- Germany
Alexander Kieneke
Senckenberg Forschunginstitut und Naturmuseum, DZMB, Faculty Member
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Species of the marine meiofauna such as Gastrotricha are known to lack dispersal stages and are thus assumed to have low dispersal ability and low levels of gene flow between populations. Yet, most species are widely distributed, and this... more
Species of the marine meiofauna such as Gastrotricha are known to lack dispersal stages and are thus assumed to have low dispersal ability and low levels of gene flow between populations. Yet, most species are widely distributed, and this creates a paradox. To shed light on this apparent paradox, we test (i) whether such wide distribution may be due to misidentification and lumping of cryptic species with restricted distributions and (ii) whether spatial structures exist for the phylogeography of gastrotrichs. As a model, we used the genus Turbanella in NW Europe. DNA taxonomy using a mitochondrial and a nuclear marker supports distinctness of four traditional species (Turbanella ambronensis, T. bocqueti, T. mustela and T. cornuta) and provides evidence for two cryptic species within T. hyalina. An effect of geography on the within-species genetic structure is indeed present, with the potential for understanding colonization processes and for performing phylogeographic inference from microscopic animals. On the other hand, the occurrence of widely distributed haplotypes indicates long-distance dispersal as well, despite the assumed low dispersal ability of gastrotrichs.
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We describe tubular structures on the cuticle of two representatives of the genus Gordius by scanning electron microscopy. One female from Korea could not be identified further while a male from New Zealand belonged to Gordius paranensis.... more
We describe tubular structures on the cuticle of two representatives of the genus Gordius by scanning electron microscopy. One female from Korea could not be identified further while a male from New Zealand belonged to Gordius paranensis. Other male specimens of G. paranensis did not show tubular structures or the corresponding pores on the cuticle. Therefore it is assumed that tubular structures are not species-specific structures, but also no artifacts or contaminations. They might be glandular products, but this has to be verified by further documentations and investigation of the inner structure of it.
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Abstract Molecular surveys and studies of the muscle anatomy made evident that the mesopsammic gastrotrich Xenotrichula intermedia, previously regarded as a cosmopolitan species, comprises several distinct taxonomic units. These entities... more
Abstract Molecular surveys and studies of the muscle anatomy made evident that the mesopsammic gastrotrich Xenotrichula intermedia, previously regarded as a cosmopolitan species, comprises several distinct taxonomic units. These entities are to date referred to as cryptic species. Although other morphological traits seemed insufficient to differentiate geographically distant populations, investigations of the myomorphology displayed significant differences. Three muscular morphotypes of X. intermedia are known and distinguishable via properties of their dorsoventral and circular musculature. However, previous studies using confocal laser scanning microscopy (CLSM) conducted observations of the muscle architecture that aimed to apply older terminology of the only existing reconstruction that was based on fluorescence microscopy. Since detailed 3D reconstructions of the myoanatomy were never performed, comparisons between different morphotypes of X. intermedia stay a difficult endeavor. In this study, the muscular system of a North Sea population of X. intermedia is investigated and reconstructed using CLSM and 3D reconstruction software. Our aim is to test whether this population, adjacent to the type locality of X. intermedia, constitutes another muscular morphotype. The overall musculature of the North-Sea population is similar to that of the Mediterranean specimens. A Baltic Sea individual appears myoanatomically identical to these populations, too. This indicates a distinct morphotype with a pan-European distribution. Since the known muscular morphotypes are clearly distinguishable, we propose the presence of a species complex comprising a pan-European X. intermedia, a Persian X. aff. intermedia and a NW Atlantic X. aff. intermedia. Furthermore, our investigation demonstrates a much higher complexity of the longitudinal musculature than previously assumed, which leads us to reinterpret earlier myomorphological data, amend some terminology, and reconsider statements of homology that will provide a feasible foundation for future comparative studies.
