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Kem WR, Rocca JR, Johnson JV, Junoy J. Discovery of the Nicotinic Receptor Toxin Anabaseine in a Polystiliferan Nemertean. Toxins (Basel) 2023; 15:46. [PMID: 36668866 PMCID: PMC9867080 DOI: 10.3390/toxins15010046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 12/25/2022] [Accepted: 12/30/2022] [Indexed: 01/06/2023] Open
Abstract
Nemerteans (also called Nemertines) are a phylum of predominantly marine worms that use toxins to capture prey and to defend themselves against predators. Hoplonemerteans have a proboscis armed with one or more stylets used in prey capture and are taxonomically divided into Order Monostilifera, whose members possess a single large proboscis stylet, and Order Polystilifera, whose members have multiple small stylets. Many monostiliferans contain alkaloidal toxins, including anabaseine, that stimulate and then desensitize nicotinic acetylcholine receptors that are present in all animals. These compounds also interact with pyridyl chemoreceptors in crustaceans, reducing predation and larval settlement. Anabaseine has been a lead compound in the design of alpha7 nicotinic acetylcholine receptor agonists like GTS-21 (also called DMXBA) to treat disorders of cognition such as Alzheimer's disease and schizophrenia. These drug candidates also display anti-inflammatory activities of potential medical importance. Most polystiliferans live deep in open oceans and are relatively inaccessible. We fortunately obtained two live specimens of a large benthic polystiliferan, Paradrepanophorus crassus (Pc), from the coast of Spain. MS and NMR analyses of the Ehrlich's reagent derivative allowed identification of anabaseine. A spectrophotometric assay for anabaseine, also based on its reaction with Ehrlich's reagent, revealed high concentrations of anabaseine in the body and proboscis. Apparently, the biosynthetic mechanism for producing anabaseine was acquired early in the evolution of the Hoplonemertea, before the monostiliferan-polystiliferan divergence.
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Affiliation(s)
- William R. Kem
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, 1200 Newell Drive, Gainesville, FL 32610, USA
| | - James R. Rocca
- AMRIS, McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Jodie V. Johnson
- Department of Chemistry, University of Florida, Gainesville, FL 32611, USA
| | - Juan Junoy
- Departamento de Ciencias de la Vida, Universidad de Alcalá, 28805 Alcalá de Henares, Spain
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Verdes A, Taboada S, Hamilton BR, Undheim EAB, Sonoda GG, Andrade SCS, Morato E, Isabel Marina A, Cárdenas CA, Riesgo A. Evolution, expression patterns and distribution of novel ribbon worm predatory and defensive toxins. Mol Biol Evol 2022; 39:6580756. [PMID: 35512366 PMCID: PMC9132205 DOI: 10.1093/molbev/msac096] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Ribbon worms are active predators that use an eversible proboscis to inject venom into their prey and defend themselves with toxic epidermal secretions. Previous work on nemertean venom has largely focused on just a few species and has not investigated the different predatory and defensive secretions in detail. Consequently, our understanding of the composition and evolution of ribbon worm venoms is still very limited. Here, we present a comparative study of nemertean venom combining RNA-seq differential gene expression analyses of venom-producing tissues, tandem mass spectrometry-based proteomics of toxic secretions, and mass spectrometry imaging of proboscis sections, to shed light onto the composition and evolution of predatory and defensive toxic secretions in Antarctonemertes valida. Our analyses reveal a wide diversity of putative defensive and predatory toxins with tissue-specific gene expression patterns and restricted distributions to the mucus and proboscis proteomes respectively, suggesting that ribbon worms produce distinct toxin cocktails for predation and defense. Our results also highlight the presence of numerous lineage-specific toxins, indicating that venom evolution is highly divergent across nemerteans, producing toxin cocktails that might be finely tuned to subdue different prey. Our data also suggest that the hoplonemertean proboscis is a highly specialized predatory organ that seems to be involved in a variety of biological functions besides predation, including secretion and sensory perception. Overall, our results advance our knowledge into the diversity and evolution of nemertean venoms and highlight the importance of combining different types of data to characterize toxin composition in understudied venomous organisms.
