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Gene Nov 1992A search for homeobox-containing genes was done in the genome of a primitive metazoan, the parasitic tapeworm Echinococcus granulosus. Five different homeoboxes were... (Comparative Study)
Comparative Study
A search for homeobox-containing genes was done in the genome of a primitive metazoan, the parasitic tapeworm Echinococcus granulosus. Five different homeoboxes were isolated, none of them belonging to the classical Antennapedia-type. Three of the homeodomains are similar to those from the Drosophila melanogaster NK-type genes. The fourth homeodomain shares extensive identity with that of the recently reported homeobox-containing gene goosecoid from Xenopus laevis. The third helix (the recognition helix) of the fifth isolated homeodomain is identical to that of the Xlim-1 gene of X. laevis and the lin11 gene of Caenorharbditis elegans. Using PCR, some Antennapedia-type homeoboxes were cloned from the genome of two other Platyhelminthes, Dugesia tigrina (planaria) and Fasciola hepatica. These data suggest that, contrary to what is found for the majority of the more complex metazoans, Platyhelminthes contain few homeobox genes belonging to the Antennapedia-type.
Topics: Amino Acid Sequence; Animals; Base Sequence; Cloning, Molecular; Echinococcus; Genes, Helminth; Genes, Homeobox; Molecular Sequence Data; Platyhelminths; Sequence Alignment; Sequence Homology, Amino Acid
PubMed: 1359988
DOI: 10.1016/0378-1119(92)90140-k -
Parazitologiia 2005The ecological scenario of the evolution of main branches of Neodermata is described. The first neodermateans (= promonogeneans) were parasites of the gill lamellae of... (Review)
Review
The ecological scenario of the evolution of main branches of Neodermata is described. The first neodermateans (= promonogeneans) were parasites of the gill lamellae of Paleozoic jawless vertebrates, which were microphagous suspension-feeding animals. The main apomorphic characters of the primary neodermateans are neodermis, cercomer (posterior hooked attachment organ) and swimming infective larva. All subsequent evolution of Neodermata was related with their acquisition new niches in hosts, which were intensively diverging in that time adapting to new food types and conquering new ecological niches. The acquisition of new microhabitats was accompanied by the development of morphological diversity in Neodermata especially in a structure of attachment and genital organs. Trematoda, Cestoda and Polyopisthocotylea comprise specialized evolutionary lineages and Monopisthocotylea is a basal taxon. Polyopisthocotylea is specialized to the blood feeding on fish gills. The common ancestors of the Trematoda and Cestoda inhabited walls of gills and pharyngeal cavities, from where they penetrated the digestive tract. The aspidogastridean multiloculate hold fast appears to be a highly specialized attachment organ of the monogenean ancestor, which inhabited muscular pharyngeal walls of Paleozoic vertebrates. The loss of cercomer hooks probably took place when mollusk-hosts have been involved in the aspidogastridean life cycle. The extinction of many chondrichthiean groups and progress of small plankton fishes (Teleostei) has led to the appearance Digenea. New vertebrate hosts needed a new infestation type and the cercaria appeared. Parthenogenesis has been developed in stages living in mollusks to counterbalance the loss of individuals at two transmission stages in the digenean cycle; this was resulted in a strong specificity to mollusk-host. Evolutionary tendencies of Trematoda and Cestoda show noticeable similarities.
Topics: Animals; Cestoda; Ecosystem; Female; Fishes; Gastrointestinal Tract; Genitalia; Gills; Host-Parasite Interactions; Larva; Male; Platyhelminths; Trematoda
PubMed: 15907023
DOI: No ID Found -
Zootaxa Sep 2020To date, only one species of Temnocephala is known from Chile, Temnocephala chilensis, and three from southern Argentina (Patagonia), namely T. chilensis, Temnocephala...
To date, only one species of Temnocephala is known from Chile, Temnocephala chilensis, and three from southern Argentina (Patagonia), namely T. chilensis, Temnocephala dionii, and Temnocephala mexicana. Here we describe a new species of Temnocephala and provide an updated description of T. chilensis based on material found on an anomuran crab (Aeglidae) from southern Chile. Additional hosts and localities are reported for both species in southern Argentina and Chile, and a diagnostic key for all species of Temnocephala hosted on Aegla and Parastacidae is included as well. In southern Chile, both T. chilensis and the new species were found on the crayfish Samastacus spinifrons and on the anomuran crabs Aegla abtao and Aegla alacalufi; in addition, the new species was found on Aegla manni, and T. chilensis on Aegla rostrata. In southern Argentina, T. chilensis and the new species were found on Aegla riolimayana and S. spinifrons. Based on their shared traits (morphology of the penial stylet, host preferences and geographic distribution), the temnocephalans hosted in Aegla are tentatively gathered into two clusters, the Chilensis and Axenos groups.
