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Aspidosiphon (Aspidosiphon) muelleri Diesing, 1851: 68, as Aspidosiphon muelleri; type locality: Palermo, Sicily, Italy). — Dean 2001: 89 (Gulf of Nicoya, Costa Rica, muddy sand). Questionable record in the TEP., Published as part of Silva-Morales, Itzahí & Gómez-Vásquez, Julio D., 2021, First records and two new species of sipunculans (Sipuncula) from the Southern Mexican Pacific, pp. 77-117 in European Journal of Taxonomy 740 (1) on page 113, DOI: 10.5852/ejt.2021.740.1283, http://zenodo.org/record/4643194

A population of the sipunculan wormAspidosiphon muelleri, located in temperate waters of the western Mediterranean Sea, was monitored monthly for a year. Some aspects related to its ecology and reproductive biology are shown in the present work. The sex-ratio for this population was close to 1:1 (54% females vs 46% males), thus indicating a dioecious reproduction, although showing a lack of sexual dimorphism. Oocytes were detected in females from 4–5 mm; this size might be reached byA. muelleriin a few months. The population density increased notably during the summer (June–August). The spawning event date was indirectly estimated from the average size of the oocytes and the percentage of females with free oocytes in the coelom. Both variables were significantly correlated to shallow water temperature (Pearson correlation;P = 0.003 andP = 0.001, respectively). Oocyte size was also significantly correlated to average irradiance level (Pearson correlation;P = 0.044). Spawning took place between August and September (when the water temperature is getting close to its annual maximum) and may last only a few weeks in these temperate waters. The abundance ofA. muelleridecreased drastically in September, likely as a consequence of the spawning event effort. Bivalves of the speciesEpilepton clarkiaewere collected together with specimens ofA. muelleriliving inside the polychaete tubes used as shelters by the sipunculans, with a prevalence of 11.64%. To a lesser extent some Foraminifera were also reported attached to the body of the sipunculans.

Aspidosiphon muelleri Diesing, 1851 (Fig. 5 I���J) Material. NhaTrang Bay: Dung Island, 15 m depth, sand, vacant gastropods shells, 3 specimens; fish trawl, 25 m depth, solitary corals (Heteropsammia cohlea), 40 specimens. Description. Trunk 5���12 mm long, 2 ���2.5 mm wide; grey, with minute papillae distributed over the entire trunk, larger papillae at anal and caudal shields; introvert 2��� 3 X of trunk length. Anal shield yellow-brown, with small units arranged into groups of various size separated by longitudinal furrows dorsally and by transverse furrows laterally; caudal shield yellow-brown, with 15���20 radial grooves. Small unidentate, compressed hooks, 20���30 ��m in height, arranged in rings distally; proximal introvert with scattered conical hooks. Continuous longitudinal musculature layer splits in the area of the anal shield; retractor muscles originate 10 % of trunk length from the caudal shield. Spindle muscle is attached posteriorly to the body wall. Nephridia are about 70 % of trunk length. Discussion. This species differs from other representatives of the subgenus Aspidosiphon (Aspidosiphon) by the structure of the anal shield with individual units that are arranged into longitudinal ridges above the dorsal region. Aspidosiphon muelleri, the most widespread representative of the genus Aspidosiphon, is a cosmopolitan species reported from shallow to bathyal depths. In the West Pacific it has been found from Australia to Japan and in the South China Sea from the Vietnam coast, Tonkin Bay and Hainan Island. Generally, it inhabits discarded mollusk shells and dead corals., Published as part of Adrianov, Andrey V. & Maiorova, Anastassya S., 2012, Peanut worms of the phylum Sipuncula from the Nha Trang Bay (South China Sea) with a key to species, pp. 41-58 in Zootaxa 3166 on page 53, DOI: 10.5281/zenodo.279772

