Structures related to attachment and motility in the marine eugregarine Cephaloidophora cf. communis (Apicomplexa) (original) (raw)
Related papers
Parasitology Research, 2019
Representatives of Apicomplexa perform various kinds of movements that are linked to the different stages of their life cycle. Ancestral apicomplexan lineages, including gregarines, represent organisms suitable for research into the evolution and diversification of motility within the group. The vermiform trophozoites and gamonts of the archigregarine Selenidium pygospionis perform a very active type of bending motility. Experimental assays and subsequent light, electron, and confocal microscopic analyses demonstrated the fundamental role of the cytoskeletal proteins actin and tubulin in S. pygospionis motility and allowed us to compare the mechanism of its movement to the gliding machinery (the so-called glideosome concept) described in apicomplexan zoites. Actin-modifying drugs caused a reduction in the movement speed (cytochalasin D) or stopped the motility of archigregarines completely (jasplakinolide). Microtubule-disrupting drugs (oryzalin and colchicine) had an even more noticeable effect on archigregarine motility. The fading and disappearance of microtubules were documented in ultrathin sections, along with the formation of α-tubulin clusters visible after the immunofluorescent labelling of drug-treated archigregarines. The obtained data indicate that subpellicular microtubules most likely constitute the main motor structure involved in S. pygospionis bending motility, while actin has rather a supportive function.
2003
The ultrastructure of zoospores of the myxogastrids Symphytocarpus impexus B. Ing et Nann. Bremek. (Stemoniida), Arcyria cinerea (Bull.) Pers. (Trichiida), and Lycogala epidendrum (L.) Fr. (Liceida) is reported for the first time, with special reference to flagellar apparatus. The cytoskeleton in all three species includes microtubular and fibrillar rootlets arising from both basal bodies of the flagellar apparatus. There is a similarity in the presence and position of the rootlets N1 5 between our species and other studied species of myxogastrids and protostelids. Thus, general conservatism of cytoskeletal characters and homology among eumycetozoa have been confirmed for these taxa. At the same time there is variation in the details of flagellar rootlets’ structure in different orders and genera. The differences concern the shape of short striated fibre (SSF) which is an organizing structure for microtubular rootlets r2, r3 and r4. Its upper strand is more prominent in L. epidendru...
Zoomorphology, 2005
The attachment complex of brachiolaria larvae of the asteroid Asterias rubens comprises three brachiolar arms and an adhesive disc located on the preoral lobe. The former are used in temporary attachment and sensory testing of the substratum, whereas the latter is used for permanent fixation to the substratum at the onset of metamorphosis. Brachiolar arms are hollow structures consisting of an extensible stem tipped by a crown of dome-like ciliated papillae. The papilla epidermis is composed of secretory cells (type A, B and C cells), non-secretory ciliated cells, neurosecretory-like cells and support cells. Type A and B secretory cells fill a large part of the papilla epidermis and are always closely associated. They presumably form a duo-gland adhesive system in which type A and B cells are respectively adhesive and de-adhesive in function. The adhesive disc is an epidermal structure mainly composed of secretory cells and support cells. Secretory cells produce the cement, which anchor the metamorphic larva to the substratum until the podia are developed. The relatedness between the composition of the adhesive material in the brachiolaria attachment complex and in the podia of adults was investigated by immunocytochemistry using antibodies raised against podial adhesive secretions of A. rubens. Type A secretory cells were the only immunolabelled cells indicating that their temporary adhesive shares common epitopes with the one of podia. The attachment pattern displayed by the individuals of A. rubens during the perimetamorphic period-tempo-rary, permanent, temporary-is unique among marine non-vertebrate Metazoa.
The enigma of eugregarine epicytic folds: where gliding motility originates?
