Christopher K. Beachy, Kiswendsida C. Ouedraogo
description
Transcript of Christopher K. Beachy, Kiswendsida C. Ouedraogo
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
R2 = 0.6564 R2 = 0.5043 R2 = 0.6897 R2=0.601
R2 = 0.2325 R2 = 0.6545 R2 = 0.5808 R2=0.771
0
50
100
150
200
250
300
350
400
1 2Temperature
Number of elements
Vomer teeth
Teeth patch
Pterygoidteeth
Maxillae teeth
Totalnumtee
HyobranchialApparatus
masvariatio8
score
Linear(Maxillaeteeth)Linear(Totalnumtee)
Linear(HyobranchialApparatus)Linear(masvariatio8)
Linear (score)
Summary of Pearson Correlation
Correlation
R2 = R2 = 0.7887 R2 = R2 = 0.0853
-20
0
20
40
60
80
100
120
140
160
0 20 40 60
Vomer teeth
Teeth on the other elements
Teeth patch
Pterygoid teeth
Maxillae teeth
Totalnumtee
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.