Structure of the Anterior Alimentary Tract of the Passively Feeding Nematode Hexatylus Viviparus (Neotylenchidae: Tylenchida)

Shepherd, Audrey M.; Clark, Sybil A.

doi:10.1163/187529276x00625

Cited by 16 publications

(18 citation statements)

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“…Both the basal bulb and overlapping glands in a number of Tylenchida have been previously demonstrated by TEM to consist of glands with some small epithelial and nerve cells, and to lack muscles (Yuen, 1968;Shepherd & Clark, 1976, 1983Baldwin et al, 1977;Chen & Wen, 1980;Shepherd et al, 1980;Baldwin, 1982;Endo, 1984;Hussey & Mims, 1990;Souza & Baldwin, 1998). Therefore, it is surprising that in B. gracilis there is a full complement of nonglandular cells including muscles.…”

Section: Discussionmentioning

confidence: 94%

“…Although the ne structure of the tylenchid pharynx has been examined in several genera (Yuen, 1968;Grootaert et al 1976a, b;Shepherd & Clark, 1976, 1983Baldwin et al, 1977;Chen & Wen, 1980;Shepherd et al, 1980;Baldwin, 1982;Endo, 1984;Hussey & Mims, 1990;Souza & Baldwin, 1998), this has not been approached from a comparative perspective. In addition, previous work typically has not included those representative taxa that are evolutionarily conserved within Tylenchida, and therefore are most informative for interpreting deeper relationships within Secernentea.…”

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confidence: 99%

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Fine structure and phylogenetic significance of a muscular basal bulb in Basiria gracilis Thorne, 1969 (Nematoda: Tylenchidae)

Baldwin¹,

Souza²,

Dolinski³

2001

Nematology

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Section: Discussionmentioning

confidence: 94%

mentioning

confidence: 99%

Fine structure and phylogenetic significance of a muscular basal bulb in Basiria gracilis Thorne, 1969 (Nematoda: Tylenchidae)

Baldwin¹,

Souza²,

Dolinski³

2001

Nematology

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“…The type I vesicles observed in this study have been described frequently in nematodes as secretion vesicles (Bird & Bird, 1991;Borgonie et al, 1995;Willems et al, 2005) and are reported as having a double membrane (Borgonie et al, 1995). The thread-like type II vesicles that emanate from the top of the microvilli in the intestine of H. gingivalis have also been observed in Hexatylus viviparus (Shepherd & Clark, 1976), a nematode species that has a fungivorous as well as an entomoparasitic lifecycle. Shepherd and Clark (1976) described these threads in H. viviparus as fine extensions of the microvillar tips which were situated in the anterior intestine as well as in the midintestine.…”

Section: Discussionmentioning

confidence: 88%

“…The thread-like type II vesicles that emanate from the top of the microvilli in the intestine of H. gingivalis have also been observed in Hexatylus viviparus (Shepherd & Clark, 1976), a nematode species that has a fungivorous as well as an entomoparasitic lifecycle. Shepherd and Clark (1976) described these threads in H. viviparus as fine extensions of the microvillar tips which were situated in the anterior intestine as well as in the midintestine. These extensions have a double membrane (see Figure 11E in Shepherd and Clark, 1976), in accordance with the thread-like type II vesicles observed in the intestine of H. gingivalis.…”

Section: Discussionmentioning

confidence: 88%

“…The intestine is a straight tube which comprises a limited number of cells organised in a single layer with a luminal surface that is lined with microvilli which mostly have a regular, cylindrical, shape, although some exceptions have been observed in A. suum (Kessel et al, 1961), Metastrongylus sp. (Jenkins & Erasmus, 1969), Hexatylus viviparus (Shepherd & Clark, 1976) and Rhabditophanes sp. (Willems et al, 2005).…”

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Intestine ultrastructure of the facultative parasite Halicephalobus gingivalis (Nematoda: Panagrolaimidae)

