The organization and fine structure of the muscles of the scolex of the cysticercoid of Hymenolepis microstoma

The organization and fine structure of the muscles of the scolex of the cysticercoid of Hymenolepis microstoma are described. The contractile apparatus consists of thick (175–325 Å diameter × 1.4 μm) and thin (60–80 Å diameter × 1 μm) filaments. The thick filaments are occasionally attached to the thin filaments by cross bridges. The thin filaments are attached to the dense bodies or to a dense zone at the sarcolemma at muscle insertions. In contracted muscle the thick filaments appear as quasi-hexagonal arrays or in lines. Each thick filament is surrounded by an orbit of up to 12 thin filaments, which in turn may be shared by adjacent thick filaments. Thin filaments may be present in quasi-rectangular or hexagonal groupings indicating some low order degree of actin lattice. The fusiform dense bodies (1,500 Å × 900 Å), consisting of up to 25 discrete substructures, are distributed uniformly throughout the myofiber and/or attached to the sarcolemma at attachment plaques. The sarcoplasmic reticulum, consisting of a presumed anastomosing network of tubules is structurally connected to the sarcolemma by periodic deposits of electron opaque material. Sarcoplasmic extensions of the myofiber(s) contain the nucleus, Golgi complexes, rough endoplasmic reticulum, ribosomes, β-glycogen, mitochondria and membrane bound electron dense structures. Upon activation of the metacestode, groups of α-glycogen and enlargement of the rough endoplasmic reticulum were observed. Microtubules which were conspicuously absent from the sarcoplasm of the unactivated worms appeared adjacent to the myofibers in activated worms.     

The fine structure of spermatogenesis in Hymenolepis diminuta (Cestoda) with a description of the mature spermatozoon

The processes of spermatogenesis and spermiogenesis in Hymenolepis diminuta were studied by electron microscopy using improved preparative techniques. Spermatogonia (Type A) are characterized by nuclei 3.79 (+/- 0.17) micrometer in diameter, dense cytoplasm packed with free ribosomes and aggregates of mitochondria. After mitoses, certain spermatogonia (Type B) assume syncytial rosettes containing eight nuclei. Primary spermatocytes maintain the rosette syncytium and have large nuclei (4.28 +/- 0.24 micrometer in diameter), smooth endoplasmic reticulum, and polysomes. The secondary spermatocyte is short-lived and is characterized by nuclei (2.0 +/- 0.11 micrometer in diai (2.0 +/- 0.11 micrometer in diameter) and perinuclear membranous lamellae. The syncytial spermatid cluster contains avoid nuclei which condense and elongate to a final diameter of 0.22 +/- 0.04 micrometer. Once elongated, these nuclei become delimited from the syncytium by invaginations of the plasma membrane. During delimitation, cortical peripheral microtubules arise beneath the spermatozoon plasmalemma and a 9 + 1 axoneme extends the length of the mature lance-shaped spermatozoon.     

The architecture of the eggshell of Hymenolepis diminuta.

Lethbridge R. C. 1976. The architecture of the eggshell of Hymenolepis diminuta. International Journal for Parasitology6: 87–90. Scanning and transmission electron microscopy demonstrated that the eggshell of H. diminuta consisted of an inner continuous band from which arose an outer zone of finger-like projections with rounded tips. These tips were revealed as globule-like units lacking a regular spatial distribution but entirely covering the eggshell's surface. The appearance of these structures suggested that the shell constituents may have been deposited in an initially plastic state and possible methods of attaining the final architecture of the hardened eggshell have been discussed on the basis of this hypothesis.