Malacoceros Fuliginosus Research Articles

Structural basis for excitatory neuropeptide signaling

Rapid signaling between neurons is mediated by ligand-gated ion channels, cell-surface proteins with an extracellular ligand-binding domain and a membrane-spanning ion channel domain. The degenerin/epithelial sodium channel (DEG/ENaC) superfamily is diverse in terms of its gating stimuli, with some DEG/ENaCs gated by neuropeptides, and others gated by pH, mechanical force or enzymatic activity. The mechanism by which ligands bind to and activate DEG/ENaCs is poorly understood. Here we dissected the structural basis for neuropeptide-gated activity of a neuropeptide-gated DEG/ENaC, FMRFamide-gated sodium channel 1 (FaNaC1) from the annelid worm Malacoceros fuliginosus, using cryo-electron microscopy. Structures of FaNaC1 in the ligand-free resting state and in several ligand-bound states reveal the ligand-binding site and capture the ligand-induced conformational changes of channel gating, which we verified with complementary mutagenesis experiments. Our results illuminate channel gating in DEG/ENaCs and offer a structural template for experimental dissection of channel pharmacology and ion conduction.

The development of early pioneer neurons in the annelid Malacoceros fuliginosus

BackgroundNervous 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 early axonal scaffold are scarce. Here we studied the first steps of nervous system development in the annelid Malacoceros fuliginosus.ResultsWe performed a dense expression profiling of a broad set of neural genes. We found that SoxB expression begins at 4 h postfertilization, and shortly later, the neuronal progenitors can be identified at the anterior and the posterior pole by the transient and dynamic expression of proneural genes. At 9 hpf, the first neuronal cells start differentiating, and we provide a detailed description of axonal outgrowth of the pioneer neurons that create the primary neuronal scaffold. Tracing back the clonal origin of the ventral nerve cord pioneer neuron revealed that it is a descendant of the blastomere 2d (2d221), which after 7 cleavages starts expressing Neurogenin, Acheate-Scute and NeuroD.ConclusionsWe propose that an anterior and posterior origin of the nervous system is ancestral in annelids. We suggest that closer examination of the first pioneer neurons will be valuable in better understanding of nervous system development in spirally cleaving animals, to determine the potential role of cell-intrinsic properties in neuronal specification and to resolve the evolution of nervous systems.

The visual pigment xenopsin is widespread in protostome eyes and impacts the view on eye evolution.

Photoreceptor cells in the eyes of Bilateria are often classified into microvillar cells with rhabdomeric opsin and ciliary cells with ciliary opsin, each type having specialized molecular components and physiology. First data on the recently discovered xenopsin point towards a more complex situation in protostomes. In this study, we provide clear evidence that xenopsin enters cilia in the eye of the larval bryozoan Tricellaria inopinata and triggers phototaxis. As reported from a mollusc, we find xenopsin coexpressed with rhabdomeric-opsin in eye photoreceptor cells bearing both microvilli and cilia in larva of the annelid Malacoceros fuliginosus. This is the first organism known to have both xenopsin and ciliary opsin, showing that these opsins are not necessarily mutually exclusive. Compiling existing data, we propose that xenopsin may play an important role in many protostome eyes and provides new insights into the function, evolution, and possible plasticity of animal eye photoreceptor cells.

Shift in benthic assemblages and organisms’ diet at salmon farms: community structure and stable isotope analyses

The extent of the influence of salmon farming on the environment and on the uptake of particulate and dissolved effluents by benthic organisms was assessed using community structure and stable isotope analyses. Sediment cores were collected in 2 directions: perpendicular and parallel to the main residual current, 0, 25 and 200 m from 2 salmon farms (Millstone and Cranford) located in Mulroy Bay, Ireland. In addition, artificial substrates were placed for 2 mo at 1 m depth 0, 25 and 200 m from one farm to trace the uptake of farm-related nutrients by fouling organisms. The extent of measurable change in benthic communities (abundance, diversity, structure, trophic composition) depended on residual current direction. Intraspecific variation in isotopic values in benthic invertebrates was mostly explained by distance from cages. Organisms collected at impacted sites exhibited a shift in isotopic composition towards that of farm wastes. A shift in δ13C was observed in several invertebrates, including the polychaetes Malacoceros fuliginosus and Nephtys hombergii, Nematoda and the anemone Anthopleura balii. Fouling communities collected on artificial structures, mainly composed of the tunicate Ascidiella aspersa, showed higher δ15N values at fish cage sites compared to sites 200 m away. The study demonstrated that fish effluents were assimilated and became food sources for several organisms.

