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Roland R Melzer - One of the best experts on this subject based on the ideXlab platform.
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Pycnogonida arthropoda from northern adriatic corallina officinalis linnaeus 1758 belts
Mediterranean Marine Science, 2020Co-Authors: Tobias Lehmann, Roland R Melzer, Jorg Spelda, Moira BursicAbstract:We studied Pycnogonida, sea spiders, collected from 54 samples of Corallina officinalis belts in the vicinity of Pula and the Brijuni National Park representing both exposed and sheltered localities as well as different levels of human impact. Seven species were identified, namely Achelia echinata , A. langi , Tanystylum conirostre , Anoplodactylus angulatus , A. pygmaeus, Trygaeus communis , and Callipallene tiberi . As we used a quantifiable standard sample size of 5 cm 2 , we could perform a statistical analysis of species richness and abundances. The exposed low human impact sites showed a significantly higher amount of both, specimens and species than the sheltered high impact sites. C. tiberi and A. echinata showed a significant preference for exposed low impact sites while T. conirostre was equally distributed among the habitat subtypes.
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Feeding ecology in sea spiders (Arthropoda: Pycnogonida): what do we know?
Frontiers in Zoology, 2018Co-Authors: Lars Dietz, Tobias Lehmann, Jana S. Dömel, Florian Leese, Roland R MelzerAbstract:Sea spiders (Pycnogonida) are a widespread and phylogenetically important group of marine arthropods. However, their biology remains understudied, and detailed information about their feeding ecology is difficult to find. Observations on Pycnogonid feeding are scattered in the literature, often in older sources written in various languages, and have never been comprehensively summarized. Here we provide an overview of all information on feeding in Pycnogonids that we have been able to find and review what is known on feeding specializations and preferences in the various Pycnogonid taxa. We deduce general findings where possible and outline future steps necessary to gain a better understanding of the feeding ecology of one of the world’s most bizarre animal taxa.
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the visual system of harvestmen opiliones arachnida chelicerata a re examination
Frontiers in Zoology, 2016Co-Authors: Tobias Lehmann, Eva Loddebensch, Roland R Melzer, Martina MetzAbstract:Background The visual systems in chelicerates are poorly understood, even though they show strong variation in eye and visual neuropil architecture, thus may provide valuable insights for the understanding of chelicerate phylogeny and eye evolution. Comparable morphological characters are desperately sought for reconstructions of the phylogeny of Chelicerata, especially with respect to Arachnida. So far, reliable data exist only for Pycnogonida, Xiphosura, Scorpiones, and Araneae. The few earlier studies of the organisation of the visual system in harvestmen are contradictory concerning the number, morphology, and position of the visual neuropils.
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scientific note a deep water Pycnogonid close to the beach colossendeis macerrima hoek 1881 spotted at 18 m in the chilean fjords chelicerata Pycnogonida colossendeidae
Spixiana, 2013Co-Authors: Gunter Forsterra, Roland R Melzer, Vreni Haussermann, Andrea WeisAbstract:Pycnogonida of the family Colossendeidae are in general deep sea inhabitants only exceptionally reported from depths less than 100 m. A face to face encounter with a Colossendeis during a scuba dive is therefore a singular experience. In the framework of the expeditions organized by the Huinay Scientific Field Station to create an inventory of Southern Chilean benthic communities and species (e. g. Haussermann & Forsterra 2009), a specimen of Colossendeis macerrima (ZSM collection number ZSMA20130110) was spotted at a depth of only 18.3 m on a rocky slope at Canal Farquhar (-48.52 S, -74.24 W) during the “HF13 – Puerto Eden” expedition to the Central Patagonian Zone. C. macerrima has a recorded range of depth between 121 and 4000 m, and in the Chilean fjord region this species was previously found at approx. 500 m (summarized in Weis & Melzer 2012). Thus, this is the only record from the upper infralitoral and euphotic zone. Earlier records of deep water species from various benthic marine groups in the upper part of the water column have been suggested to indicate deep water emergence, a special feature of the Chilean fjords (Forsterra & Haussermann 2003).
