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Fine morphology of the tentacular apparatus of the sipunculan Thysanocardia nigra Ikeda, 1904 was conducted as a part of a larger study of microscopic anatomy in the species. The tentacular apparatus is composed of two rings of tentacles, the dorsal and oral crowns. The dorsal, or nuchal, crown consists of an arc of nuchal tentacles dorsally enclosing the heart -shaped nuchal organ. The oral disk carries numerous peripheral tentacles arranged in oral crown surrounding the mouth. Peripheral tentacles are arranged in paired rows, additional tentacles being developed posteriorly so as to form a radial series of U -shaped festoons. The parallel festoons extend down the oral disk and run alongside the spherical head. New pairs of festoons appear at the base of the nuchal crown. The tentacles are heart-shaped in cross section, the oral surface being widest. The nuchal tentacles face the oral disk by the oral surface while the peripheral, or oral, tentacles are twisted at the base at nearly right angles, so to face a ciliary groove of the corresponding festoon. The central groove of festoon is composed of a median ridge bordered by longitudinal lateral ridges with long cilia. The oral surface of tentacles is constructed of a multiciliated, pseudostratified, columnal epithelium with some intraepidermal mucous cells. There are three longitudinal tentacular canals lined by peritoneum. Hemerythrocytes flow through the lumen of the canals. Tentacles and grooves of festoons form a filtering system upon which food particles can be trapped. The filtering apparatus of Thysanocardia shows remarkable similarities with a filtering system of sabellid polychaetes.

Fine morphology of the tentacular apparatus of the sipunculan Thysanocardia nigra Ikeda, 1904 was conducted as a part of a larger study of microscopic anatomy in the species. The tentacular apparatus is composed of two rings of tentacles, the dorsal and oral crowns. The dorsal, or nuchal, crown consists of an arc of nuchal tentacles dorsally enclosing the heart -shaped nuchal organ. The oral disk carries numerous peripheral tentacles arranged in oral crown surrounding the mouth. Peripheral tentacles are arranged in paired rows, additional tentacles being developed posteriorly so as to form a radial series of U -shaped festoons. The parallel festoons extend down the oral disk and run alongside the spherical head. New pairs of festoons appear at the base of the nuchal crown. The tentacles are heart-shaped in cross section, the oral surface being widest. The nuchal tentacles face the oral disk by the oral surface while the peripheral, or oral, tentacles are twisted at the base at nearly right angles, so to face a ciliary groove of the corresponding festoon. The central groove of festoon is composed of a median ridge bordered by longitudinal lateral ridges with long cilia. The oral surface of tentacles is constructed of a multiciliated, pseudostratified, columna! epithelium with some intraepidermal mucous cells. There are three longitudinal tentacular canals lined by peritoneum. Hemerythrocytes flow through the lumen of the canals. Tentacles and grooves of festoons form a filtering system upon which food particles can be trapped. The filtering apparatus of Thysanocardia shows remarkable similarities with a filtering system of sabellid polychaetes.

Summary This study presents details of the ultrastructure of spermatozeugmata and spermatozoa of the peanut worm, Thysanocardia nigra, from the Sea of Japan. Spermatozoa are tightly packaged into unencapsulated conical bundles, spermatozeugmata, with as many as 300–350 cells comprising a single packet. Within an individual spermatozeugma, cells are aligned side by side such that head of the bundle is comprised of the heads of spermatozoa and the internal cavity of the bundle harbors numerous flagella that together form a tail for the spermatozeugma. The integrity of the packet appears to be maintained by specialized junctions between adjacent cells. The spermatozeugmata break up when discharged into the sea water. Each spermatozoon is characterized by a rounded head, consisting of the acrosome, nucleus, and midpiece. The midpiece contains mitochondria, centrioles, and some residual cytoplasm that contains dark granules. The method of “sperm packaging” and morphology of spermatozeugmata are unique to the S...