Topics: Animals; Anomura; Argentina; Chile; Platyhelminths; Turbellaria
PubMed: 33056419
DOI: 10.11646/zootaxa.4852.3.9 -
International Journal For Parasitology Nov 2009Hox genes form a multigenic family that play a fundamental role during the early stages of development. They are organised in a single cluster and share a 60 amino acid...
Hox genes form a multigenic family that play a fundamental role during the early stages of development. They are organised in a single cluster and share a 60 amino acid conserved sequence that corresponds to the DNA binding domain, i.e. the homeodomain. Sequence conservation in this region has allowed investigators to explore Hox diversity in the metazoan lineages. Within parasitic flatworms only homeobox sequences of parasite species from the Cestoda and Digenea have been reported. In the present study we surveyed species of the Polyopisthocotylea (Monogenea) in order to clarify Hox identification and diversification processes in the neodermatan lineage. From cloning of degenerative PCR products of the central region of the homeobox, we report one ParaHox and 25 new Hox sequences from 10 species of the Polystomatidae and one species of the Diclidophoridae, which extend Hox gene diversity from 46 to 72 within Neodermata. Hox sequences from the Polyopisthocotylea were annotated and classified from sequence alignments and Bayesian inferences of 178 Hox, ParaHox and related gene families recovered from all available parasitic platyhelminths and other bilaterian taxa. Our results are discussed in the light of the recent Hox evolutionary schemes. They may provide new perspectives to study the transition from turbellarians to parasitic flatworms with complex life-cycles and outline the first steps for evolutionary developmental biological approaches within platyhelminth parasites.
Topics: Animals; Gene Expression; Genes, Homeobox; Molecular Sequence Data; Phylogeny; Platyhelminths; Polymerase Chain Reaction
PubMed: 19501095
DOI: 10.1016/j.ijpara.2009.05.008 -
Development Genes and Evolution Oct 1998In recent years the characterization of Hox genes in different phyla has led to the suggestion of a universal role for these genes in animal axis determination. Some...
In recent years the characterization of Hox genes in different phyla has led to the suggestion of a universal role for these genes in animal axis determination. Some phyla, such as Platyhelminthes, have not yielded easily to such analysis, although a range of Hox genes have been shown to be present. In this report we present data concerning the relatively large number of Hox genes with a close similarity to representatives of annelids, supporting a phylogenetic clustering of Platyhelminthes within the spiralian protostomes. We also point out the permanent presence of Hox transcripts in adult planarians, with two classes distinguishable by their different patterns of axial expression: some are expressed uniformly, whilst a second group shows a nested expression with graded anterior expression boundaries. During posterior regeneration the nested Hox genes increase differentially depending on the level of sectioning, and then turn on gradually to recover the differential axial pattern of intact adults. These molecular results and others at the cellular level support the previous hypothesis that Platyhelminthes may have become simplified by progenesis.
Topics: Amino Acid Sequence; Animals; Base Sequence; DNA Primers; Gene Expression Regulation, Developmental; Genes, Homeobox; Phylogeny; Platyhelminths; Regeneration; Reverse Transcriptase Polymerase Chain Reaction; Sequence Homology, Amino Acid
PubMed: 9799427
DOI: 10.1007/s004270050204 -
Zootaxa Jun 2014Cicerina debrae is described as a new species of kalyptorhynch flatworm belonging to the Cicerinidae. This species was found in surface sediment from the lower half of...
Cicerina debrae is described as a new species of kalyptorhynch flatworm belonging to the Cicerinidae. This species was found in surface sediment from the lower half of the beach at two sites in North Carolina and is identical to museum material previously collected from North Carolina and from the Atlantic coast of Florida. C. debrae differs from its congeners in the shape of the ductus spermatici and the copulatory cirrus.
