The epidermis and sensory organs of Dugesia tigrina (Turbellaria: Tricladida)

Smales, Lesley R.; Blankespoor, Harvey D.

doi:10.1007/bf00221599

Cited by 19 publications

(20 citation statements)

References 6 publications

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“…3). This finding differs from that observed with Dugesia tigrina from Smales and Blankespoor (1978), who described it as irregularly contoured. Another different point was the presence of a remarkable invagination on the epidermis of the anterior region and below the auricles in Girardia sp.…”

Section: Discussioncontrasting

confidence: 99%

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Physiological evaluation of the behavior and epidermis of freshwater planarians (Girardia tigrina and Girardia sp.) exposed to stressors

et al. 2018

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Planarians are metazoan freshwater flatworms which are free-living organisms. Their body has pluripotent stem cell promoters of tissue regeneration capacity. The water temperature and the potential of hydrogen (pH) of lentic ecosystems are important factors involved in the distribution and abundance of these animals. Although the pH factor is directly related to the physiology and behavior of planarians, their adaptive and regenerating capacities still remain unknown. The Critical Thermal Maximum (CTM) is a very widespread method used in the evaluation of thermal tolerance. In this study, Girardia tigrina (Girard, 1850) and Girardia sp., a species found in Brazil, which is under study as a new species, had their epidermis assessed by scanning electron microscopy (SEM) to analyze their physiological structures before and after exposure to different stressors. SEM was used as a method to evaluate the planarians' epidermis as a result of the increasing temperature (CTM) and pH alterations, the latter with the use of a new methodology defined as Critical Hydrogen ion concentration Maximum (CHM). In increasing temperatures from 20°C to 37°C, both Girardia tigrina and Girardia sp. proved to be adaptable to thermal stress. Girardia sp. was shown to be more resistant to higher temperatures. However, Girardia tigrina was more resistant to extreme pH conditions (4.0 to 10.0). SEM analysis showed morphological differences among planarian species, such as the arrangement of the structures and cell types of the dorsal epidermis. Moreover, planarians demonstrated the ability to change the surrounding pH of their external environment in order to maintain the function of their physiological mechanisms, suggesting that these animals have a complex survival system, possibly related to protonephridia, flame cells and excretory pores..

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Section: Discussioncontrasting

confidence: 99%

“…4A,C). Ciliated structures were not abundantly visualized in this study since they are structures commonly found in the ventral surface of Girardia tigrina and on the dorsal surface, especially in areas such as the auricles, although they can also be observed in the dorsal epidermis of other species (Smales and Blankespoor, 1978). …”

Section: Discussionmentioning

confidence: 78%

Physiological evaluation of the behavior and epidermis of freshwater planarians (Girardia tigrina and Girardia sp.) exposed to stressors

et al. 2018

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“…Further studies will elucidate whether, in a WT situation, both paralogs are involved in signal transduction for a single Wnt ligand. (25,26). To address whether Smed-dvl-1/2 functions as a component of the PCP network, we analyzed the polarization of the ventral epithelium after Smed-dvl-1/2 interference.…”

Section: Resultsmentioning

confidence: 99%

“…Because the positioning of the basal bodies is governed by actin assembly, we analyzed the role of Smed-dvl-1/2 in the assembly of the actin network and in the docking of the basal bodies in the planarian epithelium. The actin filaments are arranged as a network that defines each cell border and contains regular openings to allow mucus secretion by the rhabdomeres (25). Silencing of Smed-dvl-2 dramatically affected the arrangement of this network, resulting in an irregular net in which the cell borders and rhabdomere openings were not visible (Fig.…”

Section: Resultsmentioning

confidence: 99%

Dishevelled is essential for neural connectivity and planar cell polarity in planarians

Almuedo-Castillo

Saló

Adell

2011

Proc. Natl. Acad. Sci. U.S.A.

