On the morphology of elytra as luminescent organs in scale-worms (Polychaeta, Polynoidae)

11 páginas, 8 figuras, 1 tabla.Polynoid polychaetes are common marine invertebrates worldwide that are characterized by bearing series of paired elytra attached to dorsal prominences (the elytrophores) arising from the notopodia, and whose dorsal surface is usually ornamented with different papillae (usually thought to be sensory organs). Upon stimulation, some species of the sub-family Polynoinae are able to emit light flashes from the ventral epithelium of the elytra. This bioluminescence originates in a protein called polynoidin, and seems to be induced by the destruction of the electrochemical coupling between body and elytra when the latter are detached. However, the elytral structure, as well as the function of the papillae and tubercles in relation to the bioluminescence is poorly known. In this paper, we report on the elytral morphology of two “luminescent” and two “non-luminescent” (Nicol 1953) species from the White and Mediterranean Seas. In both polynoid types, the elytral tubercles are formed by a layer of hard, nonorganized, autofluorescent tissue, apparently filled by expansions protruding from cells forming a distinct subjacent layer. Our study allowed us to suggest that the luminescent protein is located in the cells of the basal layer, while the tubercles may act as lenses helping in the light flash transfer towards the exterior. The reasons why the studied species are or are not bioluminescent are discussed.This paper has been possible thanks to a grant of the Spanish Agency for the International Cooperation (AECI) of the “Ministerio de Esuntos Extrangeros” to the first author and a grant of the Russian Foundation for Basic Research 07-04-01545-a. The paper is a contribution to the project MARMOL (Ref Numb. CTM2007-66635-CO2-01) financed by the Spanish Commission of Science and Technology (CICYT).Peer reviewe

Eupolymnia nebulosa (Montagu, 1818) revisited: An hommage to Michel Bhaud

PósterEupolymnia nebulosa (Montagu, 1818) is a sedentary, tubicolous polychaete, inhabiting shallow waters with mixed soft and hard bottoms. It has a wide geographical distribution, which includes the Atlanto-Mediterranean Europe coasts and has been reported as having different life cycles (i.e. free-spawning and egg-brooding) in different locations (Atlantic and Mediterranean, respectively). No morphological or genetic inter-specific differences have been demonstrated between them since the first attempt by Guy Lenaers and Michel Bhaud based on French English Channel and Gulf of Lions populations. The objectives of this study are: (1) to check the postulated restriction of egg brooding in the Mediterranean and (2) to assess the possible existence of cryptic species using molecular markers, based on several Mediterranean and Atlantic populations from France, Spain, Portugal, Great Britain, and Norway.Peer reviewe

Submarine canyons as the preferred habitat for wood-boring species of Xylophaga (Mollusca, Bivalvia)

13 páginas, 9 figuras, 5 tablas.Submarine canyons are often viewed as natural “debris concentrators” on the seafloor. Organic substrates may be more abundant inside than outside canyon walls. To determine the effects of the presence these substrates in the Blanes submarine canyon (NW Mediterranean) and its adjacent western open slope, we deployed wood to study colonizing organisms. Three replicate pine and oak cubes (i.e. most common trees inland) were moored at 900, 1200, 1500 and 1800 m depth and collected after 3, 9 and 12 months. Wood from inside the canyon was significantly more heavily colonized by the five morphotypes of wood-boring bivalves than was wood on the adjacent open slope. Xylophaga sp. A dominated all wood types and locations, with peak abundance at 900 and 1200 m depth. Its growth rate was highest (0.070 mm d−1) during the first three months and was faster (or it recruits earlier) in pine than in oak. Size distribution showed that several recruitment events may have occurred from summer to winter. Xylophaga sp. B, appeared first after 9 months and clearly preferred pine over oak. As the immersion time was the same, this strongly supported a specific association between recruiters and type of substrate. Three morphotypes, pooled as Xylophaga spp. C, were rare and seemed to colonize preferentially oak inside the canyon and pine in the adjacent open slope. Individuals of Xylophaga were more abundant inside the canyon than in nearby off-canyon locations. Blanes Canyon may serve as a long-term concentrator of land-derived vegetal fragments and as a consequence sustain more animals.The present work was developed within the framework of the projects PROMETEO (CTM2007-66316-C02-02/MAR) and DOSMARES (CTM2010-21810-C03-03).The study is also a contribution of C.R. and D.M. to the Consolidated Research Group 2009SRG655 of the “Generalitat de Catalunya”.Peer reviewe

