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Korean J Parasitol > Volume 23(2):1985 > Article

Original Article
Korean J Parasitol. 1985 Dec;23(2):221-229. English.
Published online Mar 20, 1994.  http://dx.doi.org/10.3347/kjp.1985.23.2.221
Copyright © 1985 by The Korean Society for Parasitology
Metacercariae of Echinochasmus japonicus encysted in a fresh water fish, Pseudorasbora parva, and their development in experimental mice
Jong Yil Chai,Song Jong Hong,Dong Woo Son,Soon Hyung Lee and Byong Seol Seo
Department of Parasitology and Institute of Endemic Diseases, College of Medicine, Seoul National Univestiy, Seoul 110, Korea.

The echinostomatid metacercariae encysted in the gill of the fresh water fish, Pseudorasbora parva were identified through obtaining adult worms after experimental infection to mice. In addition, a brief course of worm development and maturation was observed in this experimental host. The results were as follows: The echinostomatid metacercariae were elliptical, golden yellow, 0.073-0.078 mm long and 0.054-0.065 mm wide. Their head portions were characterized by the presence of a head crown armed with collar spines of total 24 in number and interrupted at the mid-dorsal side of the oral sucker. The average rate of worm recovery from 12 mice (on the 1-21th postinfection days) was 19.4 percent and the rate revealed no decrease in accordance with the increase of infection duration. The worms were collected chiefly from the lower part of the small intestine. After the infection, their sexual maturation was attained in 5 days and their growth in size nearly completed in 7 days. The early growth curve of genital organs was S shape while that of nongenital organs was C form. In 5 day old worms, l or 2 eggs were found from their uteri and the stools of mice revealed echinostomatid eggs from the 5-6th postinfection day. The 7 day old adult worms were ovoid in shape, 0.54-0.69 mm long and 0.29-0.34 mm wide, and characterized by a well developed head crown with 24 collar spines and vitelline follicles distributed from the acetabular level down to the posterior end of body. Based on these characters they were identified to be Echinochasmus japonicus Tanabe, 1926. From these results, it is verified that P. parva is one of the second intermediate hosts of E. japonicus in Korea.


Fig. 1-4
Fig. 1. The metacercariae of E. japonicus collected from the gill of Pseudorasbora parva. Note their characteristic appearance (Scale: 80µm).

Fig. 2.Ibid in bending form (Scale: 20µm).

Fig. 3.Ibid in ventral view. Head crown (arrows) is distinct (Scale: 20µm).

Fig. 4.Ibid in ventral view. Slightly compressed. Oral sucker (os), ventral sucker (vs) and excretory corpuscles are seen (Scale: 20µm).

Fig. 5
The growth curves of E. japonicus in mice up to 21 days after experimental infection.

Fig. 6
The growth curves of E. japonicus non-genital organs in mice.

Fig. 7
The growth curves of E. japonicus genital organs in mice.

Figs. 8-10
Fig. 8. Two-day old worm of E. japonicus showing its characteristic head crown with collar spines and two suckers (Scale: 40µm).

Fig. 9. Three-day old worm showing some development of tests(T) (Scale: 40µm).

Fig. 10. Four-day old worm. Ovary (ov) and testes have markedly grown in size (Scale: 40µm). *Unstained specimens

Figs. 11-12
Fig. 11. Five-day old worm. Ovary, testes, cirrus sac and vitelline follicles are seen. One egg is formed in uterus (Scale: 40µm).

Fig. 12. Seven-day old full grown worm, the largest one observed. No egg is observed in this worm (Scale: 65µm). *Unstained specimens

Figs. 13-15
Fig. 13. Magnification of head crown in Fig. 12. Note that the spines are 24 in total number and interrupted (arrows) near the dorsal side of oral sucker (Scale: 30µm).

Fig. 14. Magnification of collar spines of another worm. Note the shape and arrangement of the spines (Scale: 20µm).

Fig. 15. Magnification of the middle portion of the worm in Fig. 11. The relationships between ventral sucker, egg, ovary and testes are shown in this figure (Scale: 20µm).


Table 1
The recovery of E. japonicus from the experimental mice

Table 2
The distribution of E. japonicus in small intestine of mice

Table 3
The measurements of E. japonicus recovered from mice according to ages of worms

Table 4
Comparative features of E. japonicus and E. perfoliatus (Rim, 1982; Yamashita, 1964)

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