Conrad Helm

Conrad Helm
Georg-August-Universität Göttingen | GAUG · Animal Evolution and Biodiversity

Dr. rer. nat.

About

63
Publications
25,416
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886
Citations
Additional affiliations
April 2017 - present
University of Bergen
Position
  • PostDoc Position
March 2015 - March 2017
University of Bergen
Position
  • Fellow
January 2013 - March 2015
University of Leipzig
Position
  • Research Assistant

Publications

Publications (63)
Article
Full-text available
Annelida is one of three animal groups possessing segmentation and is central in considerations about the evolution of different character traits. It has even been proposed that the bilaterian ancestor resembled an annelid. However, a robust phylogeny of Annelida, especially with respect to the basal relationships, has been lacking. Our study based...
Article
Full-text available
Background: Comparative investigations on bilaterian neurogenesis shed light on conserved developmental mechanisms across taxa. With respect to annelids, most studies focus on taxa deeply nested within the annelid tree, while investigations on early branching groups are almost lacking. According to recent phylogenomic data on annelid evolution Owe...
Article
Full-text available
Bilaterians usually possess a central nervous system, composed of neurons and supportive cells called glial cells. Whereas neuronal cells are highly comparable in all these animals, glial cells apparently differ, and in deuterostomes, radial glial cells are found. These particular secretory glial cells may represent the archetype of all (macro) gli...
Article
Full-text available
Background A median, segmented, annelid nerve cord has repeatedly been compared to the arthropod and vertebrate nerve cords and became the most used textbook representation of the annelid nervous system. Recent phylogenomic analyses, however, challenge the hypothesis that a subepidermal rope-ladder-like ventral nerve cord (VNC) composed of a paired...
Article
Full-text available
Background Recent phylogenomic analyses congruently reveal a basal clade which consists of Oweniidae and Mageloniidae as sister group to the remaining Annelida. These results indicate that the last common ancestor of Annelida was a tube-dwelling organism. They also challenge traditional evolutionary hypotheses of different organ systems, among them...
Article
Full-text available
Chaetopteridae-the parchment worms-comprise a group of early branching annelids with a scarcely investigated neuroanatomy and neurogenesis. Due to their phylogenetic position in the annelid tree, studying them is nevertheless inevitable for our understanding of character evolution in segmented worms. Therefore, we investigated several adult und lar...
Preprint
Step-by-step-guide how to use Blender to analyse and visualize your segmented structures, for example exporting it as a video as mp4-file.
Preprint
Full-text available
How to do data refinements like repair, smooth and simplification in MeshLab and export as -ply-file.
Preprint
How to use ImageJ in our 3D-workflow from data manipulation, import, segmentation and export as OBJ-file.
Article
Full-text available
Background Head appendages in Annelida contribute significantly to the immense morphological diversity in this spiralian taxon. Nevertheless, the evolutionary origin of annelid antennae, palps, cirri and tentacles are part of vast theories and debates that took place over decades. One of these heavily discussed groups are the Terebelliformia, which...
Article
Full-text available
The sponge‐dwelling Syllidae Ramisyllis multicaudata and Syllis ramosa are the only annelid species for which a branched body with one head and multiple posterior ends is known. In these species, the head is located deep within the sponge, and the branches extend through the canal system of their host. The morphology of these creatures has captivat...
Article
Full-text available
Phyllodocida is a clade of errantiate annelids characterized by having ventral sensory palps, anterior enlarged cirri, axial muscular proboscis, compound chaetae (if present) with a single ligament, and of lacking dorsolateral folds. Members of most families date back to the Carboniferous, although the earliest fossil was dated from the Devonian. P...
Article
Full-text available
Phyllodocida is a clade of errantiate annelids characterized by having ventral sensory palps, anterior enlarged cirri, axial muscular proboscis, compound chaetae (if present) with a single ligament, and of lacking dorsolateral folds. Members of most families date back to the Carboniferous, although the earliest fossil was dated from the Devonian. P...
Preprint
Full-text available
Background: Head appendages in Annelida highly contribute to the immense morphological diversity in this lophotrochozoan taxon. Nevertheless, the evolutionary origin of annelid antennae, palps, cirri and tentacles are part of vast theories and debates that took place over decades. One of these heavily discussed groups are the Terebelliformia, which...
Article
Full-text available
The jaw apparatus in several annelid families represents a powerful tool for systematic approaches and evolutionary investigations. Nevertheless, for several taxa, this character complex has scarcely been investigated, and complete comparative analyses of all annelid jaws are lacking. In our comprehensive study, we described the fine structure of t...
