The first discovery of larval Gnathostoma hispidum (Nematoda: Gnathostomidae) from a snake host, Agkistrodon brevicaudus
W M Sohn,*1 and S H Lee2
1Department of Parasitology, College of Medicine, Gyeongsang National University, Chinju 660-280, Korea.
Received February 06, 1998; Accepted March 28, 1998.
The present study was performed to observe the infection status of several kind of animals with indigenous Gnathostoma in Korea, and morphological characteristics of gnathostome larvae detected from pit-viper, Agkistrodon brevicaudus, for the species identification. To know the existence of Gnathostoma in Korea, 3,450 loaches, 24 bullfrogs, several kinds of snakes, i.e., 55 Elaphe rufodorsata, 2 Dinodon rufozonatum rufozonatum, 62 Rhabdophis tigrinus tigrinus and 87 Agkistrodon spp., and 438 cats were examined. A total of 21 larval gnathostomes was detected from 12 pit-vipers, A. brevicaudus. They were 2,233 × 0.343 mm in average size and covered with about 210 transverse rows of minute cuticular spines. Their characteristic head bulbs were provided with 4 rows of hooklets of which average numbers in each row were 36.8, 39.0, 41.7 and 44.3, posteriorly. In the cross sections of midgut level, the intestinal wall consisted of a single layer of 19-25 elongate epithelial cells with a single nucleus. SEM observation of the larvae revealed unique features of head bulb, cuticular spines on transverse striations and a cervical papilla. On the basis of above morphological characteristics, they were identified as the advanced third-stage larvae of Gnathostoma hispidum. It was first confirmed that the pit-viper, Agkistrodon brevicaudus is the snake intermediate host of G. hispidum.
Figs. 1-5 Fig. 1. An encysted larva of Gnathostoma hispidum from the muscle of a pit-viper, Agkistrodon brevicaudus. Fig. 2. The advanced third-stage larva (AdL3) of G. hispidum recovered from the muscle of a snake. Fig. 3. The AdL3 of G. hispidum recovered from the viscera of a snake. Figs. 4 & 5. Head-bulbs of the larvae bearing four transverse rows of hooklets.
Figs. 6-8 Cross sections of the AdL3 of G. hispidum collected from the pit-viper. Fig. 6. Esophagus level showing the cervical sacs (*), esophagus (E) and lateral cord (LC). Fig. 7. Midgut level showing the intestine (*) and lateral cord (LC). Fig. 8. Magnification of midgut level with a section of intestine consisted of single layer of elongate epithelial cells. Most epithelial cells possessed a single large nucleus.
Figs. 9-16 Scanning electron microscopic (SEM) view of the advanced third-stage larvae of Gnathostoma hispidum from the pit-viper, Agkistrodon brevicaudus. Fig. 9. Whole body showing a head-bulb with hooklets, about 210 rows of transverse striations with cuticular spines and a cervical papilla (encircled). Fig. 10. Subfrontal view of the head bulb. An amphid (A) and two labial papillae (LP) are seen on each lip. Fig. 11. Four transverse rows of hooklets on the head-bulb. Each hooklet somewhat curved posteriorly. Fig. 12. Magnification of the boxed area in Fig. 11. Two hooklets are seen on th 5th row (arrows). Fig. 13. Body surface of the anterior part having cuticular spines on the transverse striations and a dome -like cervical papilla located between the 11th and 12th transverse striations. Fig. 14. Magnification of a part of Fig. 13. Body surface consists of a highly wrinkled cuticle and posteriorly curved spines. Fig. 15. Body surface of the middle part of which cuticular spines are more sparsely distributedon the transverse striations. Fig. 16. Adjacent area of the anus of which surface consists of a highly wrinkled cuticle without spines.
Table 1 Results of a survey on the indigenous gnathostome in Korea
Table 2 Recovery of larval gnathostomes from the Korean vipers
Table 3 Measurementsa) of the larval gnathostome from Agkistrodon brevicaudus and comparison with those of previous authors
Table 5 Comparison of the number of hooklets on head-bulbs in four species of larval Gnathostoma (AdL3)
Table 6 Morphological differencesa) in cross at the midgut level in four species of larval Gnathostoma (AdL3)
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