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7 results for “18S ribosomal DNA”
Figure 3 in Diceratocephala boschmai (Platyhelminthes: Temnocephalida) from crayfish farms in Thailand: investigation of the topographic surface and analysis of 18S ribosomal DNA sequences
Figure 3. The neighbor-joining phylogenetic tree based on the 18S rDNA gene, showing the relationships of D. boschmai with 29 other turbellarian species.
Figure 2 in Diceratocephala boschmai (Platyhelminthes: Temnocephalida) from crayfish farms in Thailand: investigation of the topographic surface and analysis of 18S ribosomal DNA sequences
Figure 2. Surface topography of D. boschmai. A–C) Unhatched and hatched eggs; D) ventral view of a specimen; E) mouth with protruding pharynx; F) thread-like filaments adhered to the pharynx; G, H) a higher magnification of write-dot boxes in 2E; I, J) a higher magnification of write-dot boxes in 2D; K) ventral view of a specimen at posterior end; L) dorsal view of a specimen; M) a higher magnification of write-dot box in Figure L. ad, adhesive disc; af, adhered filaments; ci, ciliated cell; ds, double spines; fi, filament; gr, groove; gv, gravel-like units; in, intertentacular flange; mo, mouth; op, opercular plate; pe, peduncle; pi, pit; sp, single spine; tb, trabecular meshwork; tc, tentacle; th, thread-like filaments; tr, trunk; vi, villi..
Figure 1. A in Diceratocephala boschmai (Platyhelminthes: Temnocephalida) from crayfish farms in Thailand: investigation of the topographic surface and analysis of 18S ribosomal DNA sequences
Figure 1. A) C. destructor harboring adult D. boschmai and eggs of flatworm; B) dorsal view of an extending body; C) diagram of organ structures in dorsal view; D) diagram of reproductive complex; E, F) photomicrograph and diagram of penial stylet, respectively; G) unhatched and hatched eggs. ad, adhesive disc; at, atrium; cv, contractile vesicle; ds, dorsal side; es, ejaculatory sac; ey, eye; ev, excretory vesicle; fi, filament; in, intertentacular flange; ine, intestine; int, introvert; mo, mount; ov, ovary; pe, peduncle; pf, plane of fracture; ph, pharynx; pn, subepidermal pigment network; ps, penial stylet; rv, resorbens vesicle; s, stalk; se, seminal vesicle; sr, seminal receptacle; sp, sclerotized papillae; tc, tentacle; te, testis; tg, tentacular gland; ve, vasa efferentia; vg, vagina; vi, vitellaria; vs, ventral side.
Data from: Testing hypotheses of chaetognath origins: long branches revealed by 18S ribosomal DNA
Many hypotheses regarding the phylogenetic position of the Chaetognatha (arrow worms) have been proposed; these organisms are problematic primarily because their morphology offers few unambiguous systematic characters that ally them with other taxa. Early researchers proposed a plethora of phylogenetic placements for the Chaetognatha, grouping them with such divergent taxa as acanthocephalans and mollusks, but more traditional hypotheses posit that chaetognaths are, in fact, deuterostomes. Recently, Telford and Holland (1993, Mol. Biol. Evol. 10:660--676) and Wada and Satoh (1994, Proc. Natl. Acad. Sci. USA 91:1801--1804) disputed the deuterostome affinities of chaetognaths based on 18S nuclear ribosomal RNA (rDNA) gene sequence data. By employing published 18S rDNA gene sequence data, I extended these previous analyses by testing specific hypotheses of chaetognath affinities to nematodes, mollusks, acanthocephalans, and deuterostomes. Both parsimony and neighbor-joining analyses supported the monophyly of a chaetognath--nematode clade. Faith's T-PTP test and winning-sites analyses were employed to discriminate among competing hypotheses. The possibility of long-branch attraction accounting for the chaetognath--nematode relationship was explored by analyzing alternative four-taxon trees. An evolutionary scenario for the origin of the chaetognath lineage from a vermiform benthic organism is presented.