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FIGURE 2 A. Encentrum mucronatum, male. B. Encentrum martes, male. agg – accessory genital gland; br – brain; da – dorsal antenna; gly – glycogen; gp – genital pore, pg – pedal glands; rco – retrocerebral organ; ros – rostrum; rot –... more
FIGURE 2 A. Encentrum mucronatum, male. B. Encentrum martes, male. agg – accessory genital gland; br – brain; da – dorsal antenna; gly – glycogen; gp – genital pore, pg – pedal glands; rco – retrocerebral organ; ros – rostrum; rot – rotatory organ; sp – spermatozoa; st – stomach; tes – testis; to – toe; tr – testicular rods; vd – vas deferens
FIGURE 1 A–B, F. Encentrum mucronatum, male. A: Habitus in lateral view B: Close–up of retrocerebral organ F: Close–up of toe C–E. Encentrum martes, male. C: Habitus in lateral view D: Detail of testis and vas deferens. Arrows point out... more
FIGURE 1 A–B, F. Encentrum mucronatum, male. A: Habitus in lateral view B: Close–up of retrocerebral organ F: Close–up of toe C–E. Encentrum martes, male. C: Habitus in lateral view D: Detail of testis and vas deferens. Arrows point out glycogen inclusions E: Close-up of toe. agg – accessory genital gland; br – brain; da – dorsal antenna; gp – genital pore, pg – pedal glands; rco – retrocerebral organ; ros – rostrum; rot – rotatory organ; sp – spermatozoa; st – stomach; tes – testis; to – toe; tr – testicular rods; vd – vas deferens.
<p>Data generated and used for species delimitation for the article: Tang, C. Q., Leasi, F., Obertegger, U., Kieneke, A., Barraclough, T. G., & Fontaneto, D. (2012). The widely used small subunit 18S rDNA molecule greatly... more
<p>Data generated and used for species delimitation for the article: Tang, C. Q., Leasi, F., Obertegger, U., Kieneke, A., Barraclough, T. G., & Fontaneto, D. (2012). The widely used small subunit 18S rDNA molecule greatly underestimates true diversity in biodiversity surveys of the meiofauna. Proceedings of the National Academy of Sciences of the United States of America, 109, 16208–16212.</p> <p>Each dataset (of which there 55) comprises sequences either downloaded from GenBank or sequenced by the co-authors.<br>Alignments made with MAFFT within Geneious.<br>These alignments were collapsed into haplotype alignments.<br>Ultrametric trees were made from these using either BEAST or RaxML with r8s.</p> <p> </p
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Sublittoral sand from the islands of Sardinia (Italy) and Flores (Azores) – separated by more than 3700 km linear distance and 8 years between two independent sampling campaigns – yielded conspicuous specimens of two bizarre, yet... more
Sublittoral sand from the islands of Sardinia (Italy) and Flores (Azores) – separated by more than 3700 km linear distance and 8 years between two independent sampling campaigns – yielded conspicuous specimens of two bizarre, yet undescribed, species of the marine gastrotrich clade Macrodasyida. These gastrotrichs combine several character traits that were already known from two, non-related genera. Morphological data were carefully analysed and digitally documented, and nuclear and mitochondrial DNA sequences were used for phylogenetic inference. The results of these analyses claim for the erection of a new genus. Specimens of the new taxon have a body length of less than 400 µm and are characterized by a wide, funnel-shaped mouth opening shielded dorsally by an oral hood and possess a posterior peduncle that ends with a Y-shaped pair of appendages that carry the posterior adhesive tubes. Further tubes occur as anterior, ventrolateral and lateral series; the gonads are unpaired and...
A new marine gastrotrich species of the genus Cephalodasys is described from shallow sublittoral coralline sand sampled between Lee Stocking Island and Norman’s Pond Cay (Exuma Cays), Bahamas. Cephalodasys interinsularis n. sp. reach-es a... more
A new marine gastrotrich species of the genus Cephalodasys is described from shallow sublittoral coralline sand sampled between Lee Stocking Island and Norman’s Pond Cay (Exuma Cays), Bahamas. Cephalodasys interinsularis n. sp. reach-es a body length of 471 µm and is characterized by a new combination of characters including six total anterior adhesive tubes and five pairs of ventrolateral adhesive tubes. The new species is morphologically similar to C. swedmarki but can be distinguished by the different number of anterior adhesive tubes, the spatial arrangement of the ventrolateral adhesive tubes, and a shorter pharynx. We provide an updated diagnosis of the genus and a determination key to all known species of Cephalodasys. C. interinsularis n. sp. is the third known species of Cephalodasys from the Caribbean marine province.
