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Advances in Parasitology 2015Novel fossil discoveries have contributed to our understanding of the evolutionary appearance of parasitism in flatworms. Furthermore, genetic analyses with greater... (Review)
Review
Novel fossil discoveries have contributed to our understanding of the evolutionary appearance of parasitism in flatworms. Furthermore, genetic analyses with greater coverage have shifted our views on the coevolution of parasitic flatworms and their hosts. The putative record of parasitic flatworms is consistent with extant host associations and so can be used to put constraints on the evolutionary origin of the parasites themselves. The future lies in new molecular clock analyses combined with additional discoveries of exceptionally preserved flatworms associated with hosts and coprolites. Besides direct evidence, the host fossil record and biogeography have the potential to constrain their evolutionary history, albeit with caution needed to avoid circularity, and a need for calibrations to be implemented in the most conservative way. This might result in imprecise, but accurate divergence estimates for the evolution of parasitic flatworms.
Topics: Animals; Biological Evolution; Fossils; Host-Parasite Interactions; Humans; Invertebrates; Platyhelminths; Time; Vertebrates
PubMed: 26597066
DOI: 10.1016/bs.apar.2015.06.002 -
Parasitology Research Feb 2014Using network analysis, we looked for broad patterns of distribution of Monogenoidea gill parasites on Neotropical freshwater fishes within a host phylogenetic...
Using network analysis, we looked for broad patterns of distribution of Monogenoidea gill parasites on Neotropical freshwater fishes within a host phylogenetic framework. We analyzed a database of Monogenoidea parasitizing fishes from Neotropical rivers, from 23 watersheds, based on species descriptions published until 2011. Host-parasite interactions were organized into five matrices grouping species at different taxonomic levels. The network of interactions between host families and parasite genera was significantly modular and revealed that each fish order has a unique composition of parasite genera. Hence, interactions between lower taxa were analyzed separately for the largest fish orders (Perciformes, Siluriformes, and Characiformes). Networks tended to be loosely connected and organized in modules. Despite the putative high host specificity of monogenoids, some have a wider host range that includes distantly related host species. Among the hosts, the clade composed by the piranhas (Serrasalmus spp. and related species, Serrasalmidae) stands out in terms of parasite richness per host species, resulting in a more connected network. The history of the lineages of each host order within Neotropical freshwaters seems to have a great influence on the extent of parasite sharing. The observed modularity was influenced by both spatial structure and phylogenetic relatedness of species. In average, 37 % of modules of networks between host species and parasite genera were associated with a particular river basin and 63 % of modules were associated with a host family. Hence, spatial structure determines the co-occurrence of host and parasite species, but their evolutionary history is the main factor defining which interactions are possible.
Topics: Animals; Biological Evolution; Catfishes; Characiformes; Fishes; Gills; Host-Parasite Interactions; Perciformes; Phylogeny; Platyhelminths; Rivers
PubMed: 24221891
DOI: 10.1007/s00436-013-3677-8 -
Science (New York, N.Y.) Mar 1999Because of their simple organization the Acoela have been considered to be either primitive bilaterians or descendants of coelomates through secondary loss of derived...
Because of their simple organization the Acoela have been considered to be either primitive bilaterians or descendants of coelomates through secondary loss of derived features. Sequence data of 18S ribosomal DNA genes from non-fast evolving species of acoels and other metazoans reveal that this group does not belong to the Platyhelminthes but represents the extant members of the earliest divergent Bilateria, an interpretation that is supported by recent studies on the embryonic cleavage pattern and nervous system of acoels. This study has implications for understanding the evolution of major body plans, and for perceptions of the Cambrian evolutionary explosion.