A new species of echinoderid kinorhynch, Echinoderes sensibilis, is described and illustrated using light and electron microscopy. The specimens were collected from masses of the red algae Corallina pilulifera growing in intertidal pools in Tanabe Bay, Honshu Island, Japan. Diagnostic characters of E. sensibilis include the presence of middorsal spines on segments 6-10; lateral spines/tubules on segments 4, 7-12; remarkable trapezium-like subventral fields of minute cuticular hairs on segments 5-12. The positions of numerous sensory spots, large sieve areas, glandular tubes and the shape of terminal tergal and sternal extensions are also diagnostic. All taxonomic characters used for this description are illustrated by SEM. Echinoderes sensibilis constitutes the fifty-eighths valid species of the genus Echinoderes and the fourteenth species described from the Pacific Ocean. This is the third representative of Pacific kinorhynchs found only in the intertidal zone and the first Pacific Echinoderes living on red macroalgae in inter-tidal pools.

A pycnophyid kinorhynch, Pycnophyes tubuliferus Adrianov, 1989, collected from muddy sediment at Tanabe Bay, Honshu Island, Japan is re-described and illustrated. This is the first record of the order Homalorhagida and the genus Pycnophyes from Japanese waters, and the fourth genus of the class Kinorhyncha from Japan. Previously P. tubuliferus was found only in a few localities alongside the Russian and Korean coasts in the western part of the Sea of Japan, and this is the first finding of this species outside the Sea of Japan. Detailed morphology of the species has been studied using Nomarsky microscopy and SEM for the first time. Basic taxonomic characters were compared from zoogeographic points of view among specimens representing populations from the Sea of Japan (including typematerial) and the Pacific coast of the mainland of Japan. The new diagnosis of the species has been proposed.

Priapulids possess a radial symmetry that is remarkably reflected in both external morphology and internal anatomy. It results in the appearance of 25-radial (a number divisible by five) symmetry summarized as a combination of nonaradial, octaradial, and octaradial (9+8+8) symmetries of scalids. The radial symmetry is a secondary appearance considered as an evolutionary adaptation to a lifestyle within the three-dimensional environment of bottom sediment. The eight anteriormost, or primary, scalids retain their particular position because of their innervation directly from the circumpharyngeal brain. As a result of a combination of the octaradial symmetry of primary scalids, pentaradial symmetry of teeth, and the 25-radial symmetry of scalids, the initial bilateral symmetry remains characterized by the single sagittal plane. J. Morphol. 247:99–110, 2001. © 2001 Wiley-Liss, Inc.

BACKGROUND: This study aimed to investigate a possible association between low birth weight (LBW) and other perinatal major characteristics and the risk of a child having accessory pathways of conduction tissue and cardiac arrhythmia later in life. METHODS: Thirty-one children aged 1-15 years (12 boys, 19 girls), in whom the persistence of accessory pathways of conduction tissue in the heart and inducible reciprocating supraventricular tachycardia were confirmed by means of programmable transoesophageal pacing, constituted the study group. None of them exhibited signs of either inborn or acquired heart disease causing arrhythmia, and their parents and siblings did not suffer cardiac arrhythmias. The control group was formed of 62 apparently healthy children (two controls for each case) matched to cases for sex, age, date and place of birth. Information on infant perinatal and maternal characteristics was collected retrospectively. RESULTS: High risk of arrhythmia in children was associated with LBW (< 2500 g): odds ratio was equal to 14.6 (95% CI: 1.7-127.9; P = 0.015), and it remained after adjustment had been made for major potential confounders. In addition, children with arrhythmia were more often born with retarded intrauterine growth (birth weight < 10 percentile), preterm (< 37 weeks of gestation), of higher birth order, and had lower Apgar scores at 1 and 5 min. Their mothers more often had diagnosed gynaecological diseases. CONCLUSIONS: Antenatal stress leading to LBW may be associated with atypical development and maturation of cardiac conduction system and increased risk of cardiac arrhythmias later in life.

132 The bivalve mollusk Mactra chinensis Philippi, 1847 is of significant commercial importance in the Asian–Pacific area; therefore, it is studied by malacol� ogists intensely. On the basis of morphological data, researchers suggested a divergence of this species in the Sea of Japan. As a consequence of the divergence, the southern and northern populations have already appeared which are different in the shape, color, and the shell pattern. For example, in the South Korean part of the Sea of Japan, the Mactra shell is described as faintly colored, yellowish, without any brown rays, while in the Russian part of the Sea of Japan, there is