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We describe tubular structures on the cuticle of two representatives of the genus Gordius by scanning electron microscopy. One female from Korea could not be identified further while a male from New Zealand belonged to Gordius paranensis.... more
We describe tubular structures on the cuticle of two representatives of the genus Gordius by scanning electron microscopy. One female from Korea could not be identified further while a male from New Zealand belonged to Gordius paranensis. Other male specimens of G. paranensis did not show tubular structures or the corresponding pores on the cuticle. Therefore it is assumed that tubular structures are not species-specific structures, but also no artifacts or contaminations. They might be glandular products, but this has to be verified by further documentations and investigation of the inner structure of it.
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Microscopic organisms that penetrate calcareous structures by actively dissolving the carbonate matrix, namely microendoliths, have an important influence on the breakdown of marine carbonates. The study of these microorganisms and the... more
Microscopic organisms that penetrate calcareous structures by actively dissolving the carbonate matrix, namely microendoliths, have an important influence on the breakdown of marine carbonates. The study of these microorganisms and the bioerosion traces they produce is crucial for understanding the impact of their bioeroding activity on the carbonate recycling in environments under global climate change. Traditionally, either the extracted microendoliths were studied by conventional microscopy or their traces were investigated using scanning electron microscopy (SEM) of epoxy resin casts. A visualisation of the microendoliths in situ, that is within their complex microbioerosion structures, was previously limited to the laborious and time‐consuming double‐inclusion cast‐embedding technique. Here, we assess the applicability of various fluorescence staining methods in combination with confocal laser scanning microscopy (CLSM) for the study of fungal microendoliths in situ in partly t...
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Sublittoral sand from the islands of Sardinia (Italy) and Flores (Azores) – separated by more than 3700 km linear distance and 8 years between two independent sampling campaigns – yielded conspicuous specimens of two bizarre, yet... more
Sublittoral sand from the islands of Sardinia (Italy) and Flores (Azores) – separated by more than 3700 km linear distance and 8 years between two independent sampling campaigns – yielded conspicuous specimens of two bizarre, yet undescribed, species of the marine gastrotrich clade Macrodasyida. These gastrotrichs combine several character traits that were already known from two, non-related genera. Morphological data were carefully analysed and digitally documented, and nuclear and mitochondrial DNA sequences were used for phylogenetic inference. The results of these analyses claim for the erection of a new genus. Specimens of the new taxon have a body length of less than 400 µm and are characterized by a wide, funnel-shaped mouth opening shielded dorsally by an oral hood and possess a posterior peduncle that ends with a Y-shaped pair of appendages that carry the posterior adhesive tubes. Further tubes occur as anterior, ventrolateral and lateral series; the gonads are unpaired and...
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Abstract Molecular surveys and studies of the muscle anatomy made evident that the mesopsammic gastrotrich Xenotrichula intermedia, previously regarded as a cosmopolitan species, comprises several distinct taxonomic units. These entities... more
Abstract Molecular surveys and studies of the muscle anatomy made evident that the mesopsammic gastrotrich Xenotrichula intermedia, previously regarded as a cosmopolitan species, comprises several distinct taxonomic units. These entities are to date referred to as cryptic species. Although other morphological traits seemed insufficient to differentiate geographically distant populations, investigations of the myomorphology displayed significant differences. Three muscular morphotypes of X. intermedia are known and distinguishable via properties of their dorsoventral and circular musculature. However, previous studies using confocal laser scanning microscopy (CLSM) conducted observations of the muscle architecture that aimed to apply older terminology of the only existing reconstruction that was based on fluorescence microscopy. Since detailed 3D reconstructions of the myoanatomy were never performed, comparisons between different morphotypes of X. intermedia stay a difficult endeavor. In this study, the muscular system of a North Sea population of X. intermedia is investigated and reconstructed using CLSM and 3D reconstruction software. Our aim is to test whether this population, adjacent to the type locality of X. intermedia, constitutes another muscular morphotype. The overall musculature of the North-Sea population is similar to that of the Mediterranean specimens. A Baltic Sea individual appears myoanatomically identical to these populations, too. This indicates a distinct morphotype with a pan-European distribution. Since the known muscular morphotypes are clearly distinguishable, we propose the presence of a species complex comprising a pan-European X. intermedia, a Persian X. aff. intermedia and a NW Atlantic X. aff. intermedia. Furthermore, our investigation demonstrates a much higher complexity of the longitudinal musculature than previously assumed, which leads us to reinterpret earlier myomorphological data, amend some terminology, and reconsider statements of homology that will provide a feasible foundation for future comparative studies.
