Title Page

Contents

Abstract 6

1. Introduction 8

2. Materials and methods 9

3. Results 11

3.1. General description of the nematodes 11

3.1.1. Morphological features 11

3.1.2. The cordon 11

3.2. Male 14

3.2.1. Morphological features 14

3.2.2. The reproductive system 14

3.3. Female 17

3.3.1. Morphological features 17

3.3.2. The reproductive system 17

3.4. Molecular characteristics and phylogenetic position 22

4. Discussion 24

5. Conclusion 28

6. References 29

7. 국문초록 33

Fig. 1. Light microscophical view of D. invaginatus. (A) Anterior portion of female. Long muscular (ME) and glandular esophagus (GE) are shown. (B) Anterior end... 13

Fig. 2. SEM view of male D. invaginatus. (A) Whole body. (B) Apical view of cephalic end. Cordon, cephalic papillae (circle) and pseudolabia (asterisks). (C)... 16

Fig. 3. SEM view of female D. invaginatus. (A) Whole body. (B) Lateral view. A pairs of cordon (C) arise dorsally and ventrally between pseudolabia, extending... 19

Fig. 4. SEM view of posterior end of female D. invaginatus. Four types of posterior extremity (A,B,C,D). (A) Double invaginated posterior end at one side forming... 21

Fig. 5. Phylogenetic tree (Neighbor Joining) based on sequence analysis. 23