Authors: Maria Sachkova, Vengamanaidu Modepalli

The larvae of an annelid worm use nitric oxide signalling to activate the neural pathways needed to swim away from the harmful ultraviolet light of the sun.

Topics: Animals; Polychaeta; Ultraviolet Rays; Annelida; Larva; Signal Transduction

PubMed: 37850625
DOI: 10.7554/eLife.92535

Review

Authors: Diethard Tautz

The three major taxa with metameric segmentation (annelids, arthropods, and chordates) appear to use three very different molecular strategies to generate segments. However, unexpected similarities are starting to emerge from characterization of pair-rule patterning and segmental border formation. Moreover, the existence of an ancestral segmentation clock based on Notch signaling has become likely. An old concept of comparative anatomy, the enterocoele theory, is compatible with a single origin of segmentation mechanisms and could therefore provide a conceptual framework for assessing these molecular similarities.

Topics: Animals; Annelida; Body Patterning; Chickens; Chordata, Nonvertebrate; Drosophila; Embryo, Nonmammalian; Gene Expression Regulation, Developmental; Leeches; Models, Biological

PubMed: 15363406
DOI: 10.1016/j.devcel.2004.08.008

Authors: Douglas Koshland, Hugo Tapia

Climate change has accentuated the importance of understanding how organisms respond to stresses imposed by changes to their environment, like water availability. Unusual organisms, called anhydrobiotes, can survive loss of almost all intracellular water. Desiccation tolerance of anhydrobiotes provides an unusual window to study the stresses and stress response imposed by water loss. Because of the myriad of stresses that could be induced by water loss, desiccation tolerance seemed likely to require many established stress effectors. The sugar trehalose and hydrophilins (small intrinsically disordered proteins) had also been proposed as stress effectors against desiccation because they were found in nearly all anhydrobiotes, and could mitigate desiccation-induced damage to model proteins and membranes in vitro. Here, we summarize in vivo studies of desiccation tolerance in worms, yeast, and tardigrades. These studies demonstrate the remarkable potency of trehalose and a subset of hydrophilins as the major stress effectors of desiccation tolerance. They act, at least in part, by limiting in vivo protein aggregation and loss of membrane integrity. The apparent specialization of individual hydrophilins for desiccation tolerance suggests that other hydrophilins may have distinct roles in mitigating additional cellular stresses, thereby defining a potentially new functionally diverse set of stress effectors.

Topics: Adaptation, Physiological; Animals; Annelida; Climate Change; Desiccation; Droughts; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Stress, Physiological; Tardigrada; Trehalose; Water

PubMed: 30870092
DOI: 10.1091/mbc.E17-04-0257

Authors: Michel Vervoort, Eve Gazave

Regeneration, the ability to restore body parts after an injury or an amputation, is a widespread property in the animal kingdom. This chapter describes methods used to study this fascinating process in the annelid Platynereis dumerilii. During most of its life, this segmented worm is able to regenerate upon amputation the posterior part of its body, including its pygidium (terminal non-segmented body region bearing the anus) and a subterminal posterior growth zone which contains stem cells required for the formation of new segments. Detailed description of Platynereis worm culture and how to obtain large quantity of regenerating worms is provided. We also describe the staging system that we established and three important methods to study regeneration: whole mount in situ hybridization to study gene expression, 5-ethynyl-2'-deoxyuridine (EdU) labeling to characterize cell proliferation, and use of pharmacological treatments to establish putative roles of defined signaling pathways and processes.

Topics: Animals; Annelida; Cell Proliferation; Polychaeta; Signal Transduction; Stem Cells

PubMed: 35359310
DOI: 10.1007/978-1-0716-2172-1_11

Authors: Jonathan Q Henry

Topics: Animals; Annelida; Bryozoa; Developmental Biology; Embryo, Nonmammalian; Mollusca; Platyhelminths

PubMed: 25690956
DOI: 10.1387/ijdb.140289jh

Review

Authors: A M Murillo Ramos, J Y Wilson

Estrogen receptors (ERs) are thought to be the ancestor of all steroid receptors and are present in most lophotrochozoans studied to date, including molluscs, annelids, and rotifers. A number of studies have investigated the functional role of estrogen receptors in invertebrate species, although most are in molluscs, where the receptor is constitutively active. In vitro experiments provided evidence for ligand-activated estrogen receptors in annelids, raising important questions about the role of estrogen signalling in lophotrochozoan lineages. Here, we review the concordant and discordant evidence of estradiol receptor signalling in lophotrochozoans, with a focus on annelids and rotifers. We explore the de novo synthesis of estrogens, the evolution and expression of estrogen receptors, and physiological responses to activation of estrogen receptors in the lophotrochozoan phyla Annelida and Rotifera. Key data are missing to determine if de novo biosynthesis of estradiol in non-molluscan lophotrochozoans is likely. For example, an ortholog for the CYP11 gene is present, but confirmation of substrate conversion and measured tissue products is lacking. Orthologs CYP17 and CYP19 are lacking, yet intermediates or products (e.g. estradiol) in tissues have been measured. Estrogen receptors are present in multiple species, and for a limited number, in vitro data show agonist binding of estradiol and/or transcriptional activation. The expression patterns of the lophotrochozoan ERs suggest developmental, reproductive, and digestive roles but are highly species dependent. E exposures suggest that lophotrochozoan ERs may play a role in reproduction, but no strong dose-response relationship has been established. Therefore, we expect most lophotrochozoan species, outside of perhaps platyhelminths, to have an ER but their physiological role remains elusive. Mining genomes for orthologs gene families responsible for steroidogenesis, coupled with in vitro and in vivo studies of the steroid pathway are needed to better assess whether lophotrochozoans are capable of estradiol biosynthesis. One major challenge is that much of the data are divided across a diversity of species. We propose that the polychaetes Capitella teleta or Platyneris dumerilii, and rotifer Brachionus manjavacas may be strong species choices for studies of estrogen receptor signalling, because of available genomic data, established laboratory culture techniques, and gene knockout potential.