Frontiers in Zoology, 2013
Background: In the past decades, many studies focused on the cell motility of apicomplexan invasive stages as they represent a potential target for chemotherapeutic intervention. Gregarines (Conoidasida, Gregarinasina) are a heterogeneous group that parasitize invertebrates and urochordates, and are thought to be an early branching lineage of Apicomplexa. As characteristic of apicomplexan zoites, gregarines are covered by a complicated pellicle, consisting of the plasma membrane and the closely apposed inner membrane complex, which is associated with a number of cytoskeletal elements. The cell cortex of eugregarines, the epicyte, is more complicated than that of other apicomplexans, as it forms various superficial structures. Results: The epicyte of the eugregarines, Gregarina cuneata, G. polymorpha and G. steini, analysed in the present study is organised in longitudinal folds covering the entire cell. In mature trophozoites and gamonts, each epicytic fold exhibits similar ectoplasmic structures and is built up from the plasma membrane, inner membrane complex, 12-nm filaments, rippled dense structures and basal lamina. In addition, rib-like myonemes and an ectoplasmic network are frequently observed. Under experimental conditions, eugregarines showed varied speeds and paths of simple linear gliding. In all three species, actin and myosin were associated with the pellicle, and this actomyosin complex appeared to be restricted to the lateral parts of the epicytic folds. Treatment of living gamonts with jasplakinolide and cytochalasin D confirmed that actin actively participates in gregarine gliding. Contributions to gliding of specific subcellular components are discussed. Conclusions: Cell motility in gregarines and other apicomplexans share features in common, i.e. a three-layered pellicle, an actomyosin complex, and the polymerisation of actin during gliding. Although the general architecture and supramolecular organisation of the pellicle is not correlated with gliding rates of eugregarines, an increase in cytoplasmic mucus concentration is correlated. Furthermore, our data suggest that gregarines utilize several mechanisms of cell motility and that this is influenced by environmental conditions.
Microtubular cytoskeletons of the trophic cells of five eumycetozoans
Protoplasma, 1991
The trophic cells of the protostelids, Ceratiomyxella tahitiensis, Cavosteliumapophysatum, Planoprotostelium aurantium, and Clastostelium recurvatum, and the reduced myxomycete, Echinostelium bisporum, were examined with indirect immunofluorescence to determine the overall structure of the microtubular cytoskeletons of each type of cell. All five species have a distinct flagellar apparatus in the amoeboflagellate state, but they vary with respect to the presence of body microtubules, those microtubules which do not focus on the flagellar apparatus. The obligate amoebae of C. tahitiensis, C. apophysatum and C. recurvatum all have extensive microtubular cytoskeletons, but each is unique to its respective species. The obligate amoeba of C. tahitiensis has scattered microtubules which often describe curved paths. The microtubules never appear to focus on MTOCs. The microtubular cytoskeleton of C. apophysatum consists of relatively straight, rind appearing microtubules. Small subpopulations of these microtubules radiate from MTOCs near the nucleus. The obligate amoeba of C. recurvatum has a cytoskeleton consisting of numerous microtubules which radiate from a perinuclear MTOC and fill the body of the cell. These results correlate well with earlier ultrastructural observations which suggest that the amoeboflagellate state is homologous in these mycetozoans and that the obligate amoebae, when present, are unique to the various lineages in which they appear.
PeerJ, 2021
Background Gregarines are a major group of apicomplexan parasites of invertebrates. The gregarine classification is largely incomplete because it relies primarily on light microscopy, while electron microscopy and molecular data in the group are fragmentary and often do not overlap. A key characteristic in gregarine taxonomy is the structure and function of their attachment organelles (AOs). AOs have been commonly classified as “mucrons” or “epimerites” based on their association with other cellular traits such as septation. An alternative proposal focused on the AOs structure, functional role, and developmental fate has recently restricted the terms “mucron” to archigregarines and “epimerite” to eugregarines. Methods Light microscopy and scanning and transmission electron microscopy, molecular phylogenetic analyses of ribosomal RNA genes. Results We obtained the first data on fine morphology of aseptate eugregarines Polyrhabdina pygospionis and Polyrhabdina cf. spionis, the type sp...