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Affiliation(s)
- Aida Verdes
- Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (MNCN), CSIC, Madrid, Spain.,Department of Life Sciences, Natural History Museum, London, UK
| | - Sergi Taboada
- Department of Life Sciences, Natural History Museum, London, UK.,Departament of Biodiversity, Ecology and Evolution, Universidad Complutense de Madrid, Madrid, Spain
| | - Brett R Hamilton
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD, Australia.,Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, QLD, Australia
| | - Eivind A B Undheim
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD, Australia.,Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway.,Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Gabriel G Sonoda
- Departmento de Genética e Biología Evolutiva, University of Sao Paulo, Sao Paulo, Brazil
| | - Sonia C S Andrade
- Departmento de Genética e Biología Evolutiva, University of Sao Paulo, Sao Paulo, Brazil
| | - Esperanza Morato
- CBMSO Protein Chemistry Facility, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain
| | - Ana Isabel Marina
- CBMSO Protein Chemistry Facility, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain
| | - César A Cárdenas
- Departamento Científico, Instituto Antártico Chileno, Punta Arenas, Chile.,Millennium Institute Biodiversity of Antarctic and Subantarctic Ecosystems (BASE), Santiago, Chile
| | - Ana Riesgo
- Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (MNCN), CSIC, Madrid, Spain.,Department of Life Sciences, Natural History Museum, London, UK
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Murdock DJE. The ‘biomineralization toolkit’ and the origin of animal skeletons. Biol Rev Camb Philos Soc 2020; 95:1372-1392. [DOI: 10.1111/brv.12614] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 04/28/2020] [Accepted: 04/30/2020] [Indexed: 12/29/2022]
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Göransson U, Jacobsson E, Strand M, Andersson HS. The Toxins of Nemertean Worms. Toxins (Basel) 2019; 11:E120. [PMID: 30781381 PMCID: PMC6410017 DOI: 10.3390/toxins11020120] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 02/11/2019] [Accepted: 02/12/2019] [Indexed: 12/22/2022] Open
Abstract
Most ribbon worms (phylum: Nemertea) are found in marine environments, where they act as predators and scavengers. They are characterized by an eversible proboscis that isused to hunt for prey and thick mucus covering their skin. Both proboscis and epidermal mucus mediate toxicity to predators and preys. Research into the chemical nature of the substances that render toxicity has not been extensive, but it has nevertheless led to the identification of several compounds of potential medicinal use or for application in biotechnology. This review provides a complete account of the current status of research into nemertean toxins.
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Affiliation(s)
- Ulf Göransson
- Pharmacognosy, Department of Medicinal Chemistry, Biomedical Centre, Uppsala University, 75123 Uppsala, Sweden.
| | - Erik Jacobsson
- Pharmacognosy, Department of Medicinal Chemistry, Biomedical Centre, Uppsala University, 75123 Uppsala, Sweden.
| | - Malin Strand
- Swedish Species Information Centre, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.
| | - Håkan S Andersson
- Linnaeus University Centre for Biomaterials Chemistry, Department of Chemistry and Biomedical Sciences, Linnaeus University, 39231 Kalmar, Sweden.
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Abstract
We studied the ultrastructure of the proboscis endothelium of 14 nemertean species. In all nemerteans examined, the endothelium is organized as a pseudostratified myoepithelium consisting of two types of cells resting on the basal extracellular matrix: apically situated supportive cells and subapical myocytes covered by cytoplasmic sheets of the supportive cells. Myocytes form the inner circular musculature of the proboscis; the endothelium in the bulb of monostiliferous nemerteans lacks myocytes. The endothelium of the studied species differs in the number of rows of muscle fibres (one vs. several rows), the number of myofibrils in myocytes (one vs. two to five), the number of processes of myocytes covered by one supportive cell (one vs. two to 23), and in the number of processes in supportive cells (one vs. two to five). In some of the species, rudimentary cilia of supportive cells were revealed by using cLSM and an antibody against tubulin. The data obtained indicate that the proboscis endothelium in nemerteans is in fact a coelothelium, but recognition of the ancestral state of the coelomic lining in Nemertea is problematic, as the rhynchocoel peritoneum lacks myocytes.