Two new species of Kinorhyncha, Pycnophyes spitsbergensis and P. mokievskii, are described and illustrated from muddy sediments of the Greenland Sea, from the Isfjord of the West Spitsbergen Island (78°N) at a depth of 6 m. These are the first kinorhynchs described from Spitsbergen, and are the northernmost kinorhynchs found within the Arctic Circle to date. Pycnophyes spitsbergensis and P. mokievskii are the fifth and sixth members of this genus described from Arctic waters. The unique structure of the ventral posteriomesial pachycycli of the 12th segment, rectangular anteromesial ventral pachycycli of the 9th to 12th segments, and ventrolateral cuticular scars on the sternites clearly separate P. spitsbergensis from known congeners. The sympatric species, P. mokievskii, is easily separated on the basis of two closed midventral protrusions with sensory papillae at the posterior end of the body. Pycnophyes greenlandicus Higgins and Kristensen, 1988 from Greenland and P. maximus Reimer, 1963 from northern Europe are similar in size and general morphometric characters to the species described.

Aspidosiphon. elegans (Chamisso & Eysenhardt, 1821) (Fig. 5 A���C) Material. NhaTrang Bay: Mot Island, 7 m depth, coral rubble, 8 specimens; Tre Island, 6 m depth, coral rubble, 11 specimens; Tre Island, intertidal, fouling community, 7 specimens; Mung Island, 12 m depth, coral rubble, 6 specimens; Nok Island, 5 m depth, coral rubble, 2 specimens; Diamond Bay, intertidal, coral rubble, 230 specimens. Description. Trunk 10���30 mm long, 2 ���2.5 mm wide, pale, semitransparent, with minute papillae; introvert subequal in length to the trunk length. Anal shield yellow-brown, with dark brown units, ungrooved; caudal shield weakly developed, yellow-brown. Tentacular apparatus with dorsal arc of 5���7 short tentacles around the dorsal nuchal organ. Bidentate compressed hooks arranged in rings in the distal introvert; dark conical hooks are scattered proximally. Continuous longitudinal musculature layer splits in the anal shield area; two retractor muscles originate at 5���10 % of trunk length from caudal shield. Gut with 15���20 loops; spindle muscle attached posteriorly. Nephridia 75���80 % of trunk length; attached to body wall for 80���90 % of their length. Discussion. The species differs significantly from other representatives of the subgenus Aspidosiphon (Aspidosiphon) by two types of hooks, bidentate compressed and conical, and the anal shield structure. Aspidosiphon elegans is a tropical and subtropical species widely collected in the Atlantic, Indian and Pacific Oceans. In the West Pacific it has been found from Australia to Japan, while in the South China Sea it is only known from Vietnam and the Hainan Island. Usually it inhabits dead corals and soft rocks in intertidal and shallow waters., 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 51, DOI: 10.5281/zenodo.279772

Aspidosiphon (Paraspidosiphon) steenstrupii Diesing, 1859 (Fig. 5 M���Q) Material. Nha Trang Bay: Mot Island, coral rubble, 7 m depth, 2 specimens; Tre Island, coral rubble, 6 m depth, 8 specimens; Tre Island, fouling community, intertidal, 3 specimens; Mung Island, coral rubble, 12 m depth, 9 specimens; Diamond Bay, coral rubble, intertidal, 12 specimens. Description. Trunk 5���15 mm long, 3���4 mm wide, whitish pale, with light brown pre-anal region, semitransparent; introvert subequal to trunk length. Anal shield ungrooved, consists of uniform-sized rectangular units, with calcium carbonate cap. Anal shield dark colored (brown or black) in specimens from gastropod shells and pale-yellow in specimens from dead corals. Caudal shield with radial and circular grooves. Tentacles of living specimens with brown pigments; compressed bidentate hooks 25���30 ��m in height, arranged in rings, with tonguelike extension of internal clear streak; numerous pyramidal hooks 30 ��m in height, scattered proximal to the rings of bidentate hooks; tubular papillae scattered between rings and pyramidal hooks. Longitudinal musculature in anastomizing bands and retractor muscles originate 20 % of the trunk length from the caudal shield. Gut with 10���12 loops; spindle muscle attached posteriorly. Nephridia 2 / 3 of trunk length, unattached along their entire length. Discussion. An ungrooved anal shield with calcium carbonate cap, rings of compressed bidentate hooks with tongue-like extension of the clear streak, scattered pyramidal hooks, and tubular papillae, all characters that separate Aspidosiphon (Paraspidosiphon) steenstrupii from all other representatives of the subgenus Aspidosiphon (Paraspidosiphon). This species is considered as a tropical and subtropical animal found in the Atlantic, Indian and Pacific Oceans, reported from Australia to Korea in the West Pacific, and from the coast of Vietnam and Hainan Island in the South China Sea. It inhabits coral rocks and mollusk shells in shallow water., 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 pages 53-54, DOI: 10.5281/zenodo.279772

