Echinococcus granulosus: changes in the surface ultrastructure during protoscolex formation

Abstract

SUMMARYChanges in the tegumentary projections of protoscoleces ofEchinococcus granulosus, developing within brood capsules, were examined at the ultrastructural level. The original scant covering of spineless, truncated microtriches was supplemented by a population of microvilli covering the entire surface of protoscoleces in the early stages of formation. As differentiation continued, rostellar hooks were formed by enlargement of single large (T1) microtriches, and normal spined microtriches were produced on the sucker region. These were formed in two ways: by addition of spine material to the truncated microtriches, andde novofollowed by up-lifting from the tegumentary surface. A second type of large microthrix (T2) was present in a band immediately below the developing hooks. These microtriches appeared to be formed from a fusion of existing microtriches, but were subsequently lost prior to scolex invagination. The microvilli were also shed from both the sucker and soma regions, to be replaced by microtriches and small blunt elevations respectively.

Research Note. One minute, intraoperative assessment of the viability of hydatid cysts using a simple reagent strip test

“…Regarding the alkaline pH recorded in all our HCF samples, when tested by reagent strip test, calcareous corpuscles were suggested to have a chief role behind such alkalinity. These corpuscles are unique structures representing the major component of the protoscolices (Rogan & Richards, 1987). The mineral element composition of corpuscle bodies is calcium, magnesium, phosphorus, sulphur, zinc and molybdenum.…”

Sensory receptors and surface ultrastructure of trypanorhynch cestodes

“…These``truncated microtriches'' or``microvilli'' of Rogan and Richards (1987) and Lumsden et al (1982) are distinctly shorter than the pectinate microtriches, have no junctional region, and lack an electron-dense medulla. An electron-lucent center is surrounded by an electron-dense sheath.…”

“…An examination of the microthrix ultrastructure along the bothridial margins might help to clarify the real relationship of the dierent taxa to tentaculariid or nontentaculariid trypanorhynchs, such as that proposed for the Hepatoxylidae/ Sphyriocephalidae as a sister clade of the Tentaculariidae by Campbell and Beveridge (1994), Palm (1997a), and Beveridge et al (1999). Whereas pectinate microtriches have been reported from members of the Pseudophyllidea (Lumsden et al 1982), Proteocephalidea (Thomsen et al 1980), and Cyclophyllidea (Rogan and Richards 1987), indicating a plesiomorphic origin, the hook-like, acerosate, and spiniform microtriches of the tentaculariids appear to be apomorphic.…”

Biology and Systematics of Echinococcus

“…Fully developed protoscoleces are characterized by the possession of hooks on the invaginated rostellum. The spines of microtriches are the precursors of the hook blades which become enveloped by the rostellar tegument with subsequent formation of the guard and handle (Rogan and Richards, 1987) with subsequent addition of hook material in the adult worm (Hobbs et al, 1990). Hook formation must be subject to environmental factors of host origin given the variability in hook number and size in the same species of Echinococcus from different hosts.…”