Eversible Proboscis Research Articles

Evolution, Expression Patterns, and Distribution of Novel Ribbon Worm Predatory and Defensive Toxins.

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.

The Toxins of Nemertean Worms.

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 is used 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.

An updated list of Acanthocephalans (Acanthocephala) from animals in Vietnam

Acanthocephala is a phylum of parasitic worms characterized by the presence of an eversible proboscis, armed with spines, which is used to pierce and hold the gut wall of the host. In Vietnam, acanthocephalans have been studied about 50 years ago. In 1977, the first classification of the parasitic acanthocephalans, including 26 species of 10 genus, 5 families, 3 orders, from birds and mammals was published. This excluded acanthocephalans from fish. Recently, many other acanthocephans have been described from all classes of the vertebrates. In addition, the classification of acanthocephalans has been changed. This article updated the list of acanthocephalans from animals in Vietnam following the latest classification. To date, 72 species of 34 genus, 15 families, 8 orders of 3 classes (Archiacanthocephala, Eoacanthocephala and Palaeacanthocephala) were listed, consisting 13 from freshwater fishes, 21 from marine fishes, 3 from amphibians, from reptiles, 29 from birds and 5 from mammals. The list of acanthocephalans from animals in Vietnam with the information of their hosts, distributions and references were given herein.

A Polychaete's powerful punch: venom gland transcriptomics of Glycera reveals a complex cocktail of toxin homologs.

Glycerids are marine annelids commonly known as bloodworms. Bloodworms have an eversible proboscis adorned with jaws connected to venom glands. Bloodworms prey on invertebrates, and it is known that the venom glands produce compounds that can induce toxic effects in animals. Yet, none of these putative toxins has been characterized on a molecular basis. Here we present the transcriptomic profiles of the venom glands of three species of bloodworm, Glycera dibranchiata, Glycera fallax and Glycera tridactyla, as well as the body tissue of G. tridactyla. The venom glands express a complex mixture of transcripts coding for putative toxin precursors. These transcripts represent 20 known toxin classes that have been convergently recruited into animal venoms, as well as transcripts potentially coding for Glycera-specific toxins. The toxins represent five functional categories: Pore-forming and membrane-disrupting toxins, neurotoxins, protease inhibitors, other enzymes, and CAP domain toxins. Many of the transcripts coding for putative Glycera toxins belong to classes that have been widely recruited into venoms, but some are homologs of toxins previously only known from the venoms of scorpaeniform fish and monotremes (stonustoxin-like toxin), turrid gastropods (turripeptide-like peptides), and sea anemones (gigantoxin I-like neurotoxin). This complex mixture of toxin homologs suggests that bloodworms employ venom while predating on macroscopic prey, casting doubt on the previously widespread opinion that G. dibranchiata is a detritivore. Our results further show that researchers should be aware that different assembly methods, as well as different methods of homology prediction, can influence the transcriptomic profiling of venom glands.

Molecular examination of kalyptorhynch diversity (Platyhelminthes: Rhabdocoela), including descriptions of five meiofaunal species from the north-eastern Pacific Ocean

The spaces between sand grains are home to a myriad of microscopic marine eukaryotes, including kalyptorhynch rhabdocoels equipped with an eversible proboscis that enables them to capture microscopic prey living in these environments. The structure of the kalyptorhynch proboscis separates the two major subclades within the group: the Schizorhynchia (bifurcated proboscis) and the Eukalyptorhynchia (unbranched proboscis). A survey of meiofaunal metazoans in the Pacific north-west led to the discovery of three new schizorhynch species (Undicola tofinoensisgen. nov., sp. nov.,Schizorhinos vancouverensisgen. nov., sp. nov. andLinguabana tulaigen. nov., sp. nov.) and two new eukalyptorhynch species (Thinodactylaina tlaoquiahtensisgen. nov., sp. nov. andRostracilla nuuchahnulthensisgen. nov., sp. nov.). This survey also recovered the putative cosmopolitan eukalyptorhynch (Polycystididae)Gyratrix hermaphroditusEhrenberg, 1831. We performed molecular phylogenetic analyses on 18S rDNA sequences from all five novel isolates and from all available kalyptorhynch species in GenBank. The molecular data supported the monophyly of the Eukalyptorhynchia and Schizorhynchia and helped demonstrate the boundaries between different species within the Kalyptorhynchia.

