Ultrastructural characteristics of progenetic and monoxenic Archigetes sieboldi Leuckart, 1878 from the oligochaete Limnodrilus hoffmeisteri Claparède are described. Our observations demonstrate that progenetic Archigetes sieboldi shares characteristics of both larval (progenetic) and adult stages. The primary larval characteristics are: the presence of a cercomer; a surface filamentous coat covering the whole worm; the presence of the penetration glands and the absence of tegumental ones; wide sarcoplasmic processes connecting the circular and longitudinal external tegumental muscles; the absence of the dense homogenous zone of the basal lamina beneath the epithelial cytoplasm of all reproductive organs and ducts; non-functional gonopores; and an orthogonal plan of nervous system with three pairs of longitudinal nerve trunks. The principle adult characteristics are: oogenesis, spermiogenesis and vitellogenesis that produce fertilized eggs; the uterine glands; a well-developed longitudinal tegumental muscle layer between tegumental cytons; and the presence of different microtriches. As a result of this progenetic development there has been a secondary reduction in the life cycle of A. sieboldi. It is postulated that a similar process of progenesis may have played a major role in the early evolution of the Caryophyllidea by first appearing in a plerocercoid stage of an ancestral strobilate cestode from fish.
In anabiotic statě mesophyll cells of both species were filled with vacuoles, chloroplasts were round and without outer envelope and starch. During an 8-d rewatering period cell water saturation deficit continuously (from 80-85 % to 15- 20 %) declined, eliptic shape of chloroplasts was restored, their outer membrane was recovered, grana stacks grew in size and were ordered, stroma was denser, and starch grains started to be formed. The processes were more rapid in Ramonda serbica than in Haberlea rhodopensis. The course of processes was different in irradiated plants than in those kept in the dark.
Mabuya vitatta (Olivier) (Scincidae) and Agama stellio (L.) (Agamidae) were infected with Hemolivia mariae Smallridge et Paperna, 1997 by ingestion of tick viscera from Amblyomma limbatum Neumann, fed as nymphs on naturally infected Australian sleepy lizards, Tiliqua rugosa Gray. The unnatural infection apparently interfered with the developmental schedule of the parasites. Transmission electron microscopic images of merogonic stages were obtained, as well as images of early developing gametocytes. Tissue and intraerythrocytic meronts were bound by a hardened wall. Intraerythrocytic gametocytes were lodged in a parasitophorous vacuole, which was filled with granular material, and were bound by a two-membrane wall. Small and large osmiophilic bodies were located in a sub-pellicular position. With differentiation, the wall membranes tightened with the parasitophorous vacuole wall, and the osmiophilic bodies disappeared. The outer parasite membrane consolidated into a thick encasing with distinct sutures. Late infection in A. stellio comprised gametocytes only.
Subepidermal glands of the body of Troglocaridicola sp. (from the cavemicolous shrimp Troglocaris sp. in eastern Italy) were observed by transmission electron microscopy. The reservoir and duct of the glands arc lined with longitudinal microlubulcs. Membrane-bound granules inside the gland show a distinctive pattern: they contain fibres, 18 nm in diameter, regularly arranged in bundles with a 5 nm space between libres. From a survey of the available literature on glands of Platyhelminthes, it is concluded that this structure is known only in this species. Glands with regularly arranged 18 nm fibres, if characteristic for the Scutariellidae, could be considered an autapomorphy of this family, distinguishing it from other members of the Temnocephalida.
In mesophyll chloroplasts of control plants of grape vine (Vilis vinifera L.) growing in greenhouse, grana consisted of 3-10 thylakoids interconnected by long stroma thylakoids. Chloroplasts in magnesium-deficient plants were characterized by a dense stroma, poorly distinquished fme stroma lamellae, and by an accumulation of large osmiophilic globules. Under iron deficiency, the chloroplasts exerted two types of damage of intemal structure: (7) grana consisted of 2-6 thylakoids, the stroma lamellae were destructed; (2) grana were reduced, the stroma lamel ae were broken into short thick fragments, that were laid successively in the direction along the axis of the chloroplasts.
