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Philosophical Transactions of the Royal... Apr 2008Molecular approaches to the study of development and evolution have had profound effects on our understanding of the nature of the evolutionary process. Developmental... (Review)
Review
Molecular approaches to the study of development and evolution have had profound effects on our understanding of the nature of the evolutionary process. Developmental biologists became intoxicated with fanciful notions of reconstructing genetic pathways of morphogenesis while evolutionary biologists were sobered by the fallacy of reconstructing organismal relationships along increasing grades of morphological complexity. Increased taxon sampling and improvements in analytical techniques are providing a new approach and are forcing biologists to move past historical biases to allow more accurate mapping of morphological and developmental characters through evolutionary time. Here, we discuss the possible developmental and morphological features of the 'urbilaterian', the triploblastic animal with anterior-posterior and dorsoventral axes and predecessor of the protostome-deuterostome ancestor. We argue that this animal, with features resembling acoelomorph flatworms, was far simpler morphologically than the protostome-deuterostome ancestor despite possessing a nearly complete eubilaterian genome. We show that the deployment of some genes expected to pattern the protostome-deuterostome ancestor is not deployed in acoels in the predicted manner and thus might have been co-opted after the evolution of the urbilaterian. We also identify the developmental changes related to gastrulation that gave rise to the urbilaterian from a simpler cnidarian-like ancestor.
Topics: Animals; Biological Evolution; Body Patterning; Developmental Biology; Evolution, Molecular; Female; Gastrulation; Male; Models, Biological; Phylogeny; Platyhelminths
PubMed: 18192185
DOI: 10.1098/rstb.2007.2239 -
Journal of Veterinary Pharmacology and... Mar 2019Fish are common definitive and intermediate hosts for a variety of parasitic flatworms. In unstressed wild populations, parasitic infections often go unnoticed and are... (Review)
Review
Fish are common definitive and intermediate hosts for a variety of parasitic flatworms. In unstressed wild populations, parasitic infections often go unnoticed and are perceived to represent a lesser threat to fish health. In contrast, platyhelminth parasitism of captive fish often results in decreased weight gain and increased mortality which often necessitates chemotherapeutic treatment. The presence of platyhelminth parasites in fish tissues is not only unappealing but in some cases also represents a threat to human health. In veterinary medicine, one of the most commonly used agents with anti-flatworm activity is praziquantel; yet, no praziquantel products are labeled for use in fish in the United States. Veterinarians may use praziquantel preparations approved for other vertebrate species under the Animal Medicinal Drug Use Clarification Act (AMDUCA). However, such extra-label use should be informed by scientific evidence including efficacy and tissue residue studies. Herein, we review studies testing the efficacy of praziquantel for treatment of platyhelminthes along with an assessment of routes of administration, pharmacokinetics, and toxicity information.
Topics: Animals; Anthelmintics; Cestode Infections; Fish Diseases; Fishes; Platyhelminths; Praziquantel; Trematode Infections
PubMed: 30556228
DOI: 10.1111/jvp.12735 -
International Journal For Parasitology Aug 1998Phylogenetic analysis of molecular data from complete 18S rRNA and partial 28S rRNA genes, of a variety of platyhelminths, places the enigmatic Udonella caligorum firmly...
Phylogenetic analysis of molecular data from complete 18S rRNA and partial 28S rRNA genes, of a variety of platyhelminths, places the enigmatic Udonella caligorum firmly as a monopisthocotylean monogenean. Both maximum parsimony and a modified distance measure, operating under a maximum likelihood model, gave identical solutions for each data set. These data further support morphological evidence from ultrastructural studies indicating the neodermatan affinities of Udonella, namely shared features in sensory receptors, surface tegument, sperm structure and spermiogenesis. The molecular data reject the class Udonellidea and the placement of udonellids as sister-group to the Neodermata. As shown previously with molecular data, the monogeneans appear as a paraphyletic assemblage comprising strongly monophyletic Monopisthocotylea and Polyopisthocotylea. Their relationships with the trematodes and cestodes are not resolved with 28S rDNA or 18S rDNA alone.