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Affiliation(s)
- Timur Yu Magarlamov
- 1 A. V. Zhirmunsky Institute of Marine Biology, Far Eastern Branch Russian Academy of Sciences, ul. Palchevskogo 17, 690059, Vladivostok, Russia.,2 School of Biomedicine, Far Eastern Federal University, ul. Oktyabrskaya 29, 690950, Vladivostok, Russia
| | - Alexei V Chernyshev
- 1 A. V. Zhirmunsky Institute of Marine Biology, Far Eastern Branch Russian Academy of Sciences, ul. Palchevskogo 17, 690059, Vladivostok, Russia.,3 School of Natural Sciences, Far Eastern Federal University, ul. Oktyabrskaya 27, 690950, Vladivostok, Russia
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Chernyshev AV. CLSM Analysis of the Phalloidin-Stained Muscle System of the Nemertean Proboscis and Rhynchocoel. Zoolog Sci 2015; 32:547-60. [DOI: 10.2108/zs140267] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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von Reumont BM, Campbell LI, Jenner RA. Quo vadis venomics? A roadmap to neglected venomous invertebrates. Toxins (Basel) 2014; 6:3488-551. [PMID: 25533518 PMCID: PMC4280546 DOI: 10.3390/toxins6123488] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 11/21/2014] [Accepted: 12/02/2014] [Indexed: 01/22/2023] Open
Abstract
Venomics research is being revolutionized by the increased use of sensitive -omics techniques to identify venom toxins and their transcripts in both well studied and neglected venomous taxa. The study of neglected venomous taxa is necessary both for understanding the full diversity of venom systems that have evolved in the animal kingdom, and to robustly answer fundamental questions about the biology and evolution of venoms without the distorting effect that can result from the current bias introduced by some heavily studied taxa. In this review we draw the outlines of a roadmap into the diversity of poorly studied and understood venomous and putatively venomous invertebrates, which together represent tens of thousands of unique venoms. The main groups we discuss are crustaceans, flies, centipedes, non-spider and non-scorpion arachnids, annelids, molluscs, platyhelminths, nemerteans, and echinoderms. We review what is known about the morphology of the venom systems in these groups, the composition of their venoms, and the bioactivities of the venoms to provide researchers with an entry into a large and scattered literature. We conclude with a short discussion of some important methodological aspects that have come to light with the recent use of new -omics techniques in the study of venoms.
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Affiliation(s)
| | - Lahcen I Campbell
- Department of Life Sciences, the Natural History Museum, Cromwell Road, SW7 5BD London, UK.
| | - Ronald A Jenner
- Department of Life Sciences, the Natural History Museum, Cromwell Road, SW7 5BD London, UK.