Data from: The Strepsiptera Problem: Phylogeny of the Holometabolous Insect Orders Inferred from 18S and 28S Ribosomal DNA Sequences and Morphology
Phylogenetic relationships among the holometabolous insect orders were inferred from cladistic analysis of nucleotide sequences of 18S ribosomal DNA (rDNA) (85 exemplars) and 28S rDNA (52 exemplars) and morphological characters. Exemplar outgroup taxa were Collembola (1 sequence), Archaeognatha (1), Ephemerida (1), Odonata (2), Plecoptera (2), Blattodea (1), Mantodea (1), Dermaptera (1), Orthoptera (1), Phasmatodea (1), Embioptera (1), Psocoptera (1), Phthiraptera (1), Hemiptera (4), and Thysanoptera (1). Exemplar ingroup taxa were Coleoptera: Archostemata (1), Adephaga (2), and Polyphaga (7); Megaloptera (1); Raphidioptera (1); Neuroptera (sensu stricto ;eq Planipennia): Mantispoidea (2), Hemerobioidea (2), and Myrmeleontoidea (2); Hymenoptera: Symphyta (4) and Apocrita (19); Trichoptera: Hydropsychoidea (1) and Limnephiloidea (2); Lepidoptera: Ditrysia (3); Siphonaptera: Pulicoidea (1) and Ceratophylloidea (2); Mecoptera: Meropeidae (1), Boreidae (1), Panorpidae (1), and Bittacidae (2); Diptera: Nematocera (1), Brachycera (2), and Cyclorrhapha (1); and Strepsiptera: Corioxenidae (1), Myrmecolacidae (1), Elenchidae (1), and Stylopidae (3). We analyzed ~1 kilobase of 18S rDNA, starting 398 nucleotides downstream of the 5' end, and ~400 bp of 28S rDNA in expansion segment D3. Multiple alignment of the 18S and 28S sequences resulted in 1,116 nucleotide positions with 24 insert regions and 398 positions with 14 insert regions, respectively. All Strepsiptera and Neuroptera have large insert regions in 18S and 28S. The secondary structure of 18S insert 23 is composed of long stems that are GC rich in the basal Strepsiptera and AT rich in the more derived Strepsiptera. A matrix of 176 morphological characters was analyzed for holometabolous orders. Incongruence length difference tests indicate that the 28S + morphological data sets are incongruent but that 28S + 18S, 18S + morphology, and 28S + 18S + morphology fail to reject the hypothesis of congruence. Phylogenetic trees were generated by parsimony analysis, and clade robustness was evaluated by branch length, Bremer support, percentage of extra steps required to force paraphyly, and sensitivity analysis using the following parameters: gap weights, morphological character weights, methods of data set combination, removal of key taxa, and alignment region. The following are monophyletic under most or all combinations of parameter values: Holometabola, Polyphaga, Megaloptera + Raphidioptera, Neuroptera, Hymenoptera, Trichoptera, Lepidoptera, Amphiesmenoptera (Trichoptera + Lepidoptera), Siphonaptera, Siphonaptera + Mecoptera, Strepsiptera, Diptera, and Strepsiptera + Diptera (Halteria). Antliophora (Mecoptera + Diptera + Siphonaptera + Strepsiptera), Mecopterida (Antliophora + Amphiesmenoptera), and Hymenoptera + Mecopterida are supported in the majority of total evidence analyses. Mecoptera may be paraphyletic because Boreus is often placed as sister group to the fleas; hence, Siphonaptera may be subordinate within Mecoptera. The 18S sequences for Priacma (Coleoptera: Archostemata), Colpocaccus (Coleoptera: Adephaga), Agulla (Raphidioptera), and Corydalus (Megaloptera) are nearly identical, and Neuropterida are monophyletic only when those two beetle sequences are removed from the analysis. Coleoptera are therefore paraphyletic under almost all combinations of parameter values. Halteria and Amphiesmenoptera have high Bremer support values and long branch lengths. The data do not support placement of Strepsiptera outside of Holometabola nor as sister group to Coleoptera. We reject the notion that the monophyly of Halteria is due to long branch attraction because Strepsiptera and Diptera do not have the longest branches and there is phylogenetic congruence between molecules, across the entire parameter space, and between morphological and molecular data.
Data from: Testing hypotheses of chaetognath origins: long branches revealed by 18S ribosomal DNA
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Data from: The Strepsiptera Problem: Phylogeny of the Holometabolous Insect Orders Inferred from 18S and 28S Ribosomal DNA Sequences and Morphology
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