Topics: Animals; Base Sequence; DNA, Helminth; DNA, Ribosomal; Molecular Sequence Data; Phylogeny; Platyhelminths; Sequence Alignment
PubMed: 9762571
DOI: 10.1016/s0020-7519(98)00108-8 -
Antioxidants & Redox Signaling Sep 2013Platyhelminth parasites cause chronic infections that are a major cause of disability, mortality, and economic losses in developing countries. Maintaining redox... (Review)
Review
SIGNIFICANCE
Platyhelminth parasites cause chronic infections that are a major cause of disability, mortality, and economic losses in developing countries. Maintaining redox homeostasis is a major adaptive problem faced by parasites and its disruption can shift the biochemical balance toward the host. Platyhelminth parasites possess a streamlined thiol-based redox system in which a single enzyme, thioredoxin glutathione reductase (TGR), a fusion of a glutaredoxin (Grx) domain to canonical thioredoxin reductase (TR) domains, supplies electrons to oxidized glutathione (GSSG) and thioredoxin (Trx). TGR has been validated as a drug target for schistosomiasis.
RECENT ADVANCES
In addition to glutathione (GSH) and Trx reduction, TGR supports GSH-independent deglutathionylation conferring an additional advantage to the TGR redox array. Biochemical and structural studies have shown that the TR activity does not require the Grx domain, while the glutathione reductase and deglutathionylase activities depend on the Grx domain, which receives electrons from the TR domains. The search for TGR inhibitors has identified promising drug leads, notably oxadiazole N-oxides.
CRITICAL ISSUES
A conspicuous feature of platyhelminth TGRs is that their Grx-dependent activities are temporarily inhibited at high GSSG concentrations. The mechanism underlying the phenomenon and its biological relevance are not completely understood.
FUTURE DIRECTIONS
The functional diversity of Trxs and Grxs encoded in platyhelminth genomes remains to be further assessed to thoroughly understand the TGR-dependent redox network. Optimization of TGR inhibitors and identification of compounds targeting other parasite redox enzymes are good options to clinically develop relevant drugs for these neglected, but important diseases.
Topics: Animals; Cestode Infections; Helminth Proteins; Host-Parasite Interactions; Humans; Metabolic Networks and Pathways; Multienzyme Complexes; NADH, NADPH Oxidoreductases; Oxidation-Reduction; Oxidative Stress; Platyhelminths; Reactive Oxygen Species
PubMed: 22909029
DOI: 10.1089/ars.2012.4670 -
BMC Genomics Jul 2013The phylum Platyhelminthes (flatworms) contains an important group of bilaterian organisms responsible for many debilitating and chronic infectious diseases of human and...
BACKGROUND
The phylum Platyhelminthes (flatworms) contains an important group of bilaterian organisms responsible for many debilitating and chronic infectious diseases of human and animal populations inhabiting the planet today. In addition to their biomedical and veterinary relevance, some platyhelminths are also frequently used models for understanding tissue regeneration and stem cell biology. Therefore, the molecular (genetic and epigenetic) characteristics that underlie trophic specialism, pathogenicity or developmental maturation are likely to be pivotal in our continued studies of this important metazoan group. Indeed, in contrast to earlier studies that failed to detect evidence of cytosine or adenine methylation in parasitic flatworm taxa, our laboratory has recently defined a critical role for cytosine methylation in Schistosoma mansoni oviposition, egg maturation and ovarian development. Thus, in order to identify whether this epigenetic modification features in other platyhelminth species or is a novelty of S. mansoni, we conducted a study simultaneously surveying for DNA methylation machinery components and DNA methylation marks throughout the phylum using both parasitic and non-parasitic representatives.
RESULTS
Firstly, using both S. mansoni DNA methyltransferase 2 (SmDNMT2) and methyl-CpG binding domain protein (SmMBD) as query sequences, we illustrate that essential DNA methylation machinery components are well conserved throughout the phylum. Secondly, using both molecular (methylation specific amplification polymorphism, MSAP) and immunological (enzyme-linked immunoabsorbent assay, ELISA) methodologies, we demonstrate that representative species (Echinococcus multilocularis, Protopolystoma xenopodis, Schistosoma haematobium, Schistosoma japonicum, Fasciola hepatica and Polycelis nigra) within all four platyhelminth classes (Cestoda, Monogenea, Trematoda and 'Turbellaria') contain methylated cytosines within their genome compartments.
CONCLUSIONS
Collectively, these findings provide the first direct evidence for a functionally conserved and enzymatically active DNA methylation system throughout the Platyhelminthes. Defining how this epigenetic feature shapes phenotypic diversity and development within the phylum represents an exciting new area of metazoan biology.
