W. Apinhasmit et al., OPISTHORCHIS-VIVERRINI - ULTRASTRUCTURE OF THE TEGUMENT OF THE FIRST-WEEK JUVENILES AND ADULT FLUKES, International journal for parasitology, 24(5), 1994, pp. 613-621
The tegument of one-week-old and adult flukes of Opisthorchis viverrin
i were studied by transmission electron microscopy. The tegument of bo
th stages is composed of a syncytium formed by processes of the tegume
ntal cells lying underneath the outer-circular and the inner-longitudi
nal muscle layers. The tegument is bounded by trilaminate outer and in
ner membranes; the former is coated with a thin glycocalyx, while the
latter has short basal infoldings. There are 4 forms of tegumental gra
nules, namely dense spherical, dense discoid, light spherical and ligh
t discoid granules. Dense spherical and dense discoid granules have si
milar dense homogeneous and highly electron-dense matrices; thus, they
may represent different planes of sections of biconcave granules, and
may contribute their content to the formation of the outer membrane a
nd the glycocalyx. Light spherical and light discoid granules may be a
nother type of granule whose filamentous content may contribute to the
formation of the microtrabecular network in the tegument. Microvilli
start to develop in one-week-old juveniles and become fully developed
in adult stages. The size, number and cristae of the mitochondria beco
me increasingly more numerous along with the development of microvilli
; in the first-week juveniles most mitochondria are located in the bas
al portion of the tegument while in adults most lie within microvilli
underneath the outer membrane. The tegumental cell is irregular in sha
pe and contains a nucleus with a prominent nucleous, abundant rough en
doplasmic reticulum, well developed Golgi complexes, ribosomes, mitoch
ondria and numerous tegumental granules. These features indicate that
the cell is an active secretory cell, whose product is tegumental gran
ules that may be transported via microtubule-lined cytoplasmic process
es to the syncytium.