Neuromuscular development in the emerging scyphozoan model system, : implications for the evolution of cnidarian nervous systems.

The scyphozoan is an emerging cnidarian model system for studying regeneration, animal-algae symbiotic relationships, and various aspects of evolutionary biology including the early emergence of animal nervous systems. has a life cycle similar to other scyphozoans, which includes the alternation between a sessile, asexual form (polyp) and a sexually reproducing stage, the medusa. The transition between the two forms is called strobilation, where the polyp releases a miniature medusa, the iconic ephyra, that subsequently develops into the adult medusa.

Hox, homology, and parsimony: An organismal perspective.

Hox genes are important regulators in animal development. They often show a mosaic of conserved (e.g.

Sexually dimorphic characters of the ultimate legs in lithobiid centipedes (Myriapoda, Chilopoda, and Lithobiomorpha): Morphology and implications for reproductive behavior.

Many species of lithobiomorph centipedes present a pronounced sexual dimorphism reflected in remarkable structural modifications on the ultimate legs of males. Most records of these male secondary sexual characters addressed taxonomy, helping to identify and characterize species or diagnose genera, but information on their diversity, detailed morphology and possible function(s) is scarce. In this study, nine species of the two lithobiid genera Lithobius Leach, 1814 and Eupolybothrus Verhoeff, 1907 were investigated, using light and scanning electron microscopy to document the detailed morphology of secondary sexual characters of male ultimate legs.

A mosaic of conserved and novel modes of gene expression and morphogenesis in mesoderm and muscle formation of a larval bivalve.

Unlabelled: The mesoderm gives rise to several key morphological features of bilaterian animals including endoskeletal elements and the musculature. A number of regulatory genes involved in mesoderm and/or muscle formation (e.g.

Comparative Single-Cell Transcriptomics Reveals Novel Genes Involved in Bivalve Embryonic Shell Formation and Questions Ontogenetic Homology of Molluscan Shell Types.

Mollusks are known for their highly diverse repertoire of body plans that often includes external armor in form of mineralized hardparts. Representatives of the Conchifera, one of the two major lineages that comprises taxa which originated from a uni-shelled ancestor (Monoplacophora, Gastropoda, Cephalopoda, Scaphopoda, Bivalvia), are particularly relevant regarding the evolution of mollusk shells. Previous studies have found that the shell matrix of the adult shell (teleoconch) is rapidly evolving and that the gene set involved in shell formation is highly taxon-specific.

Midbody-Localized Aquaporin Mediates Intercellular Lumen Expansion During Early Cleavage of an Invasive Freshwater Bivalve.

Intercellular lumen formation is a crucial aspect of animal development and physiology that involves a complex interplay between the molecular and physical properties of the constituent cells. Embryos of the invasive freshwater mussel are ideal models for studying this process due to the large intercellular cavities that readily form during blastomere cleavage. Using this system, we show that recruitment of the transmembrane water channel protein aquaporin exclusively to the midbody of intercellular cytokinetic bridges is critical for lumenogenesis.

HES and Mox genes are expressed during early mesoderm formation in a mollusk with putative ancestral features.

The mesoderm is considered the youngest of the three germ layers. Although its morphogenesis has been studied in some metazoans, the molecular components underlying this process remain obscure for numerous phyla including the highly diverse Mollusca. Here, expression of Hairy and enhancer of split (HES), Mox, and myosin heavy chain (MHC) was investigated in Acanthochitona fascicularis, a representative of Polyplacophora with putative ancestral molluscan features.

Ecdysis-related neuropeptide expression and metamorphosis in a non-ecdysozoan bilaterian.

Ecdysis-related neuropeptides (ERNs), including eclosion hormone, crustacean cardioactive peptide, myoinhibitory peptide, bursicon alpha, and bursicon beta regulate molting in insects and crustaceans. Recent evidence further revealed that ERNs likely play an ancestral role in invertebrate life cycle transitions, but their tempo-spatial expression patterns have not been investigated outside Arthropoda. Using RNA-seq and in situ hybridization, we show that ERNs are broadly expressed in the developing nervous system of a mollusk, the polyplacophoran Acanthochitona fascicularis.

Non-collinear Hox gene expression in bivalves and the evolution of morphological novelties in mollusks.

Hox genes are key developmental regulators that are involved in establishing morphological features during animal ontogeny. They are commonly expressed along the anterior-posterior axis in a staggered, or collinear, fashion. In mollusks, the repertoire of body plans is widely diverse and current data suggest their involvement during development of landmark morphological traits in Conchifera, one of the two major lineages that comprises those taxa that originated from a uni-shelled ancestor (Monoplacophora, Gastropoda, Cephalopoda, Scaphopoda, Bivalvia).

Ancestral Role of Ecdysis-Related Neuropeptides in Animal Life Cycle Transitions.

Ecdysis or molting evolved ∼535 mya in Ecdysozoa, the most diverse and species-rich animal superphylum. A cascade of ecdysis-related neuropeptides (ERNs) controls the innate behavioral programs required for cuticle shedding in some ecdysozoan lineages (e.g.

Key novelties in the evolution of the aquatic colonial phylum Bryozoa: evidence from soft body morphology.