Burrow extension with a proboscis: mechanics of burrowing by the glycerid Hemipodus simplex

Burrowing marine infauna are morphologically diverse and ecologically important as ecosystem engineers. The polychaetes Nereis virens and Cirriformia moorei extend their burrows by crack propagation. Nereis virens does so by everting its pharynx and C. moorei, lacking an eversible pharynx or proboscis, uses its hydrostatic skeleton to expand its anterior. Both behaviors apply stress to the burrow wall that is amplified at the tip of the crack, which extends by fracture. That two species with such distinct morphologies and life histories both burrow by fracturing sediment suggests that this mechanism may be widespread among burrowers. We tested this hypothesis with the glycerid polychaete Hemipodus simplex, which has an eversible proboscis that is much longer and everts more rapidly than the pharynx of N. virens. When the proboscis is fully everted, the tip flares out wider than the rest of the proboscis, creating a shape and applying a stress distribution similar to that of N. virens and resulting in relatively large forces near the tip of the crack. These forces are larger than necessary to extend the crack by fracture and are surprisingly uncorrelated with the resulting stress amplification at the crack tip, which is also larger than necessary to extend the burrow by fracture. These large forces may plastically deform the mud, allowing the worm to build a semi-permanent burrow. Our results illustrate that similar mechanisms of burrowing are used by morphologically different burrowers.

Morphology of the Muscle Articulation Joint Between the Hooks of a Flatworm (Kalyptorhynchia, Cheliplana sp.)

Schizorhynch kalyptorhynchs are meiofaunal turbellarian predators that possess an eversible proboscis that can be armed with two stout hooks. The hooks grasp and manipulate prey using a wide range of rotations and translations. These diverse motions are possible because the hook supports may function as a muscle articulation type joint-that is, a joint formed of muscle and connective tissue that connects, separates, and moves the microscopic hooks. We analyze the morphology of the flexible joint in a species of Cheliplana by using three types of microscopy: light, laser scanning confocal, and transmission electron. Radial myofilament bundles are present in the core of the hook supports, and lateral divaricator muscle fibers are located on their lateral surfaces. We develop a novel model for movements of the proboscis and describe the tensile function of the basement membrane that surrounds each hook support's medial glandular region. Contraction of divaricator muscle fibers antagonized by contraction of radial myofilaments causes the lateral bending of the hook supports and opening of the hook apparatus. Relaxation of the divaricator fibers and maximal contraction of the radial myofilaments, which put the medial basement membranes in tension, may cause medial bending in the hook supports and closing of the hook apparatus. During proboscis retraction, closure may also be aided by the compression of the hook apparatus as the proboscis is drawn through the rostral pore. The study provides new insights into the principles of support and movement in muscle articulations.

<p class="HeadingRunIn"><strong>Evidence of a dorsal pharynx in the marine polychaete <em>Capitella</em> <em>teleta</em> (Polychaeta: Capitellidae)</strong></p>

Observations from compound, confocal, and scanning electron microscopy reveal that the buccal organ in Capitella teleta Blake, Grassle & Eckelbarger, 2009 should be classified as a dorsal pharynx. This buccal organ is an eversible proboscis that has the following characters: (1) dorsal ciliated pad, (2) well-developed pharyngeal retractor muscles, (3) pharyngeal gland-like structures, (4) cuticular fold surrounding the dorsal ciliated pad, and (5) unciliated buccal cavity and anterior ventral epithelium. All of these features are characteristic of dorsal pharyngeal organs present in oligochaetes and one terrestrial polychaete. Our observations in C. teleta confirm the presence of a dorsal pharynx in larvae, juveniles, and adults. C. teleta is a subsurface deposit feeder and a dorsal pharynx may have evolved independently in Capitellidae through selection of feeding mode in benthic marine habitats. Our results represent the first detailed description of a dorsal pharynx in a marine polychaete.