Aspidosiphon (Aspidosiphon) muelleri Diesing Figs 2 J, 3 E���F Aspidosiphon muelleri Cutler, 1994: 218 (for complete synonymy). Material examined. One specimen (NMNS- 5928 -021), Shiaoliuchiu (22 �� 20.56 ' N, 120 �� 21.53 ' E), Pingtung County, southern Taiwan, lower intertidal sandy bottom, coll. P.-W. Hsueh, 5 May 2007. Remarks. The present specimen possesses a continuous layer of longitudinal muscles, the anal shield has an extensive array of furrows (Fig. 3 E), and its other characters agree with the description by Cutler (1994). A unidentate hook (Fig. 3 F) was observed in the present specimen. However, this character is not reliable for identification as it can also be bidentate or both (Cutler 1994). The species is known as the most widespread Aspidosiphon, commonly found in northeastern Atlantic and occasionally reported from the western Pacific (Japan to Australia) (Cutler 1994). The collection of this species in Taiwan is therefore not surprising., Published as part of Hsueh, Pan-Wen & Kuo, Chia-Ming, 2009, New records of sipunculan worms from Taiwan, pp. 51-61 in Zootaxa 2067 on page 60, DOI: 10.5281/zenodo.187023, {"references":["Cutler, E. B. (1994) The Sipuncula: Their Systematics, Biology and Evolution. New York: Cornell University. 453 pp."]}

Aspidosiphon (Aspidosiphon) muelleri Diesing, 1851 Description. Body wall thin, semi-transparent. Trunk 2���16.4 mm long, 0.6���1.4 mm wide. Introvert 1.5 times trunk length. Anal and caudal shield black-brown in colour and grooved. Anal shield with 12���15 longitudinal grooves (Fig. 4 G). Caudal shield with 18���20 radial grooves. Finger-like spines (3���10 spines) on anal shield of 8 individuals, 70���120 ��m long. Spine-like papillae scattered on introvert, 12.5���22.5 ��m long. 9���12 small tentacles at end of introvert. Hooks arranged in 65���118 rings of hooks. Bidentate hooks on rings located on distal part of introvert; 15���25 ��m high, 17.5���32.5 ��m thick at base. Unidentate hooks scattered on proximal part of introvert; 17.5���30 ��m high, 20���35 ��m thick at base. Intestinal spiral with 5���24 coils. Retractor muscles attached at near posterior part of trunk. Anus and nephridiopores placed at same level. Nephridia length (largest individual) 6.3 mm; 0.4 mm wide. Trunk 2.6 times nephridia length. Two black eye spots present. Some specimens with eggs; longer axis 110���150 ��m in diameter, smaller axis 80���120 ��m in diameter. Ecology. In the study area, this species was found in sandy, muddy-sand and Posidonia oceanica biotopes at 22���77 m depth. Many specimens were found within the empty shells of gastropods and tubes of the polychaete species Vermiliopsis sp. Distribution. Indian Ocean (Saiz Salinas 1993 a), Northeastern Atlantic and Eastern Pacific Oceans, Mediterranean and Red Sea (Cutler 1994)., Published as part of A��ik, Sermin, 2009, Soft-bottom sipunculans in Izmir Bay (Aegean Sea, eastern Mediterranean), pp. 40-48 in Zootaxa 2136 on pages 45-46, DOI: 10.5281/zenodo.188511, {"references":["Saiz Salinas, J. I. (1993 a) Sipuncula from Reunion Island (Indian Ocean). Journal of Natural History, 27, 535 - 555.","Cutler, E. B. (1994) The Sipuncula. Their Systematics, Biology and Evolution. Ithaca: Comstock Publishing Associates, 433 pp."]}

Sipunculans collected during the operations of ‘Balgim’ Survey of the Centre National de la Recherche Scientifique (PIROCEAN), are recorded and data concerning them noted. The specimens come from the Alboran Sea, Straits of Gibraltar and Ibero-Moroccan Bay and from depths ranging from 115 to 2110m. Twenty-four species (plus four additional species identified incompletely) in eight genera are recognized; five of them, Nephasoma confusum, N. lilljeborgi, N. rimicola, Phascolion caupo and Aspidosiphon zinni, were not recorded hitherto from the investigated area. Not included in the identification list are several small, immature or problematical specimens, which were not assigned to any of the known species. Classification and ordination techniques indicate a close funal relationship between vertically similar stations, showing three major groups. The first one with Aspidosiphon muelleri as characteristic species, is common of shallower bottoms; the second one, with N. constrictum as characteristic species, ...

