Ultrastructural study of the tetrathyridium ofMesocestoides corti Hoeppli, 1925: Tegument and parenchyma

Abstract

The study of dividing and non-dividing tetrathyridia using electron microscopy shows that the mode of multiplication by antero-posterior fission of these larvae is due to a particular tissue which is called the "apical massif". The apical massif is a part of the tegumental syncytium. It is located at the top of the scolex. It represents a polynucleated cell mass which has cytomorphogenetic power. During asexual multiplication, it differentiates into tegumental syncytium, sub-tegumental muscles, glycogen-storing parenchyma cells, and other cell types. Parts of it remain undifferentiated. The hypothetic origin of the apical massif is discussed. Longitudinal growth of the tetrathyridia occurs by invasion of migrating cells into the tegumental syncytium. These cells also originate from the apical massif. During asexual multiplication and longitudinal growth, filamentous microtriches are synthesized below the plasmalemma of the superficial cytoplasm of the tegumental syncytium. It is supposed that the blade-like microtriches derive from filamentous forms.

A high resolution analysis of the structure and chemical composition of the calcareous corpuscles from Mesocestoides corti

“…In some cases, tiny concretions with structural characteristics similar to the whole CC can be perceived in SEM images, reminiscent of a fractal structure. This is consistent with previous reports, which state that the M. corti CCs have originated by the coalescence of "immature" smaller CCs (Hess, 1980). The layers are granular composite structures, as shown by AFM phase images.…”

Interactions between anomalous excretory and tegumental epithelia in aberrant Mesocestoides tetrathyridia from Apodemus sylvaticus in Spain

“…is uncommon in nature (Conn and Etges 1984;Conn 1990;McAllister and Conn 1990;McAllister et al 1989McAllister et al , 1991aMcAllister et al , b, c, 1992McAllister et al , 1995McAllister et al , 2005Hubbard et al 1993) but does occur in some cases by a variety of mechanisms (Specht and Voge 1965;Galán-Puchades et al 2002a, b). No asexual proliferation by fission of the scolex (Hess 1980;Conn 1986Conn , 1988a was seen in the present study, nor has it been documented in natural infections of any host outside North America, where it appears to be confined to the anomalous form of Mesocestoides vogae (Etges 1991). This sort of proliferation is very rare in nature, even in North America ) where it appears to be geographically confined primarily to western North America.…”

“…Both aberrant tetrathyridia and plerocercoids reproduce asexually by multiple budding and fission of the hindbody. Other anomalies occurring in Mesocestoides tetrathyridia involve development of multicephalic forms in Mesocestoides vogei, with numerous scoleces resulting in asexual reproduction (Specht and Voge 1965;Hess 1980;Etges 1991). Other more recent reports include acephalic and normal unicephalic forms of Mesocestoides from various hosts in North America and Spain.…”

Formation and Excretion of Calcareous Bodies by the Metacestode (Tetrathyridium) of Mesocestoides vogae

“…Such calcareous bodies can be seen even in vitro, on the bottom of containers in which tetrathyridia are kept in saline. Hess (1980) reported that calcareous corpuscles of M. corti (i.e., M. vogae) have numerous cytoplasmic filaments capable of phagocytosis and suggested that calcareous corpuscles serve "to stock metabolic end products which cannot be eliminated from the body." The results of the present study indicate that calcareous corpuscles are composed of metabolic end products that are removed from the body by passing through the tegument.…”