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fine structure of the slit organs of the Pycnogonid anoplodactylus petiolatus anoplodactylidae
Acta Zoologica, 1996Co-Authors: Roland R Melzer, Martin Heβ, Christine Dunkel, Peter Ludwig, Ulrich SmolaAbstract:Abstract The ‘slit organs’ of Anoplodactylus petiolatus are found all over the body cuticle. They are composed of a cuticular pore apparatus, an inner and an outer canal cell, and of four large and one to three small compartment cells. Plasma of the latter seven cells is almost completely filled with large membrane-enclosed compartments that contain either numerous small vesicles (one of the large cells) or homogeneous material of varying electron density (three large and all the small cells). Microvilli are found in the apical region of the compartment cells. The nucleus is situated basally where Golgi-cisternae, coated vesicles and free ribosomes are frequently found. Apical microvilli and vesicles are also formed by the inner canal cell indicating that it might directly be involved in transport. Anatomically the ‘slit organs’ are similar to class III glands described for many arthropods. In addition, discharge of secretion via large intracellular compartments is also a feature found in arthropod glands. Although Pycnogonids appear to take up substances across the cuticle, a genuine secretion rather than a more generalized transport function is suggested for the ‘slit organs’.
Claudia P Arango - One of the best experts on this subject based on the ideXlab platform.
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First description of epimorphic development in Antarctic Pallenopsidae (Arthropoda, Pycnogonida) with insights into the evolution of the four-articled sea spider cheliphore
Zoological Letters, 2019Co-Authors: Georg Brenneis, Claudia P ArangoAbstract:Background Sea spiders (Pycnogonida) are an abundant faunal element of the Southern Ocean (SO). Several recent phylogeographical studies focused on the remarkably diverse SO Pycnogonid fauna, resulting in the identification of new species in previously ill-defined species complexes, insights into their genetic population substructures, and hypotheses on glacial refugia and recolonization events after the last ice age. However, knowledge on the life history of many SO Pycnogonids is fragmentary, and early ontogenetic stages often remain poorly documented. This impedes assessing the impact of different developmental pathways on Pycnogonid dispersal and distributions and also hinders Pycnogonid-wide comparison of developmental features from a phylogenetic-evolutionary angle. Results Using scanning electron microscopy (SEM) and fluorescent nuclear staining, we studied embryonic stages and postembryonic instars of three SO representatives of the taxon Pallenopsidae ( Pallenopsis villosa , P. hodgsoni , P. vanhoeffeni ), the development of which being largely unknown. The eggs are large and yolk-rich, and the hatching stage is an advanced lecithotrophic instar that stays attached to the father for additional molts. The first free-living instar is deduced to possess at least three functional walking leg pairs. Despite gross morphological similarities between the congeners, each instar can be reliably assigned to a species based on body size, shape of ocular tubercle and proboscis, structure of the attachment gland processes, and seta patterns on cheliphore and walking legs. Conclusions We encourage combination of SEM with fluorescent markers in developmental studies on ethanol-preserved and/or long term-stored Pycnogonid material, as this reveals internal differentiation processes in addition to external morphology. Using this approach, we describe the first known cases of pallenopsid development with epimorphic tendencies, which stand in contrast to the small hatching larvae in other Pallenopsidae. Evaluation against current phylogenetic hypotheses indicates multiple gains of epimorphic development within Pycnogonida. Further, we suggest that the type of development may impact Pycnogonid distribution ranges, since free-living larvae potentially have a better dispersal capability than lecithotrophic attaching instars. Finally, we discuss the bearing of Pycnogonid cheliphore development on the evolution of the raptorial first limb pair in Chelicerata and support a multi-articled adult limb as the plesiomorphic state of the chelicerate crown group, arising ontogenetically via postembryonic segmentation of a three-articled embryonic limb.
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feeding biology of carnivore and detritivore mediterranean Pycnogonids
Journal of the Marine Biological Association of the United Kingdom, 2013Co-Authors: Anna Solermembrives, Claudia P Arango, Montserrat Cuadrado, Tomas MunillaAbstract:The digestive system of sea spiders (Pycnogonida) presents peculiarities that have not been discussed in the context of their ecology or feeding behaviour. We investigated the digestive system of two Mediterranean species, a carnivorous species Ammothella longipes and a detritivorous Endeis spinosa , with special focus on its correlation with behavioural feeding habits. The midgut and hindgut sections did not present significant differences between the two species, but major differences were observed in the foregut, reflecting concordance to their diet and their feeding behaviour. Jaws, setose lips, the structure of the pharyngeal filter and musculature of the proboscis are the main differential elements when comparing feeding habits of A. longipes and E. spinosa . These elements are responsible for the reduction of the food pulp down to subcellular size. The digestion process observed in the species studied agrees with that observed in other Pycnogonid lineages, but differs from most marine arthropods mainly because of the absence of midgut gland cells and the presence of a unique multifunctional type of midgut epithelial cell. Epithelial digestive cells are present in a small ‘resting’ form during starvation periods. During digestion, secretion granules possibly containing zymogen move to their apical border to be secreted to the midgut lumen, secondary lysosomes are formed and intracellular digestion occurs within them. Residual bodies are formed within the epithelial cell and released to the midgut lumen to be transported towards the hindgut. The characteristics of the digestive process of the Pycnogonids studied seem to reflect a plesiomorphic state in arthropods.