Aspidosiphon (Aspidosiphon) muelleri cf. kovalevskii Murina, 1964 Aspidosiphon (Aspidosiphon) muelleri kovalevskii: Murina et al. 1999: 826 ���827; Pancucci��Papadopoulou et al. 1999: 90���91, fig. 34. Aspidosiphon (Aspidosiphon) kovalevskii: Murina & Zavodnik 1985 / 1986: 26���28, fig. 1; Saiz Salinas 1988 b: 10, figs 1 a���d. Aspidosiphon kovalevskii: Stephen & Edmonds 1972: 229; Murina & Zavodnik 1979: 245 ���251, figs 2, 3. Material examined: ESFM ��� SIP / 97 ��� 10, T 4, trawl, start: 35 �� 22.9 ' N ��� 33 ��41.0' E, finish: 35 �� 22.4 ' N ��� 33 �� 39.3 ' E, 12 May 1997, 38��� 45 m, sandy mud with Halophila stipulacea and Caulerpa racemosa, 3 specimens; ESFM ��� SIP / 97 ��� 13, T 8, trawl, start: 35 �� 40.9 ' N ��� 34 �� 35.4 ' E, finish: 35 �� 40.6 ' N ��� 34 �� 35.9 ' E, 16 May 1997, 27��� 45 m, sand and Posidonia oceanica, 4 specimens [one individual within a shell of Bittium jadertinum (Brusina 1865), one individual within a shell of Gibbula guttadauri (Philippi 1836)]; ESFM ��� SIP / 97 ��� 11, D 1, dredge, 35 �� 22.5 ' N ��� 33 ��05.2' E, 10 May 1997, 50 m, hard substratum, 6 specimens; ESFM ��� SIP / 97 ��� 12, D 2, dredge, 35 �� 22.4 ' N ��� 33 �� 39.5 ' E, 12 May 1997, 35 m, on P. oceanica, 7 specimens; ESFM ��� SIP / 98 ��� 25, D 16, dredge, 35 �� 43.8 ' N ��� 34 �� 37.3 ' E, 16 July 1998, 300 m, mud with shell fragments, 1 specimen; ESFM ��� SIP / 98 ��� 24, D 17, dredge, 35 ��08.7' N ��� 34 ��00.1' E, 18 July 1998, 120 m, mud, 1 specimen; ESFM ��� SIP / 98 ��� 28, K 1, Guzelyurt Bay, 14 July 1998, 1 m, on Cystoseira crinita, 2 specimens; ESFM ��� SIP / 98 ��� 27, K 3, Karpas Cape, 18 July 1998, 10 m, on P. oceanica, 1 specimen; ESFM ��� SIP / 98 ��� 22, K 5, Karpas Cape, 19 July 1998, 0���2 m, on rocks, 1 specimen; ESFM ��� SIP / 98 ��� 26, K 8, Limanbasi Cape, 20 July 1998, 3 m, on C. crinita, 3 specimens; ESFM ��� SIP / 98 ��� 21, K 9, Girne, 21 July 1998, 2 m, on rocks, 2 specimens; ESFM ��� SIP / 98 ��� 23, K 9, Girne, 21 July 1998, 5 m, on P. oceanica, 1 specimen; ESFM ��� SIP / 98 ��� 20, K 10, Malazgirt, 21 July 1998, 2 m, on rocks, 1 specimen. Remarks: Body cylindrical or rod��like. Trunk 2���17 mm in lenght, 0.6���2.5 mm in width. Introvert 0.8���7.5 mm long, 0.3���1 mm wide. Trunk 2.3���2.5 times introvert length. Hooks yellow, dark brown. All introvert hooks unidentate; 13���53 ��m long, 15���38 ��m thick at base. Longitudinal grooves on anal shield numbering 15���20. Anal shields usually with spines. Radiale grooves on caudal shield numbering 16���20. Finger��like spines on introvert 10���38 ��m long. Intestinal spiral with 11���26 coils. Nephridiopores located just posterior to anus or at level of anus. Some specimens with eggs in coelom cavity, elliptical; longer axis 48���95 ��m in diameter, smaller axis 33���85 ��m in diameter. A total of 8 specimens of parasites (ectoprocts) were found to be attached to the anal shields and the proximal part of the introvert of two individuals. Distribution: Arabian Sea, South China, Mediterranean, middle and North Atlantic (Murina & Zavodnik 1979; Pancucci��Papadopoulou et al. 1999). Depth range: 1��820 m (Murina & Zavodnik 1985 / 1986; Murina et al. 1999)., Published as part of A��ik, S., Murina, G. V., ��inar, M. E. & Ergen, Z., 2005, Sipunculans from the coast of northern Cyprus (eastern Mediterranean Sea), pp. 1-23 in Zootaxa 1077 on pages 10-11, DOI: 10.5281/zenodo.170329, {"references":["Murina, G. V. V. (1964) Sipunculid fauna of the Mediterranean Sea. Trudy Sevastopolskoj Biologicheskoi Statsii, 17, 51 - 76 [In Russian].","Murina, G. V. V. & Zavodnik, D. (1985 / 1986) Sipuncula of the Adriatic Sea. Thalassia Jugoslavica, 21 / 22, 23 - 73.","Saiz Salinas, J. I. (1988 b) Sipunculiden (Sipuncula) des ostlichen Nordatlantik, gesammelt wahrend der Fahrten des FS Meteor. Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut, 85, 7 - 23.","Stephen, A. C. & Edmonds, S. J. (1972) The Phyla Sipuncula and Echiura. London: Trustees of the British Museum (Natural History), 528 pp.","Murina, G. V. V. & Zavodnik, D. (1979) Cruises of the research vessel Vila Velebita in the Kvarner Region of the Adriatic Sea. XVI. Sipuncula. Thalassia Jugoslavica, 15, 245 - 255."]}

Aspidosiphon (Aspidosiphon) muelleri muelleri Diesing, 1851 Aspidosiphon (Aspidosiphon) muelleri muelleri: Pancucci��Papadopoulou et al. 1999: 92 ���93, fig. 35. Aspidosiphon (Aspidosiphon) muelleri: Saiz Salinas 1984: 177 ���178, fig. 2; Saiz Salinas 1986: 9 ���11, fig. 1; Saiz Salinas 1993 b: 135 ���140, figs 72 ���74, 92c���d; Cutler 1994: 218 ���220, figs 55 e, 57 a, 58 a, 60 b���d. Aspidosiphon muelleri: Wesenberg��Lund 1957: 197 ���198; Stephen 1958: 133 ���134; Stephen & E dmonds 1972: 231���233, figs 26 a���d; Murina & Zavodnik 1985 / 1986: 29���31, fig. 3. Material examined: ESFM ��� SIP / 97 ��� 6, T 4, trawl, start: 35 �� 22.9 ' N ��� 33 ��41.0' E, finish: 35 �� 22.4 ' N ��� 33 �� 39.3 ' E, 12 May 1997, 38��� 45 m, on sandy mud with Halophila stipulacea (Forssk��l) Ascherson and Caulerpa racemosa (Forssk��l) J. Agardh, 1 specimen; E SFM��� SIP / 97 ��� 9, T 8, trawl, start: 35 �� 40.9 ' N ��� 34 �� 35.4 ' E, finish: 35 �� 40.6 ' N ��� 34 �� 35.9 ' E, 16 May 1997, 27��� 45 m, on sand and Posidonia oceanica, 4 specimens [one individual within a shell of Rissoa violacea Desmarest 1814, one individual within a tube of Vermiliopsis infundibulum (Gmelin 1788)]; ESFM ��� SIP / 97 ��� 8, D 1, dredge, 35 �� 22.5 ' N ��� 33 ��05.2' E, 10 May 1997, 50 m, on hard substratum, 1 specimen; ESFM ��� SIP / 97 ��� 5, D 3, dredge, 35 �� 20.7 ' N ��� 33 �� 28.3 ' E, 12 May 1997, 35 m, on P. oceanica, 2 specimens; E SFM��� SIP / 97 ��� 7, D 4, dredge, 35 �� 37.8 ' N ��� 34 �� 21.1 ' E, 15 May 1997, 35 m, on P. oceanica, 1 specimen; ESFM ��� SIP / 98 ��� 19, D 15, dredge, 35 �� 33.8 ' N ��� 34 ��13.0' E, 16 July 1998, 32 m, P. oceanica, 1 specimen; ESFM ��� SIP / 98 ��� 16, D 17, dredge, 35 ��08.7' N ��� 34 ��00.1' E, 18 July 1998, 120 m, mud, 1 specimen; ESFM ��� SIP / 98 ��� 14, K 1, Guzelyurt Bay, 14 July 1998, 5 m, on P. oceanica, 8 specimens; ESFM ��� SIP / 98 ��� 18, K 3, Karpas Cape, 18 July 1998, 10 m, on P. o c e a n i c a, 2 specimens; ESFM ��� SIP / 98 ��� 17, K 4, Gazi Magosa Bay, 18 July 1998, 4 m, on P. oceanica, 2 specimens; ESFM ��� SIP / 98 ��� 15, K 5, Carpas Cape, 19 July 1998, 7 m, on P. oceanica, 1 specimen; ESFM ��� SIP / 98 ��� 10, K 5, Carpas Cape, 19 July 1998, 0���2 m, on rocks, 1 specimen; ESFM ��� SIP / 98 ��� 11, K 8, Limanbasi Cape, 20 July 1998, 3 m, on Cystoseira crinita, 8 specimens; ESFM ��� SIP / 98 ��� 8, K 8, Limanbasi Cape, 20 July 1998, 0���5 m, on rocks, 7 specimens; ESFM ��� SIP / 98 ��� 13, K 9, Girne, 21 July 1998, 2 m, on rocks, 1 specimen; ESFM ��� SIP / 98 ��� 12, K 10, Malazgirt, 21 July 1998, 2 m, on rocks, 4 specimens; E SFM��� SIP / 98 ��� 9, K 11, Kormakiti Cape, 21 July 1998, 0���15 m, P. oceanica, 5 specimens. Remarks: Body wall thin, semi��transparent. Trunk 1.4���13.6 mm long, 0.6���3.1 mm wide. Introvert 0.7���11.9 mm long, 