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

Apionsoma trichocephalus Sluiter, 1902 (Fig. 4 E���F) Material. Nha Trang Bay: Diamond Bay, intertidal, coral rubble, 1 specimen. Description. Trunk spindle-shaped, 3���4 mm long, 1 mm wide; very thin introvert 10 X longer than the length of the trunk. Fold-like dorsal arc with 6 minute rudimentary tentacles, usually invisible in the dissecting microscope. Hooks scanty, barely visible, without accessory combs of spinelets, arranged in one incomplete ring. Discussion. This species differs from other representatives of the subgenus Apionsoma by having scanty hooks lacking spinelets and a reduced tentacular apparatus. Apionsoma trichocephalus is a circumtropical species, known from the Atlantic, Indian and Pacific Oceans. It inhabits sandy and muddy sediment from the intertidal to bathyal depths, and has been recorded in the West Pacific from New Zealand to Japan., 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 pages 50-51, DOI: 10.5281/zenodo.279772, {"references":["Sluiter, S. P. (1902) Die Sipunculiden und Echiuriden der Siboga Expedition, nebst Zusammenstellung der Ueberdies aus den indischen Archipel bekannten Arten. Siboga Expeditie, Monographie, 25, 1 - 53."]}

A. antillarum (Grübe & Oersted, 1858) (Fig. 4 A) Material. Nha Trang Bay: Tre Island, intertidal, fouling community, 11 specimens. Description. Trunk 10–20 mm in length, 4 mm in width, yellow-brown, with dark brown papillae especially large, crowded at anterior trunk and introvert base; distal introvert smooth, yellow, with distinct collar. Introvert shorter than trunk; numerous (up to 70–80) digitiform tentacles with brown strips and patches, surrounding the nuchal organ; hooks absent. Discussion. This is the only species of the genus Antillesoma. It is a circumtropical and subtropical species that is known from the Atlantic, Indian and Pacific Oceans. In the West Pacific, it has been reported from Australia to Taiwan, and is usually found at intertidal and shallow depths in soft rocks and dead corals.

Themiste (Lagenopsis) cymodoceae (Edmonds, 1956) (Fig. 2 D) Material. Nha Trang Bay: Diamond Bay, 1���2 m depth, coral rubble, 1 specimen. Description. Trunk pyriform or flask-shaped, 4 mm long, 2 mm wide in anterior trunk, about 2 mm in width in posterior trunk. Introvert about 2.5��� 3 X shorter than trunk length, pale, without pigmented collar; hooks absent. Tentacular apparatus with four short stems; stems are equal in size, with bush-like tentacular branches; tentacles brown proximally, and in living specimens yellow distally. Discussion. T. cymodoceae, T. lageniformis and T. dehamata are the only three species in the subgenus Themiste (Lagenopsis) that have no introvert hooks. T. lageniformis is well distinguished from T. cymodoceae by having a purple pigmented introvert collar. T. dehamata is characterized by an elongated cylindrical trunk and tentacular stems of unequal length, while T. lageniformis and T. cymodoceae possess a pyriform trunk and tentacle stems of equal length. In contrast to the smaller bodied T. lageniformis, adult specimens of T. cymodoceae (previously known only from Australia) are much larger (trunk length commonly more than 40 mm). This is the first record of an adult specimen (with mature eggs) with trunk only 5 mm in length. It inhabits intertidal and shallow water areas, seagrass beds, 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 46, DOI: 10.5281/zenodo.279772