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dna barcoding and molecular systematics of the benthic and demersal organisms of the ceamarc survey
Polar Science, 2011Co-Authors: Agnes Dettai, Claudia P Arango, Corinne Cruaud, Sarah J Adamowizc, Louise Allcock, David K A Barnes, Iain Barratt, Anne Chenuil, Arnaud Couloux, Bruno DavidAbstract:The Dumont d'Urville Sea (East Antarctic region) has been less investigated for DNA barcoding and molecular taxonomy than other parts of the Southern Ocean, such as the Ross Sea and the Antarctic Peninsula. The Collaborative East Antarctic MARine Census (CEAMARC) took place in this area during the austral summer of 2007e2008. The Australian vessel RSVAurora Australis collected very diverse samples of demersal and benthic organisms. The specimens were sorted centrally, and then distributed to taxonomic experts for molecular and morphological taxonomy and identification, especially barcoding. The COI sequences generated from CEAMARC material provide a sizeable proportion of the Census of Antarctic Marine Life barcodes although the studies are still ongoing, and represent the only source of sequences for a number of species. Barcoding appears to be a valuable method for identification within most groups, despite low divergences and haplotype sharing in a few species, and it is also useful as a preliminary taxonomic exploration method. Several new species are being described. CEAMARC samples have already provided new material for phylogeographic and phylogenetic studies in cephalopods, Pycnogonids, teleost fish, crinoids and sea urchins, helping these studies to provide a better insight in the patterns of evolution in the Southern Ocean.
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genetic diversity of nymphon arthropoda Pycnogonida nymphonidae along the antarctic peninsula with a focus on nymphon australe hodgson 1902
Marine Biology, 2008Co-Authors: Claudia P Arango, Andrew R Mahon, Kenneth M HalanychAbstract:Sea spiders are conspicuous, and often abundant, members of the Antarctic benthic community. Nymphonidae (Pycnogonida) in Southern Ocean waters comprise over 240 species which are often difficult to assign due to their intraspecific ‘highly variable’ morphology. In particular, Nymphon australe, the numerically dominant species in Antarctic waters is known to have a high level of phenotypic variation in external morphology and is also reported to have a circumpolar distribution. Circumpolarity seems contradictory to the Pycnogonid’s brooding lifestyle and presumably limited dispersal. Here we examine the genetic diversity of several Nymphon species collected in the Antarctic Peninsular region. Concomitantly, we assess the genetic structure of N. australe to gain insight into Nymphon dispersal capacity. Cytochrome c oxidase subunit I (COI) and 16S ribosomal gene data suggest a recent common history and/or recent gene-flow of N. australe populations across nearly 800 km of the Antarctic Peninsula. Furthermore, these data support that the Antarctic Peninsula region may hold two previously unrecognized species of Nymphon.