The scolex surface of the mature spathebothriidean Cyathocephalus truncatus (Pallas, 1781), a parasite of the brown trout Salmo trutta fario L., was studied using scanning and transmission electron microscopy. A particular attention was paid to microtriches, unique structure on the surface of the Cestoda. The scolex of C. truncatus is covered with two types of filiform microtriches (filitriches): aciculate (≈ 3 µm long) and capillate (≈ 10 µm long). Capillate microtriches, which have never been reported in any other spathebothriideans, are described for the first time using transmission electron microscopy. The tegument covered with filiform microtriches only (no spiniform microtriches are present) is typical of cestode groups supposed to be the most basal, e.g., Gyrocotylidea, Spathebothriidea, and Caryophyllidea.
Ultrastructural characters of spermiogenesis and mature spermatozoon of Triaenorhina rectangula (Fuhrmann, 1908) are examined by transmission electron microscopy. Spermiogenesis follows the Bâ and Marchand's Type III spermiogenesis of cestodes. The process begins with the formation of a differentiation zone containing two centrioles and a cytoplasmic protrusion. The centrioles are associated with vestigial striated roots. One of the centrioles develops a free flagellum externally to the cytoplasmic protrusion. After a slight rotation, the free flagellum fuses with the cytoplasmic protrusion. In the final stage of spermiogenesis, a single crested body appears in the anterior part of the differentiating spermatozoon. The anterior extremity of the mature spermatozoon is characterised by an apical cone and a single crested body. The axoneme is of the 9+''1'' trepaxonematan type. A periaxonemal sheath and electron-dense rods are described in some parts of the mature spermatozoon. The nucleus is electron-dense and spirally coiled around the axoneme. The cortical microtubules are spirally arranged at an angle of about 40° to the spermatozoon axis. The present results show that the ultrastructural characters of spermiogenesis and mature spermatozoon of T. rectangula resemble most closely those in taeniids and metadilepidids. The comparison of these results with the only previous spermiological description of a paruterinid species reveals differences relative to the occurrence of filamentous rods of electron-dense material versus intracytoplasmic walls in the mature spermatozoon that may reflect the polyphyletic character of the Paruterinidae.
Ultrastructural analysis revealed that the spermatozoon of Discocotyle sagittata (Leuckart, 1842) is composed of two parallel axonemes, mitochondrion, nucleus and cortical microtubules. The nucleus, which occupies a central/distal position and has an unusual crescent-shaped profile, is slightly shorter than the mitochondrial rod. The two axonemes, which are of unequal length, and the cortical microtubules (up to 68 forming a continuous ring in the principal region) extend almost the entire length of the spermatozoon. A fold of the plasma membrane creates a unilateral flange or undulating membrane. Epifluorescence microscopy indicated that spermatogenesis gives rise to clusters of 64 spermatids connected to a common cytophore. Spermiogenesis and the structure of the filiform sperm of D. sagittata conform to the typical polyopisthocotylean pattern.
Spermiogenesis in Phyllobothrium lactuca Beneden, 1850 begins with the formation of a differentiation zone bordered by cortical microtubules and containing a nucleus and two ccntrioles separated by an intercentriolar body and disposed one in the prolongation of the other. Later, formation of flagellar buds, striated roots and a median cytoplasmic extension takes place. Each centriole gives rise to a flagellimi that rotates and fuses with the median cytoplasmic extension. At this stage, arched membranes appear at the front of the differentiation zone. The nucleus elongates, becomes filiform and migrates between the striated roots into the spermatid. After the migration of the nucleus, the old spermatid separates from the residual cytoplasm by strangulation of the ring of arched membranes. Absence of striated roots, right at the beginning of spermiogenesis has never been described before in the Tctraphyllidea. Likewise, centrioles made up of doublets of microtubules and spermatids with two axonemes have never been reported before during spermiogenesis of a Phyllobothriidae. In this work we show, for the first time, the existence in cestodes of thick-walled microtubulcs surrounded by a layer of electron-dense material. In addition, we describe, for the first time, the existence of an accumulation of electron-dense granules around striated roots and an hour-glass-shaped constriction at the anterior extremity of a median cytoplasmic extension in a platyhelminth.