Topics: Animals; Biological Evolution; DNA, Helminth; DNA, Ribosomal; Evolution, Molecular; Genes, rRNA; Invertebrates; Molecular Sequence Data; Phylogeny; Platyhelminths; RNA, Ribosomal, 18S; Sequence Analysis, DNA
PubMed: 10082465
DOI: 10.1126/science.283.5409.1919 -
International Journal For Parasitology Jun 1997The epidermis of members of the major parasitic taxon Neodermata is distinctive among flatworms, being a syncytial, insunk, non-ciliated epidermis that develops through... (Review)
Review
The epidermis of members of the major parasitic taxon Neodermata is distinctive among flatworms, being a syncytial, insunk, non-ciliated epidermis that develops through a wholesale replacement of larval epidermis at metamorphosis when the larva attacks a host. How it arose in evolution from what must have been a turbellarian-like ancestor is not immediately evident. While many turbellarian flatworms have also adopted a symbiotic way of life, the literature on ultrastructure of epidermis in these symbionts shows quite a variety of morphologies, many not so different from that of their free-living relatives. Various turbellarians do have syncytial or insunk epidermises or reduction of epidermal ciliation as is characteristic of the Neodermata, but co-occurrence in a single turbellarian of all features common to neodermatans has not been reported. Urastoma cyprinae, for example, which is ectosymbiotic on bivalves, has a ciliated cellular epidermis that is little different from what is known of epidermises of its free-living relatives. The endoparasitic Anoplodium hymanae, from the coelom of sea cucumbers, also bears a ciliated cellular epidermis, as is typical of many other rhabdocoels, but it shows marked phagocytic activity as well as incorporation of endosymbiotic bacteria. The closest similarity to neodermatan epidermis is that of the turbellarian Genostoma kozloffi, an ectosymbiont of the crustacean Nebalia: covering the bulk of the body is a non-ciliated syncytium with multiple branching connections to insunk nucleated portions, much as in epidermis of adult neodermatans and, on its ventral surface, is a field of ciliated cellular insunk epidermis resembling the epidermis of some larval neodermatans. Developmental clues to the origin of the neodermatan epidermis can be seen in turbellarian embryos. Before hatching, embryos of proseriate and triclad embryos go through 3 generations of epidermis, each replacing the next; 2 generations of epidermis are reported in the literature on rhabdocoel embryos. This process of replacement parallels the epidermal replacement that larval neodermatans undergo at metamorphosis. Ultrastructural study of developing acoel, polyclad and macrostomid embryos shows that they, too, have epidermal replacement and growth through immigration of deeper-lying cells, comparable to the processes seen in higher flatworms. Succession of distinct generations of epidermis in such animals as the proseriates, triclads and rhabdocoels is probably an adaptation to development of ectolecithal eggs, providing the means for the embryo to use yolk that resides in vitellocytes, outside its blastomeres. We propose that the Neodermata has taken advantage of this developmental mechanism, producing successive generations of epidermal cells even in its larval stages, to counter the defenses of hosts.
Topics: Absorption; Animals; Cilia; Epidermis; Microscopy, Electron; Platyhelminths; Symbiosis; Turbellaria
PubMed: 9229254
DOI: 10.1016/s0020-7519(97)00013-1 -
Journal of Morphology Feb 2017Previous studies demonstrated complex architecture of the muscular system of Macrostomum species, especially in the rostrum area and the pharynx. However, little is...
Previous studies demonstrated complex architecture of the muscular system of Macrostomum species, especially in the rostrum area and the pharynx. However, little is known about the differences in muscular pattern between species of the genus. This study examines and compares the muscular systems of specimens belonging to three freshwater Macrostomum species (M. quiritium, M. tuba and M. velastylum), labeled with phalloidin-rhodamine and studied by confocal microscopy. Our results agree with the previous descriptions, confirming that the muscular patterns for the body wall, rostrum area, pharynx and caudal region differ among species. The muscles of the body wall follow the typical architecture, but the number of fibers in the species analyzed varies between dorsal and ventral surfaces, ranging from 80 to 100 fibers, this record being higher than previous observations. The arrangement of the fibers in the rostrum is complex, especially in the brain area. Macrostomum tuba and M. quiritium have a set of two muscles crossing at brain level and forming an "X," which is not evident in M. velastylum. We identified five different sets of fibers associated to the pharynx and mouth at ventral, medium and deep levels. These different sets are present in all three species studied. The caudal plate in M. tuba has an additional layer of diagonal fibers in the body wall, which is not evident in the other two species. The muscles of the reproductive system are independent of the body wall musculature in the species analyzed, but connected to the intestinal wall by specific fibers that may serve as an anchor. J. Morphol. 278:264-282, 2017. © 2016 Wiley Periodicals,Inc.
Topics: Animals; Muscles; Platyhelminths
PubMed: 27900777
DOI: 10.1002/jmor.20633 -
Molecular Phylogenetics and Evolution Sep 2000Proseriate flatworms are common members of the interstitial benthic fauna worldwide, predominantly occupying marine environments. As minute animals, having relatively...