Topics: Animal Structures; Animals; Female; Florida; Male; North Carolina; Platyhelminths
PubMed: 24989762
DOI: 10.11646/zootaxa.3821.4.8 -
Wiadomosci Parazytologiczne 2005The aim of this article was to present the development of ideas about the provenience of parasitic helminths and the phylogenetical relationships within this taxon,... (Review)
Review
The aim of this article was to present the development of ideas about the provenience of parasitic helminths and the phylogenetical relationships within this taxon, since the publication of the "cercomer theory" just to nowadays. The following essentials of the Janicki theory are outlined: main differences between free-living Turbellaria and parasitic platyhelminths (ciliated epithelium in Turbellaria versus unciliated surface in the others); universality of the cercomer presence in Monogenea, Digenea and Cestoda; evolutionary changes in the morphology and function of the cercomer; homology of the caudal appendices of all parasitic helminths; the subsequent evolution of parasitic platyhelminthes from the ancestor to Monogena, Digenea and Cestoda; proposition to establish a new common taxon--Cercomerophora--for these three groups. In this background the evolution of evolutionary ideas is reviewed, divided into two periods: up to the eighties of the XX century, and up to date. The first period can be characterised by the criticism of some points of the "cercomer theory" and formulation of some new hypotheses; these are those of Fuhrmann, Bychovsky, Llewellyn, Price and Malmberg, which: questioned the homology of the cercarial tail with the caudal appendices of Monogenea and Cestoda; rejected Digenea from the common group; established the common taxon--Cercomeromorpha--comprising only Monogenea and Cestoda; opposed the idea of radial evolution of three main groups of Platyhelmithes (Turbellaria, Digenea and Cercomeromorpha) to the idea of subsequent evolution presented by Janicki. The differences between these last hypotheses are also underlined, arising mainly from the different ideas on the importance of particular features as the evolutionary indicators of affinities between and within the taxons. As to the hypotheses dealing with the evolution of particular groups of parasitic platyhelminths formulated at the same period, the publications of Freeman and Jarecka (Cestoda), Heynemann, Ginetsinskaja, Pearson, Cable, Rhode and Gibson (Trematoda), Bychovsky, Lambert and Malmberg (Monogenea) are referred, with special emphasises on the differences in the ideas presented by their authors. In the second period two points are underlined: a dynamic development of new techniques and methods (including molecular investigations) allowing to gather more and more different data on the parasites, and, as a consequence of this phenomenon, a new approach to the evolutionary problems--the birth of numeric and phylogenetic systematics. In this period "the cercomer theory", as well as supporting the group Cercomeromorphae generally are not accepted (exception: Brooks et al.). In contrast, the new taxon--Neodermata has been created by Ehlers. The importance of this publication for further evolutionary study is stressed. In this background some publications are quoted, especially those, presenting the results of searching for monophyletic groups and joining them in hieratic kladograms (Brooks and al., Rohde at al., Littlewood at al., and the others). It is stated, that in spite of some differences in the kladograms builded by various authors (resulting mainly from the set of features being analysed) the monophyly of big taxons of Neodermata (Trematoda, Monogenea, Cestoda) is fairly well documented. In conclusion several points connected with the "cercomer theory" are emphasized. It is now obvious, that the base of this theory--homology of caudal appendices of Janicki's Cercomerophora has to be rejected, as well as his concept of subsequent evolution of Platyhelminthes. But the base of his joining of Monogena, Trematoda (in his theory--Digenea) and Cestoda in one group (lack of cilia on the body surface), opposite to the Turbellaria (ciliary ephitelium) is maintained by the creation of Neodermata, undoubtedly documented better and in a different way. Also his idea (after many years of rejecting) on close affinity of Digenea and Cestoda seems to have returned due to the study of Lockyer at al., who write: "Among the Neodermata, the Cercomeromorphae (Cestoda + Monogenea) was not supported, whereas Cestoda + Trematoda was supported".