<strong>Biodiversity of polychaetous annelids from the peninsula of Cap Bon, northeast coast of Tunisia</strong>

in Tunisia, polychaete studies are very rare (Fauvel 1924 a, b; Westheide 1972; Zibrowius 1970, 1971; Cantone 1978; Ben Amor 1984; Zaâbi & Afli 2005). The aim of this study was to update and fill in gaps in data of polychaetes of Tunisia. Samples were taken aboard the research vessel R/V Hannibal with a Van Veen grab (0.1 m²) and a core (0.009 m²). Nine sites located on the peninsula of Cap Bon on the NE coast of Tunisia, from Sidi Daoud to Ras Lahmer, were sampled in 2005 and 2006. A total of 5,920 individuals in 29 families and 88 species of polychaetes were identified. Twenty-nine species were newly recorded for Tunisia, including the ampharetid Isolda pulchella O.F. Müller, 1858 and the paraonid Aricidea cerrutii (Laubier, 1966). Diversity parameters were established. Abundance and species richness were higher in shallow waters dominated by Protodorvillea kefersteini (McIntosh, 1869) and Malacoceros fuliginosus (Claparède, 1868) than in deep waters where Aponuphis fauveli (Rioja, 1918) and Euclymene palermitana (Grube, 1840) dominated. Multivariate methods, including the Shannon diversity index, cluster analysis, and rank frequency analysis, were used to characterize the spatial structure and temporal variability of the different communities.

Phylogeny of the mud worm genus Marenzelleria (Polychaeta, Spionidae) inferred from mitochondrial DNA sequences

The taxonomy of the cryptic morphospecies of the mud worm genus Marenzelleria is particularly difficult and the phylogenetic relationship within the genus is unknown. Herein we reconstructed the phylogeny of all five species of this genus using sequence data of three mitochondrial genes (16SrDNA, cytochrome b, cytochrome oxidase subunit I) from 104 specimens out of 26 populations. For the three invasive species of the genus, Marenzelleria neglecta, M. viridis and M. arctia, individuals from native populations as well as from recently invaded populations were included. Nuclear 18S rDNA sequences were used to evaluate the appropriate outgroup taxon among several spionid polychaete species. The results supported the monophyly of Marenzelleria, and Malacoceros fuliginosus was found to be a suitable outgroup for the analysis of the mitochondrial gene segments. All phylogenetic reconstructions revealed a basal position of M. arctia and M. wireni, which have primarily Arctic distribution, with M. arctia obtaining the most basal position. Together with the present‐day distribution of the species, this indicates an origin of the genus in the Arctic region. The relationship of the species M. neglecta, M. viridis and M. bastropi could not be resolved sufficiently due to genealogical discordance that might reflect relatively young cladogenetic events.

Biogeochemistry in highly reduced mussel farm sediments during macrofaunal recolonization by Amphiura filiformis and Nephtys sp.

Mussel farming is considered a viable means for reducing coastal eutrophication. This study assessed the importance of bioturbation by recolonizing fauna for benthic solute fluxes and porewater distributions in manipulated mussel farm sediments. Three consecutive time-series flux incubations were performed during an experimental period of three weeks in sieved farm sediment treated with the brittle star Amphiura filiformis and the polychaete Nephtys sp. The functional behavior of Nephtys sp. and interactions between Nephtys sp. and the spontaneously colonizing spionid Malacoceros fuliginosus determined the biogeochemical response in the Nephtys sp. treatment. For example, the oxic zone was restricted and benthic nitrate and silicate fluxes were reduced compared to the brittle star treatment. A. filiformis seemed to enhance the bioadvective solute transport, although an increased supply of oxygen was due to the highly reducing conditions of the sediment mainly seen as secondary effects related to porewater distributions and benthic nutrient fluxes.

Annelid fauna of a Mediterranean lagoon (Gialova Lagoon, south-west Greece): community structure in a severely fluctuating environment

The annelid community of a shallow Mediterranean lagoon (Gialova Lagoon, Ionian Sea) was studied on a seasonal basis. Out of the 39 species identified eight are reported for the first time from the central Mediterranean. The dominant species were the polychaetes Capitella capitata, Neodexiospira pseudocorrugata, Malacoceros fuliginosus, Perinereis cultrifera, Hediste diversicolor, Heteromastus filiformis and the oligochaete Limnodriloides maslinicensis. Uni- and multivariate methods were employed to study the community structure. The coenocline observed is strongly related to the degree of isolation; its main features (i.e. number of species, density, geometric abundance and size-classes) in space and time are presented and discussed in detail. The distribution pattern of the annelid community has been found to be governed by a different set of environmental factors in each season. Although this narrow lagoonal habitat suffers severe dystrophic episodes it manages to recover, demonstrating a seasonal community pattern.

