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Korean J Parasitol > Volume 25(2):1987 > Article

Original Article
Korean J Parasitol. 1987 Dec;25(2):129-140. English.
Published online Mar 20, 1994.  http://dx.doi.org/10.3347/kjp.1987.25.2.129
Copyright © 1987 by The Korean Society for Parasitology
Ultrastructural studies on the surface of Paragonimus westermani metacercaria
Kyong Min Kim,Myoung Hee Ahn and Duk Young Min
Department of Parasitology, Hanyang University Medical College, Seoul 133, Korea.

The present study was undertaken to demonstrate the surface structure of Paragonimus westermani metacercaria in Korea with special reference to the distribution of sensory papillae. Metacercariae were isolated from crayfish, one of the second intermediate host of P. westermani in Bogil island, Chollanam-do (Province), Korea, where has been known as an endemic area of human paragonimiasis. Isolated metacercariae were excysted and examined with light, scanning and transmission electron microscopes for morphological features. On the surface of metacercariae, three types of sensory papillae were identified. Large domed papillae (3-5 µm), which were covered with wrinkled plasma membrane of the worm, were distributed on the oral and ventral suckers only. On the oral sucker, these large domed papillae were 12-13 in number. On the other hand large domed papillae on the ventral sucker were constantly 6 in number and hexagonal in distribution. Small domed papillae (2-3 µm), of which surface was more smooth than those of large ones, were distributed symmetrically on the ventral (30-32 pairs) and dorsal surfaces (40-42 pairs). Ciliated papillae (0.8-1.5 µm) were observed about 5-6 in number around the oral sucker and 3-5 pairs each on the ventral and dorsal surface of the body. Single pointed spines covered the entire surface of the body except around the excretory pore. Spines on the anterior part of the body were 0.9-2.0 µm in length and 45-55/100 square µm in number, and were gradually reduced in length (0.4-1.4 µm) and in number (12-27/100 square µm) toward the posterior part. The body wall of P. westermani metacercariae was consisted with anucleated syncytium layer, fibrous interstitial layer and musclar layer. In the anucleated syncytium, biconcave (0.15-0.55 µm) and spherical (0.08-0.16 µm) secretory granules, which were transferred from epidermal cells via protoplasmic tubules, mitochondria and ribosomes, were observed. Spines originated around the basement membrane protruded externally. Epidermal cells were consisted with a nucleus and a cytoplasm, and connected to syncytium with protoplasmic tubules. In the cytoplasm many secretory granules, mitochondria, Golgi complex, endoplasmic reticula, ribosomes and lipid droplets were observed.


Diagram 1
Schematic diagram of tegumental differentiation of excysted metacercaria of P. westermani, ventral (A) and dorsal (B) view.

(a: large domed papillae, b: small domed papillae, c: ciliated papillae, d: large spine, e: small spine)

Diagram 2
Schematic diagram of sensory papillae around oral(A) and ventral suckers (B).

(◦ : large domed papillae, • : small domed papillae)

Figs. 1-4
Fig. 1. Excysted metacercariae of Paragonimus westermani.

Fig. 2.Ibid, ventral view. (EB: excretory bladder, I: intestine, Os: oral sucker, Vs: ventral sucker)

Fig. 3.Ventral view of an excysted metacercaria of P. westermani with SEM (×300). (Os: oral sucker, Vs: ventral sucker)

Fig. 4.Dorsal SEM view of an excysted metacercaria of P. westermani (×300).

Figs. 5-8
Fig. 5. Large domed papilla (sp) of P. westermani metacercaria around oral sucker (×20,000).

Fig. 6. Small domed papilla (sp) of P. westermani metacercaria on the ventral surface of anterior body. Single pointed spines(s) are seen (×14,000).

Fig. 7. Ciliated papilla (arrow) of P. westermani metacercaria.

Fig. 8. Oral sucker (Os) of P. westermani metacercaria. Large and small domed papillae (SP) are distinguished (×1,400).

Figs. 9-12
Fig. 9. Ventral sucker (Vs) of P. westermani metacercaria. Large and small domed papillae(SP) are well recognized (×840).

Fig. 10. Single pointed spines(s) on the dorsal surface of anterior part of P. westermani metacercaria (×14,000).

Fig. 11. Ibid, on the ventral surface of posterior body of P. westermani metacercaria (×14,000).

Fig. 12. Posterior end of P. westermani metacercaria. Spine is not seen around excretory pore (EP) (×5,000).

Figs. 13-14
Fig. 13. Sectioned tegument of P. westermani metacercaria. (BM: basement membrane, EP: epidermal cell, Mu: muscular layer, N: nucleus of epidermal cell) (×14,000).

Fig. 14. Spine of P. westermani metacercaria. (Mu: circular muscle layer, Mi: mitochondria, PT: protoplasmic tubule, Sg: secretory granules, Sp: spine) (×30,000).

Figs. 15-16
Fig. 15. Large domed sensory papilla on the ventral sucker of P. westermani metacercaria (DB: dense body of papilla, Sp: spine) (×10,000).

Fig. 16. Small domed sensory papilla on the dorsal surface of P. westermani metacercaria (Sp: spine, V: vesicle of papilla) (×12,500).


Table 1
Surface findings of excysted P. westermani metacercaria by SEM

Table 2
Number of sensory papillae of excysted P. westermani metacercaria

Table 3
Size and frequency of spines of excysted P. westermani metacercaria

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