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Korean J Parasitol > Volume 24(2):1986 > Article

Original Article
Korean J Parasitol. 1986 Dec;24(2):109-114. English.
Published online Mar 20, 1994.  http://dx.doi.org/10.3347/kjp.1986.24.2.109
Copyright © 1986 by The Korean Society for Parasitology
Growth and development of Fibricola seoulensis metacercariae in tadpoles
Soon Hyung Lee,Shon Moon Shin,Sung Tae Hong,Woon Mok Sohn,Jong Yil Chai and Byong Seol Seo*
Department of Parasitology and Institute of Endemic Diseases, College of Medicine, Seoul National University, Seoul 110, Korea.
*Department of Parasitology, College of Medicine, Inha University, Inchon, 160-01, Korea.

In order to observe the growth and development of Fibricola seoulensis metacercariae, the tadpoles of Rana nigromagulata were experimentally infected with the cercariae. The metacercariae of various developmental stages were recovered from the tadpoles after 2 to 65 days of infection. They were prepared for morphological observation, and were given orally to mice to observe their infectivity. The following results were obtained. All of the tadpoles exposed to the cercariae were observed to harbour the larvae in their abdominal cavity. The young metacercariae of 2 days after infection were 121.1 µm long and 63.3 µm wide. They grow linearly for the first 14 days to be 262.0 µm long and 166.4 µm wide. Thereafter, no more growth recognized until 65 days. The larvae of 2 days old were similar with cercarial body and had 2 suckers, a pharynx, two ceca and a primordium of germ cells but no tribocytic organ. On the 8th day, they had tribocytic organ, and their morphology resembled that of mature metacercariae. The metacercariae younger than 10 days could not infect the mice. Only the metacercariae older than 14 days had infectivity. The recovery rate increased by the age of metacercariae from 19.0% in 14 days old to 70.0% in 40 days old. Above findings indicate that the tadpole is indispensible for metacercarial development and it needs at least 2 weeks for maturation. The tadpole is a pivotal host in the life cycle of F. seoulensis for connection between the snail and the frog.


Fig. 1
The growth curve of the metacercariae of Fibricola seoulensis recovered from the experimentally infected tadpoles by age.

Figs. 2-7
Fig. 2. A 2-day old metacercaria of F. seoulensis recovered from tadpoles, acetocarmine stained (scale; 50µm).

Fig. 3. A 3-day old metacercaria of F. seoulensis. acetocarmine stained (scale; 50µm).

Fig. 4. A 5-day old metacercaria of F. seoulensis. acetocarmine stained (scale; 50µm, GCM; germ cell mass).

Fig. 5. A 8-day old metacercaria of F. seoulensis. acetocarmine stained (scale; 50µm, OS; oral sucker, VS; ventral sucker, TO; tribocytic organ).

Fig. 6. A 14-day old metacercaria of F. seoulensis. acetocarmine stained (scale; 100µm).

Fig. 7. A metacercaria of F. seoulensis form the naturally infected snake, acetocarmine stained (scale; 100µm).


Table 1
Measurements of acetocarmine stained metacercariae of Fibricola seoulensis recovered from experimentally infected tadpoles (average of 10 metacercariae)

Table 2
The infectivity of Fibricola seoulensis metacercariae by age

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