Article
Full-text available
Background: Nervous system development is an interplay of many processes: the formation of individual neurons, which depends on whole-body and local patterning processes, and the coordinated growth of neurites and synapse formation. While knowledge of neural patterning in several animal groups is increasing, data on pioneer neurons that create the...
Article
A new species of Syllis Grube, 1850 (Syllidae, Annelida) from marine aquaria is described in this study, including information about its life cycle, laboratory cultures, transcriptomic data, and an updated phylogeny of the group. Syllis malaquini sp. nov. is diagnosed by a slender body with a colour pattern consisting of dorsal dark lines on each s...
Preprint
Full-text available
Background: Nervous system development is an interplay of many processes: the formation of individual neurons which depends on whole-body and local patterning processes and the coordinated growth of neurites and synapse formation. While knowledge of neural patterning in several animal groups is increasing, data on pioneer neurons that create the ea...
Preprint
Full-text available
Background Nervous system development is an interplay of many processes: the formation of individual neurons, which depends on whole-body and local patterning processes, and the coordinated growth of neurites and synapse formation. While knowledge of neural patterning in several animal groups is increasing, data on pioneer neurons that create the e...
Article
Full-text available
Background: The annelid anterior central nervous system is often described to consist of a dorsal prostomial brain, consisting of several commissures and connected to the ventral ganglionic nerve cord via circumesophageal connectives. In the light of current molecular phylogenies, our assumptions on the primary design of the nervous system in Anne...
Article
Full-text available
Background: Sabellarids, also known as honeycomb or sandcastle worms, when building their tubes, produce chemical signals (free fatty acids) that are responsible for larval settlement and the formation of three-dimensional aggregations. The larval palps and the dorsal hump (becoming the median organ in adults) are presumed to participate in such a...
Preprint
Full-text available
A median, segmented, annelid nerve cord has repeatedly been compared to the arthropod and vertebrate nerve cords and became the most used textbook representation of the annelid nervous system. Recent phylogenomic analyses, however, challenge the hypothesis that a subepidermal rope-ladder-like ventral nerve cord (VNC) composed of a paired serial cha...
Article
Full-text available
Background We present the first molecular characterization of glycerotoxin (GLTx), a potent neurotoxin found in the venom of the bloodworm Glycera tridactyla (Glyceridae, Annelida). Within the animal kingdom, GLTx shows a unique mode of action as it can specifically up-regulate the activity of Cav2.2 channels (N-type) in a reversible manner. The la...
Data
Table S1. Sampling sites and fixation of specimens.; Figure S2. Comparison of conserved protein domains of Ofu-SCO with that of other members of the Thrombospondin-family.
Article
Full-text available
Sensory organs in Annelida are very diverse and may be useful for assessments of morphological adaptation and character evolution. We used several methods to provide new insights into processes underlying the evolutionary radiation of anterior sensory organs in Sabellariidae. The presence and morphological diversity of the median organ (MO) found i...
Chapter
Orbiniidae are a taxon of sedentary annelids which vary in size from a few mm up to 50 cm. 180 species are described and most species can be found burrowing in sediment. Orbiniids are known from all marine habitats, including intertidal forms from sandy and rocky shores, as well as deep-sea forms. The body is usually homonomously segmented and can...
Article
Amphinomidae or so-called “fireworms” are known for their inflammatory substances and their regeneration ability. Recent transcriptome-based molecular analyses revealed that these remarkable annelids are a basal branching taxon outside the annelid main radiation (Pleistoannelida). Although several studies dealing with analyses of the morphology of...
Article
The embryology of Scoloplos armiger (“intertidalis clade”) was described in detail using light microscopy in a landmark paper by DT Anderson in 1959. To expand these investigations, we used immunohistochemical staining techniques (phalloidin, anti-FMRFamide, anti-serotonin, and anti-α-tubulin) coupled with confocal laser scanning microscopy to desc...
Chapter
Full-text available
Annelids are a taxon of protostomes comprising more than 1–7,0–00 worldwide–013;distributed species, which can be found in marine, limnic, and terrestrial habitats (Zhang 2–011). Their phylogeny was under discussion for a long time, but recent phylogenomic analyses resulted in a solid backbone of this group (Struck et al. 2–011; Weigert et al. 2–01...
Article
Full-text available
Introduction: Annelids exhibit great regenerative abilities, which are mainly used after injury or during reproduction. These lophotrochozoans thus represent excellent models for regeneration research. However, detailed morphological studies concerning annelid musculature and nervous system redevelopment are limited to few taxa, and do not allow f...