Functional morphology and feeding strategy of the hydrothermal-vent polychaete Archinome rosacea (family Archinomidae)

Polychaetes are a large component of deep-sea hydrothermal-vent invertebrate faunas, yet little is known about the trophic ecology of most species. In this study, the feeding mode of a common and widespread vent polychaete, Archinome rosacea (order Amphinomida), is investigated through morphological studies and gut-content analyses. The foregut of this polychaete is similar in structure to that of other shallow-water Amphinomida. Prey capture is facilitated by a ventral muscular eversible proboscis with two glandular lateral-lip structures. Extracellular digestion is suggested by packets of digestive enzymes observed to be discharged from the apical ends of the midgut epithelial cells into the lumen. Midgut tissues also contain inclusions resembling spherocrystals, possibly sites where toxic materials are sequestered. Gut-content analyses indicate a preference for mobile prey, including polychaetes and crustaceans. We propose that predation and scavenging are important trophic strategies for A. rosacea.

Glycerotoxin from Glycera convoluta stimulates neurosecretion by up-regulating N-type Ca2+ channel activity.

We report here the purification of glycerotoxin from the venom of Glycera convoluta, a novel 320 kDa protein capable of reversibly stimulating spontaneous and evoked neurotransmitter release at the frog neuromuscular junction. However, glycerotoxin is ineffective at the murine neuromuscular junction, which displays a different subtype of voltage- dependent Ca(2+) channels. By sequential and selective inhibition of various types of Ca(2+) channels, we found that glycerotoxin was acting via Ca(v)2.2 (N-type). In neuroendocrine cells, it elicits a robust, albeit transient, influx of Ca(2+) sensitive to the Ca(v)2.2 blockers omega-conotoxin GVIA and MVIIA. Moreover, glycerotoxin triggers a Ca(2+) transient in human embryonic kidney (HEK) cells over-expressing Ca(v)2.2 but not Ca(v)2.1 (P/Q-type). Whole-cell patch-clamp analysis of Ca(v)2.2 expressing HEK cells revealed an up-regulation of Ca(2+) currents due to a leftward shift of the activation peak upon glycerotoxin addition. A direct interaction between Ca(v)2.2 and this neurotoxin was revealed by co-immunoprecipitation experiments. Therefore, glycerotoxin is a unique addition to the arsenal of tools available to unravel the mechanism controlling Ca(2+)-regulated exocytosis via the specific activation of Ca(v)2.2.

Tetracycline Labeling Studies of Calcification in Nemertean Worms

Tetracycline Labeling Studies of Calcification in Nemertean Worms

The Stylet Apparatus of Monostiliferous Hoplonemerteans

This paper compares the ultrastructure, development, and functional morphology of the stylet apparatus in monostiliferous hoplonemerteans (Phylum Nemertea: Class Enopla). The apparatus occurs in the middle region of the worm's eversible proboscis and consists of two main components: 1) a central stylet that is attached to an anchoring device called the basis; and 2) reserve stylet sacs that contain nail-like reserve stylets. The knob-shaped proximal piece of the central stylet is embedded in the anterior end of the basis, and the tapered shaft of the stylet is directed anteriorly. When the proboscis is fully everted, the central stylet is used to stab such prey as polychaete worms and small crustaceans. Wounds inflicted by the stylet allow the introduction of paralytic neurotoxins that are produced by glandular cells in the epithelial lining of the proboscis. Reserve stylets form intracellularly within the reserve stylet sacs and serve to replace the central stylet when it becomes lost or damaged. Fully developed stylets typically measure 50 to 250 μm in length and comprise an organic core surrounded by an inorganic cortex that contains calcium phosphate. In juvenile worms that are four days to several weeks old, reserve stylets are assembled before other components of the stylet apparatus are fully differentiated. Subsequently, a reserve stylet is transferred to the central region of the proboscis and placed on the basis. Stages in the process of stylet attachment are described, and the probable sequence by which the stylet apparatus co-evolved with toxin-producing cells is discussed.