Fonderie

Willems

Bert

et al. 2009

Nematol

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Halicephalobus gingivalis, classified as a free-living nematode, is a known facultative parasite of horses, zebras and humans. However, detailed information concerning its internal morphology is lacking, especially in relation to possible adaptations to its lifestyle as a facultative parasite. The research presented here uses TEM and PI staining to analyse the morphology of the intestine of H. gingivalis. Specimens cultured under different conditions were included to determine if differences in ultrastructure are induced by culturing method. TEM analysis revealed that the intestinal tract comprises a single layer of cells in which nine pairs of nuclei can be distinguished. Further, unusual dichotomously and trichotomously branched microvilli were observed next to finger-like cylindrical microvilli, the latter being the most commonly described form in nematodes. Finally, three different types of secretion vesicles, i.e., spherical (type I), thread-like (type II) and enlarged globular (type III), occurred independently from each other along the intestinal tract. The relationship of morphological adaptations of the microvilli to parasitism in nematodes is discussed

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Three‐dimensional reconstruction of the stomatostylet and anterior epidermis in the nematode Aphelenchus avenae (Nematoda: Aphelenchidae) with implications for the evolution of plant parasitism

Ragsdale¹,

Crum²,

Ellisman³

et al. 2008

Journal of Morphology

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A three-dimensional model of the stomatostylet and associated structures has been reconstructed from serial thin sections of Aphelenchus avenae, a representative of Tylenchomorpha, a group including most plant parasitic nematodes. The reconstruction is compared with previous work on bacteriovorous cephalobids and rhabditids to better understand the evolution of the stylet and its associated cells. Two arcade syncytia ("guide ring") line the stylet shaft, supporting the hypothesis that the stylet shaft and cone (into which the shaft extends and which is not lined by syncytia) are homologous with the gymnostom of cephalobids, the sister taxon of tylenchids. Epidermal syncytia, HypA, HypB, HypC, and HypE, line the cephalic framework, vestibule, and vestibule extension, congruent with the hypothesis that these components are homologous with the cephalobid cheilostom. Relative to outgroups, HypC is expanded in A. avenae, enclosing sensilla that fill most of the cephalic framework. The homolog of syncytium HypD in the cephalobid Acrobeles complexus is not observed in A. avenae. Arcade syncytia are reduced compared with those of cephalobids. Stylet protractor muscles in A. avenae are homologous with the most anterior set of radial muscles of cephalobids. Observations to date test and verify our previous hypotheses of homology of the stomatostylet with respect to the stoma of bacteriovorous outgroups. Reconstruction of the stegostom and pharynx will provide further tests of homology and evolution of feeding structure adaptations for plant parasitism. KeywordsAcrobeles complexus; arcade syncytia; Caenorhabditis elegans; Cephalobomorpha; feeding; fine structure; free living; homology; modeling; muscle; phylogeny; stoma; syncytium; transmission electron microscopy Molecular phylogenies often raise questions of morphological evolution where they impose a new paradigm on classical scenarios reliant on opposing ideas of phylogeny. One pressing case of incongruence has been shown in nematodes regarding the evolution of the Tylenchomorpha, which include most species of plant parasitic nematodes, as well as many insect parasites and *Correspondence to: Erik J. Ragsdale, Department of Nematology, University of California, Riverside, CA 92521. erik.ragsdale@email.ucr.edu. Additional Supporting Information may be found in the online version of this article. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript fungivores. With finer phylogenetic resolution based on molecular analyses, it is apparent that evolution of feeding structures for a parasitic lifestyle can no longer be explained by traditional scenarios, with which new hypotheses of relationships are incongruent. Accumulating evidence suggests that Tylenchomorpha, with a specialized stomatostylet, are sister taxon to or nested within the Cephalobomorpha (Aleshin et al., 1998;Blaxter et al., 1998;Holterman et al., 2006;Meldal et al., 2007;Nadler et al., 2006;Smythe and Nadler, 2006), which lack a stylet and instead have an open...

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Structure of the Anterior Alimentary Tract of the Passively Feeding Nematode Hexatylus Viviparus (Neotylenchidae: Tylenchida)

Cited by 16 publications

References 0 publications

Fine structure and phylogenetic significance of a muscular basal bulb in Basiria gracilis Thorne, 1969 (Nematoda: Tylenchidae)

Fine structure and phylogenetic significance of a muscular basal bulb in Basiria gracilis Thorne, 1969 (Nematoda: Tylenchidae)

Intestine ultrastructure of the facultative parasite Halicephalobus gingivalis (Nematoda: Panagrolaimidae)

Three‐dimensional reconstruction of the stomatostylet and anterior epidermis in the nematode Aphelenchus avenae (Nematoda: Aphelenchidae) with implications for the evolution of plant parasitism

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