Proseriate flatworms are common members of the interstitial benthic fauna worldwide, predominantly occupying marine environments. As minute animals, having relatively few characters useful for cladistic analysis, they have been difficult to present in a phylogenetic framework using morphology alone. Here we present a new morphological matrix consisting of 16 putatively homologous characters and two molecular data sets to investigate further this major group of free-living members of the Platyhelminthes. Complete 18S rDNA (representing 277 parsimony-informative characters) from 17 ingroup taxa and partial 28S rDNA spanning variable expansion regions D1 to D3 and D1 to D6 (representing 219 and 361 parsimony-informative characters, respectively) from 27 and 14 ingroup taxa, respectively, were determined and aligned as complementary data sets. Morphological and molecular data sets were analyzed separately and together to determine underlying phylogenetic patterns and to resolve conflict between published scenarios based on morphology alone. The monophyly of the Proseriata cannot be confirmed categorically with any of these data sets. However, the constituent taxa are confirmed as basal members of the Neoophora, and a sister group relationship with Tricladida is rejected. Similarly, the monophyly of one of the two subtaxa of the Proseriata, the Lithophora, could not be confirmed with molecules. Concerning intragroup relationships, we could reject one of the two phylogenetic trees formerly proposed, as well as the clade Otoplanidae + Coelogynoporidae. However, a clade Otoplanidae + Archimonocelididae + Monocelididae (to which the Monotoplanidae belong) was supported, and the position of the genus Calviria shifted from the Archimonocelididae to the Coelogynoporidae.
Topics: Animals; DNA, Ribosomal; Molecular Sequence Data; Phylogeny; Platyhelminths; RNA, Ribosomal, 18S; RNA, Ribosomal, 28S; Sequence Analysis, DNA
PubMed: 10991797
DOI: 10.1006/mpev.2000.0802 -
Zoological Science Oct 2006In this work, two new species of the genus Macrostomum (M. velastylum n. sp. and M. puntapiedrensis n. sp.) are described from the littoral benthos of the Río de la...
In this work, two new species of the genus Macrostomum (M. velastylum n. sp. and M. puntapiedrensis n. sp.) are described from the littoral benthos of the Río de la Plata estuary, Argentina. This is the first description of members of the Macrostomidae from Argentina, and of a species documented from both limnic and brackish-water environments. Macrostomum velastylum differs from its congeners in the fine details of its stylet, which are described using a new technique for stylet isolation and observation (scanning electron microscope). This method provides new information on stylet structure relative to traditional whole-mount techniques. Macrostomum puntapiedrensis differs from others species of the M. orthostylum group in the length and morphology of the distal tip of the stylet. Further details are provided on additional macrostomids from Argentina, including potential conspecifics of M. vejdovskyi, M. viride, and M. lineare.
Topics: Animals; Argentina; Platyhelminths; Species Specificity
PubMed: 17116988
DOI: 10.2108/zsj.23.853 -
Acta Parasitologica Mar 2014Unilatus irae sp. nov. (Dactylogyridae) is described from the gills of the armored catfish, Leporacanthicus galaxias Isbrücker et Nijssen (Loricariidae: Ancistrinae),...
Unilatus irae sp. nov. (Dactylogyridae) is described from the gills of the armored catfish, Leporacanthicus galaxias Isbrücker et Nijssen (Loricariidae: Ancistrinae), from Guamá river, Pará State, Brazil. The new species can be differentiated from its cogeneners by the combination of the following features: anterior anchor with well-developed superficial root, inconspicuous deep root, shaft bent at midpoint, forming angle of approximately 60°, evenly short curved point; posterior anchor with inconspicuous roots, sclerotized cap of base with small protuberance for articulation to posterior bar; evenly curved shaft and short point; anterior bar broadly V-shaped, with small posteromedial projection; and posterior bar anteriorly expanded on it midportion, with expanded ends slightly curved in posterior direction.
Topics: Animals; Brazil; Catfishes; Fish Diseases; Gills; Platyhelminths
PubMed: 24570054
DOI: 10.2478/s11686-014-0213-7 -
Hospital Practice (1995) Jul 1996
Topics: Animals; Female; Humans; Male; Nematoda; Phylogeny; Platyhelminths; Reproduction
PubMed: 8682886
DOI: 10.1080/21548331.1996.11443308 -
ELife Apr 2015Understanding the evolutionary relationships between species could help researchers select better model organisms to study in the laboratory.
Understanding the evolutionary relationships between species could help researchers select better model organisms to study in the laboratory.
Topics: Animals; Biological Evolution; Cell Nucleus; Genome; Platyhelminths
PubMed: 25879271
DOI: 10.7554/eLife.07431