2007
Almost all ascidian larvae bear three mucus secreting and sensory organs, the adhesive papillae, at the anterior end of the trunk, which play an important role during the settlement phase. The morphology and the cellular composition of these organs varies greatly in the different species. The larvae of the Clavelina genus bear simple bulbous papillae, which are considered to have only a secretory function. We analysed the adhesive papillae of two species belonging to this genus, C. lepadiformis and C. phlegraea, by histological sections and by immunolocalisation of β-tubulin and serotonin, in order to better clarify the cellular composition of these organs. We demonstrated that they contain at least two types of neurons: central neurons, bearing microvilli, and peripheral ciliated neurons. Peripheral neurons of C. lepadiformis contain serotonin. We suggest that these two neurons play different roles during settlement: the central ones may be chemo-or mechanoreceptors that sense the substratum, and the peripheral ones may be involved in the mechanism that triggers metamorphosis.
European Journal of Protistology, 1999
Scanning and Transmission Electron Microscopy, and Atomic Force Microscopy techniques were used to study different topographic and cytological aspects of the architecture of the sporogonial stages of the eimeriorin coccidian Aggregata octopiana. Ultrastructural studies concerning the formation of sporoblast, sporocysts and number of sporozoites were presented for the first time for this coccidian species. Sporocysts are 11 to 15 pm in diameter, the wall is 0.25-0.35 pm thickness in tangential section. The sporocyst wall surfaces present projections or spiny which are 0.32 urn long. Each sporocyst contains probably 8 sporozoites. The microscopic analysis of the spiny sporocyst cover in A octopiana, a very important diagnostic character for the taxon, makes it possible to clear up the diagnoses of the species, allowing the taxonomic reappraisal of A spinosa Moroff, 1908 as a synonymy of A octopiana Schneider, 1875.
Scientific reports, 2017
Although there have been extensive studies on the larval adhesion of acorn barnacles over the past few decades, little is known about stalked barnacles. For the first time, we describe the larval adhesive systems in the stalked barnacle, Octolasmis angulata and the findings differ from previous reports of the temporary (antennulary) and cement glands in thoracican barnacles. We have found that the temporary adhesives of cyprid are produced by the clustered temporary adhesive glands located within the mantle, instead of the specialised hypodermal glands in the second antennular segment as reported in the acorn barnacles. The temporary adhesive secretory vesicles (TASV) are released from the gland cells into the antennule via the neck extensions of the glands, and surrounded with microtubules in the attachment disc. Cement glands undergo a morphological transition as the cyprid grows. Synthesis of the permanent adhesives only occurs during the early cyprid stage, and is terminated onc...
Fisheries and Aquaculture Journal, 2015
Surface topography of anterior adhesive apparatus was studied of the gill monogenean parasite Diplectanum sp. Diesing, 1858 inhabiting the marine water fish Dicentrachus sp. using SEM. The study revealed that the parasite has three head lobes on each anterolateral region of the head; each lobe accommodates a single, ventrally located adhesive sac. These sacs receive secretion from glands openings that located on the lumen of these sacs. Rodshaped secretory bodies and granular irregularly shaped bodies which may be secretory bodies of the adhesive gland cells were seen open into the adhesive sacs. The tegument of the anterior adhesive area of Diplectanum sp. was characterized by many microvillous like structure. The possible functions of these distinctive features in the temporary attachment are discussed. Numerous adhesive papillae presumed sensory structures were found associated with the tegument of the anterior adhesive area and ventral surface of the body. A single ciliary structure supported by a collar of tegument occurs singly close to the mouth opening. It is suspected to be ciliated sensory ending serve to locate feeding sites. The possible functions of these presumed sensory structures were discussed. The parasite adaptation in its microhabitat in facing the strong water current inside the host fish gills was discussed.