Topics: Amino Acid Sequence; Animals; Conserved Sequence; CpG Islands; Cytosine; DNA (Cytosine-5-)-Methyltransferases; DNA Methylation; DNA-Binding Proteins; Epigenesis, Genetic; Molecular Sequence Data; Platyhelminths
PubMed: 23837670
DOI: 10.1186/1471-2164-14-462 -
Parasitology Oct 2016We studied the monogenean communities of 34 species of butterflyfish from the tropical Indo-West Pacific, identifying 13 dactylogyrid species (including two species that...
We studied the monogenean communities of 34 species of butterflyfish from the tropical Indo-West Pacific, identifying 13 dactylogyrid species (including two species that are presently undescribed). Monogenean assemblages differed significantly between host species in terms of taxonomic structure, intensity and prevalence. Parasite richness ranged from 0 (Chaetodon lunulatus) to 11 (C. auriga, C. citrinellus and C. lunula). Host specificity varied between the dactylogyrids species, being found on 2-29 of the 34 chaetodontid species examined. Sympatric butterflyfish species were typically parasitized by different combinations of dactylogyrid species, suggesting the existence of complex host-parasite interactions. We identified six clusters of butterflyfish species based on the similarities of their dactylogyrid communities. Dactylogyrid richness and diversity were not related to host size, diet specialization, depth range or phylogeny of butterflyfish species. However, there was a weak positive correlation between monogenean richness and diversity and host geographical range. Most communities of dactylogyrids were dominated by Haliotrema aurigae and H. angelopterum, indicating the importance of the genus Haliotrema in shaping monogenean communities of butterflyfishes. This study casts light on the structure of the monogenean communities of butterflyfishes, suggesting that the diversity and complexity of community structures arises from a combination of host species-specific parameters.
Topics: Animals; Biota; Cestode Infections; Fish Diseases; Fishes; Gills; Host Specificity; Host-Parasite Interactions; Pacific Islands; Platyhelminths
PubMed: 27573880
DOI: 10.1017/S0031182016001463 -
Parasites & Vectors Sep 2020The flatworms (Lophotrochozoa: Platyhelminthes) are one of the major phyla of invertebrates but their interrelationships are still not well understood including...
BACKGROUND
The flatworms (Lophotrochozoa: Platyhelminthes) are one of the major phyla of invertebrates but their interrelationships are still not well understood including unravelling the most closely related taxon of the Neodermata, which includes exclusively obligate parasites of all main groups of vertebrates with some 60,000 estimated species. Recent phylogenomic studies indicate that the freshwater 'microturbellarian' Bothrioplana semperi may be the closest ancestor to the Neodermata, but this hypothesis receives little morphological support. Therefore, additional morphological and ultrastructural characters that might help understand interrelations within the Neodermata are needed.
METHODS
Ultrastructure of the excretory ducts of representatives of the most basal parasitic flatworms (Neodermata), namely monocotylid (Monopisthocotylea) and chimaericolid (Polyopisthocotylea) monogeneans, aspidogastreans (Trematoda), as well as gyrocotylidean and amphilinidean tapeworms (Cestoda), were studied using transmission electron microscopy (TEM).
RESULTS
The present study revealed the same pattern of the cytoarchitecture of excretory ducts in all studied species of the basal neodermatans. This pattern is characterised by the presence of septate junctions between the adjacent epithelial cells and lateral ciliary flames along different levels of the excretory ducts. Additionally, a new character was observed in the protonephridial terminal cell of Gyrocotyle urna, namely a septate junction between terminal and adjacent duct cells at the level of the distal extremity of the flame tuft. In Amphilina foliacea, a new type of protonephridial cell with multiple flame bulbs and unique character of its weir, which consists of a single row of the ribs, is described. A remarkable difference has been observed between the structure of the luminal surface of the excretory ducts of the studied basal neodermatan groups and B. semperi.
CONCLUSIONS
The present study does not provide ultrastructural support for a close relationship between the Neodermata and B. semperi.
Topics: Animals; Biological Evolution; Cestoda; Microscopy, Electron, Transmission; Phylogeny; Platyhelminths; Trematoda
PubMed: 32887664
DOI: 10.1186/s13071-020-04307-8 -
Cell and Tissue Research Mar 2007Neoblasts are potentially totipotent stem cells and the only proliferating cells in adult Platyhelminthes. We have examined the cellular dynamics of neoblasts during the...