Setal Structure and Chaetogenesis in Scolelepis squamata and Malacoceros fuliginosus (Spionidae, Annelida)

AbstractIn Scolelepis squamata and Malacoceros fuliginosus two alternatingly arranged transverse rows of setae are found in each ramus. These are capillary setae in all thoracic setigers, whereas in abdominal setigers they may alternate with hooded hooks. In M. fuliginosus only the abdominal neuropodia bear hooded hooks, whereas in S. squamata these setae are present in both rami in the abdomen. Here every second seta (the capillary one) degenerates before its formation is complete, leading to a single row of hooded hooks. In the transverse rows new setae are formed in a medio‐lateral formative site in both species. Additionally in each ramus there exists one longitudinal row of capillaries which each possesses its own formative site. Ultrastructure and formation of the hooded hooks in S. squamata is very similar to that of hooded hooks in Capitellidae. The hood is preformed by a certain group of microvilli of the chaetoblast, which soon differentiates two layers of microvilli, raising an inner and an outer hood lamella. The hooded hooks and their arrangement are regarded as homologous characters in Spionidae and Capitellidae. This indicates a closer relationship of Spionidae with a taxon consisting of Capitellidae, Arenicolidae, Maldanidae, Oweniida, Terebellida, Sabellida, and Pogonophora.

Colonisation patterns of adult macrobenthos in a polluted North Sea estuary.

Natural or anthropogenic disturbances, such as those caused by storm events, dredging, or pollution can lead to total or partial defaunation of sediments. Following such events, recovery of the community occurs through an influx of adults and propagules. The numbers and species of individuals arriving in the initial phase might be expected to vary according to natural environmental factors. In this study, adult macrofaunal colonisation was investigated with respect to season and tidal flow. Trays of azoic sediment were placed subtidally in the Tyne estuary, north-east England for 24 h periods, at approximately 4 week intervals between November 1992 and June 1994. Colonisation by the crustacean Parathalestris clausi, the oligochaete Tubificoides benedii and the polychaete Ophryotrocha hartmanni varied significantly with season, but not with tidal range. Colonisation of the sediments by the crustacean Carcinus maenas varied significantly with tidal range, but not with season. Colonisation by the polychaetes Capitella spp., Phyllodoce maculata, Eteone longa, Malacoceros fuliginosus, Nereis diversicolor,andTharyx spp. did not vary significantly according to season or tidal range.

Responses of estuarine benthic macrofauna in copper-contaminated sediments to remediation of sediment quality

A 2-year microcosm experiment was undertaken to investigate the impact of copper on the benthic fauna of the lower Tyne Estuary (UK). During a 1-year simulated contamination period, 1 mg l −1 copper was supplied at 2-weekly 30% water changes, at the end of which the sediment concentrations of copper in contaminated microcosms reached 411 μg g −1. Toxicity effects reduced populations of the four dominant taxa ( Malacoceros fuliginosus, Capitella capitata, nematodes and Tubificoides spp.). When copper dosage was ceased and clean water supplied, sediment copper concentrations fell by 50% in less than 4 days, but faunal recovery took up to 1 year, with the pattern varying between taxa. Since the copper leach rate was so rapid it is concluded that after remediation, contaminated sediments show rapid improvements in chemical concentrations, but faunal recovery may not be detected until some time later. Reasons for this are discussed.

Toxicity of sewage sludge to marine organisms: A review

Results of laboratory, mesocosm, and field studies on the toxicity of sewage sludge to marine organisms are summarised. The 24 taxa tested included adults, juveniles, larvae, embryos, sperm and algal zoospores. These toxicity studies are discussed in relation to sewage sludge dispersion and dilution, and observed effects in the field. The 96 h LC 50 averages for sewage sludges ranged from 20% wet volume of sludge in seawater for polychaetes ( Malacoceros fuliginosus and Scolelepis squamata) to 0·0003% for shrimp larvae ( Crangon crangon). One third of the tests reviewed found minimum toxic concentrations of less than or equal to 0·1%. The cause of toxicity cannot be attributed to any single component, but contaminants from industrial wastes can be a significant factor. There is no indication of any build up of toxicity in the studies. Components of sewage can be utilised by phytoplankton, zooplankton, detrivorous invertebrates, and ingested by fish. Bioaccumulation of contaminants can occur through the diet. In general, dilution after dumping at sea is less than 0·1% (1 in 1000) within 30 min and 0·01% within 1 h. Based on these figures, acute toxicity is unlikely to occur at ecologically significant or detectable levels at dump sites. However, at some dump sites chronic effects due to organic enrichment are evident as changes in the species richness, relative abundance, and biomass of macroinvertebrate species.