Topics: Animals; Biological Evolution; Classification; History, 20th Century; Humans; Life Cycle Stages; Mentors; Parasitology; Platyhelminths; Poland; Research; Russia (Pre-1917)
PubMed: 16913510
DOI: No ID Found -
Parasitology Feb 2015The genomes of more than 20 helminths have now been sequenced. Here we perform a meta-analysis of all sequenced genomes of nematodes and Platyhelminthes, and attempt to... (Meta-Analysis)
Meta-Analysis Review
The genomes of more than 20 helminths have now been sequenced. Here we perform a meta-analysis of all sequenced genomes of nematodes and Platyhelminthes, and attempt to address the question of what are the defining characteristics of helminth genomes. We find that parasitic worms lack systems for surface antigenic variation, instead maintaining infections using their surfaces as the first line of defence against the host immune system, with several expanded gene families of genes associated with the surface and tegument. Parasite excretory/secretory products evolve rapidly, and proteases even more so, with each parasite exhibiting unique modifications of its protease repertoire. Endoparasitic flatworms show striking losses of metabolic capabilities, not matched by nematodes. All helminths do however exhibit an overall reduction in auxiliary metabolism (biogenesis of co-factors and vitamins). Overall, the prevailing pattern is that there are few commonalities between the genomes of independently evolved parasitic worms, with each parasite having undergone specific adaptations for their particular niche.
Topics: Adaptation, Physiological; Animals; Biological Evolution; Genome, Helminth; Helminths; Immune System; Nematoda; Parasites; Platyhelminths; Transcriptome
PubMed: 25482650
DOI: 10.1017/S0031182014001449 -
Journal of Helminthology Oct 2020Temnocephala axenos Monticelli, 1898 was described based on specimens from an unidentified host collected in Blumenau, Santa Catarina, Brazil. Information about type...
Temnocephala axenos Monticelli, 1898 was described based on specimens from an unidentified host collected in Blumenau, Santa Catarina, Brazil. Information about type locality was imprecise and the host was later identified as Aegla laevis (Latreille, 1818). However, it is known that A. laevis is not present on the eastern side of the Andes. Also, only histological preparations from one specimen studied by Monticelli are currently available in the Museum für Naturkunde Berlin, but it showed none of the taxonomic characters needed for the characterization of the species. Although the updated description of the species based on Uruguayan specimens, neither the author nor the several previous studies about the species showed a search for the type material, a resolution for the misidentification of the type host or the imprecise type locality due to the subsequent geographical division of the municipality cited in the description. The Uruguayan specimens were not even geographically close to the type locality and a neotype was not designed to validate the species' taxonomic status again. Specimens from Santa Catarina and Paraná States, Brazil, were studied, as well as restudied Argentinean specimens. The new data were compared with the update description of the species. The historical background and the discussion about geographical origins and hosts of the species, as well as a designation of a neotype, allow comparative material of the type locality and type host to exist, eliminating doubts about the identification of T. axenos.
Topics: Animals; Anomura; Brazil; Female; Geography; Male; Platyhelminths
PubMed: 33087190
DOI: 10.1017/S0022149X20000851 -
Molecular Phylogenetics and Evolution Aug 1998Nucleotide sequences of 18S ribosomal RNA from 71 species of Platyhelminthes, the flatworms, were analyzed using maximum likelihood, and the resulting phylogenetic trees...
Nucleotide sequences of 18S ribosomal RNA from 71 species of Platyhelminthes, the flatworms, were analyzed using maximum likelihood, and the resulting phylogenetic trees were compared with previous phylogenetic hypotheses. Analyses including 15 outgroup species belonging to eight other phyla show that Platyhelminthes are monophyletic with the exception of a sequence putatively from Acoela sp., Lecithoepitheliata, Polycladida, Tricladida, Trematoda (Aspidobothrii + Digenea), Monogenea, and Cestoda (Gyrocotylidea + Amphilinidea + Eucestoda) are monophyletic groups. Catenulids form the sister group to the rest of platyhelminths, whereas a complex clade formed by Acoela, Tricladida, "Dalyellioida", and perhaps "Typhloplanoida" is sister to Neodermata. "Typhloplanoida" does not appear to be monophyletic; Fecampiida does not appear to belong within "Dalyellioida," nor Kalyptorhynchia within "Typhloplanoida." Trematoda is the sister group to the rest of Neodermata, and Monogenea is sister group to Cestoda. Within Trematoda, Aspidobothrii is the sister group of Digenea and Heronimidae is the most basal family in Digenea. Our trees support the hypothesis that parasitism evolved at least twice in Platyhelminthes, once in the ancestor to Neodermata and again in the ancestor of Fecampiida, independently to the ancestor of putatively parasitic "Dalyellioida."
Topics: Animals; DNA, Helminth; DNA, Ribosomal; Molecular Sequence Data; Phylogeny; Platyhelminths; RNA, Ribosomal, 18S
PubMed: 9751913
DOI: 10.1006/mpev.1997.0483