Search

Family Trichobranchidae Malmgren, 1866 Figs 1A, 7���8 Diagnosis (after Hutchings et al. 2021a, most important diagnostic characters highlighted in bold) Transverse prostomium attached to dorsal surface of upper lip; basal part as thick crest, eyespots sometimes present; distal part at base of upper lip or extending along lip. Buccal tentacles of two types, uniformly cylindrical and expanded at tips, spatulate. Peristomium forming lips, sometimes also a ventral lobe, as an extension of the lower lip; lips expanded, circular upper lip, distal margin folded or convoluted; lower lip button-like, usually continuing by ventral lobe, or expanded, forming large scoop-shaped process (Figs 7A���C, 8A, C���D). Segment I usually short, frequently only visible ventrally; anterior margin of anterior segments with lobes as low, even-length collars covering posterior margins of preceding segments, at least ventrally; ventro-lateral or lateral lobes on anterior segments sometimes present. Anterior segments poorly glandular ventrally, smooth, discrete shields absent; midventral groove extending from posterior segments with notopodia. Two to four pairs of branchiae, beginning from SGII, each pair with single, thick and elongate, tapered or foliaceous filament, or two pairs fused in single four lobed structure originating mid-dorsally between SGII���III or II���IV (Figs 7C, 8C���D). Notopodia beginning from SGIII���VI, typically terminating at SGXX; short, conical notopodia, chaetae emerging from central core on top, distal lobes absent; narrowly-winged notochaetae in both rows throughout. Neuropodia beginning on same segment as notopodia or slightly posteriorly, rarely beginning before notopodia; sessile neuropodia until termination of notopodia, neurochaetae emerging directly from body wall, as rectangular to foliaceous pinnules after termination of notopodia; thoracic neurochaetae as acicular uncini (Figs 1A, 7D, 8F), sometimes with small hood or beard below main fang; avicular abdominal uncini, with secondary teeth in rows on top and laterally to main fang. Nephridial papillae on SGIII usually present, other papillae sometimes present on SGVI and SGVII, but reduced to inconspicuous in most taxa. Pygidium smooth to slightly crenulate, sometimes bilobed. Remarks In the past, the Trichobranchidae family was considered to be a subfamily of Terebellidae (Fauvel 1927; Day 1967; Garrafoni & Lana 2004), but recent phylogenetic analyses support the hypothesis of a valid family (Glasby et al. 2004; Nogueira et al. 2013). The family includes only three genera, i.e., Octobranchus Marion & Bobretzky, 1875, Terebellides Sars, 1835, and Trichobranchus Malmgren, 1866. For Trichobranchus and Octobranchus, only three species of each occur in Europe. The genus Terebellides is very speciose and is represented in Europe by 19 species, 13 of them described in the last two years (Lavesque et al. 2019b; Parapar et al. 2020a) (Table 1). Main morphological characters for European species The number of branchiae is the best character to discriminate the different genera, with Terebellides having a single large branchia, Trichobranchus with two or three pairs of branchiae and finally Octobranchus with four pairs. Trichobranchus species are easy to differentiate based on the number of branchiae (two vs three) (Figs 7C, 8C) and the absence or presence of eyespots. In Octobranchus, the species differ by the shape of the branchiae (Fig. 8D) and the number of secondary teeth above the main fang of the uncini. Regarding Terebellides species, recent studies highlighted that several characters are very important for identification to the species level (Lavesque et al. 2019a; Parapar et al. 2020a, 2020b). However, as many cryptic species occur at a small geographical scale (Nygren et al. 2018), which currently are confirmed only by molecular analyses (Parapar et al. 2020a) much more work needs to be done to resolve all the species present. BRANCHIAE. Even if Terebellides branchiae seem to be very similar within the genus (Figs 7A���B, 8A���B), several morphological characters permit the discrimination of species, such as the presence of a fifth anterior branchial lobe (e.g., T. europaea), the degree of fusion of both upper and lower lobes (e.g.. not fused on T. ceneresi), the presence of long terminal filaments (e.g., in T. shetlandica) or short posterior processes (Fig. 7B), and finally the presence and the shape of papillae situated on the margins of the branchial lamellae (Fig. 8B) (e.g., T. lilasae). NOTOCHAETAE FROM FIRST CHAETIGER. The size of notochaetae of the first chaetiger varies between species. For most of the species, these chaetae are of a similar size compared to those of the following chaetigers. However, they can be absent or much shorter (e.g., T. ceneresi) or much longer (e.g., T. mediterranea). PRESENCE OF GENICULATE CHAETAE ON ONE OR TWO CHAETIGERS. The geniculate chaetae are exclusive to members of Terebellides and they are typically present on CH 6 (SG VIII) only (Fig. 8E), but in some species they are present on two chaetigers, as for example in T. bigeniculatus. UNCINI DENTICULATION. The different types of uncini follow the classifications provided by Parapar et al. (2020b) for thoracic uncini (Fig. 8F) and Parapar et al. (2020a) for abdominal uncini. These classifications are based on the ratio between the length of the main fang (rostrum) and the crest of secondary teeth (capitium), and the size and number of the secondary teeth. THORACIC CILIATED PAPILLAE. Following the recent study of Parapar et al. (2020a), the absence or the presence of thoracic ciliated papillae allow for the discrimination of Terebellides species. These papillae are situated dorsally to the thoracic notopodia (see for example Parapar et al. 2020a; Fig. 7B). METHYL GREEN PATTERN. The colouration of Terebellides specimens prior to identification is essential. Indeed, MG staining highlights the presence and the shape of the glandular region of the third thoracic chaetiger (e.g., undulating glandular region present and in members of T. gentili, oval for T. lilasae Fig. 7B) and the compact/striped pattern of the ventral part of anterior chaetigers (e.g., CH 4 (SG VI) white in T. ceneresi). Key to European species of Trichobranchidae (after Lavesque et al. 2019a and Parapar et al. 2020a) 1. One large branchia consisting of a stem and four lobes with transverse lamellae.....5 (Terebellides) ��� Two or three pairs of branchiae........................................................................... 2 (Trichobranchus) ��� Four pairs of branchiae........................................................................................... 