0.3���1.3 mm wide. Trunk 1.1���2 times introvert length. Longitudinal musculature continuous. Anterior and posterior shields brown��black in colour. Anterior shield semi��elliptical with longitudinally arranged grooves. Caudal shield disc��like with radiating grooves. Longitudinal muscle layer continuous. Nephridiopores located at level of anus. Spine��like papillae scattered on introvert, tending to decrease towards anterior part of introvert; 13���30 ��m long. Hooks arranged in rings. Introvert with 30���100 rings. One specimen bearing a pair of black eye spots and 120 rings of hooks on introvert. Bidentate hooks mainly on distal part of introvert; 10���38 ��m tall, 15���45 ��m thick at base. Unidentate hooks located mostly on posterior part of introvert; 13���35 ��m long, 11���40 ��m wide. Longitudinal grooves on anal shield numbering 10���22. Radiale grooves on caudal shield numbering 15���19. Some specimens with eggs in coelomic cavity; elliptical; longer axis 63���120 ��m in diameter, smaller axis 60���95 ��m in diameter. Distribution: Common in the northeast Atlantic, Mediterranean, Red Sea, Indian Ocean, Pacific Ocean (Cutler & Cutler 1989). Depth range: 0���1470 m (Saiz Salinas 1986; Saiz Salinas & Villafranca Urchegui 1988)., Published as part of A��ik, S., Murina, G. V., ��inar, M. E. & Ergen, Z., 2005, Sipunculans from the coast of northern Cyprus (eastern Mediterranean Sea), pp. 1-23 in Zootaxa 1077 on pages 9-10, DOI: 10.5281/zenodo.170329, {"references":["Saiz Salinas, J. I. (1984) Gusanos Sipunculidos (Sipuncula) de varias localidades de la costa de Portugal. In: Monteiro-Marques, V. (Ed.), Actas do IV Simposio Iberico de Estudos do Benthos Marinho. Associacao de Estudantes da Faculdade de Ciencias de Lisboa, 177 - 188 pp.","Saiz Salinas, J. I. (1986) Los Gusanos Sipunculidos (Sipuncula) de los fondos litorales y circalitorales de las costas de la Peninsula Iberica, Islas Baleares, Canarias y Mares Adyacentes. Monografias Instituto Espanol de Oceanografia, 1, 1 - 84.","Saiz Salinas, J. I. (1993 b) Sipuncula. In: Ramos M. A. et al. (Ed.), Fauna Iberica, vol. 4, Museo Nacional de Ciencias Naturales CSIC, Madrid, 200 pp.","Cutler, E. B. (1994) The Sipuncula. Their Systematics, Biology and Evolution. Ithaca: Comstock Publishing Associates, 433 pp.","Wesenberg-Lund, E. (1957) Sipunculoidea from the coast of Israel. Bulletin of the Research Council of Israel, 6 B, 193 - 200.","Stephen, A. C. (1958) The Sipunculids of Haifa Bay and neighbourhood. Bulletin of the Research Council of Israel, 7 B, 129 - 136.","Murina, G. V. V. & Zavodnik, D. (1985 / 1986) Sipuncula of the Adriatic Sea. Thalassia Jugoslavica, 21 / 22, 23 - 73.","Cutler, E. B. & Cutler, N. J. (1989) A revision of the genus Aspidosiphon (Sipuncula: Aspidosiphonidae). Proceedings of the Biological Society of Washington, 102, 826 - 865.","Saiz Salinas, J. I. & Villafranca Urchegui, L. (1988) Gusanos sipunculidos (Sipuncula) de las zonas adyacentes al estrecto de Gibraltar. Biologia Ambiental Congreso Mundial Vasco, 2, 57 - 63."]}

