaterSnak.gif>
Family (Colubridae)
Behavioral Thermoregulation
Daytime Body Temperature
versus Ambient Temperature
*
Decision
s
decision
s.
*<httpwww.science.mcmaster.caBiologyHarbourSPECIESCGARTERPICTURES>
Schmidt-Nielsen, Animal Physiology, 5th Ed. 1997.
Energetic Costs Of Reproduction Directly
Affect Fitness  Evolution & Ecology
I’m too
Cold!
Gravid ♀
I’m cold
but...
Non-gravid♀
Costs of Basking
• Increased
risk of predation
•Time spent basking is not available for foraging
Does gravidity affect
thermoregulatory behavior in
female Red-sided Garter snakes?
Scoring Basking Behavior
Covered
1/3 Exposed
2/3 Exposed
Fully Exposed
Avg. % Snakes (G or NG)
Thermoregulatory Response to Gravidity
100
90
80
70
60
50
40
30
20
10
0
Covered
1/3 exposed
2/3 exposed
3/3 exposed
Non-gravid (n=25)
Gravid (n=20)
Temperature Range in Aquaria
26°C
24°C
41°C
28°C
Body Temperature (°C)
Thermoregulatory Response to Gravidity
31.5
31
30.5
30
29.5
29
28.5
28
27.5
a
b
Gravid
(n = 20)
Non-gravid
(n = 25)
Relationship Between Body Temperature and
Metabolic Rate
10
9
Metabolic Rate
8
Maximum Metabolic Rate
7
6
5
4
3
2
1
0
0
5
10
15
20
25
30
35
40
45
50
o
Temperature ( C)
Graph modified from: <http://www.morris.umn.edu/~goochv/AnimalPhys/temperature/temperature.html>
“Measures of the Metabolic Cost of Reproduction”
Extra cost
Heart Rate:
Metabolic Rate:
Metabolic rate (V O2 cm3 O2 hr-1)
Gravid ♀
40
20
G
Metabolic rate
(V O2 cm3 O2 hr-1)
Beats/ minute
60
NG
12
8
4
G
F
NG Sum
4
3
2
1
10
20
30
Fetuses
Non-gravid ♀
Number of Fetuses
All graphs modified from: Birchard et al.(1984). Journal of Comparative Biochemistry & Physiology
Anaerobic Metabolism
• Most ectotherms rely
heavily on anaerobic
metabolism
• Lactate or lactic acid is a
product of anaerobic
metabolism
• High Energetic Demands
of gravidity may increase
anaerobic metabolism
Why Anaerobic Metabolism?
Ovaries
Lung
<http://www.biologycorner.com/resources/anatomy_snake.jpg>
Is there a difference in the
blood-lactate levels
between gravid and
non-gravid females?
Measuring Lactate In Gravid & Non-gravid Snakes
Over Time
21 ♀
Non-Gravid Snakes
&
15 ♀
= 36 per week
Gravid Snakes
Lactate
Levels
Lactate Levels in Gravid & Non-gravid
Red-sided Garter Snakes
60
Gravid (n = 15)
Non-gravid (n = 21)
[Lactate] (mg/dL)
50
40
30
20
10
0
0
1
2
3
Time (weeks)
4
5
6
Previous Study on Red-spotted Garter Snakes
(Thamnophis sirtalis concinnus)
[Lactate] (mg/dL)
50
40
Gravid
Non-gravid
30
20
10
a
b
0
Before Exercise
Late in Gestation
After Exercise
Lactate Levels in Gravid & Non-gravid
Red-sided Garter Snakes
60
Gravid (n = 15)
Non-gravid (n = 21)
[Lactate] (mg/dL)
50
40
30
20
10
0
0
1
2
3
4
Time (weeks)
5
6
Do higher lactate levels explain
differences in thermoregulatory behavior
of gravid & non-gravid females?
Thermoregulatory Response to Lactate
12 ♀ Non-gravid Snakes:
Each snake received
both the lactate treatment &
control treatment
Treatment:
lactic acid injection
Control Treatment:
saline injection
15°C
40°C
[THERMAL GRADIENT]
Thermoregulatory Response to Lactate
Average Tb (°C)
Average Preferred Body Temperature (Tb)
1 Hour after injection
35
30
a
a
25
20
15
10
5
0
Lactate
Control
(n = 12 for each)
Summary
• Gravid females tend to bask more than nongravid females
• Gravid females maintain higher Tb than nongravid females
• There is an upward trend toward higher lactate
levels in gravid females
• However, lactate injections do not initiate a
positive thermoregulatory response
Acknowledgements
•
Funding:
– HHMI
– URISC
•
Mentors:
– Dr. Robert T. Mason
– Deborah I. Lutterschmidt
•
Lab Group:
– Heather Waye
– Rocky Parker
– Torrin Rosegold (visiting ASE
high school student)
Special Thanks To:
Dr. Kevin Ahern
The Weis Lab
IN CONCLUSION…..
....Thank You.
Lactate Metabolism
Lactic Acid & Saline
injection
Dose = 40mg/ kg of snake
Measure
Blood lactate at
0,1,2,4 & 6 hours
(n = 6)
Lactate Metabolism
100
[Lactate] (mg/dL)
80
b
60
a,b
a,b
40
20
a,b
a
0
0
1
2
3
4
Time (hours)
5
6
7
Manitoba’s Red-sided Garter Snakes
Manitoba’s Red-sided Garter Snakes