4 (Octobranchus) 2. Two pairs of branchiae...................................................................................................................... 3 ��� Three pairs of branchiae, eyespots present................................................................................................................................................................................. Trichobranchus glacialis Malmgren, 1866 3. Eyespots absent......................................................................... Trichobranchus roseus Malm, 1874 ��� Eyespots present.................................................................................................................................... Trichobranchus demontaudouini Lavesque, Hutchings, Daffe, Nygren & Londo��o-Mesa, 2019 4. Pairs of branchiae of different shapes; abdominal uncini with three rows of secondary teeth above the main fang..................................................... Octobranchus floriceps Kingston & Mackie, 1980 ��� All pairs of branchiae similar; abdominal uncini with two rows of secondary teeth above the main fang..................................................................................... Octobranchus lingulatus (Grube, 1863) ��� Bases of branchiae covered by dorso-lateral lobes, abdominal uncini with two rows of secondary teeth above the main fang.............................. Octobranchus sikorskii (Leontovich & Jirkov. 2001) 5. Geniculate acicular chaetae on CH 5 (SG VII) and CH 6 (SG VIII)............................................................................................................. Terebellides bigeniculatus Parapar, Moreira & Helgason, 2011 ��� Geniculate acicular chaetae on CH 6 (SG VI) only........................................................................... 6 6. Branchial lamellae without marginal papillae.................................................................................. 7 ��� Branchial lamellae with marginal papillae..................................................................................... 15 7. Lower branchial lobes with long filaments....................................................................................... 8 ��� Lower branchial lobes with or without short projections................................................................. 9 8. Glandular region on CH 3 (SG V) present; branchial lamellae pointed; notochaetae from CH 1 longer than following ones; dorsal papillae absent............................................................................................................... Terebellides parapari Lavesque, Hutchings, Daffe, Nygren & Londo��o-Mesa, 2019 ��� Glandular region on CH 3 (SG V) absent; branchial lamellae rounded; all notochaetae equal-sized; dorsal papillae present........................ Terebellides shetlandica Parapar, Moreira & O���Reilly, 2016 9. Ventral white band present on CH 4 (SG VI) after MG staining..................................................... 10 ��� No distinct pattern on CH 4 (SG VI) after MG staining...................................................................11 10. Large species (> 30 mm); 5 th branchial lobe present; notochaetae of CH 1 (SG III) similar to following ones; main fang of thoracic uncini straight.................................... Terebellides gracilis Malm, 1874 ��� Small species (Terebellides ceneresi Lavesque, Hutchings, Daffe, Nygren & Londo��o-Mesa, 2019 11. First notopodia and notochaetae longer than following ones............................................................................................................................... Terebellides mediterranea Parapar, Mikac & Fiege, 2013 ��� First notopodia and notochaetae similar or shorter than following ones........................................ 12 12. Large-sized species (> 50 mm); dorsal rounded projections on CH 1��� CH 5 conspicuous............... 13 ��� Small-sized species (Terebellides kongsrudi Parapar, Capa, Nygren & Moreira, 2020 and Terebellides bakkeni Parapar, Capa, Nygren & Moreira, 2020 complex ��� Abdominal uncini of type 2 (capitium of about same length as main fang, capitium complex composed of a first row of 4(5) denticles and a variable number of teeth in two more rows)..................................................................................................................... Terebellides stroemii Sars, 1835 14. Glandular region on CH 3 (SG V) and 5 th branchial lobe both absent................................................................................................................................................... Terebellides atlantis Williams, 1984 ��� Glandular region on CH 3 (SG V) and 5 th branchial lobe both present............................................................................ Terebellides gralli Lavesque, Hutchings, Daffe, Nygren & Londo��o-Mesa, 2019 15. Glandular region on CH 3 (SG V) rounded or oval......................................................................... 16 ��� Glandular region on CH 3 (SG V) otherwise.................................................................................. 17 16. Glandular region on CH 3 (SG V) staining in white, branchial lamellae with rounded papillae, CH 1��� 3 without conspicuous dorsal projection....................................................................................................................... Terebellides lilasae Lavesque, Hutchings, Daffe, Nygren & Londo��o-Mesa, 2019 ��� Glandular region on CH 3 (SG V) staining in blue, branchial lamellae with conical papillae, CH 1���3 with conspicuous dorsal projection................................................................................................................................ Terebellides bonifi Lavesque, Hutchings, Daffe, Nygren & Londo��o-Mesa, 2019 17. Most branchial lamellae with marginal papillae............................................................................. 18 ��� Only anterior branchial lamellae with marginal papillae................................................................ 