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 SourceWilk’sFP Temperature <0.001 Thyroxin Temperature*Thyroxin

Summary of Pearson Correlation

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.