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A detailed description is given of the males of Encentrum mucronatum Wulfert, 1936 and Encentrum martes Wulfert, 1939. The degree of miniaturisation relative to the corresponding females is assessed and compared to males in selected... more
A detailed description is given of the males of Encentrum mucronatum Wulfert, 1936 and Encentrum martes Wulfert, 1939. The degree of miniaturisation relative to the corresponding females is assessed and compared to males in selected planktonic rotifers. Different degrees of miniaturisation are related to differences in population dynamics.
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Members of the freshwater family Dasydytidae belong to the rarest gastrotrichs although some species like Stylochaeta scirtetica may develop high population densities (Schwank 1990). The taxon Dasydytidae is characterised by several... more
Members of the freshwater family Dasydytidae belong to the rarest gastrotrichs although some species like Stylochaeta scirtetica may develop high population densities (Schwank 1990). The taxon Dasydytidae is characterised by several apomorphic features correlated to a semi-planktonic lifestyle. Species of Dasydytidae have, for example, completely lost their caudal adhesive tubes, they possess a system of ciliary bands in the head region with which they swim like ciliated larvae of annelids, and most species have motile spines to perform saltatory movements in the water column. So far, our knowledge on the biology, life cycle and their distribution is very limited. This is probably due to the rareness and difficult preparation and handling of Dasydytidae.
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Species of the marine meiofauna such as Gastrotricha are known to lack dispersal stages and are thus assumed to have low dispersal ability and low levels of gene flow between populations. Yet, most species are widely distributed, and this... more
Species of the marine meiofauna such as Gastrotricha are known to lack dispersal stages and are thus assumed to have low dispersal ability and low levels of gene flow between populations. Yet, most species are widely distributed, and this creates a paradox. To shed light on this apparent paradox, we test (i) whether such wide distribution may be due to misidentification and lumping of cryptic species with restricted distributions and (ii) whether spatial structures exist for the phylogeography of gastrotrichs. As a model, we used the genus Turbanella in NW Europe. DNA taxonomy using a mitochondrial and a nuclear marker supports distinctness of four traditional species (Turbanella ambronensis, T. bocqueti, T. mustela and T. cornuta) and provides evidence for two cryptic species within T. hyalina. An effect of geography on the within-species genetic structure is indeed present, with the potential for understanding colonization processes and for performing phylogeographic inference from microscopic animals. On the other hand, the occurrence of widely distributed haplotypes indicates long-distance dispersal as well, despite the assumed low dispersal ability of gastrotrichs.