19 18. Branchial lamellae with digitiform papillae, upper lip elongated; MG staining pattern as compact bands from CH 1���5.................................................................................................................................................... Terebellides resomari Lavesque, Hutchings, Daffe, Nygren & Londo��o-Mesa, 2019 ��� Branchial lamellae with widely spaced, small and elongated digitiform papillae; MG staining pattern leaving white stripes from CH 1���5................................................................................................................................ Terebellides gentili Lavesque, Hutchings, Daffe, Nygren & Londo��o-Mesa, 2019 19. Thoracic uncini type 1 (main fang vs capitium length ratio 2(3)/1; capitium with 2(3) large teeth, following ones much smaller).................................................................................................................................................................. Terebellides ronningae Parapar, Capa, Nygren & Moreira, 2020 ��� Thoracic uncini type 3 (main fang vs. capitium length ratio 1/1; capitium with 4(5) mid-sized teeth, following ones slightly smaller)..................................................................................................... 20 20. Deep-water species, mostly found below 200 m deep.............................................................................................................................. Terebellides norvegica Parapar, Capa, Nygren & Moreira, 2020 ��� Shallow-water species, mostly found above 100 m deep.................................................................................. Terebellides europaea Lavesque, Hutchings, Daffe, Nygren & Londo��o-Mesa, 2019 and Terebellides scotica Parapar, Capa, Nygren & Moreira, 2020 complex, Published as part of Lavesque, Nicolas, Hutchings, Pat, Londo��o-Mesa, Mario H., Nogueira, Jo��o M. M., Daffe, Guillemine, Nygren, Arne, Blanchet, Hugues, Bonif��cio, Paulo, Broudin, Caroline, Dauvin, Jean-Claude, Droual, Gabin, Gouillieux, Benoit, Grall, Jacques, Guyonnet, Benjamin, Houbin, C��line, Humbert, Suzie, Janson, Anne-Laure, Jourde, J��r��me, Labrune, C��line, Lamarque, Bastien, Latry, Lise, Garrec, Vincent Le, Pelaprat, Corine, Pezy, Jean-Philippe, Sauriau, Pierre-Guy & Montaudouin, Xavier De, 2021, The " Spaghetti Project ": the final identification guide to European Terebellidae (sensu lato) (Annelida, Terebelliformia), pp. 108-156 in European Journal of Taxonomy 782 (1) on pages 136-141, DOI: 10.5852/ejt.2021.782.1593, http://zenodo.org/record/5781605, {"references":["Malmgren A. J. 1866. Nordiska Hafs-Annulater. Ofversigt af Kongliga Vetenskaps-Akademiens Forhandlingar 22: 355 - 410. Available from https: // www. biodiversitylibrary. org / part / 244483 [accessed 8 Nov. 2021].","Hutchings P., Nogueira J. M. N. & Carrerette O. 2021 a. Terebellidae Johnston, 1846. In: Schmidt- Rhaesa A. Hr., Beutel R. G., Glaubrecht M., Kristensen N. P., Prendini L., Purschke G., Richter S., Westheide, W. & Leschen R. Z. E. (eds) Handbook of Zoology. A Natural History of the Phyla of the Animal Kingdom: 1 - 64. Walter de Gruyter & Co, Berlin.","Fauvel P. 1927. Polychetes Sedentaires. Addenda aux Errantes, Archiannelides, Myzostomaires. Faune de France 16, Lechevalier, Paris.","Day J. H. 1967. A Monograph on the Polychaeta of Southern Africa. Part 2. Sedentaria. Trustees of the British Museum (Natural History), London. https: // doi. org / 10.5962 / bhl. title. 8596","Glasby C. J., Hutchings P. & Hall K. 2004. Assessment of monophyly and taxon affinities within the polychaete clade Terebelliformia (Terebellida). Journal of the Marine Biological Association of the United Kingdom 84: 961 - 971. https: // doi. org / 10.1017 / S 0025315404010252 h","Nogueira J. M. M., Fitzhugh K. & Hutchings P. 2013. The continuing challenge of phylogenetic relationships in Terebelliformia (Annelida: Polychaeta). Invertebrate Systematics 27: 186 - 238. https: // doi. org / 10.1071 / IS 12062.","Marion A. F. & Bobretzky N. V. 1875. Etude des Annelides du Golfe de Marseille. Annales des Sciences Naturelles, Sixieme Serie 2: 1 - 106. Available from https: // www. biodiversitylibrary. org / page / 33155516 [accessed 8 Nov. 2021].","Sars M. 1835. Beskrivelser og Iagttagelser over nogle maerkelige eller nye i Havet ved den Bergenske Kyst Levende Dyr af Polypernes, Acalephernes, Radiaternes, Annelidernes og Molluskernes classer, med en kort Oversigt over de hidtil af Forfatteren sammesteds fundne Arter og deres Forekommen. T. Hallager, Bergen. https: // doi. org / 10.5962 / bhl. title. 13017","Lavesque N., Daffe G., Grall J., Zanol J., Gouillieux B., Hutchings P. 2019 b. Guess who? On the importance of using appropriate name: case study of Marphysa sanguinea (Montagu, 1813). ZooKeys 859: 1 - 15. https: // doi. org / 10.3897 / zookeys. 859.34117","Parapar J., Capa M., Nygren A. & Moreira J. 2020 a. To name but a few: descriptions of five new species of Terebellides (Annelida, Trichobranchidae) from the North East Atlantic. ZooKeys 992: 1 - 58. https: // doi: 10.3897 / zookeys. 992.55977","Lavesque N., Hutchings P., Daffe G., Nygren A. & Londono-Mesa M. H. 2019 a. A revision of the French Trichobranchidae (Polychaeta), with descriptions of nine new species. Zootaxa 4664 (2): 151 - 190. https: // doi. org / 10.11646 / zootaxa. 4664.2.1","Parapar J., Martin D. & Moreira J. 2020 b. On the diversity of Terebellides (Annelida, Trichobranchidae) in West Africa, seven new species and the redescription of T. africana Augener, 1918 stat. prom. Zootaxa 4771 (1): 1 - 61. https: // doi. org / 10.11646 / zootaxa. 4771.1.1.","Nygren A., Parapar J., Pons J., Meissner K., Bakken T., Kongsrud J. A., Oug E., Gaev D., Sikorski A., Johansen R. A., Hutchings P., Lavesque N. & Capa M. 2018. A megacryptic species complex hidden among one of the most common annelids in the North East Atlantic. PLoS One 13 (6): e 0198356. https: // doi. org / 10.1371 / journal. pone. 0198356","Grube A. E. 1863. Beschreibung neuer oder wenig bekannter Anneliden. Sechster Beitrag. Archiv fur Naturgeschichte 29: 37 - 69. Available from https: // doi. org / 10.5962 / bhl. part. 9306 [accessed 8 Nov. 2021].","Malm A. W. 1874. Annulata i hafvet utmed Sveriges westkust och omkring Goteborg. Goteborgs Koniglich vetenskaps - och vitterhetssamhalles handlingar [Zoologiska observationer. VII.] 14: 67 - 105.","Kingston P. F. & Mackie A. S. Y. 1980. Octobranchus floriceps sp. nov. (Polychaeta: Trichobranchidae) from the northern North Sea with a re-examination of O. antarcticus Monro. Sarsia 65: 249 - 254. https: // doi. org / 10.1080 / 00364827.1980.10431487","Parapar J., Moreira J. & Helgason G. V. 2011. Taxonomy and distribution of Terebellides (Polychaeta, Trichobranchidae) in Icelandic waters, with the description of a new species. Zootaxa 2983 (1): 1 - 20. https: // doi. org / 10.11646 / zootaxa. 2983.1.1","Parapar J., Moreira J. & O'Reilly M. 2016. A new species of Terebellides (Polychaeta: Trichobranchidae) from Scottish waters with an insight into branchial morphology. Marine Biodiversity 46 (3): 211 - 225. https: // doi. org / 10.1007 / s 12526 - 015 - 0353 - 5","Parapar J., Mikac B. & Fiege D. 2013. Diversity of the genus Terebellides (Polychaeta: Trichobranchidae) in the Adriatic Sea with the description of a new species. Zootaxa 3691 (3): 333 - 350. https: // doi. org / 10.11646 / zootaxa. 3691.3.3","Williams S. J. 1984. The status of Terebellides stroemi (Polychaeta; Trichobranchidae) as a cosmopolitan species, based on a worldwide morphological survey, including description of new species. In: Hutchings P. A. (ed.) Proceedings of the First International Polychaete Conference, Sydney, Australia, 1984: 118 - 142. The Linnean Society of New South Wales, Sydney, Australia."]}