Aspidosiphon (Paraspidosiphon) laevis de Quatrefages, 1865 (Fig. 5 K���L) Material. Nha Trang Bay: Diamond Bay, intertidal, 10 specimens. Trunk 15���20 mm long, 3���4 mm wide, pale yellow, semitransparent, with minute papillae; introvert about 1.5 X trunk length, whitish pink in living specimens. Anal shield yellow-brown, with 10���12 longitudinal grooves. Caudal shield yellow-brown, with 17���18 radial grooves. Unidentate compressed hooks arranged in rings. Longitudinal musculature splits into 25���30 bands; retractor muscles originate at 10���15 % of trunk length from the caudal shield, fused for most of their length. Gut with about 30 loops; spindle muscle attached posteriorly, may be bifurcated at the anterior end. Nephridia are about 40 % of trunk length, about 1 / 3 attached to the body wall. Discussion. The only other representative of the subgenus Aspidosiphon (Paraspidosiphon) with grooved anal shield is A. coyi, which differs from A. laevis by the presence of distal hooks with secondary tooth and the position of retractor muscles that originate anterior to the caudal shield at the posterior end. Aspidosiphon laevis is a tropical species that is widespread in the Atlantic, Indian and Pacific Oceans. In the West Pacific it is known from Australia to Japan, and inhabits coral rocks in shallow water., 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 (Paraspidosiphon) tenuis Sluiter, 1886 (Fig. 5 R���S) Material. NhaTrang Bay: Mot Island, coral rubble, 7 m depth, 3 specimens; Tre Island, coral rubble, 6 m depth, 6 specimens; Tre Island, intertidal, fouling comunity, 5 specimens; Diamond Bay, coral rubble, intertidal, 20 specimens. Description. Trunk 5���15 mm long, 2���3 mm wide, pale or light brown, semitransparent; introvert 1.5��� 2 X trunk length. Anal shield green or brown-green, smooth and glossy, sometimes saddle-shaped or concave, composed of small dark units, with short marginal grooves; caudal shield brown-green, with radial grooves. Tentacles with white pigments; bidentate hooks 30 ��m in height, arranged in rings on the distal introvert; unidentate hooks scattered on the proximal introvert. Pyramidal hooks absent. Longitudinal musculature splits into 23���25 anastomozing bands; retractor muscles originate 10 % of trunk length from the caudal shield. Gut with 10���15 loops. Nephridia are about 80���90 % of trunk length, unattached. Discussion. This species differs from other representatives of the subgenus Aspidosiphon (Paraspidosiphon) by the anal shield structure, the presence of both bidentate and unidentate hooks, and the absence of pyramidal hooks. This is a tropical Indo-West Pacific species known from Australia to Taiwan. It inhabits coral rocks and shells in shallow water., 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 54, DOI: 10.5281/zenodo.279772

Siphonosoma australe (Keferstein, 1865) (Fig. 1 B���D) Material. Nha Trang Bay: estuary of B river, muddy sand at depth 25���40 cm, 50 specimens; Tre Island, intertidal, 3 specimens; Nha Trang fish market, 10 specimens. Worms can be found by characteristic holes of their burrows in intertidal and shallow subtidal zones. Description. Trunk up to 150 mm long and 12���15 mm wide; introvert about subequal in length to trunk with large, simple dark pointed hooks, 150���200 ��m tall in about 50 rings. Tentacular apparatus subdivided in dorsal arc with 15���20 tentacles enclosing the nuchal organ; oral crown with 10���14 longitudinal festoons bearing up to 30 tentacles. Tentacles of living specimens with yellowish oral and greenish aboral surfaces, becoming whitish in preserved specimens. Body wall musculature often visible through the skin, with 15���16 longitudinal muscle bands. Dorsal retractors originate anterior to the ventral ones. Oesophagus with 2 fixing muscles, gut with 35���40 loops; spindle muscle with up to 3 branches. Contractile vessel with tiny villi, is contracted and indistinct in preserved specimens. Nephridia are free, about 40 % of trunk length. Discussion. The species is similar to S. rotumanun but can be easily separated by having characteristic hooks closely associated with large papillae. Another Indo-West Pacific species, S. cumanense, differs from S. australe by lacking introvert hooks and by the origin of dorsal and ventral retractor muscles at the same anterior-posterior level. S. funafuti, known from Southern Japan, Taiwan and South China Sea, differs by lacking hooks, and S. vastum, also widespread in the Indo-West Pacific, has multiple clusters of caecum on the rectum that are absent in S. australe. Siphonosoma australe has a tropical and subtropical distribution and is found in shallow and intertidal waters, preferring sandy and muddy areas. It is known in the Indian Ocean from Indonesia to India and Madagascar. In the West Pacific it is reported from Australia and New Zealand to South China. Worms may be found by characteristic holes of their burrows in intertidal and shallow subtidal zones., 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 44, DOI: 10.5281/zenodo.279772