Molecular techniques are currently the leading tools for reconstructing phylogenetic relationships, but our understanding of ancestral, plesiomorphic and apomorphic characters requires the study of the morphology of extant forms for testing these phylogenies and for reconstructing character evolution. This review highlights the potential of soft body morphology for inferring the evolution and phylogeny of the lophotrochozoan phylum Bryozoa. This colonial taxon comprises aquatic coelomate filter-feeders that dominate many benthic communities, both marine and freshwater.

Methods in Brain Development of Molluscs.

Representatives of the phylum Mollusca have long been important models in neurobiological research. Recently, the routine application of immunocytochemistry and gene expression analyses in combination with confocal laserscanning microscopy has allowed fast generation of highly detailed reconstructions of neural structures of even the smallest multicellular animals, including early developmental stages. As a consequence, large-scale comparative analyses of neurogenesis-an important prerequisite for inferences concerning the evolution of animal nervous systems-are now possible in a reasonable amount of time.

Complete mitochondrial genomes of two scaphopod molluscs.

Complete mitochondrial genomes were determined for two scaphopod molluscs: the dentaliid and an unidentified Antarctic gadilid. Both genomes are complete except, in Gadilida sp. indet.

The quagga mussel genome and the evolution of freshwater tolerance.

Freshwater dreissenid mussels evolved from marine ancestors during the Miocene ∼30 million years ago and today include some of the most successful and destructive invasive species of freshwater environments. Here, we sequenced the genome of the quagga mussel Dreissena rostriformis to identify adaptations involved in embryonic osmoregulation. We provide evidence that a lophotrochozoan-specific aquaporin water channel, a vacuolar ATPase subunit and a sodium/hydrogen exchanger are involved in osmoregulation throughout early cleavage, during which time large intercellular fluid-filled 'cleavage cavities' repeatedly form, coalesce and collapse, expelling excess water to the exterior.

Life in a tube: morphology of the ctenostome bryozoan .

Bryozoa is a large phylum of colonial aquatic suspension feeders. The boring ctenostome is unique and inhabits parchment-like polychaete tubes. Morphological studies date back to the nineteenth century, but distinct adaptations to this specific habitat have not been properly analysed, which prompted us to reexamine the morphology of this recently encountered species.

Ancient origins of arthropod moulting pathway components.

Ecdysis (moulting) is the defining character of Ecdysoza (arthropods, nematodes and related phyla). Despite superficial similarities, the signalling cascade underlying moulting differs between Panarthropoda and the remaining ecdysozoans. Here, we reconstruct the evolution of major components of the ecdysis pathway.

A mating plug in a squid? Sneaker spermatophores can block the female sperm-storage organ in Doryteuthis plei.

Males from numerous animal taxa have evolved strategies for obstructing the female genitalia with copulatory plugs, reducing the risk of sperm competition and thus resulting in an advantage in sexual selection. Several lines of evidence suggest that sperm competition is a common feature in the complex squid mating systems, which include the evolution of alternative mating tactics (consort vs. sneaker).

Staggered Hox expression is more widespread among molluscs than previously appreciated.

Hox genes are expressed along the anterior-posterior body axis in a colinear fashion in the majority of bilaterians. Contrary to polyplacophorans, a group of aculiferan molluscs with conserved ancestral molluscan features, gastropods and cephalopods deviate from this pattern by expressing Hox genes in distinct morphological structures and not in a staggered fashion. Among conchiferans, scaphopods exhibit many similarities with gastropods, cephalopods and bivalves, however, the molecular developmental underpinnings of these similar traits remain unknown.

Unity in diversity: a survey of muscular systems of ctenostome Gymnolaemata (Lophotrochozoa, Bryozoa).

Background: Myoanatomical studies of adult bryozoans employing fluorescent staining and confocal laser scanning microscopy (CLSM) have been chiefly conducted on freshwater bryozoans. The diversity of muscular systems in the marine bryozoans is currently not well known with only two species being studied in more detail. The aim of this study is to unravel the diversity of muscle systems of 15 ctenostome bryozoans by phalloidin-coupled fluorescence stainings combined with CLSM.

Morphology of the bryozoan Cinctipora elegans (Cyclostomata, Cinctiporidae) with first data on its sexual reproduction and the cyclostome neuro-muscular system.

Background: Cyclostome bryozoans are an ancient group of marine colonial suspension-feeders comprising approximately 700 extant species. Previous morphological studies are mainly restricted to skeletal characters whereas data on soft tissues obtained by state-of-the-art methods are still lacking. In order to contribute to issues related to cyclostome ground pattern reconstruction, we analyzed the morphology of the neuromuscular system Cinctipora elegans by means of immunocytochemical staining, confocal laser scanning microscopy, histological sections and microCT imaging.

Towards a ground pattern reconstruction of bivalve nervous systems: neurogenesis in the zebra mussel .

Bivalvia is a taxon of aquatic mollusks that includes clams, oysters, mussels, and scallops. Within heterodont bivalves, is a small, mytiliform, freshwater mussel that develops indirectly via a planktotrophic veliger larva. Currently, only a few studies on bivalve neurogenesis are available, impeding the reconstruction of a ground pattern in Bivalvia.

Expression of six3 and otx in Solenogastres (Mollusca) supports an ancestral role in bilaterian anterior-posterior axis patterning.

The homeodomain transcription factors six3 and otx are involved in patterning the anterior body and parts of the central nervous system (CNS) in bilaterians. Their similar expression patterns have been used as an argument for homology of heads, brains, segmentation, and ciliated larvae. We investigated the developmental expression of six3 and otx in the aplacophoran mollusk Wirenia argentea.