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Hlavní autor:	Bonifácio, Paulo
Médium:	Recurso digital
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Vydáno:	Zenodo 2026
Témata:	Biodiversity Taxonomy Animalia Annelida Polychaeta Scalibregmatidae Scalibregma Scalibregma drouali
On-line přístup:	https://doi.org/10.5281/zenodo.19488489
Tagy:	Přidat tag Žádné tagy, Buďte první, kdo vytvoří štítek k tomuto záznamu!

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Scalibregma drouali sp. nov.(Figs 2–3, Tables 1–2)Type material: Holotype, MNHN-2000-2115, complete specimen, ovigerous, length 17.4 mm, width 1.6 mm, widest 2.9 mm, 39 chaetigers with two more achaetous segments and one more without chaetae or cirri, Northeast Atlantic Ocean, France, Bay of Biscay, around Oléron site 2, continental shelf, station 109, replicate b, collected 12 October 2023, Day grab, 45.807666º N, 2.20514884º W, 82 m depth. Paratype 1, MNHN-2000-2116, incomplete specimen, length 10 mm, width 1.9 mm, widest 3.0 mm, 27 segments, Northeast Atlantic Ocean, Bay of Biscay, around Oléron site 2, continental shelf, station 104, replicate b, collected 12 October 2023, Day grab, 45.76243293º N, 2.152739676º W, 83 m depth. Paratype 2, MNHN-2000-2117, incomplete specimen, length 12.0 mm, width 1.9 mm, widest 3.5 mm, 29 segments, Northeast Atlantic Ocean, Bay of Biscay, around Oléron site 2, continental shelf, station 105, replicate a, collected 30 April 2024, Day grab, 45.75710897º N, 2.177357192º W, 88 m depth, DNA extracted. Paratype 3, MNHN-2000-2118, complete specimen, length 15.2 mm, width 1.6 mm, widest 3.0 mm, 39 chaetigers with two more achaetous segments and one more segment without chaetae or cirri, Northeast Atlantic Ocean, Bay of Biscay, within Oléron site 1, continental shelf, station 7, replicate c, collected 10 October 2023, Day grab, 45.85058453º N, 1.96193461º W, 67 m depth. Paratype 4, SMF 33431, complete specimen, length 19.5 mm, width 1.7 mm, widest 3.0 mm, 39 chaetigers, posterior end not clear if last segments are with or without chaetae/cirri, Northeast Atlantic Ocean, Bay of Biscay, within Oléron site 1, continental shelf, station 60, replicate b, collected 6 November 2024, Day grab, 45.85144389º N, 1.98979028º W, 69 m depth.Comparative material. MNHN-2001-158, Scalibregma celticum, incomplete specimen, 34 chaetigers, Northeast Atlantic Ocean, Bay of Biscay, around Oléron site 2, continental shelf, station 109, replicate b, collected 30 April 2024, Day grab, 45.807666º N, 2.20514884º W, 89 m depth. MNHN-2001-159, Scalibregma inflatum, incomplete specimen, 25 chaetigers, Northeast Atlantic Ocean, Bay of Biscay, around Oléron site 2, continental shelf, station 103, replicate d, collected 24 May 2024, Day grab, 45.73714882º N, 2.138872225º W, 83 m depth.1 https://www.ncbi.nlm.nih.gov/genbank/2 http://www.boldsystems.org3 https://github.com/rambaut/figtree/releasesDescription (based on holotype). Holotype complete specimen, with 39 chaetigers, 17.4 mm long, 2.9 mm in widest section (about chaetiger 10), 1.6 mm wide (chaetiger 4). Paratypes complete specimens measuring 15.2–19.5 mm long for 2.9–3.5 mm at widest section for 39 chaetigers.Body arenicoliform, expanded from chaetiger 6 to 12; surface covered by annulated secondary rings; anteriorly, each one formed by numerous rectangular pads; posteriorly, individual pads less distinct particularly on dorsal side; giving a complex areolate appearance (Fig. 2A); not pigmented or colored in ethanol, pale white (Fig. 2).Hexagonal prostomium, T-shaped, anterior margin smooth, with two long lateral horns, about as long as the prostomium length (Fig. 2B–D). Eyes present as two horizontal, red lines (V-shaped; Fig. 2B, C). Nuchal organs not everted in holotype or paratypes, dorso-lateral grooves observed. Peristomium achaetous, biannulate dorsally and ventrally (Fig. 2B–D); second ring composed by a row of 4–5 small pads dorsally (Fig. 2C). Mouth horizontal formed by anterior and posterior lips (Fig. 2D); anterior lip formed by paired triangular lobes with very small central pad; posterior lip formed by a central plicated pad with about 6 lobes. Proboscis not everted.Ventral groove starting from posterior lip to end of body forming a mid-ventral ridge