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Research Interests: Biology, Ecology, Biodiversity, Medicine, DNA Barcoding, and 15 moreMultidisciplinary, Phylogeny, Species Richness, Species Delimitation, Metabarcoding, Genetic variation, Base Sequence, Likelihood Functions, Environmental DNA, Genetic Markers, DNA Barcodes, Predictive value of tests, Metagenome, Molecular Sequence Data, and Meiobenthos
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ABSTRACT
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We present a reconstruction of the nervous system of Neodasys chaetonotoideus Remane, 1927 (Gastrotricha, Chaetonotida) based on different microscopical methods: (1) immunohistochemistry (anti-acetylated α- and β-tubulin-, anti-5-HT- and... more
We present a reconstruction of the nervous system of Neodasys chaetonotoideus Remane, 1927 (Gastrotricha, Chaetonotida) based on different microscopical methods: (1) immunohistochemistry (anti-acetylated α- and β-tubulin-, anti-5-HT- and anti-FMRFamide labelling) and (2) histochemistry (labelling of musculature and nuclei) by the means of confocal laser scanning microscopy (cLSM) and (iii) ultrastructure by means of transmission electron microscopy (TEM). All parts of the nervous system contain structures with an immunoreaction against the used immunohistochemical markers and labelling of histochemical markers. Results of both techniques (cLSM, TEM) reveal that the nervous system of N. chaetonotoideus is composed of a “dumb-bell-shaped” brain and one pair of posterior longitudinal neurite bundles. The brain is made up of a pair of laterally located clusters of neuronal somata, a large dorsal interconnecting dorsal commissure and two tiny ventral commissures in the region of the lateral clusters. From this, it follows that the brain is circumpharyngeal in position. The innervation of the head region is conducted by three pairs of anterior-directed neurite bundles. We describe here the gross anatomy of the nervous system and give additional details of the ultrastructure and the 5-HT and RFamide-like IR components of the nervous system. We compare our newly obtained data with already published data on the nervous system of gastrotrichs to reconstruct the hypothetical ground pattern of the nervous system in Gastrotricha, respectively, in Macrodasyida.
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This study presents the results of confocal laser scanning microscopy and fluorescence-labelled phalloidin used to visualize the system of body musculature in Beauchampiella eudactylota. Moreover, the poorly known trophi of B. eudactylota... more
This study presents the results of confocal laser scanning microscopy and fluorescence-labelled phalloidin used to visualize the system of body musculature in Beauchampiella eudactylota. Moreover, the poorly known trophi of B. eudactylota are described based on scanning electron microscopy. In total, four paired longitudinal muscles (musculi longitudinales I–IV) and three circular muscles (musculi circulares I–III) were identified. Among these are the musculus longitudinalis ventralis, the musculus longitudinalis dorsalis and the musculus circumpedalis as documented in previous studies for other rotifer species. Compared to other species, B. eudactylota is characterized by the low number of lateral longitudinal muscles and the absence of some longitudinal muscles (musculi longitudinales capitum) and circular muscles (corona sphincter, musculus pars coronalis). Moreover, scanning electron microscopic data on the trophi of B. eudactylota reveal a number of striking similarities to the trophi in some species of Epiphanidae. This suggests that either (1) these similarities represent plesiomorphic characters present both in Epiphanidae and B. eudactylota or (2) they are synapomorphic features of B. eudactylota and some species of Epiphanidae, which would question the monophyly of Euchlanidae.
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The taxon Neodasys has a basal position within Gastrotricha. This makes it very interesting for phylogenetic considerations in this group. To complete the reconstruction of the nephridial system in the stem species of Gastrotricha started... more
The taxon Neodasys has a basal position within Gastrotricha. This makes it very interesting for phylogenetic considerations in this group. To complete the reconstruction of the nephridial system in the stem species of Gastrotricha started earlier, we have studied the whole protonephridial system of Neodasys chaetonotoideus by means of complete sets of ultrathin sections and TEM. In many characters, protonephridia of N. chaetonotoideus resemble those of macrodasyidan gastrotrich species. For example, each of the six protonephridia, arranged in three pairs, consists of three distinct cells that constitute the continuous protonephridial lumen. Especially, the terminal cell of the protonephridia of N. chaetonotoideus shows a striking pattern: The perforation of the filter region is a meandering cleft that is continuous with the seam of the enfolded lumen of that cell. With the results presented here and that of former TEM studies, we give a comprehensive idea of the excretory organs in the ground pattern of Gastrotricha. Moreover, we can elaborate on the hypothesized protonephridial system in the stem species of Bilateria. We suggest that a meandering filtration cleft is a feature of the ground pattern of the Bilateria. J. Morphol., 2007. © 2007 Wiley-Liss, Inc.