Comparative Ultrastructure and the Evolution of Nemertines

Nemertines are traditionally viewed as acoelomates with blood vascular systems and a specialized cavity housing an eversible proboscis, or, as coelomates with modified coelomic cavities forming the rhynchocoel, lateral vessels and gonadal sacs. Comparative ultrastructural data such as cell polarity, the occurrence of podocytes and mesodermal cells with rudimentary cilia for proboscis, rhynchocoel, lateral and dorsal vessels, and gonadal linings are consistent with their interpretation as modified coelomic cavities as found, analogously, in the higher leeches. These and additional data regarding musculature, connective tissue, glia-like cells and gametes for 13 species affirm that nemertines are intermediate between full-blown coelomate and acoelomate grades of organization. A comparison of ultrastructural details, however, indicates that their acoelomate attributes evolved secondarily from a more typical coelomate condition.

The ultrastructure of venom-producing cells in Paranemertes peregrina (Nemertea, Hoplonemertea).

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.

The stylet apparatus of the nemertean Paranemertes Peregrina: Its ultrastructure and role in prey capture

The nemertean Paranemertes peregrina captures prey by using an eversible proboscis that is armed with a stylet apparatus. The apparatus consists of several reserve stylet sacs and a central stylet that is attached to a granular mass, called the basis. When the proboscis is everted, the central stylet is used to stab prey such as nereid polychaetes, and paralytic neurotoxins, produced in the proboscis, are inserted in the stylet-induced wounds. The central stylet averages 85 μm in length and has helically-arranged grooves along its shaft. The proximal piece of the central stylet is anchored to the basis, apparently by adhesive granules in the anterior end of the basis. A basis sheath surrounds the basis and is continuous posteriorly with a duct, called the ductus ejaculatorius. Secretions in the ductus ejaculatorius may contain some of the toxin that is used to immobilize the prey. The contents of the duct are probably injected into the prey by way of the grooves on the central stylet. In the region anterior to the central stylet, there are numerous glandular cells and anchor cells that are believed to attach the stylet apparatus to the prey during attack. Each reserve stylet sac is lined by a simple epithelium. One of the epithelial cells, called the styletocyte, is greatly enlarged and fills the lumen of the sac. Several reserve stylets are assembled in a styletocyte. Each reserve stylet is formed within a membrane-bound vacuole associated with the Golgi apparatus and is composed of an inner organic core surrounded by an inorganic cortex. A duct connects each reserve stylet sac with the area around the central stylet and provides a pathway for the transfer of reserve stylets during replacement of the central stylet.

The functional anatomy and histology of the alimentary canal of the maldanid polychaetes Clymenella torquata and Euclymene oerstedi

The alimentary canal of the maldanid polychaetes Clymenella torquata (Leidy), and Euclymene oerstedi (Claparède (=Caesicirrus neglectus Arwidsson, 1911) resembles, in many ways, that of the arenicolids. It is divided into buccal mass, pharynx, oesophagus, stomach and intestine, the three latter regions showing further subdivision. The buccal mass and anterior pharynx together form an eversible proboscis. The pharynx, oesophagus, and greater part of the intestine are ciliated. Simple feeding experiments, and histochemical tests, suggest that the stomach is concerned with the digestion and absorption of proteins, fats and carbohydrates, that the anterior intestine is a digestive and major absorptive region, and that the posterior intestine is a storage region. Waste materials are stored mainly in the wall of the oesophagus. A certain amount of intracellular digestion is carried out in the intestine of Euclymene but not in Clymenella. The difference is attributed to the richer, diatomaceous diet of Clymenella. British individuals of this species, being apparently selective feeders, differ not only from Euclymene but also from American ones, both of which ingest the substratum non‐selectively.The pharynx, oesophagus and rectum are surrounded by plexuses of blood capillaries, while the remaining regions are associated with a blood sinus system which varies in position and form in the different regions, lying deepest in the absorptive intestine. The gut muscle seems to be more concerned with moving the blood forward through the sinus system and into the anterior plexus than with moving the food backward. One region of the stomach musculature is especially concerned with this circulation. Rectal respiration probably occurs.