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Whelan NV, Kocot KM, Santos SR, Halanych KM. Nemertean toxin genes revealed through transcriptome sequencing. Genome Biol Evol 2014; 6:3314-25. [PMID: 25432940 PMCID: PMC4986456 DOI: 10.1093/gbe/evu258] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Nemerteans are one of few animal groups that have evolved the ability to utilize toxins for both defense and subduing prey, but little is known about specific nemertean toxins. In particular, no study has identified specific toxin genes even though peptide toxins are known from some nemertean species. Information about toxin genes is needed to better understand evolution of toxins across animals and possibly provide novel targets for pharmaceutical and industrial applications. We sequenced and annotated transcriptomes of two free-living and one commensal nemertean and annotated an additional six publicly available nemertean transcriptomes to identify putative toxin genes. Approximately 63–74% of predicted open reading frames in each transcriptome were annotated with gene names, and all species had similar percentages of transcripts annotated with each higher-level GO term. Every nemertean analyzed possessed genes with high sequence similarities to known animal toxins including those from stonefish, cephalopods, and sea anemones. One toxin-like gene found in all nemerteans analyzed had high sequence similarity to Plancitoxin-1, a DNase II hepatotoxin that may function well at low pH, which suggests that the acidic body walls of some nemerteans could work to enhance the efficacy of protein toxins. The highest number of toxin-like genes found in any one species was seven and the lowest was three. The diversity of toxin-like nemertean genes found here is greater than previously documented, and these animals are likely an ideal system for exploring toxin evolution and industrial applications of toxins.
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Affiliation(s)
- Nathan V Whelan
- Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama
| | - Kevin M Kocot
- Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama Present address: School of Biological Sciences, University of Queensland, Brisbane, QLD, Australia
| | - Scott R Santos
- Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama
| | - Kenneth M Halanych
- Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama
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Hindinger S, Schwaha T, Wanninger A. Immunocytochemical studies reveal novel neural structures in nemertean pilidium larvae and provide evidence for incorporation of larval components into the juvenile nervous system. Front Zool 2013; 10:31. [PMID: 23701905 PMCID: PMC3670813 DOI: 10.1186/1742-9994-10-31] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 05/13/2013] [Indexed: 11/30/2022] Open
Abstract
Introduction Nemertea is one of the least studied lophotrochozoan phyla concerning neurogenesis. The sparse data available do not unambiguously allow for answering questions with respect to the neural groundplan of the phylum or the fate of larval neural structures during metamorphosis. In order to contribute to this issue, we studied neurotransmitter distribution during development of the pilidiophoran Lineus albocinctus Verrill, 1900. Results Two serotonin-like immunoreactive (lir) neurons are present in the anterior part of the apical plate. They send numerous processes into the four lobes of the pilidium larva, where they form a complex subepithelial nerve net. All four larval lobes are underlain by a marginal neurite bundle, which is associated with numerous serotonin-lir monociliated perikarya. A serotonin-lir oral nerve ring encircles the stomach sphincter and is associated with few serotonin-lir conical cells. Two suboral neurites descend from the oral nerve ring and merge with the marginal neurite bundle. The oral nerve ring and the suboral neurites contain the mollusk-specific VD1/RPD2 α-neuropeptide. The lateral lobes of the larva have three and the anterior and the posterior lobes two VD1/RPD2-lir marginal neurite bundles. The lobar FMRFamide-lir plexus of Lineus albocinctus is much more complex than previously described for any pilidium larva. It includes a circumesophageal neurite that descends along each side of the larval esophagus and together with the inner marginal neurite bundle gives rise to the lobar plexus of the lateral lobes. An outer FMRFamide-lir marginal neurite bundle with numerous associated FMRFamide-lir marginal sensory cells surrounds all four lobes. FMRFamide-lir structures are absent in the larval apical region. The oral nerve ring and the two suboral serotonin-lir neurites are incorporated into the juvenile nervous system. Conclusion Our study confirms the presence of serotonin-lir components in the apical region of the pilidium larva of Lineus albocinctus and thus contradicts an earlier study on the same species. We show that the nervous system of pilidium larvae, especially the FMRFamide-lir components, is much more complex than previously assumed. The presence of the VD1/RPD2-α-neuropeptide indicates that this compound may have been part of the lophotrochozoan neural groundplan.
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Affiliation(s)
- Sabine Hindinger
- Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Althanstr, 14, Vienna, 1090, Austria.