Family Polycirridae Malmgren, 1866 Figs 1B, 2 Diagnosis (after Hutchings et al. 2021a; most important diagnostic characters highlighted in bold) Transverse prostomium attached to dorsal surface of upper lip; basal part usually as thick horse-shoe shaped crest, eye spots absent; distal part either as another thick crest, with flaring distal lobes, with or without mid-dorsal process, or extending along upper lip until near anterior margin of lip; prostomium frequently extending ventrally, terminating laterally to mouth (Fig. 2A���D). Buccal tentacles of two types at least, short ones thin, uniformly cylindrical, long tentacles stouter, expanded at tips to variable degrees, distally spatulate (Fig. 2B, D) or more specialised. Peristomium forming lips; lips expanded, upper lip large, frequently circular and convoluted, folded into three lobes; swollen lower lip, only midventral or cushion-like across ventrum, sometimes extending posteriorly for a few segments (Fig. 2A��� D). Segment I reduced, frequently only visible ventrally, sometimes completely hidden. Segment II distinctly narrower than following segments, constricting body posteriorly to ���lips head���; SG II usually with rectangular or pentagonal mid-ventral shield at beginning of mid-ventral groove, sometimes extending anteriorly through SG I until near posterior margin of lower lip (Fig. 2C). Anterior segments highly glandular ventrally, frequently papillose or tessellated, with paired ventro-lateral pads separated from each other within pairs by mid-ventral groove extending from SG II���IV to posterior body (Fig. 2A���D). Branchiae absent. Notopodia, if present, from SG III (Fig. 2A���D), extending for variable number of segments, usually few; bilobed, elongate notopodia, post-chaetal lobes sometimes longer, notochaetae originating between lobes along all extension of notopodia, separating lobes from base on ventral side of notopodia (Fig. 2A���D); notochaetae winged (Fig. 2E) and/or pinnate, wings of variable width. Neuropodia, if present, located posteriorly to notopodia, frequently from posterior thoracic segments or only on abdomen; neurochaetae as acicular spines or avicular uncini, of two types, and arranged in a single row (Figs 1C, 2F���G). Nephridial and genital papillae usually present, at anterior bases of all notopodia, or only at anteriormost notopodia (Fig. 2A). Pygidium smooth or with rounded ventral papilla. Remarks This family was previously considered as a subfamily of Terebellidae (Polycirrinae Malmgren, 1866), but was recently raised to familial level after a comprehensive phylogenetic analysis showed the monophyly of this group (Nogueira et al. 2013). Polycirridae is represented by six genera (Amaeana Hartman, 1959; Biremis Polloni, Rowe & Teal, 1973; Enoplobranchus Verrill, 1879; Hauchiella Levinsen, 1893; Lysilla Malmgren, 1866 and Polycirrus Grube, 1850), distinguished from each other by the presence/ absence of noto- and neuropodia, and if present, the type of neurochaetae. Only Amaeana (Fig. 2A, C), Hauchiella, Lysilla and Polycirrus (Fig. 2B, D���G) are represented in European waters (Lavesque et al. 2020b) (Table 1). Main morphological characters of European species PARAPODIA. The parapodia of the members of this family are extremely important to separate the different genera. The genus Hauchiella is characterised by the absence of parapodia and Lysilla by the absence of neuropodia only. The neuropodia of members of Amaeana are characterised by the presence of spines, while those of Polycirrus bear avicular uncini (Figs 1B, 2F���G). Within the genus Polycirrus, the number and location of segments with notopodia and/or neuropodia are of important taxonomic value. Particularly, some species have uncini present only on abdominal segments, i.e., on segments without notopodia, and others have uncini starting before the end of the thorax, on segments bearing also notopodia. SHAPE OF THE LIPS. As for other terebellids, polycirrids have a peristomium with well-defined upper and lower lips. The upper lip is large and can be trilobed (Fig. 2B) or with a single medial lobe (Fig. 2D). Generally, the upper lip is trilobed but the lobes differ in size and shape and lateral lobes can be reduced or well developed. The shape and the size of the lower lip is also highly variable between species. This lip can be rectangular, squared, rounded or subtriangular, swollen or not, longer than wide or wider than long (Fig. 2B���D). . NOTOCHAETAE. Two types of notochaetae can be present: winged chaetae as for P. glasbyi (Fig. 2E) and/ or pinnate as for P. plumosus. The winged notochaetae have wings of different width which are often conspicuous under light microscope but appear hirsute under SEM (Fig. 2E). UNCINI SHAPE AND DENTICULATION. In Polycirrus two types of uncini are present: Type 1 with a short occipitum (back) and a straight to slightly convex base (Fig. 1B); and Type 2 with a long occipitum and a concave base (Glasby & Hutchings 2014). To date, all described European species have Type 1 uncini. The denticulation of uncini is also helpful in separating species, with the presence (as for P. catalanensis) (Fig. 2F) or the absence (as for P. arenivorus) of a main tooth above the main fang, and the number of rows of secondary teeth. Key to European species of Polycirridae (after Lavesque et al. 2020b) 1. Parapodia absent (no chaetae)............................................. Hauchiella tribullata (McIntosh, 1869) ��� Parapodia present.............................................................................................................................. 2 2. Only notopodia present....................................................................................................... 3 (Lysilla) ��� Notopodia and neuropodia present................................................................................................... 4 3. Notochaetae with smooth tips, 6 pairs of thoracic papillae............... Lysilla loveni Malmgren, 1866 ��� Notochaetae with plumose tips, 9 pairs of thoracic papillae............ Lysilla nivea Langerhans, 1884 4. Neuropodia with spines..................................................................................................5 (Amaeana) ��� Neuropodia with avicular uncini..................................................................................6 (Polycirrus) 5. Upper lip without lobe, lower lip rounded, long achaetous region.......................................................................................................... A. gremarei Lavesque, Hutchings, Daffe & Londo��o-Mesa, 2020 ��� Upper lip with trilobed, lower lip rectangular, short achaetous region......................................................................................................................................................... Amaeana trilobata (Sars, 1863) 6. With 28 or more segments with notochaetae.................................................................................... 7 ��� With 22 or fewer segments with notochaetae................................................................................... 8 7. With 29 segments with notopodia, neuropodia from SG XII, lower lip longer than wide, uncini without a main tooth above the main fang........................... Polycirrus arenivorus (Caullery, 1915) ��� With 46 segments with notopodia, neuropodia from SG XIV, lower lip longer than wide, uncini with a main tooth above the main fang............................................. Polycirrus aurantiacus Grube, 1860 ��� With 28 segments with notopodia, neuropodia from SG XV, lower lip wider than long, uncini with a main tooth above the main fang........................................................................................................................................... Polycirrus gujanensis Lavesque, Hutchings, Daffe & Londo��o-Mesa, 2020 8. Neuropodia beginning before SG VIII............................................................................................. 9 ��� Neuropodia beginning between SG IX and SG XII....................................................................... 10 ��� Neuropodia beginning after SG XIII.............................................................................................. 14 9. Upper lip trilobed, lower lip wider than long, uncini with 2 rows of teeth above the main tooth.......................................................................................... Polycirrus asturiensis Cepeda & Lattig, 2016 ��� Upper lip with single medial lobe, lower lip longer than wide, uncini with 1 row of teeth above the main tooth........................... Polycirrus idex Lavesque, Hutchings, Daffe & Londo��o-Mesa, 2020b 10. Uncini without a main tooth about the main fang.............. Polycirrus norvegicus Wollebaek, 1912 ��� Uncini with a main tooth about the main fang................................................................................11 11. Lower lip subtriangular, pointed towards mouth............................................................................ 12 ��� Lower lip oval or oblong................................................................................................................ 13 12. With 12 or 13 segments with notopodia, lower lip longer than wide......................................................................................................................................... Polycirrus denticulatus Saint-Joseph, 1894 ��� With 16 segments with notopodia, lower lip wider than long........................................................................................................................................................... Polycirrus elisabethae McIntosh, 1915 13. With 18 or more segments with notopodia, lower lip oval, ventro-lateral pads not separated by a large mid-ventral groove............................................................................................................................................................... Polycirrus glasbyi Lavesque, Hutchings, Daffe & Londo��o-Mesa, 2020 ��� Fewer than 18 segments with notopodia, lower lip oblong, ventro-lateral pads separated by a large midventral groove................ Polycirrus readi Lavesque, Hutchings, Daffe & Londo��o-Mesa, 2020 14. With 16 or more segments with notopodia..................................................................................... 15 ��� Fewer than 16 segments with notopodia........................................................................................ 17 15. Neuropodia beginning from SG XIV���XVI.................................................................................... 16 ��� Neuropodia beginning from SG XVIII���XX....................... Polycirrus plumosus (Wollebaek, 1912) 16. Upper lip elongated, uncini with a main tooth above the main fang, ventro-lateral pads well developed..................... Polycirrus nogueirai Lavesque, Hutchings, Daffe & Londo��o-Mesa, 2020 ��� Upper lip semicircular, uncini without a main tooth above the main fang, ventro-lateral pads poorly defined................................................................................................ Polycirrus arcticus Sars, 1865 17. Neuropodia beginning from SG XIV, uncini with four teeth above the main fang arranged in single vertical series; lower lip large, shield-like, wider than long......... Polycirrus latidens Eliason, 1962 ��� Neuropodia beginning from SG XV or after, secondary teeth of uncini not as above................... 18 18. Upper lip trilobed, lower lip subtriangular pointed toward mouth............................................................................................................................................................... Polycirrus medusa Grube, 1850 ��� Upper lip with a single median lobe, lower lip not subtriangular.................................................. 