Article
Full-text available
Syllids are one of the most speciose annelid taxa and characterized by their variety of reproductive modes. We provide the description of a new species of Syllidae (Annelida, Phyllodocida), Typosyllis antoni n. sp., which is characterized by its distinct color pattern consisting of transversal red lines on the dorsum of anterior segments; long ante...
Article
Full-text available
The nereidid annelid Platynereis dumerilii emerged as a well-understood model organism. P. dumerilii and P. massiliensis are sister taxa, which are morphologically indistinguishable as adults. Interestingly, they exhibit highly contrasting life-histories: while P. dumerilii is a gonochorostic species with planktonic feeding larvae, P. massiliensis...
Article
Full-text available
Sphaerodoridae is a group of benthic marine worms (Annelida) characterized by the presence of spherical tubercles covering their whole surface. They are commonly considered as belonging to Phyllodocida although sistergroup relationships are still far from being understood. Primary homology assessments of their morphological features are lacking, hi...
Article
Cover illustration. Cirratulidae are a family of marine sedentary annelids with a remarkable regenerative ability. In this issue of the Journal of Morphology,Weidhase et al. (pp. 1418–1430, 10.1002/jmor.20316) investigated the structure of musculature and nervous system in intact and anterior regenerating individuals of Cirratulus cf. cirratus usin...
Article
Full-text available
Although part of the annelid radiation, Myzostomida exhibit a highly specialized body plan that lacks many typical annelid characters. Their annelid ancestry is evident from their trochophora-like larvae, adult myoanatomy and parts of the nervous system, whereas segmentation is considered at best to be incomplete in myzostomids. We analyzed the mor...
Chapter
Myzostomida are enigmatic protostome animals and their phylogenetic position has puzzled researchers for nearly 200 years. Here we summarize the history of the classification of these animals and introduce their biology and anatomy. Synthesizing recent analyses of ultrastructural, immunohistochemical, and genomic data we show strong support for pla...
Article
Full-text available
Even though chitin is one of the most abundant biopolymers in nature, current knowledge on chitin formation is largely based only on data from fungi and insects. This study uncovers unanticipated broad taxonomic distribution as well as extensive diversification of chitin synthases in Metazoa, shedding new light on the relevance of chitin in animals...
Data
In situ hybridization of Piwi-like genes in adult Myzostoma cirriferum in dorsal view. Anterior is up. Light microscopical image. a Expression of Mc-Piwi1 in an early adult stage, where development of the female gonadal system is jet not completed. Scale bar 100 μm. b Control sense riboprobe of Mc-Piwi1 in an adult specimen. No signal could be dete...
Article
The variety of annelid larval types and developmental modes reflects the high diversity and variability within these lophotrochozoans. However, our knowledge of pattern formation and tissue development in annelids and allies is scarce. In order to gain more data concerning neurogenesis and myogenesis in annelid trochophores, we analyzed different l...
Article
Full-text available
Piwi-like genes are a subgroup of Argonaute genes which participate as gene regulators by gene silencing. In most bilaterians, such as mouse, human, insects, and zebrafish, their expression is mostly limited to gonadal stem cells. But there are some striking exceptions to this pattern; flatworms and acoels also express Piwi-like genes in somatic st...
Article
Studies of rare genomic marker systems suggest that Myzostomida are a subgroup of Annelida and phylogenomic analyses indicate an early divergence of this taxon within annelids. However, adult myzostomids show a highly specialized body plan, which lacks typical annelid features, such as external body annulation, coelomic cavities with metanephridia,...
Article
Full-text available
In trying to understand the evolutionary relationships of organisms, the current flood of sequence data offers great opportunities, but also reveals new challenges with regard to data quality, the selection of data for subsequent analysis, and the automation of steps that were once done manually for single-gene analyses. Even though genome or trans...
Data
De novo assembly of the Illumina reads. Assembly computed with the CLC Genomic Workbench 4.0 using default parameters. (PDF)
Article
A detailed study of the exoskeleton and musculature of the phallic organ of Oxyartes lamellatus (Kirby, 1904) (Phasmatodea: Necrosciinae) is here presented – the first study of this kind for Phasmatodea. The asymmetrical phallic organ shows a highly complicated morphology, with several sclerites and many formative structural elements, of which a sc...
Article
Full-text available
We studied the spatial activity of a small population of the Eurasian otter (Lutra lutra Linnaeus, 1758) in a landscape with eight groups of ponds, which comprise roughly 100 km², by synchronous repeated collecting of faeces or secretions. The duration of the study was five consecutive days. The daily sum of fresh faeces found within the study area...

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