Aspidosiphon muelleri Diesing Aspidosiphon muelleri Diesing, 1851: 68. Type locality: Mediterranean Sea. Remarks: The single representative of this species was removed from a piece of calcareous polychaete tube and is only 5 mm long. The anal shield is not dark but shows the square and rectangular units divided by grooves typical for this species. The caudal shield with radiating grooves is clearly developed and many rings of hooks can be seen. Distribution: Common in the northeastern Atlantic from Norway to West Africa (48 ��� 10 �� N). It extends through the Mediterranean into the Red Sea and the Gulf of Aden along the coast of East Africa to Madagascar and South Africa. Also recorded from Sri Lanka, and there are sparse reports from central Japan through Thailand, Vietnam, Indonesia, and down to Australia, New Guinea, and the Kermadec Islands. It is not found in most of the Pacific Ocean; one record from Juan Fernandez Island off Chile and one from southern Brazil are the only reports from near the American continents. The species inhabits shelf depths (5���400 m) throughout most of its range, but there are a few as deep as 2900 m. It is most often found in discarded mollusc shells. Some from shallow, warm water live in the bases of solitary corals that have overgrown small gastropods, forming a commensal relationship. This is a new record for New Zealand, but only a modest extension of its known range., Published as part of Cutler, Edward B., Schulze, Anja & Dean, Harlan K., 2004, Zealand species, pp. 1-19 in Zootaxa 525 on page 14, DOI: 10.5281/zenodo.158002, {"references":["Diesing, K. M. (1851) Systema Helminthum. Braumiller, Vindobonae."]}

We analysed the distribution of soft bottom sipunculans from San Pedro del Pinatar (Western Mediterranean). This study was carried out from December 2005 to June 2010, sampling with biannual periodicity (June and December). Physical and chemical parameters of the sediment were analysed (granulometry, organic matter content, pH, bottom salinity and shelter availability). Nine different species and subspecies were identified, belonging to five families. Aspidosiphon muelleri muelleri was the dominant species, accumulating 89.06% of the total abundance of sipunculans. Higher sipunculan abundances were correlated with stations of higher percentage of coarse sand, empty mollusc shells and empty tubes of the serpulid polychaete Ditrupa arietina, where some of the recorded species live. Sediment characteristics played the main role controlling the sipunculans distribution. Anthropogenic impacts could be indirectly affecting their distribution, changing the sediment characteristics. Key words: Sipuncula, Aspidosiphon muelleri, Mediterranean, Anthropogenic impact, Soft–bottom., Se analizó la distribución de los sipuncúlidos de fondos blandos de San Pedro del Pinatar (Mediterráneo occidental). Este estudio se llevó a cabo entre diciembre de 2005 y junio de 2010, muestreando con periodicidad semestral (junio y diciembre). Se analizaron parámetros físicos y químicos del sedimento (granulometría, contenido de materia orgánica, pH, salinidad de fondo y disponibilidad de refugio). Nueve especies y subespecies diferentes fueron identificadas, pertenecientes a cinco familias. Aspidosiphon muelleri muelleri fue la especie dominante, acumulando el 89,06% de la abundancia total de sipuncúlidos. Las mayores abundancias de sipuncúlidos se correlacionaron con las estaciones con mayores porcentajes de arena gruesa, conchas de moluscos vacías y tubos vacíos del poliqueto serpúlido Ditrupa arietina, donde viven algunas de las especies registradas. Las características del sedimento jugaron el papel principal en el control de la distribución de sipuncúlidos. Los impactos antropogénicos podrían estar afectando indirectamente su distribución, cambiando las características del sedimento. Palabras clave: Sipuncúlidos, Aspidosiphon muelleri, Mediterráneo, Impacto antropogénico, Fondos blandos.