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Surface ultrastructure of metacercaria and adult of Gymnophalloides seoi(Digenea: Gymnophallidae)
Min-Ho Choi,*1Weon Jin Park,2Jong-Yil Chai,1 and Soon-Hyung Lee1
1Department of Parasitology and Institute of Endemic Diseases, Seoul National University College of Medicine, Seoul 110-799, Korea.
2Department of Plastic Surgery, Samsung Medical Center, Seoul 135-230, Korea.
Abstract
The surface ultrastructure of metacercariae and adults of Gymnophalloides seoi, the only known gymnophallid infecting humans, was observed by scanning electron microscopy. Metacercariae were ovoid or pyriform in shape and slightly concave ventrally. The oral sucker had two sizes of type I papillae, small and large, encircling its lip. Type I papillae were arranged in a row on both side of the body. The ventral pit had several type I papillae on its inner surface. The ventral sucker was covered with cobble-stone like cytoplasmic processes and had 6 type I papillae on its lip. The surface of the body was covered with the tegumental spines except for the ventromedian area between the two suckers. The spines at anterior body were digitated into 3-5 points, and their size decreased at posterior one third of the body. Adult worms were rhomboid or ellipsoid in shape and covered with tegumental spines except for the ventromedian area. The shape and distribution of the tegumental spines and sensory papillae were similar to those of metacercariae. However, sensory papillae arranged in a row on the ventral surface of metacercariae were not observed in adults. The ventral pit became larger and more prominent as the fluke grew. It is suggested that the ventral pit function as an additional adhesive organ to the host tissue.
Figures
Figs. 1-5 Scanning electron micrographs (SEM) of anterior half of G. seoi metacercaria.
Fig. 1. Whole ventral view. EP, excretory; OS, oral sucker; VL, ventrolateral lip; VP, ventral pit; VS, ventral sucker. Bar = 61.9 µm. Fig. 2. Oral sucker showing two sizes of type I papillae, small (open arrowheads) and large ones (closed arrowheads), and ventrolateral lips (arrows). Bar = 10.0 µm. Fig. 3. Magnification of the ventrolateral lip, showing 3-5 digitated tegumental spines and type I papillae. Bar = 2.4 µm. Fig. 4. Tegumental spines below the level of the oral sucker. Bar = 2.0 µm. Fig. 5. Tegument between the oral sucker and the ventral pit, showing median area devoid of spines and scattered type I papillae. Bar = 6.1 µm.
Figs. 6-10 SEM of posterior half of G. seoi metacercaria. Fig. 6. Postero-ventral surface showing the ventral pit (VP), genital pore (GP) and ventral sucker (VS). Bar = 7.4 µm. Fig. 7. Ventral sucker protruded. Bar = 6.3 µm. Fig. 8. Terminal portion of the body showing the excretory pore (arrow). Bar = 5.3 µm. Fig. 9. Tongue-shaped tegumental spines on antero-dorsal surface. Bar = 1.3 µm. Fig. 10. Poorly digitated tegumental spines on postero-dorsal surface. Bar = 1.2 µm.
Figs. 11-18 SEM on ventral surface of a 3-day old worm. Fig. 11. Whole ventral view. Bar = 60.0 µm. Fig. 12. Oral sucker and ventrolateral lips (arrows). Many type I papillae, small and large ones, encirled the lip of oral sucker. Bar = 10.0 µm. Fig. 13. Tegumental spines around the oral sucker. Bar = 1.0 µm. Fig. 14. Surface between the oral sucker and the ventral pit showing two grouped type I papillae. Bar = 5.0 µm. Fig. 15. Tegumental spines at the level of the ventral pit. Bar = 1.0 µm. Fig. 16. Type I papillae (arrows) on inner surface of the ventral pit. Bar = 3.0 µm. Fig. 17. Transverse cytoplasmic wrinklings between the ventral pit and ventral sucker showing type I papillae (arrows). Bar = 10.0 µm. Fig. 18. Ventral sucker with type I papillae (arrows). Bar = 5.0 µm.
Figs. 19-22 SEM on dorsal surface of a 3-day old worm. Fig. 19. Whole view showing type I papillae (arrowheads) scattered singly. Bar = 50.0 µm. Fig. 20. Tegumental spines with 8-10 points at anterior one-third of the body. Bar = 1.0 µm. Fig. 21. Tegumental spines with 6-7 points at mid-portion of the body. Bar = 1.0 µm. Fig. 22. Tegumental spines at posterior third of the body. Bar = 1.0 µm.
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