Innervation of luminescence in scale-worms (Polychaeta, Polynoidae)

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Population ecology of two scale-worm polychaetes

9 páginas, 7 figuras, 1 tabla.INTAS-OPEN-97-0916Peer reviewe

Role of diet on population dynamics of the scale-worms Lepidonotus squamatus and Harmothoe imbricata(Polychaeta, Polynoidae) in the White Sea

11 páginasUnder the harsh environmental conditions of the White Sea, the polynoid polychaetes Lepidonotus squamatus and Harmothoe imbricata coexist in the same habitats, often showing recurrent alternations in dominance. The present study focused on their diet and food preferences based on the analyses of gut contents (after dissection of preserved specimens) and faecal pellets (released by selected living specimens). Our results pointed out that the dietary regimes were significantly dependent on the collection site (and the respective dominant prey species) and not on the scale-worm species, suggesting that L. squamatus and H. imbricata are non-selective at the species level. There was also a significant overlap of their dietary regimes and our data support the existence of intra- and inter-specific aggressive behaviour, with H. imbricata being more aggressive than L. squamatus. These findings, combined with their life cycle strategies and other biological and environmental constraints, arose as significant driving forces explaining the population dynamics of the two studied scale-worms in the White Sea.Peer reviewe

Life cicle strategy and population ecology of polychaete polynoids Lepidonotus squamatus and Harmothoe imbricata in the White Sea

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Microbial communities associated with the degradation of oak wood in the Blanes submarine canyon and its adjacent open slope (NW Mediterranean)

7 páginas, 5 figuras, 2 tablas.Submarine canyons can trap and concentrate organic falls, like terrestrial debris, including wood. Sunken wood creates a unique ecosystem in the deep sea, which base, i.e. the microbial communities directly degrading this wood, remains poorly studied. Our aim was thus to examine the wood degrading microbial community by comparing oak samples experimentally deployed in experimental mooring arrays in the Blanes Canyon (BC) and its adjacent open slope (NW Mediterranean Sea). We analyzed the microbial community by parallel tag pyrosequencing of the16S rRNA genes from wood samples recovered from different depths after 9 and 12 months of deployment. In this first study of the phylogenetic description of wood associated microbial community by high throughput molecular techniques, we found that the microbial diversity was higher in samples from BC compared to the open slope. The structure of the communities were, however, not significantly different from each other, although we observed an apparent clustering according to time of immersion. Furthermore, an in depth taxonomic analysis revealed that Alphaproteobacteria was the dominant microbial taxa, with the Roseobacter clade seeming to have a specialized role in the degradation of oak in BC and its adjacent slope.The research conducted by SKF and PEG is supported by the Agence Nationale de la Recherche (ANR) through the MICADO project (ANR-11-JSV7-003-01).The present work was developed within the PROMETEO (CTM 2007- 66316-C02-02/MAR), DOS MARES (CTM2010-21810-C03-03/ MAR) and HERMIONE (European Community FP7/2007-2013, grant agreement n 226354) projects, and is a contribution of CR and DM to the Consolidated Research Group 2009SRG665 of the ‘‘Generalitat de Catalunya’’. CR was supported by a JAE postdoctoral fellowship. This work was also funded by CNRS and by the UMPC-Fondation TOTAL chair ‘Extreme marine environments, biodiversity and global change’. The LECOB group is part of the GDRE DIWOOD research network supported by CNRS.Peer reviewe

Spectral characteristics of the fluorescence in scale worms (Polychatea, Polynoidae)

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