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Abstract. The reproductive anatomy of gastrotrichs is well known for several species, especially for the marine taxon Macrodasyida. However, there is little information on the reproductive organs and the modes of mating and sperm transfer... more
Abstract. The reproductive anatomy of gastrotrichs is well known for several species, especially for the marine taxon Macrodasyida. However, there is little information on the reproductive organs and the modes of mating and sperm transfer in putative basal taxa, which is necessary for accurate reconstruction of the ground pattern of the Gastrotricha. We present the first detailed morphological investigation of the reproductive system of a putative basal gastrotrich, Dactylopodola typhle, using transmission and scanning electron microscopy, histology, and microscopic observations of living specimens. Dactylopodola typhle is a hermaphrodite that possesses paired female and male gonads, an unpaired uterus with an outlet channel that we call the cervix, and an additional accessory reproductive organ, the so-called caudal organ. We hypothesize that the hollow, secretory caudal organ serves for picking up autospermatozoa (self-sperm), for spermatophore formation, and finally for transferring the autospermatophore to a mating partner. The allospermatophore (foreign spermatophore) is stored within the uterus where fertilization occurs. We think that the mature and fertilized egg is released through the cervix and the dorsolateral female gonopore, and not by rupture of the body wall. Based on the morphology, we provide a plausible hypothesis for spermatophore formation and transfer in D. typhle. Preliminary phylogenetic considerations indicate that the stem species of Macrodasyida, perhaps that of all Gastrotricha, had paired ovaries and paired testes, an unpaired uterus, and only one accessory reproductive organ.
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This study presents the first phylogenetic analysis of Dicranophoridae (Rotifera: Monogononta), a species rich rotifer family of about 230 species currently recognized. It is based on a maximum parsimony analysis including 77 selected... more
This study presents the first phylogenetic analysis of Dicranophoridae (Rotifera: Monogononta), a species rich rotifer family of about 230 species currently recognized. It is based on a maximum parsimony analysis including 77 selected ingroup and three outgroup taxa and a total of 59 phylogenetically informative morphological characters. Character coding is based on personal investigation of material collected by the authors and an extensive survey of the literature. Apart from covering general body organization, character coding primarily relies on scanning electron microscopic preparations of the mastax jaw elements. Our study suggests monophyly of Dicranophoridae with a clade of Dicranophorus and Dorria as the sister taxon of all other dicranophorid species. Monophyly of Encentrum, the most species rich genus within Dicranophoridae, cannot be demonstrated. Within Dicranophoridae our study identifies the monophyletic taxa Caudosubbasifenestrata, Intramalleata, Praeuncinata and Proventriculata, each based on unambiguous character transformations evolved in their stem lineages. However, resolution within Praeuncinata and Proventriculata is very limited. Although some terminal clades within Praeuncinata and Proventriculata are recognized, basal splits remain obscure. Probably, other characters such as DNA sequence data are needed to further our understanding of phylogenetic relationships within these poorly resolved taxa.Die hier vorgelegte Studie stellt die erste phylogenetische Analyse des Taxons Dicranophoridae (Rotifera: Monogononta) dar, einer artenreichen Familie der Rotiferen mit zurzeit etwa 230 validen Arten. Die resultierenden phylogenetischen Verwandtschaftsbeziehungen fußen auf einer Maximum Parsimonie Analyse mit 77 ausgewählten Vertretern der Innen– und 3 Vertretern der Außengruppe bei insgesamt 59 Parsimonie–informativen Merkmalen. Die Kodierung der Merkmale basiert einerseits auf Material, das von den Autoren selbst gesammelt und bestimmt wurde und andererseits auf einem ausgedehnten Studium der relevanten Literatur. Neben der Erfassung von Merkmalen zur allgemeinen Körperorganisation stützt sich die Merkmalskodierung vor allem auf rasterelektronenmikroskopische Präparationen der Hartelemente des Mastax. Das Ergebnis der Analyse stützt die Monophylie der Dicranophoridae. Innerhalb der Dicranophoridae stellt ein monophyletisches Taxon, das die Gattungen Dicranophorus und Dorria umfasst, die Schwestergruppe aller übrigen Dicranophoridae dar. Die bei weitem artenreichste Gattung Encentrum lässt sich nicht als Monophylum begründen. Als monophyletische Teilgruppen innerhalb der Dicranophoridae identifiziert unsere Analyse die Taxa Caudosubbasifenestrata, Intramalleata, Praeuncinata und Proventriculata, die jeweils durch mindestens eine unzweideutige Merkmalstransformation in ihren Stammlinien begründet werden. Innerhalb der Taxa Praeuncinata und Proventriculata bietet unsere Analyse nur sehr begrenzte Auflösung. Obgleich sich einzelne Teilgruppen über unzweideutige Merkmalstransformationen als Monophyla begründen lassen, fehlen Merkmale für die Auflösung der basalen Verzweigungen innerhalb der Praeuncinata und Proventriculata. Es ist zu erwarten, dass andere Merkmalssysteme, wie zum Beispiel DNA Sequenzdaten, bei der Aufklärung der Verwandtschaftsbeziehungen innerhalb dieser Teilgruppen Klärung erbringen.
