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Korean J Parasitol > Volume 33(3):1995 > Article

Original Article
Korean J Parasitol. 1995 Sep;33(3):165-172. English.
Published online Sep 20, 1995.  http://dx.doi.org/10.3347/kjp.1995.33.3.165
Copyright © 1995 by The Korean Society for Parasitology
TEM ultrastructure of the tegumental layer of Gymnophalloides seoi (Digenea: Gymnophallidae)
M Seo,J Y Chai,* and S H Lee
Department of Parasitology and Institute of Endemic Diseases, Seoul National University College of Medicine, Seoul 110-799, Korea.
Received July 14, 1995; Accepted August 01, 1995.


A transmission electron microscopic study was performed on the ultrastructure of the tegumental layer of Gymnophalloides seoi (Digenea: Gymnophallidae) metacercariae and adults. The metacercariae were obtained from naturally infected oysters, Crassostrea gigas, and the adults from experimentally infected C3H mice. The tegumental layer generally revealed a small number of foldings, numerous small vacuoles, sines, and muscle bundles. Beneath the muscle layer, nuclei of the tegumental cells were located. There was little difference in the structure of the tegument between the metacercariae and adults. The oral sucker, having well-developed muscle layers, showed a similar structure to the ventral sucker except numerous foldings in the ventral sucker. The ventral pit was surrounded by a thin syncytial layer, where a number of microtubules and mitochondria were seen. Around the ventral pit located well-developed circular and longitudinal muscles. The results showed that the ultrastructure of the tegumental layer of G. seoi metacercariae and adults revealed little difference from other trematodes in general. The ventral pit, a peculiar structure of this trematode, seems to function as a sphincter or an accessory adhesive organ.


Figs. 1-6
Fig. 1. The tegumental layer of a G. seoi metacercaria showing the spines (S), basement membrane (BM), circular (C) and longitudinal (L) muscle bundles. ×5,000. Fig. 2. The tegument of another metacercaria. The nucleus (N) of a tegumental cell is seen. ×6,000. Fig. 3. The tegument of an adult worm. Numerous small vacuoles (SV) and eletron-dense granules (EDF) are seen inth syncytial layer. ×5,000. Fig. 4. Magnification of the tegumental layer of an adult worm. SV (small vacuole), EDG (electron-dense granules). ×10,000. Fig. 5. A tegumental spine (S) on the tegument. It is surrounded by the extension of external plasma membrane of the tegument. ×25,000. Fig. 6. The oral sucker of a metacercaria. A number of small vacuoles and well-developed circular (C) and longitudinal (L) muscle bundles are seen.

Figs. 7-10
Fig. 7. The oral sucker of a G. seoi metacercaria. In the tegumental layer, numerous small vacuoles (SV) and electron-dense granules (EDG) are seen. ×15,000. Fig. 8. Deeper part of the oral sucker of metacercaria. Below the basement membrane (BM), several electron-dense granules (EDG) are seen. ×15,000. Fig. 9. The oral sucker of an adult worm. Circular (C) and longitudinal (L) muscles are seen. ×12,000. Fig. 10. Deeper part of the oral sucker of an adult worm. Well-developed longitudinal muscle bundles (L) are seen. ×12,000.

Figs. 11-14
Fig. 11. The ventral sucker of an adult worm. The muscle bundles (Mb) ard not apparent in comparison with those of the oral sucker. The round lumen (Lu) side is seen. ×5,000. Fig. 12. A tegumental cell of the ventral sucker is seen among the circular muscle bundles (C). A nucleus (N) with dense chromatins (Cm) is seen. ×15,000. Fig. 13. The ventral pit of an adult G. seoi. Circular (C) and longitudinal (L) muscles are seen. The lumen (Lu) id leaf-like, and beneath the tegumental layer (TL) located a basement membrane (BM). Below it, circular (C) and longitudinal (L) muscles ard seen. ×5,000. Fig. 14. Magnification of the ventral pit, showing many mitochondria (arrows) and microtubules (arrow heads) in the tegumental layer. In a longitudinal muscle (L) layer, a pair of mitochondria (M) are seen, C: circular muscle. ×20,000.

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