Cloeosiphon aspergillus (de Quatrefages, 1865) (Fig. 6 C���D) Material. Nha Trang Bay: Mot Island, coral rubble, 7 m, May 2008, 12 specimens; Tre Island, coral rubble, 6 m, Jun 2008, 18 specimens; Tre Island, biofouling, intertidal, Nov 2009, 6 specimens; Mung Island, coral rubble, 12 m, May 2008, 15 specimens; Nok Island, coral rubble, 5 m, 8 specimens; Diamond Bay: coral rubble, intertidal, Jun 2008, 25 specimens; Nov 2009, 16 specimens; Mar 2010, 8 specimens. Description. Trunk up to 70 mm long, 4���5 mm wide, light brown or grey, with minute brown papillae, semitransparent; introvert shorter than trunk. Anal shield consists of white rhomboid or polygonal mosaicly arranged, calcareous units, with a dark central pore; caudal shield absent. Introvert protruded through the center of the anal shield; bidentate hooks arranged in rings distally. Longitudinal musculature continuous; retractor muscles originate in the middle of the trunk. Gut with 10 loops. Nephridia are about 70���90 % of trunk length, completely attached to the body wall. Discussion. This is the only species of the genus Cloeosiphon, and because of its unique configuration between the anal shield and the introvert by far the most distinctive species of sipunculans. This tropical species is widely distributed in the Indo-West Pacific. In the West Pacific it has been reported from Australia to Hainan Island, inhabiting coral rocks in shallow water., 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 55, DOI: 10.5281/zenodo.279772, {"references":["Maiorova A. & Adrianov A. (2010) Distribution of peanut worms (Sipuncula) in the West Pacific. Proceedings of China-Russian Bilateral symposium on \" Comparison on Marine Biodiversityin the Northwest Pacific Ocean. 10 - 11 November Qingdao, China, pp. 13 - 17."]}

Phascolosoma stephensoni (Stephen, 1942) (Fig. 3 G���I) Material. Nha Trang Bay: Tre Island, 20 m depth, sand, boring in shell of Placuna sella, 1 specimen. Description. Trunk 20 mm long, 4 mm wide; from light brown in anterior and middle trunk to dark brown posteriorly, with large conelike papillae concentrated at the anterior and posterior end. Introvert subequal to trunk length, with pigmented bands; hooks with smooth clear streak, clear triangular area, crescent and distinct secondary tooth on the concave side, with about six cuticular warts basally. Longitudinal musculature splits into 15���20 anastomizing bands; dorsal and ventral retractors originate 40 % and 20 % of trunk length from the posterior end, respectively. Gut with about 10 loops; spindle muscle attached posteriorly. Nephridia about 70���80 % of trunk length with about 1 / 6 attached to the body wall; nephridiopores and anus at the same level. Discussion. The internal structure of the hooks and the conical preanal and caudal papillae clearly distinguish P. stephensoni from other closely related species of the genus Phascolosoma. This species is known from the Mediterranean, eastern Atlantic, Indian, and Pacific Oceans. It inhabits sandy bottoms and mollusk shells at shallow depths., 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 49, DOI: 10.5281/zenodo.279772