19 19. Upper lip with thick medial lobe, uncini with two small lateral teeth above the main tooth, lower lip rectangular longer than wide................................................................................................................................................ Polycirrus catalanensis Lavesque, Hutchings, Daffe & Londo��o-Mesa, 2020 ��� Upper lip with elongated triangular medial lobe, uncini with two rows of teeth above the main tooth, lower lip oval and wider than long.................................................................................................................................................... P. pennarbedae Lavesque, Hutchings, Daffe & Londo��o-Mesa, 2020, Published as part of Lavesque, Nicolas, Hutchings, Pat, Londo��o-Mesa, Mario H., Nogueira, Jo��o M. M., Daffe, Guillemine, Nygren, Arne, Blanchet, Hugues, Bonif��cio, Paulo, Broudin, Caroline, Dauvin, Jean-Claude, Droual, Gabin, Gouillieux, Benoit, Grall, Jacques, Guyonnet, Benjamin, Houbin, C��line, Humbert, Suzie, Janson, Anne-Laure, Jourde, J��r��me, Labrune, C��line, Lamarque, Bastien, Latry, Lise, Garrec, Vincent Le, Pelaprat, Corine, Pezy, Jean-Philippe, Sauriau, Pierre-Guy & Montaudouin, Xavier De, 2021, The " Spaghetti Project ": the final identification guide to European Terebellidae (sensu lato) (Annelida, Terebelliformia), pp. 108-156 in European Journal of Taxonomy 782 (1) on pages 112-123, DOI: 10.5852/ejt.2021.782.1593, http://zenodo.org/record/5781605, {"references":["Malmgren A. J. 1866. Nordiska Hafs-Annulater. Ofversigt af Kongliga Vetenskaps-Akademiens Forhandlingar 22: 355 - 410. Available from https: // www. biodiversitylibrary. org / part / 244483 [accessed 8 Nov. 2021].","Hutchings P., Nogueira J. M. N. & Carrerette O. 2021 a. Terebellidae Johnston, 1846. In: Schmidt- Rhaesa A. Hr., Beutel R. G., Glaubrecht M., Kristensen N. P., Prendini L., Purschke G., Richter S., Westheide, W. & Leschen R. Z. E. (eds) Handbook of Zoology. A Natural History of the Phyla of the Animal Kingdom: 1 - 64. Walter de Gruyter & Co, Berlin.","Nogueira J. M. M., Hutchings P. & Fukuda M. V. 2010. Morphology of terebelliform polychaetes (Annelida: Polychaeta: Terebelliformia), with a focus on Terebellidae. Zootaxa 2460 (1): 1 - 185. https: // doi. org / 10.11646 / zootaxa. 2460.1.1","Lavesque N., Londono-Mesa M. H., Daffe G. & Hutchings P. 2020 a. A revision of the French Telothelepodidae and Thelepodidae (Annelida, Terebelliformia), with descriptions of three species and first European record of a non-indigenous species. Zootaxa 4810 (2): 305 - 327. https: // doi. org / 10.11646 / zootaxa. 4810.2.4","Lavesque N., Daffe G., Londono-Mesa M. H. & Hutchings P. 2021. Revision of the French Terebellidae sensu stricto (Annelida, Terebelliformia), with descriptions of nine species. Zootaxa 5038 (1): 1 - 63. https: // doi. org / 10.11646 / zootaxa. 5038.1.1","Lavesque N., Bonifacio P., Londono-Mesa M. H., Le Garrec V. & Grall J. 2017 a. Loimia ramzega sp. nov., a new giant species of Terebellidae (Polychaeta) from French waters (Brittany, English","Marenzeller E. 1884. Sudjapanische Anneliden. II. Ampharetea, Terebellacea, Sabellacea, Serpulacea. Denkschriften der Akademie der Wissenschaften, Mathematisch-Naturwissenschaftliche Classe 49 (2): 197 - 224.","Nogueira J. M. M., Fitzhugh K. & Hutchings P. 2013. The continuing challenge of phylogenetic relationships in Terebelliformia (Annelida: Polychaeta). Invertebrate Systematics 27: 186 - 238. https: // doi. org / 10.1071 / IS 12062.","Hartman O. 1959. Catalogue of the polychaetous annelids of the world. Part II. Occasional Papers of the Allan Hancock Foundation 23: 355 - 628.","Polloni P. T., Rowe G. T. & Teal J. M. 1973. Biremis blandi (Polychaeta: Terebellidae), new genus, new species, caught by D. S. R. V. \" Alvin \" in the Tongue of the Ocean, New Providence, Bahamas. Marine Biology 20: 170 - 175. https: // doi. org / 10.1007 / BF 00351456","Verrill A. E. 1879. Preliminary Check-list of the marine Invertebrata of the Atlantic Coast, from Cape Cod to the Gulf of St. Lawrence. Tuttle, Morehouse & Taylor, New Haven.","Levinsen G. M. R. 1893. Annulata, Hydroidae, Anthozoa, Porifera. Udbytte af Kanonbaaden \" Hauche \" togter i de Danske indenfor Skagen i Aarene 1893: 321 - 464.","Grube A. E. 1850. Die Familien der Anneliden. Archiv fur Naturgeschichte 16 (1): 249 - 364. Available from https: // www. biodiversitylibrary. org / page / 6958350 [accessed 8 Nov. 2021].","Lavesque N., Hutchings P., Daffe G. & Londono-Mesa M. H. 2020 b. Revision of the French Polycirridae (Annelida, Terebelliformia), with descriptions of eight new species. Zootaxa 4869 (2): 151 - 186. https: // doi. org / 10.11646 / zootaxa. 4869.2.1","Sars M. 1863. Geologiske og zoologiske lagttagelser, anstillede paa en Reise i en Deel af Trondhjems stift i Sommeren 1862. Nyt magazin for naturvidenskaberne 12: 253 - 340. Available from https: // biodiversitylibrary. org / page / 8058512 [accessed 8 Nov. 2021].","McIntosh W. C. 1869. On the structure of the British nemerteans, and some new British annelids. Transactions Royal Society of Edinburgh 25: 249 - 252. https: // doi. org / 10.1017 / S 0080456800035262","Langerhans P. 1884. Die Wurmfauna von Madeira. IV. Zeitschrift fur wissenschaftliche Zoologie 40: 247 - 285.","Sars M. 1865. Fortsatte Bidrag til Kundskaben om Norges Annelider. Forhandlinger i Videnskabs- Selskabet i Christiania 1864: 5 - 20. Available from https: // biodiversitylibrary. org / page / 44007149 [accessed 8 Nov. 2021].","Caullery M. 1915. Sur les Terebelliens de la sous-famille Polycirridae Malmgr. 1. Delimitation des genres. 11. Polycirrus arenivorus n. sp. Societe Zoologique de France Bulletin 40: 239 - 248.","Cepeda D. & Lattig P. 2016. A new species of Polycirridae (Annelida: Terebellida) and three new reports for Cantabrian and Mediterranean Seas. Cahiers de Biologie Marine 57: 371 - 387. https: // doi. org / 10.21411 / CBM. A. AE 1327 D 3","Grube A. E. 1860. Beschreibung neuer oder wenig bekannter Anneliden. Beitrag: Zahlreiche Gattungen. Archiv fur Naturgeschichte 26: 71 - 118. https: // doi. org / 10.5962 / bhl. title. 11291","Saint-Joseph A. 1894. Annelides Polychetes des cotes de Dinard. Troisieme Partie. Annales des Sciences naturelles Zoologie et Paleontologie 17: 1 - 395.","McIntosh W. C. 1915. Notes from the Gatty Marine Laboratory, St Andrews. Annals and Magazine of Natural History Series 8 15: 1 - 58. https: // doi. org / 10.1080 / 00222931508693614","Eliason A. 1962. Die Polychaeten der Skagerak-Expedition 1933. Zoologiska bidrag fran Uppsala 33: 207 - 293.","Wollebaek A. 1912. Nordeuropaeiske Annulata Polychaeta 1. Ammocharidae, Amphictenidae, Ampharetidae, Terebellidae og Serpulidae. Skrifter utgit av Videnskapsselskapet i Kristiana 1911. 1. Mathematisk-naturvidenskabelig klasse 1911 (18): 1 - 144. https: // doi. org / 10.5962 / bhl. title. 11634","Muller O. F. 1776. Zoologicae Danicae Prodromus, seu Animalium Daniae et Norvegiae indigenarum characteres, nomina et synonyma imprimis popularium. Hallageriis, Copenhagen [Havniae]. https: // doi. org / 10.5962 / bhl. title. 63795","Quatrefages A. de. 1866. Note sur la Classification des Annelides. Annales des Sciences Naturelles 5: 253 - 296.","Jirkov I., Ravara A. & Cunha M. R. 2018; Amphitrite fauveli sp. n. (Polychaeta: Terebellidae) from the Bay of Biscay and the Gulf of Cadiz (NE Atlantic). Invertebrate Zoology 15 (1): 85 - 91. https: // doi. org / 10.15298 / invertzool. 