|
|
Functional Ultrastructure of Hymenopteran Stingers: Devastating Spear or Delicate Syringe
ČERNÝ, Jan
In this study, we tested the hypothesis that a micro-serrated edge on the honey bee Apis mellifera stinger tip serves as a tool for more intensive crushing of cell membranes in the victim's tissues. This could have mechanical consequences as well as initiate metabolic pathways linked to cell membrane breakdown (e.g., production of biogenic amines). Accordingly, we found that hymenopteran species that use their stingers as an offensive or defensive weapon to do as much damage to the victim's body as possible had this cuticular microstructure. In parasitic hymenopterans, on the other hand, this structure was missing, as stingers are solely used to delicately transport venom to the victim's body in order to do little mechanical harm. We also demonstrated that the stinger lancets of the honey bee A. mellifera are living organs with sensilla innervated by sensory neurons and containing other essential tissues, rather than mere cuticular structures.
|
|
|
Cambarellinae: Trpaslíci ve světě račích spermií?
TOMAN, Jan
Recently, the ultrastructure of crayfish spermatozoa has become an increasingly studied topic. Up to now, the ultrastructure has been studied and defined in about fifteen species of freshwater species from all four crayfish families, however it has not yet been studied in a group of dwarf crayfish (subfamily Cambarellinae). Present work aimed to describe the spermatozoa ultrastructure of two dwarf crayfish species, specifically the Orange dwarf crayfish Cambarellus patzcuarensis and the Texas dwarf crayfish C. texanus. These species were then compared with the species already studied using morphological traits and biometric data. The ultrastructure of their spermatozoa shows commonly known patterns that include the acrosome and subacrosome in the front and the nucleus on the opposite side of the cell . Furthermore, radial arms typical for the superfamily Astacoidea that wrap around the nucleus and the whole cell enclosed by the extracellular capsule. The results show that the size of the acrosomes of Parastacidae membres is the smallest, while the crayfish of the Astacidae family show the largest acrosome. The current study points out a medium-sized acrosome of dwarf crayfish and Cambaridae in general, although they are located at the lower margin of this family with the Brazos crayfish being close to representatives of the Parastacidae. In conclusion, it is important to say that the combination of the morphological traits and biometric data of sperm acrosomes allows distinguishing individual crayfish groups to a large extent. This study may help to identify other species that have not been studied so far and could be a valuable basis for subsequent research of the ultrastructure and biometrics of crayfish spermatozoa.
|
|
|
Diversity and phylogeny of Archamoebae
Zadrobílková, Eliška ; Čepička, Ivan (advisor) ; Kostka, Martin (referee) ; Bardůnek Valigurová, Andrea (referee)
Members of the group Archamoebae are free-living or endobiotic amoeboid flagellates and amoebae. They live in anoxic or microoxic habitats, and their mitochondria have been reduced. They were originally thought to lack mitochondria and represent one of the earliest eukaryotes. However, this hypothesis has been refuted, and now it is evident that the Archamoebae belongs to the lineage Conosa within the supergroup Amoebozoa, together with aerobic slime molds (Macromycetozoa) and variosean amoebae and flagellates. Relatively simple microtubular cytoskeleton is a characteristic feature of Archamoebae. It consists of a single basal body from which a flagellum arises, lateral root, and microtubular cone. Cytoskeleton of aflagellated genera has been completely reduced. About 350 species names of Archamoebae have been created so far. However, most descriptions were based on inadequate morphological features. The identity of numerous species is uncertain, and many of them are likely synonymous. Another problem is a small amount of available molecular data. During our project, we have substantially improved the dataset of DNA sequences of archamoebae. On the basis of molecular and morphological data, we described 13 new species. We showed that genus Rhizomastix belongs to Archamoebae and displays a new type...
