Light and electron microscopy observations of embryogenesis and egg development in the human liver fluke, Opisthorchis viverrini (Platyhelminthes, Digenea)

Khampoosa, Panita, Jones, Malcolm K., Lovas, Erica M., Srisawangwong, Tuanchai, Laha, Thewarach, Piratae, Supawadee, Thammasiri, Chalida, Suwannatrai, Apiporn, Sripanidkulchai, Bungorn, Eursitthichai, Veerachai and Tesana, Smarn (2012) Light and electron microscopy observations of embryogenesis and egg development in the human liver fluke, Opisthorchis viverrini (Platyhelminthes, Digenea). Parasitology Research, 110 2: 799-808. doi:10.1007/s00436-011-2557-3


Author Khampoosa, Panita
Jones, Malcolm K.
Lovas, Erica M.
Srisawangwong, Tuanchai
Laha, Thewarach
Piratae, Supawadee
Thammasiri, Chalida
Suwannatrai, Apiporn
Sripanidkulchai, Bungorn
Eursitthichai, Veerachai
Tesana, Smarn
Title Light and electron microscopy observations of embryogenesis and egg development in the human liver fluke, Opisthorchis viverrini (Platyhelminthes, Digenea)
Formatted title
Light and electron microscopy observations of embryogenesis and egg development in the human liver fluke, Opisthorchis viverrini (Platyhelminthes, Digenea)
Journal name Parasitology Research   Check publisher's open access policy
ISSN 0932-0113
1432-1955
Publication date 2012
Year available 2011
Sub-type Article (original research)
DOI 10.1007/s00436-011-2557-3
Volume 110
Issue 2
Start page 799
End page 808
Total pages 10
Place of publication Heidelberg, Germany
Publisher Springer
Collection year 2012
Language eng
Formatted abstract
Eggs of most species digenean flukes hatch in the external environment to liberate larvae that seek and penetrate a snail intermediate host. Those of the human liver flukes, Opisthorchis viverrini, hatch within the gastrointestinal canal of their snail hosts. While adult parasites are primarily responsible for the pathology in cases of human opisthorchiasis, their eggs also contribute by inducing granulomata and in serving as nidi for gallstone formation. In view of the peculiar biology of O. viverrini eggs and their contribution to pathology, we investigated embryogenesis in this species by light and transmission electron microscopy. Egg development was traced from earliest stages of coalescence in the ootype until full embryonation in the distal region of the uterus. Fully mature eggs were generally impermeable to resin and could not be examined by conventional electron microscopy methods. However, the use of high-pressure freezing and freeze-substitution fixation of previously fixed eggs enabled the internal structure of mature eggs, particularly the subshell envelopes, to be elucidated. Fertilization occurs in the ootype, and the large zygote is seen therein with a single spermatozoon wrapped around its plasma membrane. As the zygote begins to divide, the spent vitellocytes are pushed to the periphery of the eggs, where they progressively degrade. The early eggshell is formed in the ootype by coalescing eggshell precursor material released by approximately six vitelline cells. The early eggs have a thinner eggshell and are larger than, but lack the characteristic shape of, mature eggs. Characteristic shell ornamentation, the "muskmelon" appearance of eggs, appears after eggshell polymerization in the ootype. Pores are not present in the shell of O. viverrini eggs. The inner and outer envelopes are poorly formed in this species, with the outer envelope evident beneath the eggshell at the opercular pole of the mature egg. The miracidium has a conical anterior end that lacks the distinctive lamellar appearance of the terebratorium of other digeneans, such as the schistosomes. The miracidium is richly glandular, containing an apical gland in the anterior end, large cephalic gland, and posterior secretory glands. Each gland contains a secretory product with different structure. The paucity of vitelline cells associating with eggs, the reduced size of eggs, and reduced complexity of the extraembryonic envelopes are interpreted as adaptations to the peculiar hatching biology of the miracidia.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Online First. 23 July 2011

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2012 Collection
School of Veterinary Science Publications
 
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Citation counts: TR Web of Science Citation Count  Cited 11 times in Thomson Reuters Web of Science Article | Citations
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Created: Thu, 13 Oct 2011, 07:43:23 EST by Erica Lovas on behalf of School of Veterinary Science