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microscopic anatomy of Pycnogonida ii digestive system iii excretory system
Journal of Morphology, 2007Co-Authors: W H Fahrenbach, Claudia P ArangoAbstract:The digestive system of several species of sea spiders (Pycnogonida, Arthropoda) was studied by electron microscopy. It is composed of the foregut inside a long proboscis, a midgut and a hindgut. Lips near the three jaws at the tip of the proboscis receive several hundred ductules originating from salivary glands. These previously undetected glands open on the lips, a fluted, projecting ridge at the external hinge line of the jaws, i.e., to the outside of the mouth. This disposition suggests affinities to the chelicerate line. The trigonal esophagus within the proboscis contains a complex, setose filter device, operated by dedicated muscles, that serves to reduce ingested food to subcellular dimensions. The midgut has diverticula into the bases of all legs. Its cells differentiate from the basal layer and contain a bewildering array of secretion droplets, lysosomes and phagosomes. In the absence of a hepatopancreas, the midgut serves both digestive and absorptive functions. The cuticle-lined hindgut lies in the highly reduced, peg-like abdomen. Traditionally, Pycnogonids have been claimed to have no excretory organ at all. Such a structure, however, has been located in at least one ammotheid, Nymphopsis spinosissima, in which a simple, but standard, excretory gland has been found in the scape of the chelifore. It consists of an end sac, a straight proximal tubule, a short distal tubule, and a raised nephropore. The end sac is a thin-walled and polygonal chamber, about 150 μm in cross section, suspended in the hemocoel of the appendage, its edges radially tethered to the cuticle at more than half a dozen locations. This wall consists of a filtration basement membrane, 1–4 μm thick, facing the hemocoel, and internally of a continuous carpet of podocytes and their pedicels. The podocytes, measuring maximally 10 by 15 μm, have complex contents, of which a labyrinthine system of connected intracellular channels stands out. These coated cisternae open into a central vacuole that often rivals the nucleus in size. The design of the organ closely approximates that of the primitive crustacean Hutchinsoniella macracantha. J. Morphol., 2007. © 2007 Wiley-Liss, Inc.
Andrew R Mahon - One of the best experts on this subject based on the ideXlab platform.
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phylogenomics of the longitarsal colossendeidae the evolutionary history of an antarctic sea spider radiation
Molecular Phylogenetics and Evolution, 2019Co-Authors: Lars Dietz, Jana S. Dömel, Florian Leese, Andrew R Mahon, Christoph MayerAbstract:Abstract Sea spiders (Pycnogonida) constitute a group of marine benthic arthropods that has a particularly high species diversity in the Southern Ocean. The “longitarsal” group of the sea spider family Colossendeidae is especially abundant in this region. However, this group also includes some representatives from other oceans, which raises the question where the group originates from. Therefore, we here investigated the phylogeny of the group with a hybrid enrichment approach that yielded a dataset of 1607 genes and over one million base pairs. We obtained a well-resolved phylogeny of the group, which is mostly consistent with morphological data. The data support an Antarctic origin of the longitarsal Colossendeidae and multiple dispersal events to other regions, which occurred at different timescales. This scenario is consistent with evidence found in other groups of marine invertebrates and highlights the role of the Southern Ocean as a source for non-Antarctic biota, especially of the deep sea. Our results suggest an initially slow rate of diversification followed by a more rapid radiation possibly correlated with the mid-Miocene cooling of Antarctica, similar to what is found in other taxa.
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diversity and distribution within the sea spider genus pallenopsis chelicerata Pycnogonida in the western antarctic as revealed by mitochondrial dna
Polar Biology, 2016Co-Authors: Avril M Harder, Kenneth M Halanych, Andrew R MahonAbstract:Pycnogonids are marine arthropods with cosmopolitan and eurybathic distribution. Of the approximately 1300 Pycnogonid species described worldwide, over 260 species occur in the Southern Ocean, and over half of those are endemic to the Antarctic. Morphological data suggest circumpolar distributions for multiple Antarctic species; however, recent molecular inquiries into the genetic structure of Antarctic benthic invertebrate populations have revealed varying patterns of genetic connectivity and, in many cases, radiation of morphologically cryptic species incompatible with the previously hypothesized genetic homogeneity for Southern Ocean invertebrates. To date, little is known about genetic connectivity within Antarctic Pallenopsis species populations, and Pallenopsis phylogeny remains poorly resolved. This study describes genetic structure of Pallenopsis populations of western Antarctic coastal regions, the Scotia Arc, Falkland Islands, and Chilean coast. We present the results of analyses derived from the mitochondrial COI gene that demonstrate patterns of connectivity for these populations. Examination of genetic characters has allowed for the identification of divergent mitochondrial lineages within Pallenopsis and will lead to a description of at least one new species. Future sampling and analyses from other areas of the Antarctic coastline will provide a broader context for the phylogeny of Pallenopsis.