|
|
|
Evolution of mastigont in Excavata
Táborský, Petr ; Čepička, Ivan (advisor) ; Hampl, Vladimír (referee)
In recent years we have been discovering a huge diversity of eukaryotic organisms. One of the big super-groups is Excavata. Examination of the organisms from this group is fairly important as far as theoretical and practical reasons are concerned. A significant number of authors believe that there is the root of all eukaryotic organisms in this group. And what is more, a lot of studies prove the point. Within Excavata group we can find the organisms with the most primitive mitochondrial genome which is known. Several other representatives are an important human pathogenes. In the first part of the thesis I focus on the historical review of the creation of the super-group Excavata and I also include a part regarding the theory about Archezoa. The next section deals with the general description of mastigont (basal bodies and cytoskeleton that is associated with them). The last part presents mastigont descriptions of some derived representatives of Excavata. Some of these organisms may be free-living and some live inside other organisms.
|
|
|
The role of chloroplasts in the stele of epiphytic orchid roots
Ungrová, Anna ; Ponert, Jan (advisor) ; Lhotáková, Zuzana (referee)
The photosynthesis of the aerial roots of epiphytic orchids has been the subject of numerous studies. However, the roots are always evaluated as a homogeneous structure, even though they actually consist of significantly different areas. This work deals for the first time with the possibility of the spatial distribution of photosynthesis between the root layers, specifically the cortex and the stele. A combination of various microscopic techniques, the histochemical characterization of the apoplastic barriers and the immunohistochemical localization of the photosynthetic enzyme phosphoenolpyruvate carboxylase has been used. The results show that well-developed chloroplasts in the stele probably occur in the subfamily Epidendroideae in all epiphytic representatives, while in the subfamily Vanilloideae they occur occasionally. The ultrastructure of chloroplasts from both areas is systematically different, so it is likely that their functions also differ. Apoplastic barriers are prominent in the roots and differentiate early during root development, which can effectively isolate chloroplasts in the stele from the cortex. Chloroplasts also occur in the sclerenchyma cells of the stele, where were identified hitherto unknown pits in cell walls that could provide gas exchange within the stele....
|
|
|
Development of surface and body musculature of the bird schistosome Trichobilharzia regenti
Bulantová, Jana
Description of Trichobilharzia regenti as a new species of nasal bird schistosome in 1998 was only the first step in our knowledge of this extraordinary parasite. Natural definitive hosts of T. regeni are anseriform birds, but infective larvae - cercariae - are able to penetrate also into mammalian hosts including humans. There they are causative agents of hypersensitive skin immune reaction called cercarial dermatitis or swimmer's itch. Contrary to other schistosomes, miracidia of T. regenti hatch directly inside the definitive host tissue. Schistosomula migrate through the nervous system of vertebrates and, together with adult worms, they have predominantly extravascular localization in definitive hosts. Adult worms have a short lifespan and low degree of sexual dimorphism, connected with lower dependence of adult females on long-term contact with males. During the life cycle, T. regenti can be found within three different environments (freshwater, tissue of intermediate molluscan host and tissue of vertebrate host). Each of the seven developmental stages has a different role in the life cycle which corresponds with different organization of various organ systems. The introductory part of the thesis is focused entirely on ontogenetic changes of surface ultrastructure and body musculature of...
|
|
|
Species delimitation in lobose amoebae
Foučková, Martina ; Čepička, Ivan (advisor) ; Škaloud, Pavel (referee)
Lobose amoebae - amoebas that create lobopodia - are distributed among the supergroup Amoebozoa, Excavata, Rhizaria and the genus Anaeramoeba (Eukaryota incertae sedis). For their species delimitation (i.e., pinpointing boundaries between particular species), morphological features are used most often, such as the size and shape of the cell, appearance of the hyaloplasm, pseudopodia and subpseudopodia, granuloplasm with cytoplasmatic inclusions, number and size of nuclei, shape of the uroid and cysts if present. The morphological characteristics are easily documented using a light microscope. Ultrastructural features, such as the ultrastructure of nuclei and nucleoli, surface structures, and organelles, are used as well. Nowadays, species are also described and distinguished employing molecular methods, mostly analyses of the SSU rRNA and actin genes, COI barcoding, and ITS sequences, which allow detection of cryptic species. Before the sequencing era, RFLP, RAPD and isozymes methods were also used for delimitation of species. This thesis focuses on particular methods and features used for species delimitation of lobose amoebae on the basis of 125 selected species belonging to Amoebozoa (orders Acanthamoebida, Pellitida, Himatismenida, Dermamoebida, Thecamoebida, Vannellida, Dactylopodida,...
