[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

CHAPTER 10 The Cestodes
247
Hexacanth embryo
Colorless
embryophore
Capsule
Embryophore
A
Three pairs
Polar thickening
of hooklets
Average size: 55 m by 85 m
Hexacanth
embryo
FIGURE 10-7 A, Hymenolepis diminuta egg. B, Hymenolepis diminuta egg. (B from Bowman DD: Georgis’ parasitology
for veterinarians, ed 9, St. Louis, 2009, Saunders.)
B
TABLE 10-3
Hymenolepis diminuta
Egg: Typical Characteristics
at a Glance
Parameter
Description
Average size 55 by 85 µm
Hooklets
Three pairs; hexacanth embryo
Polar thickenings Present
Polar filaments Absent
Embryophore
Present; colorless
Suckers
Rostellum
(no hooks)
Hymenolepis diminuta
(high”men-ol’e-pis/dim-in-oo’tuh)
Common name: Rat tapeworm.
Common associated disease and condition
names: Hymenolepiasis, rat tapeworm disease.
Morphology
Eggs. The average Hymenolepis diminuta
egg measures 55 by 85 µm. The hexacanth
embryo contains three pairs of hooks (Fig. 10-7;
Table 10-3). A shell surrounds the embryo that
exhibits distinct polar thickenings and no polar
filaments (see Fig. 10-10A, H. nana egg, for filaments).
A colorless embryophore encloses the
entire structure.
FIGURE 10-8 Hymenolepis diminuta scolex.
Scolices. The H. diminuta scolex is equipped
with four suckers. A small rostellum bearing no
hooks protrudes from the anterior end of the
scolex (Fig. 10-8; Table 10-4).
Proglottids. Proglottids are typically rectangular,
measuring just under 1 mm by over 2 mm
(Table 10-4). Each mature segment contains one
set of female and one set of male reproductive
organs. The gravid proglottid (Fig. 10-9) consists