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Korean J Parasitol > Volume 22(1):1984 > Article

Original Article
Korean J Parasitol. 1984 Jun;22(1):1-10. Korean.
Published online Mar 20, 1994.  http://dx.doi.org/10.3347/kjp.1984.22.1.1
Copyright © 1984 by The Korean Society for Parasitology
Study on Metagonimus yokogawai(Katsurada, 1912) in Korea VII. Electron microscopic observation on the tegumental structure
Soon Hyung Lee,Byong Seol Seo,Jong Yil Chai and Sung Jong Hong
Department of Parasitology and Institute of Endemic Diseases, College of Medicine, Seoul National University, Korea.

This study was performed to observe the chronological changes in the tegumental structure of M. yokogawai using scanning electron microscope. The subjected worms were excysted metacercariae obtained from sweetfish, and 2-day, 1-week and 4-week old worms experimentally reared in albino rats. The results are as follows: The tegument of excysted metacercariae showed many transverse shallow rugae, which were more remarkable in posterior half body, i.e., posterior to ventral sucker. The whole surface was armed with many scale-like spines; 7-8 pointed ones on anterior body and 2-3 pointed on posterior body. The ciliated knob-like papillae (Type I) were abundant around oral and ventral suckers, which grouped 2, 3 or 4 in number in most cases. A few round swellings of tegument (Type II) were observed only on oral sucker. The tegumental surface of 2-day old worms showed deeper rugae, and the anterior half covered with knob-like processes of distal cytoplasm and the posterior half with cobblestone-like ones. Interspinous space became more wide and 9 pointed spines appeared on anterior dorsal surface. The sensory papillae enlarged but not changed in their distribution. The tegument of 1-week old worms revealed knob-like cytoplasmic processes in posterior half body and velvety ones around oral sucker. The scale-Iike spines of anterior half body changed remarkably to the slender ones of posterior body at the level of ventral sucker. In dorsal surface, the arrangement of the Type I papillae were bilaterally symmetrical. The tegument of 4-week old worms were finely differentiated and the posterior tegument covered with velvety cytoplasmic processes. The spines had remarkably grown in length and width but the density remained nearly unchanged. The papillae also became larger but their morphology and distribution were not different from younger worms. However, the round elevation of cytoplasmic ridges (Type III papilla) appeared bilaterally on inner wall of oral sucker, approximately 8 in number. From the above results, it is considered that the tegument of juvenile M. yokogawai continued to differentiate until 4 weeks after infection.


Figs. 1-8
*Scale unit is micrometer(µm).

Fig. 1-5. Scanning electron microscopy(SEM) of excysted metacercaria.

Fig. 1. Ventral view of anterior halfbody showing oral sucker(OS), retracted ventral sucker(VS),transverse wrinklings, and circlings of spines. ×1,060.

Fig. 2. Circlings of 7-8 pointed scale-like spines on anterior body forming another diagonallines. ×10,300.

Fig. 3. Dorsal surface of posterior body. Note the transverse shallow rugae and textile-like arrangement of 2-3 pointed spines(S). ×10,000.

Fig. 4. Higher magnification of boxed area in Fig. 1 showing quadruple ciliated knob-like arrangement of 2-3 pointed spines(S). ×10,000.

Fig. 5. The under-developed round swellings (Type II papillae; P) on the rim of OS and single, double or triple Type I papillae(S, D & T). ×2,510.

Fig. 6-9. SEM of 2-day old worm.

Fig. 6. Anteriorly faced VS in tegumental pit. ×2,510

Fig. 7. Ventro-mid-median surface of anterior body showing sharp triangular spines. ×10,300.

Fig. 8. Anteriormost dorsal surface showing knob-like cytoplasmic processes and 9 pointed scale-like spines. ×10,000.

Fig. 9-14
*Scale unit is micrometer(µm).

Fig. 6-9. SEM of 2-day old worm.

Fig. 9. The cobblestone-like cytoplasmic processes(C) and acute angled spines(S) on ventro-midian surface of posterior body. ×10,000.

Fig. 10-12. SEM of 1-week old worm.

Fig. 10. General view of ventral surface showing well developed VS and conspicuous difference in distribution of spines in anterior and posterior bodies. ×408.

Fig. 11. The diagonal arrangement of spines and symmetrical distribution of Type I papillae (arrow) in dorsal surface. ×800.

Fig. 12. The velvety tegumental processes of OS and Type II papillae(P2), and the Type I papillae(P1) around OS. ×5,060.

Fig. 13-20. SEM of 4-week old worm.

Fig. 13. Anterodorsal surface showing knob-like cytoplasmic processes, 7-9 pointed spines(S) and triple Type I papillae(P). ×5,000.

Fig. 14. Dorso-median surface of posterior one-third showing velvety cytoplasmic processes and 3-5 pointed spines(S). ×10,200.

Fig. 15-20
*Scale unit is micrometer(µm).

Fig. 13-20. SEM of 4-week old worm.

Fig. 15. Tegumental surface of posterodorsal end showingf more velvety cytoplasmic processes and slender 3-5 pointed spines(S). ×10,200.

Fig. 16. The contracted muscular VS in tegumental pit. ×3,500.

Fig. 17. The excretory pore(EP), velvety and aspinous. ×10,000.

Fig. 18. Scale-like spines between oral and ventral suckers. ×10,000.

Fig. 19. The round swelling of cytoplasmic ridges (Type III papillae: P) on the inner wall of OS. ×2,010.

Fig. 20. Higher magnification of Type III papillae in Fig. 19. ×10,000.


Table 1
Summary of scanning electron microscopic findings of Metagonimus yokogawaiby age of worms

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