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A cladistic analysis of Gastrotricha based on morphological characters is presented. Unlike previous morphological analyses, our study uses species rather than higher level taxa, for which the ground pattern is often unknown. The analysis... more
A cladistic analysis of Gastrotricha based on morphological characters is presented. Unlike previous morphological analyses, our study uses species rather than higher level taxa, for which the ground pattern is often unknown. The analysis comprises 79 ingroup taxa, 4 outgroup taxa and 135 binary and multistate characters in total. Character coding is based on a careful assessment of original species descriptions. Characters included cover general body organization, internal and external features as, for example, data on the adhesive tubes, digestive tract or cuticle armament. Character systems such as many ultrastructural findings, for which it was problematic to obtain data for a large set of the included taxa, were not considered. To minimize a priori assumptions, all characters were treated with equal weight and left unordered. The four outgroup representatives were chosen in accordance with the current sister group hypotheses for Gastrotricha. Two search strategies, a heuristic search (maximum parsimony) and a parsimony ratchet search, reveal a comparable scenario. Gastrotricha split into two sister taxa. One group comprises genus Neodasys only, the sister group N.N.1 (Eutubulata nom. nov.) consists of all remaining Gastrotricha. Within Eutubulata, monophyletic Macrodasyida s. str. and N.N.2 (Abursata nom. nov.) are sister taxa of highest rank. Abursata consists of the ‘freshwater macrodasyids’Marinellina and Redudasys as sister group of monophyletic Paucitubulatina. Some traditional families are supported by this analysis. We evaluate possible apomorphies for the most basal stem lineages and track the evolution of selected organs. Our findings reveal that secondary character loss may play an important role in the stem lineage of Abursata and further in Paucitubulatina. Moreover, according to this analysis there might have been a single invasion of the freshwater environment in the stem lineage of Abursata followed by several independent returns to marine habitats within the monophylum Paucitubulatina.
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Fluorescence-labelled phalloidin in combination with confocal laser scanning microscopy (cLSM) has been used to reconstruct the body musculature in Encentrum mucronatum and Dicranophorus forcipatus in order to gain insight into the... more
Fluorescence-labelled phalloidin in combination with confocal laser scanning microscopy (cLSM) has been used to reconstruct the body musculature in Encentrum mucronatum and Dicranophorus forcipatus in order to gain insight into the architecture of body musculature in representatives of the hitherto uninvestigated Dicranophoridae.In both species, a system of outer circular and inner longitudinal muscles has been found. In E. mucronatum, seven circular muscles (musculi circulares I–VII) and six paired longitudinal muscles (musculi longitudinales I–VI) have been identified. In D. forcipatus, eight circular muscles (musculi circulares I–VIII) and nine paired longitudinal muscles (musculi longitudinales I–IX) are present. In both species, some of the longitudinal muscles span the whole specimen, while others are shorter and connect head and trunk or foot and trunk. Differences in shape and extension of the circular muscles in both species are related to differences in structure of the trunk integument.Surveying the literature on rotifer musculature, muscles identified in this study are homologised across Rotifera and given individual names. Based on the study of E. mucronatum and D. forcipatus and previous studies on other rotifers, a system of musculature in the ground pattern of Ploima comprising at least three circular muscles (pars coronalis, corona sphincter, musculus circumpedalis) and three pairs of longitudinal muscles (musculi longitudinales ventrales, musculi longitudinales dorsales and musculi longitudinales capitum) is suggested.