15.1.06","Dalyell J. G. 1853. The Powers of the Creator displayed in the Creation: or, Observations on Life amidst the various Forms of the humbler Tribes of animated Nature with practical Comments and Illustrations, Vol. 2. John van Voorst. London. https: // doi. org / 10.5962 / bhl. title. 10022","Risso A. 1826. Histoire naturelle des principales productions de l'Europe meridionale et particulierement de celles des environs de Nice et des Alpes Maritimes. Volume 4. Levrault, Paris. https: // doi. org / 10.5962 / bhl. title. 58984","Jirkov I. 2020. Review of the European Amphitrite (Polychaeta: Terebellidae) with description of two new species. Invertebrate Zoology 17 (4) 311 - 360. https: // doi. org / 10.3853 / j. 0067 - 1975.40.1988.150","Arvanitidis C. & Koukouras A. 1995. Amphitritides kuehlmanni sp. nov. (Polychaeta, Terebellidae, Amphitritinae) from the Aegean Sea, with comments on the genus Amphitritides Augener. Ophelia 40 (3): 219 - 227. https: // doi. org / 10.1080 / 00785326.1995.10430587","Annenkova N. P. 1924. Neues uber die Verbreitung einiger Arten der Polychaeten. Comptes Rendus de l'Academie des Sciences de Russie 1924: 125 - 128.","Montagu G. 1819. Descriptions of five British species of the genus Terebella. Transactions of the Linnean Society of London 12 (2): 340 - 344. https: // doi. org / 10.1111 / j. 1095 - 8339.1817. tb 00231. x","Malm A. W. 1874. Annulata i hafvet utmed Sveriges westkust och omkring Goteborg. Goteborgs Koniglich vetenskaps - och vitterhetssamhalles handlingar [Zoologiska observationer. VII.] 14: 67 - 105.","Pallas P. S. 1766. Miscellanea Zoologica quibus novae imprimis atque obscurae animalium species describunture et observationibus iconibusque illustrantur. Apud Petrum van Cleef, the Hague [Hague Comitum]. https: // doi. org / 10.5962 / bhl. title. 69851","Savigny J. C. 1822. Systeme des annelides, principalement de celles des cotes de l'Egypte et de la Syrie, offrant les caracteres tant distinctifs que naturels des Ordres, Familles et Genres, avec la Description des Especes. Description de l'Egypte ou Recueil des Observations et des Recherches qui ont ete faites en Egypte pendant l'Expedition de l'Armee francaise, publie par les Ordres de sa Majeste l'Empereur Napoleon le Grand, Histoire Naturelle, Paris 1 (3): 1 - 128. https: // doi. org / 10.5962 / bhl. title. 66284","Orsted A. S. 1844. Zur Classification der Annulaten mit Beschreibung einiger neuer oder unzulanglich bekannter Gattungen und Arten. Archiv fur Naturgeschichte 10 (1): 99 - 112. Available from https: // www. biodiversitylibrary. org / page / 13704002 [accessed 8 Nov. 2021].","Ssolowiew M. 1899. Polychaeten-Studien I. Die Terebelliden des Weissen Meeres. Annuaire du Musee Zoologique de l'Academie Imperiale des Sciences de St. Petersbourg 4 (2): 179 - 220. Available from https: // biodiversitylibrary. org / page / 39099726 [accessed 8 Nov. 2021].","Southward E. C. 1956. On some Polychaeta of the Isle of Man. Annals and Magazine of Natural History Series 12 9 (100): 257 - 270. https: // doi. org / 10.1080 / 00222935608655812","Langerhans P. 1880. Die Wurmfauna von Madeira. III. Zeitschrift fur wissenschaftliche Zoologie 34 (1): 87 - 143.","Mikac B. & Hutchings P. 2017. One new species of Pista Malmgren, 1866 (Annelida: Terebellidae) and one new species of Pistella Hartmann-Schroder, 1996 (Annelida: Terebellidae) from the Adriatic Sea (Mediterranean). Journal of the Marine Biological Association of the United Kingdom 97 (5): 943 - 953. https: // doi. org / 10.1017 / s 0025315417000868","Saphronova M. A. 1988. On cosmopolitan distribution of Pista cristata (Polychaeta, Terebellidae). Zoologicheskii zhurnal 67 (6): 888 - 897.","Labrune C., Lavesque N., Bonifacio P. & Hutchings P. 2019. A new species of Pista Malmgren, 1866 (Annelida, Terebellidae) from the Western Mediterranean Sea. ZooKeys 838: 71 - 83. https: // doi. org / 10.3897 / zookeys. 838.28634","Gaillande D. 1970. Une polychete Terebellidae nouvelle des cotes de Provence: Pista mediterranea n. sp. Tethys 2 (2): 443 - 448.","McIntosh W. C. 1885. Report on the Annelida Polychaeta collected by H. M. S. Challenger during the years 1873 - 1876. Report on the Scientific Results of the Voyage of H. M. S. Challenger during the years 1873 - 76. Zoology 12: 1 - 554. Available from https: // www. biodiversitylibrary. org / page / 50688432 [accessed 8 Nov. 2021].","Pearson T. H. 1969. Scionella lornensis sp. nov., a new terebellid (Polychaeta: Annelida) from the west coast of Scotland, with notes on the genus Scionella Moore, and a key to the genera of the Terebellidae recorded from European waters. Journal of Natural History 3 (4): 509 - 516. https: // doi. org / 10.1080 / 00222936900770441","Linnaeus C. 1767. Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Editio duodecima reformata. Typis Ioannis Thomae von Trattner, Wien [Vindobonae]. https: // doi. org / 10.5962 / bhl. title. 156772","Lezzi M. & Giangrande A. 2019. New species of Streblosoma (Thelepodidae, Annelida) from the Mediterranean Sea: S. pseudocomatus sp. nov., S. nogueirai sp. nov. and S. hutchingsae sp. nov. Journal of Natural History 52 (43 - 44): 2857 - 2873. https: // doi. org / 10.1080 / 00222933.2018.1556357","Sars G. O. 1872. Diagnoser af nye Annelider fra Christianiaforden, efter Professor M. Sar's efterladte Manuskripter. Forhandlinger i Videnskabs-Selskabet i Christiania 1871: 406 - 417. Available from https: // biodiversitylibrary. org / page / 44067540 [accessed 8 Nov. 2021]","Fabricius O. 1780. Fauna Groenlandica, systematice sistens, Animalia Groenlandiae occidentalis hactenus indagata, quoad nomen specificum, triviale, vernaculumque synonyma auctorum plurium, descriptionem, locum, victum, generationem, mores, usum, capturamque singuli prout detegendi occasio fuit, maximaque parte secundum proprias observations. Impensis Ioannis Gottlob Rothe, Copenhagen et Leipzig [Hafniae et Lipsiae]. https: // doi. org / 10.5962 / bhl. title. 