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genetic diversity of nymphon arthropoda Pycnogonida nymphonidae along the antarctic peninsula with a focus on nymphon australe hodgson 1902
Marine Biology, 2008Co-Authors: Claudia P Arango, Andrew R Mahon, Kenneth M HalanychAbstract:Sea spiders are conspicuous, and often abundant, members of the Antarctic benthic community. Nymphonidae (Pycnogonida) in Southern Ocean waters comprise over 240 species which are often difficult to assign due to their intraspecific ‘highly variable’ morphology. In particular, Nymphon australe, the numerically dominant species in Antarctic waters is known to have a high level of phenotypic variation in external morphology and is also reported to have a circumpolar distribution. Circumpolarity seems contradictory to the Pycnogonid’s brooding lifestyle and presumably limited dispersal. Here we examine the genetic diversity of several Nymphon species collected in the Antarctic Peninsular region. Concomitantly, we assess the genetic structure of N. australe to gain insight into Nymphon dispersal capacity. Cytochrome c oxidase subunit I (COI) and 16S ribosomal gene data suggest a recent common history and/or recent gene-flow of N. australe populations across nearly 800 km of the Antarctic Peninsula. Furthermore, these data support that the Antarctic Peninsula region may hold two previously unrecognized species of Nymphon.
Martina Metz - One of the best experts on this subject based on the ideXlab platform.
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the visual system of harvestmen opiliones arachnida chelicerata a re examination
Frontiers in Zoology, 2016Co-Authors: Tobias Lehmann, Eva Loddebensch, Roland R Melzer, Martina MetzAbstract:Background The visual systems in chelicerates are poorly understood, even though they show strong variation in eye and visual neuropil architecture, thus may provide valuable insights for the understanding of chelicerate phylogeny and eye evolution. Comparable morphological characters are desperately sought for reconstructions of the phylogeny of Chelicerata, especially with respect to Arachnida. So far, reliable data exist only for Pycnogonida, Xiphosura, Scorpiones, and Araneae. The few earlier studies of the organisation of the visual system in harvestmen are contradictory concerning the number, morphology, and position of the visual neuropils.
Tobias Lehmann - One of the best experts on this subject based on the ideXlab platform.
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Pycnogonida arthropoda from northern adriatic corallina officinalis linnaeus 1758 belts
Mediterranean Marine Science, 2020Co-Authors: Tobias Lehmann, Roland R Melzer, Jorg Spelda, Moira BursicAbstract:We studied Pycnogonida, sea spiders, collected from 54 samples of Corallina officinalis belts in the vicinity of Pula and the Brijuni National Park representing both exposed and sheltered localities as well as different levels of human impact. Seven species were identified, namely Achelia echinata , A. langi , Tanystylum conirostre , Anoplodactylus angulatus , A. pygmaeus, Trygaeus communis , and Callipallene tiberi . As we used a quantifiable standard sample size of 5 cm 2 , we could perform a statistical analysis of species richness and abundances. The exposed low human impact sites showed a significantly higher amount of both, specimens and species than the sheltered high impact sites. C. tiberi and A. echinata showed a significant preference for exposed low impact sites while T. conirostre was equally distributed among the habitat subtypes.
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Feeding ecology in sea spiders (Arthropoda: Pycnogonida): what do we know?
Frontiers in Zoology, 2018Co-Authors: Lars Dietz, Tobias Lehmann, Jana S. Dömel, Florian Leese, Roland R MelzerAbstract:Sea spiders (Pycnogonida) are a widespread and phylogenetically important group of marine arthropods. However, their biology remains understudied, and detailed information about their feeding ecology is difficult to find. Observations on Pycnogonid feeding are scattered in the literature, often in older sources written in various languages, and have never been comprehensively summarized. Here we provide an overview of all information on feeding in Pycnogonids that we have been able to find and review what is known on feeding specializations and preferences in the various Pycnogonid taxa. We deduce general findings where possible and outline future steps necessary to gain a better understanding of the feeding ecology of one of the world’s most bizarre animal taxa.
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the visual system of harvestmen opiliones arachnida chelicerata a re examination
Frontiers in Zoology, 2016Co-Authors: Tobias Lehmann, Eva Loddebensch, Roland R Melzer, Martina MetzAbstract:Background The visual systems in chelicerates are poorly understood, even though they show strong variation in eye and visual neuropil architecture, thus may provide valuable insights for the understanding of chelicerate phylogeny and eye evolution. Comparable morphological characters are desperately sought for reconstructions of the phylogeny of Chelicerata, especially with respect to Arachnida. So far, reliable data exist only for Pycnogonida, Xiphosura, Scorpiones, and Araneae. The few earlier studies of the organisation of the visual system in harvestmen are contradictory concerning the number, morphology, and position of the visual neuropils.
