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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

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Christopher K. Beachy, Kiswendsida C. Ouedraogo

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  1. 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 Desmognathusquadramaculatus:Roles of temperature and thyroid hormone.

  2. I-Hypotheses Temperature and Thyroid hormone have an effect on cranial metamorphosis of Desmognathus quadramaculatus

  3. II-Background • Description of Plethodontidae salamanders -Variable life cycle -Sensitivity to Temperature and Thyroid hormone

  4. 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

  5. III-Materials and Method • Characteristics of the salamanders • Larval size • Place of collection • Gott Farm Creek, Bald Mountains, NC

  6. 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)

  7. 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

  8. 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)

  9. Skull of larvae Desmognathus quadramaculatus (dorsal view)

  10. Skull of adult Desmognathus quadramaculatus (dorsal view)

  11. Skull of adult Desmognathus quadramaculatus (ventral view)

  12. 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

  13. 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

  14. Thyroid Hormone • No effect of Thyroid hormone

  15. Multivariate Analysis

  16. Summary of Pearson Correlation

  17. 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

  18. 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

  19. 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.

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