13489","Grube A. E. 1855. Beschreibungen neuer oder wenig bekannter Anneliden. Archiv fur Naturgeschichte 21 (1): 81 - 136. Available from https: // doi. org / 10.5962 / bhl. part. 13989 [accessed 8 Nov. 2021].","Kingston P. F. & Mackie A. S. Y. 1980. Octobranchus floriceps sp. nov. (Polychaeta: Trichobranchidae) from the northern North Sea with a re-examination of O. antarcticus Monro. Sarsia 65: 249 - 254. https: // doi. org / 10.1080 / 00364827.1980.10431487","Grube A. E. 1863. Beschreibung neuer oder wenig bekannter Anneliden. Sechster Beitrag. Archiv fur Naturgeschichte 29: 37 - 69. Available from https: // doi. org / 10.5962 / bhl. part. 9306 [accessed 8 Nov. 2021].","Williams S. J. 1984. The status of Terebellides stroemi (Polychaeta; Trichobranchidae) as a cosmopolitan species, based on a worldwide morphological survey, including description of new species. In: Hutchings P. A. (ed.) Proceedings of the First International Polychaete Conference, Sydney, Australia, 1984: 118 - 142. The Linnean Society of New South Wales, Sydney, Australia.","Parapar J., Capa M., Nygren A. & Moreira J. 2020 a. To name but a few: descriptions of five new species of Terebellides (Annelida, Trichobranchidae) from the North East Atlantic. ZooKeys 992: 1 - 58. https: // doi: 10.3897 / zookeys. 992.55977","Parapar J., Moreira J. & Helgason G. V. 2011. Taxonomy and distribution of Terebellides (Polychaeta, Trichobranchidae) in Icelandic waters, with the description of a new species. Zootaxa 2983 (1): 1 - 20. https: // doi. org / 10.11646 / zootaxa. 2983.1.1","Parapar J., Mikac B. & Fiege D. 2013. Diversity of the genus Terebellides (Polychaeta: Trichobranchidae) in the Adriatic Sea with the description of a new species. Zootaxa 3691 (3): 333 - 350. https: // doi. org / 10.11646 / zootaxa. 3691.3.3","Parapar J., Moreira J. & O'Reilly M. 2016. A new species of Terebellides (Polychaeta: Trichobranchidae) from Scottish waters with an insight into branchial morphology. Marine Biodiversity 46 (3): 211 - 225. https: // doi. org / 10.1007 / s 12526 - 015 - 0353 - 5","Sars M. 1835. Beskrivelser og Iagttagelser over nogle maerkelige eller nye i Havet ved den Bergenske Kyst Levende Dyr af Polypernes, Acalephernes, Radiaternes, Annelidernes og Molluskernes classer, med en kort Oversigt over de hidtil af Forfatteren sammesteds fundne Arter og deres Forekommen. T. Hallager, Bergen. https: // doi. org / 10.5962 / bhl. title. 13017","Glasby C. J. & Hutchings P. 2014. Revision of the taxonomy of Polycirrus Grube, 1850 (Annelida: Terebellida: Polycirridae). Zootaxa 3877 (1): 1 - 117. https: // doi. org / 10.11646 / zootaxa. 3877.1.1"]}

International audience; The north Atlantic coast of South America is influenced by the Amazon River. This coast is considered the muddiest in the world due to the enormous suspended sediment input from the Amazon River. The mobility of the sediment imposes a geomorphological dynamic with a rapid change of shoreline and fast alternation of facies types of the sediment. This study first describes the spatial and functional structure of meiofauna communities of highly unstable intertidal flats along coasts of French Guiana and Suriname in relation to environmental variables. Six sampling sites, composed mainly of muddy sediment, were located 700 km (Kourou) to 1200 km (Nickerie) from the mouth of the Amazon River. The granulometry, chlorophyll a biomass, prokaryote abundance, percentage of organic matter, meiofauna abundance and feeding guilds of nematodes in sediment stations were independent of the distance of the Amazon River mouth and likely were more influenced by the local dynamism of migration of mudbanks. Meiofauna was not more abundant when the sediment was dominated by the finest sediment particles and also when chlorophyll a and prokaryotes, potential prey of meiofauna, were greater. However, as a percentage, small nematodes (biomass of 0.07 ± 0.001 µg ind-1), which are mainly epigrowth-feeders, were more abundant in very fluid mud. Local granulometry and organic matter content appeared to be driving factors of the size structure and functional characteristics of nematodes. Despite the high instability of mudflats, chlorophyll a biomass and meiofauna abundance always tended to be higher toward other world areas. No foraminifera among the six stations of the study were found. Very fluid mud with physical instability of sediment caused a large perturbation to the settlement of meiofauna; the least amounts of chlorophyll a biomass and prokaryotic and meiofauna abundances were found there. Thus, the probable mobility of sediment may select for smaller meiobenthic organisms, mainly epigrowth-feeders nematodes, and disturb the larger organisms in the sediment, and, therefore, they would not permit the settlement of the foraminifera. In addition, no non-permanent meiofauna largely was found in the sediment.

Asthenognathus atlanticus Monod, 1932, has been reported for the first time from the eastern part of the Bay of Seine (eastern English Channel). A total of 30 specimens were collected between the years 2008 and 2011, along the Normandy coast from Ouistreham to Antifer, mainly on mud and muddy sand habitats, between 10 and 25 m depth. The distribution range of A. atlanticus has been previously known to cover eastern Atlantic coasts from Angola to the western English Channel, where it reached its northern limits. It is also present in the western part of the Mediterranean Sea. The changes in the sediment composition of the eastern Bay of Seine have probably led to the development of a potentially favorable habitat for this species. However, the data collected have not yet been sufficient to ascertain the origin, and the method of introduction of the eastern English Channel specimens. In the discussion, we ponder if they might have originated from the western English Channel populations, and was transported as larvae in the eastern English Channel; they could have originated from a more distant population, and have been brought to the eastern English Channel through human activities. Each hypothesis is possible in theory.

Since late 1990s the annelid polychaete Melinna palmata and the mollusc bivalve Ensis directus have been collected in the eastern part of the Bay of Seine (English Channel), indicating changes in the benthic communities. Melinna palmata was never collected prior to 2002, whereas it was reported in the muddy fine sands of the western part of the Channel, along the French (e.g. Bay of Cherbourg) and southern UK (e.g. Southampton Waters) coasts. Ensis directus was first reported in 1998 and now appears to be well implanted, given the abundant population collected in 2006. The colonization of Melina palmata seems to be a consequence of recent increase of the fine sediment in the eastern part of the Bay, while that of the invasive Ensis directus seems more likely to be related to its southwest expansion, from the Scheldt estuary (Belgium and Netherlands) towards the Bay. Since both species have complex life cycles including planktonic larval phases, their colonisation may also be favoured either by an accidental introduction via ballast waters or by larval dissemination from neighbouring populations.