line; chaetiger 1 with hexagonal, large pad; then two, square to round central pads by segment, longitudinally positioned (Fig. 2D), merged from chaetiger 7. Segmental annulations distinct along body, dorsally and ventrally; chaetiger 1 triannulate, then quadriannulate from chaetiger 2 to the end of body (Fig. 2A–D).Branchiae present from chaetiger 3 to 5, posterior to notochaetae (Figs 2B–D, 3G). First pair smaller than second and third (Fig. 3G) one, of similar size. Two main stems, pinnated branchiae then bifurcated branches (Figs 2B, 3G).Parapodia poorly developed on chaetiger 1 (Fig. 3A) and chaetigers 7 to 15; inconspicuous in inflated chaetigers; from chaetiger 17, developed, larger, triangular, distally blunt (Fig. 3I). Ventral cirri present from chaetiger 16, very small; and dorsal cirri present from chaetiger 17, small; both becoming full size by about 3 rd to 5 th chaetigers. Cirri subtriangular, distally blunt to pointed, of similar size; about same size that parapodia (Fig. 3I). Interramal papilla present from chaetiger 16, very small, following chaetigers small but distinct; knob-like (Fig. 2E). Three additional posteriormost segments with reduced parapodia: two cirrigerous and achaetous, and one without chaetae or cirri; triannulate. Pygidium with crenulate margin around anal aperture (Fig. 2F); with five anal cirri (two short and three 2x longer). Glands absent.Notopodia and neuropodia with bundle of smooth (some with a hirsute margin, Fig. 3F, but some difficult to see), short and long capillaries (chaetiger 1 with 10–20 observed, chaetiger 2 with 40–50, chaetiger 3 with 50–60, chaetiger 18 with about 10) present in all chaetigers in (Fig. 3A, D, G). Notopodia and neuropodia from chaetiger 1 (5 in noto- and neuropodia) and 2 (9 in noto- and 11 in neuropodia) with short, acicular chaetae, in a row, blunt tip; anterior to capillaries and near their basis (Fig. 3B, C, E, F). Replacing these in notopodia and neuropodia from chaetiger 3 (Fig. 3H) to the end by lyrate chaetae (about 13 anteriorly and posteriorly), in a row, with not equal tynes, spinous in inner tynes (Fig. 3H, J); similar along body, average ratio between tynes in chaetiger 3 1.2 (standard error: 0.01), in chaetiger 18 1.3 (0.04) and chaetiger 24 1.3 (0.09).Morphological variation. Paratype 3 showed prostomium with frontal horns shorter than prostomium length that seems contracted likely due fixation and pygidium with 6 anal cirri arranged as following: one short (halflength) medially inserted, laterally inserted three more in one side of short, median (three quarters-length) and long lengths, and two in other side of short and long lengths. Additional material (not included here) presented everted branched-like structure as nuchal organs.Reproduction notes. Holotype is a large and ovigerous specimen.Staining pattern. Staining with methyl blue (Paratype 4) and shirlastain (Paratype 1), but no specific pattern was observed.Remarks. Among the 26 described species (Blake 2025) in the genus Scalibregma only S. stenocerum, S. hanseni, S. lanai Mendes, Rizzo & De Paiva, 2023 and S. drouali sp. nov., show branchiae from chaetigers 3 to 5. Scalibregma hanseni described from Norwegian and Greenland seas (Fig. 1A), is the only species lacking eyes and having simpler branchiae with 1–4 filaments (Bakken et al. 2014), whereas S. lanai, described from Brazilian continental shelf (Fig. 1A), is the unique species showing lyrate chaetae with equal sized tines (Mendes et al. 2023). Thus, the new species is closely related to S. stenocerum, described for west Atlantic (Fig. 1A), by sharing the presence of eyes, lyrate chaetae with unequal size tines of similar ratio (1.3 from Fig. D in Bertelsen & Weston 1980) and brushy branchiae. However, S. drouali sp. nov. differs from S. stenocerum by having slightly more acicular chaetae in neuropodia of chaetiger 2 (up to 11 observed), presence of hirsute capillaries, branchiae with 2 stems pinnated with bifurcations that appear larger, 3 last segments achaetous instead up to six acicular in first two chaetigers, smooth capillaries, branchiae pinnate each pinna with bifurcations that appear smaller, and no achaetous segments (at least not mentioned) as found in S. stenocerum. Interestingly, the