Neoblasts are potentially totipotent stem cells and the only proliferating cells in adult Platyhelminthes. We have examined the cellular dynamics of neoblasts during the posterior regeneration of Macrostomum lignano. Double-labeling of neoblasts with bromodeoxyuridine and the anti-phospho histone H3 mitosis marker has revealed a complex cellular response in the first 48 h after amputation; this response is different from that known to occur during regeneration in triclad platyhelminths and in starvation/feeding experiments in M. lignano. Mitotic activity is reduced during the first 8 h of regeneration but, at 48 h after amputation, reaches almost twice the value of control animals. The total number of S-phase cells significantly increases after 1 day of regeneration. A subpopulation of fast-cycling neoblasts surprisingly shows the same dynamics during regeneration as those in control animals. Wound healing and regeneration are accompanied by the formation of a distinct blastema. These results present new insights, at the cellular level, into the early regeneration of rhabditophoran Platyhelminthes.
Topics: Amputation, Surgical; Animals; Bromodeoxyuridine; Cell Proliferation; Histones; In Vitro Techniques; Mitosis; Platyhelminths; Regeneration; S Phase; Time Factors; Totipotent Stem Cells; Wound Healing
PubMed: 17043794
DOI: 10.1007/s00441-006-0299-9 -
International Journal For Parasitology Sep 2009Available evidence shows that short amidated neuropeptides are widespread and have important functions within the nervous systems of all flatworms (phylum...
Available evidence shows that short amidated neuropeptides are widespread and have important functions within the nervous systems of all flatworms (phylum Platyhelminthes) examined, and could therefore represent a starting point for new lead drug compounds with which to combat parasitic helminth infections. However, only a handful of these peptides have been characterised, the rigorous exploration of the flatworm peptide signalling repertoire having been hindered by the dearth of flatworm genomic data. Through searches of both expressed sequence tags and genomic resources using the basic local alignment search tool (BLAST), we describe 96 neuropeptides on 60 precursors from 10 flatworm species. Most of these (51 predicted peptides on 14 precursors) are novel and are apparently restricted to flatworms; the remainder comprise nine recognised peptide families including FMRFamide-like (FLPs), neuropeptide F (NPF)-like, myomodulin-like, buccalin-like and neuropeptide FF (NPFF)-like peptides; notably, the latter have only previously been reported in vertebrates. Selected peptides were localised immunocytochemically to the Schistosoma mansoni nervous system. We also describe several novel flatworm NPFs with structural features characteristic of the vertebrate neuropeptide Y (NPY) superfamily, previously unreported characteristics which support the common ancestry of flatworm NPFs with the NPY-superfamily. Our dataset provides a springboard for investigation of the functional biology and therapeutic potential of neuropeptides in flatworms, simultaneously launching flatworm neurobiology into the post-genomic era.
Topics: Amino Acid Sequence; Animals; Computational Biology; Conserved Sequence; Expressed Sequence Tags; Female; Genome, Helminth; Helminth Proteins; Humans; Molecular Sequence Data; Neuropeptides; Phylogeny; Platyhelminths; Receptors, Neuropeptide; Sequence Alignment; Structure-Activity Relationship
PubMed: 19361512
DOI: 10.1016/j.ijpara.2009.03.005 -
Development Genes and Evolution Feb 2007Traditionally, regeneration research has been closely tied to flatworm research, as flatworms (Plathelminthes) were among the first animals where the phenomenon of... (Review)
Review
Traditionally, regeneration research has been closely tied to flatworm research, as flatworms (Plathelminthes) were among the first animals where the phenomenon of regeneration was discovered. Since then, the main focus of flatworm regeneration research was on triclads, for which various phenomena were observed and a number of theories developed. However, free-living flatworms encompass a number of other taxa where regeneration was found to be possible. This review aims to display and to compare regeneration in all major free-living flatworm taxa, with special focus on a new player in the field of regeneration, Macrostomum lignano (Macrostomorpha). Findings on the regeneration capacity of this organism provide clues for links between regeneration and (post-)embryonic development, starvation, and asexual reproduction. The role of the nervous system and especially the brain for regeneration is discussed, and similarities as well as particularities in regeneration among free-living flatworms are pointed out.
Topics: Animals; Brain; Female; Male; Nervous System Physiological Phenomena; Ovary; Platyhelminths; Regeneration; Reproduction; Species Specificity; Totipotent Stem Cells; Turbellaria
PubMed: 17146688
DOI: 10.1007/s00427-006-0120-5