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A cladistic analysis of Gastrotricha based on morphological characters is presented. Unlike previous morphological analyses, our study uses species rather than higher level taxa, for which the ground pattern is often unknown. The analysis... more
A cladistic analysis of Gastrotricha based on morphological characters is presented. Unlike previous morphological analyses, our study uses species rather than higher level taxa, for which the ground pattern is often unknown. The analysis comprises 79 ingroup taxa, 4 outgroup taxa and 135 binary and multistate characters in total. Character coding is based on a careful assessment of original species descriptions. Characters included cover general body organization, internal and external features as, for example, data on the adhesive tubes, digestive tract or cuticle armament. Character systems such as many ultrastructural findings, for which it was problematic to obtain data for a large set of the included taxa, were not considered. To minimize a priori assumptions, all characters were treated with equal weight and left unordered. The four outgroup representatives were chosen in accordance with the current sister group hypotheses for Gastrotricha. Two search strategies, a heuristic search (maximum parsimony) and a parsimony ratchet search, reveal a comparable scenario. Gastrotricha split into two sister taxa. One group comprises genus Neodasys only, the sister group N.N.1 (Eutubulata nom. nov.) consists of all remaining Gastrotricha. Within Eutubulata, monophyletic Macrodasyida s. str. and N.N.2 (Abursata nom. nov.) are sister taxa of highest rank. Abursata consists of the ‘freshwater macrodasyids’Marinellina and Redudasys as sister group of monophyletic Paucitubulatina. Some traditional families are supported by this analysis. We evaluate possible apomorphies for the most basal stem lineages and track the evolution of selected organs. Our findings reveal that secondary character loss may play an important role in the stem lineage of Abursata and further in Paucitubulatina. Moreover, according to this analysis there might have been a single invasion of the freshwater environment in the stem lineage of Abursata followed by several independent returns to marine habitats within the monophylum Paucitubulatina.
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... Lepidodermella squamata, structure and development of the reproductive system (parthenogenetic and postparthenogenetic ... reproductive system based on serial ultrathin sections (TEM) andhistology, Ruppert 1978a. ... This term is used... more
... Lepidodermella squamata, structure and development of the reproductive system (parthenogenetic and postparthenogenetic ... reproductive system based on serial ultrathin sections (TEM) andhistology, Ruppert 1978a. ... This term is used ambiguously in a comparative study of the ...
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ABSTRACT
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Species of the freshwater gastrotrich taxon Dasydytidae show a set of conspicuous structural and behavioural adaptations to a semi-planktonic life. Conspicuously, most dasydytids have several groups of strong, moveable spines that can... more
Species of the freshwater gastrotrich taxon Dasydytidae show a set of conspicuous structural and behavioural adaptations to a semi-planktonic life. Conspicuously, most dasydytids have several groups of strong, moveable spines that can actively be abducted to perform saltatory movements, change the overall direction of locomotion, or enable the animals to rest in a defensive position. So far, there are only vague ideas of how these spine movements are achieved in dasydytid species. In order to gain insight into the possible morpho-functional coupling of body musculature and motile spines, we have carried out a study targeting the muscular system in two species of Dasydytidae by means of phalloidin staining and confocal laser scanning microscopy.For spine movements in both species studied, Stylochaeta scirtetica and Dasydytes (Setodytes) tongiorgii, we have identified an antagonistic system of segmented longitudinal and oblique somatic muscle pairs. In both species, contraction of the musculi obliqua abduct the paired groups of ventro-lateral spines; contraction of the segments of musculi laterales causes their adduction.A comparison of the muscular system of the studied species to that of other gastrotrichs reveals several homologous muscle pairs, visceral as well as somatic, that might be features of the stem species of a clade comprising all Paucitubulatina exclusive of Xenotrichulidae. The pairs of oblique somatic muscles are most probably an autapomorphy of Dasydytidae.