Topics: Animals; Signal Transduction; Receptors, Estradiol; Annelida; Receptors, Estrogen; Rotifera; Estradiol

PubMed: 38677339
DOI: 10.1016/j.ygcen.2024.114519

Authors: José M Martín-Durán, Kevin Pang, Aina Børve...

It has been hypothesized that a condensed nervous system with a medial ventral nerve cord is an ancestral character of Bilateria. The presence of similar dorsoventral molecular patterns along the nerve cords of vertebrates, flies, and an annelid has been interpreted as support for this scenario. Whether these similarities are generally found across the diversity of bilaterian neuroanatomies is unclear, and thus the evolutionary history of the nervous system is still contentious. Here we study representatives of Xenacoelomorpha, Rotifera, Nemertea, Brachiopoda, and Annelida to assess the conservation of the dorsoventral nerve cord patterning. None of the studied species show a conserved dorsoventral molecular regionalization of their nerve cords, not even the annelid Owenia fusiformis, whose trunk neuroanatomy parallels that of vertebrates and flies. Our findings restrict the use of molecular patterns to explain nervous system evolution, and suggest that the similarities in dorsoventral patterning and trunk neuroanatomies evolved independently in Bilateria.

Topics: Animals; Annelida; Biological Evolution; Body Patterning; Central Nervous System; Invertebrates; Nerve Net; Neural Plate; Phylogeny; Rotifera

PubMed: 29236686
DOI: 10.1038/nature25030

Comparative Study Review

Authors: Roman P Kostyuchenko, Vitaly V Kozin

The question of why animals vary in their ability to regenerate remains one of the most intriguing questions in biology. Annelids are a large and diverse phylum, many members of which are capable of extensive regeneration such as regrowth of a complete head or tail and whole-body regeneration, even from few segments. On the other hand, some representatives of both of the two major annelid clades show very limited tissue regeneration and are completely incapable of segmental regeneration. Here we review experimental and descriptive data on annelid regeneration, obtained at different levels of organization, from data on organs and tissues to intracellular and transcriptomic data. Understanding the variety of the cellular and molecular basis of regeneration in annelids can help one to address important questions about the role of stem/dedifferentiated cells and "molecular morphallaxis" in annelid regeneration as well as the evolution of regeneration in general.

Topics: Animals; Annelida; Head; Regeneration; Tail

PubMed: 34440322
DOI: 10.3390/genes12081148

Authors: Dolma Michellod, Tanja Bien, Daniel Birgel...

Sterols are vital for nearly all eukaryotes. Their distribution differs in plants and animals, with phytosterols commonly found in plants whereas most animals are dominated by cholesterol. We show that sitosterol, a common sterol of plants, is the most abundant sterol in gutless marine annelids. Using multiomics, metabolite imaging, heterologous gene expression, and enzyme assays, we show that these animals synthesize sitosterol de novo using a noncanonical C-24 sterol methyltransferase (C-SMT). This enzyme is essential for sitosterol synthesis in plants, but not known from most bilaterian animals. Our phylogenetic analyses revealed that C-SMTs are present in representatives of at least five animal phyla, indicating that the synthesis of sterols common to plants is more widespread in animals than currently known.

Topics: Animals; Cholesterol; Phylogeny; Plants; Sitosterols; Annelida

PubMed: 37141360
DOI: 10.1126/science.add7830

Authors: Christina Zakas, Nathan D Harry, Elizabeth H Scholl...

Streblospio benedicti is a common marine annelid that has become an important model for developmental evolution. It is the only known example of poecilogony (where two distinct developmental modes occur within a single species) that is due to a heritable difference in egg size. The dimorphic developmental programs and life-histories exhibited in this species depend on differences within the genome, making it an optimal model for understanding the genomic basis of developmental divergence. Studies using S. benedicti have begun to uncover the genetic and genomic principles that underlie developmental uncoupling, but until now they have been limited by the lack of availability of genomic tools. Here, we present an annotated chromosomal-level genome assembly of S. benedicti generated from a combination of Illumina reads, Nanopore long reads, Chicago and Hi-C chromatin interaction sequencing, and a genetic map from experimental crosses. At 701.4 Mb, the S. benedicti genome is the largest annelid genome to date that has been assembled to chromosomal scaffolds. The complete genome of S. benedicti is valuable for functional genomic analyses of development and evolution, as well as phylogenetic comparison within the annelida and the Lophotrochozoa. Despite having two developmental modes, there is no evidence of genome duplication or substantial gene number expansions. Instead, lineage-specific repeats account for much of the expansion of this genome compared with other annelids.

Topics: Animals; Annelida; Larva; Phylogeny; Polychaeta; Sequence Analysis, DNA

PubMed: 35078222
DOI: 10.1093/gbe/evac008