ventral annulation in S. drouali sp. nov. is much more similar to S. celticum with distinct mid-ventral row of large (double) epidermal pads (Mackie 1991) instead of indistinct mid-ventral row as observed in S. stenocerum (Bertelsen & Weston 1980). Morphologically, S. drouali sp. nov. seems to have much more in common with S. celticum because high similarities in external annulation in anterior (biannulated peristomium) and posterior end (cirrigerous and achaetous), and by showing the presence of hirsute capillaries (difficult to see if all of them or just some). Among the undescribed species, S. drouali sp. nov. is close of Scalibregma sp. nov. (Gil 2011) by sharing the presence of branchiae in segments 3 to 5, but differs by having eyes.Few DNA sequences are currently available (i.e., two species and four MOTUs in GenBank; one species in BOLD), yet the newly sequenced specimens found a perfect match (1–1.3% of genetic divergence) with specimens identified as Scalibregmatidae from Moroccan coast (two specimens at 102 m depth sampled in 2011; Table 1).Scalibregma stenocerum (type-locality: West Atlantic) has been recorded in European waters: Northern United Kingdom, around the Shetland Islands in 20 to 130 m depth (R. Barnich pers. comm.); Irish sea in 53 m depth (Mackie et al. 1995); east coast of England, Humber and Outer Wash Region (Pears & Worsfold 2011); Northern Ireland, Outer Ards penninsula (Agri-Food and Biosciences Institute 2019); and eastern of English Channel (Hawes et al. 2019). The wide distribution of the S. drouali sp. nov. suggest that the European records of S. stenocerum could belong to S. drouali sp. nov.The genetic sequences obtained during the present study characterize the following species for 16S rDNA and COI genes: S. celticum, S. inflatum and S. drouali sp. nov. Scalibregma inflatum has been recorded from numerous sites distant to the type-locality which is Molde (Norway) resulting in few sequences that seem likely to represent different genetic lineages (Fig. 4) or undescribed species. Because only 6 out of 15 species included in the phylogenetic analysis had 16S rDNA gene available, the phylogenetic analysis presented is limited to COI gene, as the genetic divergence. After more than three decades (Mackie 1991), S. celticum is here genetically characterized for 16S rDNA and COI genes. It shows high genetic divergence when comparing the COI gene in relation to S. inflatum (31.5%) and S. drouali sp. nov. (26.3%), all sampled in the Bay of Biscay. Genetic divergence between S. inflatum and S. drouali sp. nov. was slightly lower (27.1%). As suggested above and based on morphological analysis, S. celticum was found as sister-group of S. drouali sp. nov. with marginal high support. High confidence support was observed only for the clade composed of S. drouali sp. nov. specimens which showed an intra genetic divergence between 0.3 to 1.3%.Etymology. This species is named for Gabin Droual (Ifremer) in recognition of his valued friendship and our shared passion for polychaete worms.Genetic data. DNA sequencing for this species was successful for 16S rDNA (423 bp length) and COI (669 bp length; Table 1). Intraspecific variation for COI divergence was in average 0.89% (standard error: 0.29%).Distribution. Most of the examined material comes from the Bay of Biscay (Northeast Atlantic), collected during a survey (178 specimens sampled during four sampling time between 55 and 88 m depth; Fig. 1B). The genetic match between specimens from the Bay of Biscay and those from the Moroccan coast (104 m depth) suggests that S. drouali sp. nov. may have gone hidden because of misidentifications with S. celticum, with its range potentially extending from France to Morocco.Ecological notes. Temporal variability in abundance was marked by high values in autumn (82 and 53 individuals in 2023 and 2024, respectively) and low values in spring (15 and 28 individuals in 2024 and 2025, respectively). Most species occurrences (69%) were associated with gravelly sand sediments, followed by 17% in slightly gravelly sand (Folk 1954). Sediment composition averaged 12.9% gravel (standard error: 1%), 84.9% sand (1.1%), and 2.2% mud (0.4%).

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