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Junoy J, Montalvo S, Roldán C, García-Corrales P. Ultrastructural study of the bacillary, granular and mucoid proboscidial gland cells of Riseriellus occultus (Nemertini, Heteronemertini). ACTA ZOOL-STOCKHOLM 2001. [DOI: 10.1046/j.1463-6395.2000.00053.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Montalvo S, Junoy J, Roldán C, García-Corrales P. Ultrastructural study of sensory cells of the proboscidial glandular epithelium of Riseriellus occultus (Nemertea, Heteronemertea). J Morphol 1996; 229:83-96. [PMID: 29852637 DOI: 10.1002/(sici)1097-4687(199607)229:1<83::aid-jmor5>3.0.co;2-q] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Only one sensory cell type has been observed within the glandular epithelium of the proboscis in the heteronemertine Riseriellus occultus. These bipolar cells are abundant and scattered singly throughout the proboscis length. The apical surface of each dendrite bears a single cilium enclosed by a ring of six to eight prominent microvilli. The cilium has the typical 9×2 + 2 axoneme arrangement and is equipped with a cross-striated vertical rootlet extending from the basal body. No accessory centriole or horizontal rootlet was observed. Large, modified microvilli (stereovilli) surrounding the cilium are joined together by a system of fine filaments derived from the glycocalyx. Each microvillus contains a bundle of actin-like filaments which anchor on the indented inner surface of a dense, apical ring situated beneath the level of the ciliary basal body. The tip of the cilium is expanded and modified to form a bulb-like structure which lies above the level where the surrounding microvilli terminate. In the region where the cilium emerges from the microvillar cone, the membrane of the microvillar apices makes contact with a corresponding portion of the ciliary membrane. At this level microvilli and cilium are apparently firmly linked by junctional systems resembling adherens junctions. The results suggest that these sensory cells may be mechanoreceptors. © 1996 Wiley-Liss, Inc.
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Affiliation(s)
- Sagrario Montalvo
- Department of Animal Biology, University of Alcalá de Henares, E-28871, Alcalá de Henares, Madrid, Spain
| | - Juan Junoy
- Department of Animal Biology, University of Alcalá de Henares, E-28871, Alcalá de Henares, Madrid, Spain
| | - Carmen Roldán
- Department of Animal Biology I, Faculty of Biology, University Complutense, E-28040, Madrid, Spain
| | - Pedro García-Corrales
- Department of Animal Biology, University of Alcalá de Henares, E-28871, Alcalá de Henares, Madrid, Spain
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Shinn GL, Stricker SA, Cavey MJ. Ultrastructure of transrectal coelomoducts in the sea cucumber Parastichopus californicus (Echinodermata, Holothuroida). ZOOMORPHOLOGY 1990. [DOI: 10.1007/bf00312470] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Strieker SA, Cavey MJ. Calcareous Concretions and Non-Calcified Hooks in the Body Wall of Nemertean Worms. ACTA ZOOL-STOCKHOLM 1988. [DOI: 10.1111/j.1463-6395.1988.tb00899.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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NORENBURG JON. Redescription of a brooding nemertine, Cyanophthalma obscura (Schultze) gen. et comb.n., with observations on its biology and discussion of the species of Prostomatella and related taxa*+. ZOOL SCR 1986. [DOI: 10.1111/j.1463-6409.1986.tb00229.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Stricker SA. The fine structure and development of calcified skeletal elements in the body wall of holothurian echinoderms. J Morphol 1986; 188:273-288. [DOI: 10.1002/jmor.1051880303] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Amorphous calcium phosphate in the stylets produced by a marine worm (Nemertea). ACTA ACUST UNITED AC 1985. [DOI: 10.1007/bf01964805] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Stricker SA. An ultrastructural study of larval settlement in the sea anemoneUrticina crassicornis (Cnidaria, Actiniaria). J Morphol 1985. [DOI: 10.1002/jmor.1051860208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Stricker SA. The ultrastructure and formation of the calcareous ossicles in the body wall of the sea cucumber Leptosynapta clarki (Echinodermata, Holothuroida). ZOOMORPHOLOGY 1985. [DOI: 10.1007/bf00311965] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Stricker SA, Reed CG. The ontogeny of shell secretion in Terebratalia transversa (Brachiopoda, Articulata). II. Formation of the protegulum and juvenile shell. J Morphol 1985; 183:251-71. [PMID: 4039010 DOI: 10.1002/jmor.1051830303] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The fine structure of the shell and underlying mantle in young juveniles of the articulate brachiopod Terebratalia transversa has been examined by electron microscopy. The first shell produced by the mantle consists of a nonhinged protegulum that lacks concentric growth lines. The protegulum is secreted within a day after larval metamorphosis and typically measures 140-150 micron long. A thin organic periostracum constitutes the outer layer of the protegulum, and finely granular shell material occurs beneath the periostracum. Protegula resist digestion in sodium hypochlorite and are refractory to sectioning, suggesting that the subperiostracal portion of the primordial shell is mineralized. The juvenile shell at 4 days postmetamorphosis possesses incomplete sockets and rudimentary teeth that consist of nonfibrous material. The secondary layer occuring in the inner part of the juvenile shell contains imbricated fibers, whereas the outer portion of the shell comprises a bipartite periostracum and an underlying primary layer of nonfibrous shell. Deposition of the periostracum takes place within a slot that is situated between the so-called lobate and vesicular cells of the outer mantle lobe. Vesicular cells deposit the basal layer of the periostracum, while lobate cells contribute materials to the overlying periostracal superstructure. Cells with numerous tonofibrils and hemidesmosomes differentiate in the outer mantle epithelium at sites of muscle attachments, and unbranched punctae that surround mantle caeca develop throughout the subperiostracal portion of the shell. Three weeks after metamorphosis, the juvenile shell averages about 320 micron in length and is similar in ultrastructure to the shells secreted by adult articulates.
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Stricker SA. Styletogenesis in nemertean worms: The ultrastructure of organelles involved in intracellular calcification. J Morphol 1984; 179:119-134. [DOI: 10.1002/jmor.1051790202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Stricker SA, Cloney RA. The ultrastructure of venom-producing cells in Paranemertes peregrina (Nemertea, Hoplonemertea). J Morphol 1983; 177:89-107. [PMID: 30075619 DOI: 10.1002/jmor.1051770108] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The nemertean Paranemertes peregrina uses its long, eversible proboscis to capture nereid polychaetes. During prey capture, the glandular epithelium of the everted proboscis secretes a sticky venom that contains a potent neurotoxin. In this study, the ultrastructure of the venom-producing epithelium is examined before and after capture of nereid prey. Four types of cells can be distinguished in the glandular epithelium, based on the shape and staining properties of their secretory products. The cells contain fusiform or coalescent types of rhabdoids, acidophilic granules, or flocculent material. All four cell types occur in the anterior part of the proboscis, but only cells with acidophilic granules have been observed in the posterior chamber. The glandular epithelium of the anterior chamber secretes sheets of venomous mucus that are composed of the four types of secretory products fused together, while the epithelial cells of the posterior chamber produce a granulated discharge. Cells that contain flocculent material also occur in the epidermis of P. peregrina. The flocculent material is believed to contain the toxic component of the venom, as its distribution in the anterior proboscis chamber and body wall correlates with previous reports of toxin concentrations that were derived from assays of tissue extracts.
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Affiliation(s)
- Stephen A Stricker
- Department of Zoology, University of Washington, Seattle, Washington 98195.,Friday Harbor Laboratories, Friday Harbor, Washington 98250
| | - Richard A Cloney
- Department of Zoology, University of Washington, Seattle, Washington 98195.,Friday Harbor Laboratories, Friday Harbor, Washington 98250
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STRICKER STEPHENA. The Morphology of Paranemertes sanjuanensis sp.n. (Nemertea, Monostilifera) from Washington, U.S.A. ZOOL SCR 1982. [DOI: 10.1111/j.1463-6409.1982.tb00523.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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