|
|
|
Loss of excavate features in Excavata
Pavlátová, Magdaléna ; Čepička, Ivan (advisor) ; Němcová, Yvonne (referee)
Excavata is a supergroup of protists belonging to the Eukaryota domain. It is a very diverse taxon that comprises free-living organisms, commensals, and also parasits of animals and humans. Excavata is divided into two main lineages, Metamonada and Discoba, but from the morphological point of view the group Malawimonadida should belong here as well. The internal relationships as well as the monophyly of excavates have not been satisfactorily elucidated yet. The last common ancestor of excavates, perhaps even of all eukaryotes, had a ventral feeding groove, which was associated with a recurrent flagellum. This organism also possessed certain cytoskeletal structures that supported the ventral groove and vanes on the recurrent flagellum. These features have been preserved in some excavates to this day. However, the ventral groove has been reduced or lost in many lineages during the evolution and these representatives, which I refer to as non-excavate excavates, prevail. The aim of this thesis is to describe the ultrastructure of particular lineages of non-excavate excavates and to compare their cytoskeletal system with the cytoskeleton of typical excavates. The loss of excavate features in these lineages is discussed. Key words: excavate, non-excavate excavate, typical excavate, ultrastructure,...
|
|
|
Vliv adipokinetického hormonu na působení jedu z vosičky, \kur{Habrobracon hebetor}, ve svalové tkáni octomilky, \kur{Drosophila melanogaster}
PODLAHOVÁ, Šárka
Adipokinetic hormone (AKH) delays or reduces neuromuscular paralysis caused by the venom of the parasitic wasp Habrobracon hebetor, however the associated mechanism is not known yet. This thesis describes in detail the technique of preparation of semithin and ultrathin sections analyzed by a transmission electron microscopy that enabled detailed observation of changes in muscular ultrastructure of the Drosophila melanogaster thorax after the wasp venom and AKH treatments. The results revealed that the wasp venom induced significant changes in the ultrastructure of myofibrils and mitochondria; however, the changes were reduced after co-application with AKH. AKH itself did not affect organization of muscle fibres but elicited vacuolization in mitochondria. Furthermore the wasp venom treatment led to significant prolongation of sarcomeres.
|
|
|
Ultrastructural interactions of larval bird schistosome Trichobilharzia regenti and immune cells of hosts nervous system
Krčmářová, Veronika ; Bulantová, Jana (advisor) ; Hodová, Iveta (referee)
Trichobilharzia regenti is a neurotropic fluke belonging to family Schistosomatidae. Larvae called schistosomula migrate in the definitive hosts (anseriform birds) throuth the central nervous system (CNS) to their final location in nasal mucosa, where they mature and lay eggs. In contrast with that, the infection of accidental mammalian hosts (including human), is often stopped already in the skin immediately after entering the host. However, some schistosomula are able to reach CNS of experimentally infected mice, and survive there temporarily. Reaction to the CNS infection of mice is usually provided by microglia, astrocytes or the other immune cells infiltrated from the hosts blood. Parasite protects itself against the host reaction with its tegument. It does not serve only as mechanical barrier, but also as main secretoric organ that is capable of active immune evasion. Changes within CNS of the vertebrate hosts, caused by migrating schistosomula of T. regenti, were already described by routine histological and immunohistochemical methods. Till now, there was a lack of informations about interactions of immune cells of the host and the tegument of the parasite on ultrastructural level. To fill this gap in knowledge, two different methods were used: (1) imunohistochemistry in light and electron...
|
guest ::