Elevage de spionidés (Annélides, Polychètes) en cycle complet

Techniques for the laboratory culture of larvae and adults belonging to the “form C” of Malacoceros fuliginosus are described. Larvae can develop under different experimental conditions: • - In stagnant water, without an aeration system: 100 larvae are maintained in 150 cc of sea water. Under these conditions it is important to feed the animals with very small amounts of food. • - In aerated water: 100 or 200 larvae grown in 1.2 l water; bubbles must be large because very small ones are ingested and larvae die after intestinal occlusion. Growth and survival are better than in static conditions. • - In mechanically agitated sea water: 5000 larvae in 12 or 18 l water. At 19°C larval development lasted between 9 and 14 days, depending on diet and rearing conditions. After metamorphosis, sexual maturity was reached in 1 month. For larvae, various kinds of strictly artificial diets were used: • - macrophytic algae ( Padina, Ulva, Enteromorpha), • - lyophilised (Cerophyl) or congealed cereal germ, • - different diets for fish and human alimentation. Most of these diets were ground in a mortar with an organic sand, then filtered through a sieve of 20 or 56 μm, and diluted in sea water. Algae were dispensed according to two different schemes: either a constant amount of food was given every day [between 0.1 and 1 mg/day (dry weight)] or the amount of food was increased over 2 or 3 days (between 0.045 and 0.470 mg/day the last day). In non-aerated sea water, good results were obtained with Cerophyl and Enteromorpha; other diets were inadequate. With air bubbles, almost all diets enabled metamorphosis to take place. In mechanically agitated water and Ulva plus Enteromorpha, over 95% of larvae developed to metamorphosis. The diet ratio varied between 2.3 and 9.4 mg/day. Adults were reared under one of three conditions: (a) non-aerated (one pair in 150 cc), (b) mechanically agitated (3000–5000 individuals), (c) in a recirculating system (several thousand individuals in 100 l). However, attempts to rear large numbers of adults failed. There was always significant mortality, even though numerous cocoons were deposited. Tetramin was the only satisfactory diet for adults. Advantages of agitation are discussed from different points of view: survival, rate of development, nutrition, maintenance of good conditions, and inhibition of bacterial development. A comparison with other techniques of agitation and a review of different inert diets offered to polychaete and mollusc larvae are proposed.

Life History Patterns of Polychaete Species of the Family Spionidae

The reproductive morphology and larval development in Spionidae has been dealt with extensively by Soderström (1920), Hannerz (1956), Orrhage (1964). Simon (1967), Blake (1969) and Rice (1980). The family shows a considerable variation in gamete morphology, modes of sperm transfer and types of larval development. One might also expect variability in features of the life history patterns, such as the life span, reproductive age, reproductive cycles and fecundity, both between and within species.Previous population studies on spionids include the work on populations of Polydora ciliata (Johnston) (Dorsett, 1961); (Daro & Polk, 1973), on populations of Scolelepis squamata (Müller) (Joyner, 1962); (Richards, 1970), on a population of Scolecolepides viridis (Verrill) (George, 1966) and on a laboratory reared population of Malacoceros cf. fuliginosus (Guérin, 1973). The present paper is an attempt to analyse the patterns of life history as they appear in littoral populations of Spio martinensis Mesnil, Polydora ciliata (Johnston), Pygospio elegans Claparede and Malacoceros fuliginosus (Claparède) at localities in N. E. England. The main features considered here are the changes in the size (age) distributions, the annual cycles of reproduction, the output of offspring and population density changes.The Spio species in the population at Black Middens, North Shields, which is referred to S. martinensis Mesnil (1896) in this paper, was previously referred to S. filicornis (Müller, 1776) by Brady (1943). This species is identical to Mesnil's species, both in morphology and with regard to known biological features, while S. filicornis differs from it morphologically and its distribution pattern (Hannerz, 1956; Rasmussen, 1973; Wolff, 1973, Gudmundsson, in preparation).

Browsing: Important in marine sedimentary environments? spionid polychaete examples

Data on the morphology and behavior of five species of spionid polychaete from muddy sand habitats in both the United Kingdom and the northwest coast of North America are presented. The data are consistent with the hypothesis that browsing predation by visual predators is important now and has been important in the evolutionary past. As predicted by such a hypothesis, regenerating individuals are common in all the populations examined. Individuals belonging to species that expose their anterior ends while feeding and/or defecating have cryptic anteriors ( Pygospio elegans Claparède, Rhynchospio glutaeus (Ehlers), Malacoceros fuliginosus (Claparède), and Spiophanes bombyx (Claparède)). Individuals belonging to species that do not expose their anteriors while feeding and/or defecating do not have cryptic anteriors ( Pseudopolydora kempi (Southern)). Given these data it is still unclear as to how many of the geographic patterns of coloration that have been reported for infauna are associated with the presence of visual predation. Further investigations are suggested.