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The Wingless/Integrated (Wnt) signaling pathway controls multiple events during development and homeostasis. It comprises multiple branches, mainly classified according to their dependence on β-catenin activation. The Wnt/β-catenin branch is essential for the establishment of the embryonic anteroposterior (AP) body axis throughout the phylogenetic tree. It is also required for AP axis establishment during planarian regeneration. Wnt/β-catenin-independent signaling encompasses several different pathways, of which the most extensively studied is the planar cell polarity (PCP) pathway, which is responsible for planar polarization of cell structures within an epithelial sheet. Dishevelled (Dvl) is the hub of Wnt signaling because it regulates and channels the Wnt signal into every branch. Here, we analyze the role of Schmidtea mediterranea Dvl homologs (Smed-dvl-1 and Smed-dvl-2) using gene silencing. We demonstrate that in addition to a role in AP axis specification, planarian Dvls are involved in at least two different β-catenin-independent processes. First, they are essential for neural connectivity through Smed-wnt5 signaling. Second, Smed-dvl-2, together with the S. mediterranea homologs of Van-Gogh (Vang) and Diversin (Div), is required for apical positioning of the basal bodies of epithelial cells. These data represent evidence not only of the function of the PCP network in lophotrocozoans but of the involvement of the PCP core elements Vang and Div in apical positioning of the cilia.neural patterning | axial polarity | cilia basal body W ingless/Integrated (Wnt) signaling controls multiple events, including cell migration, planar cell polarity (PCP), and stem cell self-renewal (1, 2). It acts through two main pathways: the canonical or β-catenin-dependent pathway and the noncanonical or β-catenin-independent pathways, which include the PCP and Wnt/calcium pathways. Dishevelled (Dvl) is common to all three pathways (3). In the β-catenin-dependent pathway, Dvl is recruited by the receptor Frizzled (Fz), promoting disassembly of the β-catenin destruction complex through the subsequent recruitment of Axin. As a consequence, β-catenin translocates to the nucleus, where it acts as a master regulator. A common role of the β-catenin/Wnt pathway is in establishing the anteroposterior (AP) axis during development (4). PCP signals are transmitted from cell to cell and are responsible for the polarization of cell structures. During PCP signaling, Dvl is also recruited by a Fz receptor and promotes the asymmetrical localization of the PCP core proteins within the cell, such that the Fz-Dvl-Diversin (Div)/-Diego (Dgo) complex is oppositely localized to the Strabismus (Stbm)/Van-Gogh (Vang)-Prickle (Pk) complex. The asymmetrical subcellular localization of these elements in an epithelial sheet directs cytoskeletal reorganization that results, for instance, in a hair emerging solely from the distal edge of the cell (5-7). The same mechanism is used in mesenchymal cells to direct cell movement and migration during gastrulat...

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“…Only recently has scanning electron microscopy been applied increasingly to the Turbellaria (e.g. Reuter 1978;Smales & Blankespoor 1978;Williams 1978). The order Tricladida figured greatly in the early phase of Turbellarian fine structural research (e.g., Klima 1959Klima , 1961Pedersen 1959aPedersen , b, 1961aSkaer 1961) but the interest soon expanded to include other orders, especially the Acoela (e.g.…”

Section: Introductionmentioning

confidence: 99%

Morphology of the Turbellaria at the ultrastructural level

Rieger

1981

Hydrobiologia

112

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The paper reviews the following systems: body wall, nervous system, protonephridia, parenchyma, digestive system, reproductive system, and includes a summary of the literature. New information is presented for the catenulid and neoophoran body wall-construction, the kalyptorhynch proboscis, the catenulid and haplopharyngid protonephridial construction, and the prolecithophoran spermatozoon and female germ cell. Examples of new features, as well as examples of how electron microscopy has clarified the relative position of structures and their substructures are given from the subcellular level to the organization of whole organs. Fine structural features linking different turbellarian orders are summarized. They apparently support Karling's (1974) latest assessment of the affinities between the turbellarian orders which is based primarily on light histological data, they add the recognition of a special link between the Macrostomida and Haplopharyngida and they suggest the existence of three main evolutionary lines within the Turbellaria.

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The epidermis and sensory organs of Dugesia tigrina (Turbellaria: Tricladida)

Cited by 19 publications

References 6 publications

Physiological evaluation of the behavior and epidermis of freshwater planarians (Girardia tigrina and Girardia sp.) exposed to stressors

Physiological evaluation of the behavior and epidermis of freshwater planarians (Girardia tigrina and Girardia sp.) exposed to stressors

Dishevelled is essential for neural connectivity and planar cell polarity in planarians

Morphology of the Turbellaria at the ultrastructural level

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