Download PPT - Department of Biology

Christopher K. Beachy, Kiswendsida C. Ouedraogo
Department of Biology, Minot State University, 500 University Avenue West, Minot, North Dakota 58707,
USA
Cranial development in a miniaturized form of the
salamander Desmognathus quadramaculatus:Roles of
temperature and thyroid hormone.
I-Hypotheses
Temperature and Thyroid hormone
have an effect on cranial
metamorphosis of Desmognathus
quadramaculatus
II-Background
• Description of Plethodontidae salamanders
-Variable life cycle
-Sensitivity to Temperature and Thyroid
hormone
• Effect of temperature
– Effect on metamorphosis
• High temperature effect
• Low temperature effect
– Structures affected during metamorphosis
• External structures: the skin
• Internal structures: skeletal elements
• Effect of Thyroid hormone
– Criteria of TH action
• TH concentration
• Size-age of the animal
III-Materials and Method
• Characteristics of the salamanders
– Larval size
– Place of collection
• Gott Farm Creek, Bald Mountains, NC
• Experimental Procedure
– Number of salamanders
– Habitat
• Room
–
–
–
–
Boxes: 8*3*4 LWH
110g sands
100g gravel
250 Ml of distilled water
• House : Coolers
– Variation in Temperature
• Beginning of the experiment
– Low temperature (7 C, 11C)
• In the course of the experiment
– High temperature (11C, 15C)
– TH treatment
• TH (1.2*10-8 M )
• Control ( 0.0 M)
– Variation in the intensity of the treatment factors
• Temperature
– 1 C every two days
• Thyroid hormone
– 1.2*10-8 M every two weeks
– Four final treatment groups
•
•
•
•
11C and 4.8*10-8 M
15 C and 4.8*10-8 M
11 C and control
15 C and control
– Evaluation of the internal metamorphosis
• The idea of the Bone-Cartilage evaluation
– Double-Staining Technique
• The idea of the number of teeth and hyobranchial apparatus
– Four Dermatocranial elements
» Vomer
» Parasphenoid
» Pterygoid
» Maxilla
– Hyobranchial Apparatus
» Ceratohyal (1)
» Basibranchials(2)
» Ceratobranchials(2)
» Epibranchials (4)
Skull of larvae Desmognathus quadramaculatus
(dorsal view)
Skull of adult Desmognathus quadramaculatus
(dorsal view)
Skull of adult Desmognathus quadramaculatus
(ventral view)
• The statistical analysis
– Multivariate Analysis of Variance
• =0.05
• Test statistics: Wilk’s Lambda
– Pearson Correlation
• Identification of the nature of the effects of the factors
• Identification of the patterns of skeletal elements development
IV-Results
• Temperature effect
– The changes in the hyobranchial apparatus
• Changes in the shape
• Reduction in the number of structures
– The four bones
• Vomer
– Remodeling of the vomer
– Reduction in the number of teeth
• Parasphenoid tooth patch
– Formation and formation of the teeth
• Maxilla
– Formation and formation of teeth
• Pterygoid
– Regression and complete disappearance
• Thyroid Hormone
– No effect of Thyroid hormone
Multivariate Analysis
Source
Wilk’s
F
P
Temperature
0.11
11.07
<0.001
Thyroxin
0.69
0.64
0.716
Temperature*Thyroxin
0.54
1.22
0.373
Temperature Effect
Vomer teeth
400
Teeth patch
350
Pterygoid
teeth
Number of elements
300
Maxillae teeth
250
200
Totalnumtee
150
Hyobranchial
Apparatus
100
masvariatio8
50
score
0
1
Temperature
R2 = 0.6564 R2 = 0.5043 R2 = 0.6897
2
2
R2 = 0.2325 R = 0.6545 R = 0.5808
2
Linear
(Maxillae
teeth)
R2=0.601
Linear
(Totalnumtee)
R2=0.771
Linear
(Hyobranchial
Apparatus)
Linear
Summary of Pearson Correlation
Correlation
160
Teeth patch
Teeth on the other elements
140
120
Pterygoid teeth
100
80
Maxillae teeth
60
40
Totalnumtee
20
0
-20
0
20
40
60
Vomer teeth
2
R =
2
R = 0.7887
2
R =
2
R = 0.0853
V-Discussion
• Temperature
– Effect of temperature on amphibians
– Similarity in the action
• Nature of the similarity
• Possible conclusion: temperature action is beyond the simple
stimulation for regressive or progressive development of
skeletal elements
• Thyroid Hormone
– sensitivity to TH is not related only to metamorphic salamanders.
– Insensitivity to TH is not the matter of only non-metamorphic
salamanders.
– TH may be a secondary factor in metamorphosis
• Possible factors:
– Mechanical stress:
» Internal mechanical stress:Interaction between skeletal elements
» External mechanical stress:Action of muscles and feeding system on the
skeletal elements
– Mechanical stress-inducing factors:Temperature
ACKNOWLEDGEMENT
Special Thanks to:
-The Faculty of the Biology Department of Minot State University
and Dr Richard Barkosky
-The International Students Office particularly:
.Mrs. Ronnie Walker and her family:
.Mr. Gary Loper
.Beth
.Sarah
.Davis
-Minot Community particularly:
.Mr. Tim Eighmy
.Mrs. Kathy Hammond
.Mrs. Shirley Hintz
.Mrs. Margret Lowe
.Mr. Berb Williams
-Mr. Stuart Melby and Mrs. Karen Melby
-Dr David McCormack in the Mathematics Department.