Thysanocardia catharinae (Gr��be, 1868) (Fig. 2 C) Material. Nha Trang Bay: Mung Island, 12���25 m depth, muddy sand, 5 specimens. Description. Spindle-shaped, sand-coloured trunk 3���9 mm long, 1 ���1.5 mm wide, with minute papillae and characteristic sinuous wrinkles of cuticular microrelief; introvert subequal to or 1.5 X trunk length. Tentacular apparatus with dorsal arc of tentacles, oral crown with longitudinal festoon of tentacles; tentacles of living specimens with yellow tips, colourless in fixed worms. Body wall with continuous muscle layers. Two wide retractor muscles originate in the posterior trunk, about 10���15 % of trunk length from the posterior end. Gut with 6���10 loops. Spindle muscle not attached posteriorly. Contractile vessel with numerous villi. Nephridia are free, about 35 % of trunk length; nephridiopores are at the level of the anus. Discussion. There are only three species known for this genus worldwide. T. nigra can be well separated from T. catharinae by presence of dark pigments in colored tentacles of both dorsal and oral tentacular crowns. T. nigra is also characterized by having long branched contractile vessel villi. Both species are common in North-West Pacific, while the third species, T. procera, is known only from the Atlantic. Thysanocardia catharinae has a temperate and tropical distribution, can be found mainly subtidally inhabiting sand, silty sand, and dead corals. It is known in the West Pacific from the Gulf of Siam to the Sea of Japan., 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 45, DOI: 10.5281/zenodo.279772

Lihacrosiphon cristatus (Sluiter, 1902) (Fig. 6 A���B) Material. Nha Trang Bay: Mot and Tre Islands, 4���7 m depth, coral rubble. Description. Trunk 10���15 mm long, 3���4 mm wide, light brown, semitransparent; introvert subequal to trunk length. Anal shield furrowed longitudinally with about 20 grooves and often covered by red, yellow and white calcareous deposit which masks these grooves. Bidentate hooks arranged in rings on the distal introvert; unidentate hooks scattered over the proximal introvert. Longitudinal musculature splits into 15���20 anastomozing bands. Retractor muscles originate 10 % of trunk length from the caudal shield. Nephridia are about 40���45 % of trunk length. Discussion. The species differs from the other representative of this genus, Lithacrosiphon maldivensis, in structure of the anal shield, which is ungrooved, granular, and bullet-shaped in L. maldivensis. Lithacrosiphon cristatus is a tropical species, known from the Atlantic and Pacific Oceans. In the West Pacific it has been reported from Indonesia to southern Japan. It can be found inside coral rocks in shallow water., 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 54, DOI: 10.5281/zenodo.279772, {"references":["Sluiter, S. P. (1902) Die Sipunculiden und Echiuriden der Siboga Expedition, nebst Zusammenstellung der Ueberdies aus den indischen Archipel bekannten Arten. Siboga Expeditie, Monographie, 25, 1 - 53."]}

Apionsoma misakianum (Ikeda, 1904) (Fig. 4 B���D) Material. Nha Trang Bay: Mot Island, 10 m depth, coral rubble and empty bivalve shells, 5 specimens; Mung Island, 25 m depth, muddy sand, 4 specimens; Tre Island, intertidal, fouling community, 3 specimens; Diamond Bay, intertidal, coral rubble, 2 specimens. Description. Trunk spindle-shaped, 2���5 mm long, 0.7 mm wide; posterior trunk with numerous papillae; body wall pale and translucent, muscle layers continuous. Introvert 7���10 X longer than trunk, tentacular apparatus with 5���7 tentacles around the dorsal nuchal organ; hooks with accessory comb of 3���5 basal spinelets. The four retractor muscles originate at the midtrunk area. Gut with 15���20 loops; spindle muscle attached posteriorly. Nephridia bilobed and about 50 % of trunk length. Discussion. In contrast to A. misakianum, A. murinae is characterized by a thick opaque body wall with large trunk papillae, while A. trichocephalus has a considerably long and vermiform body that lacks tentacles and hooks. Apionsoma misakianum is a tropical and subtropical species, widespread in the Atlantic, Indian and Pacific Oceans. This species inhabits coral, sand and algae mats in tidal pools and shallow waters. In the West Pacific it is known from Polynesia to Japan and in the South China Sea from the Hainan Island., 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 49, DOI: 10.5281/zenodo.279772

Sipunculus nudus Linnaeus, 1766 (Fig. 1 A) Material. Nha Trang Bay: Mung Island, depth 14���15 m, muddy sand, 1 specimen; Kay River mouth, intertidal, 1 specimen; local fish-markets in Nha Trang, 10 specimens. Description. Trunk 120���140 mm in length and 10���12 mm wide; introvert about �� trunk length. Tentacular apparatus with four main branched stems, two dorsal 2 X as long as ventral pair. Longitudinal musculature splits into 28���32 bands. Nephridia partially (up to 50 %) attached to the body wall; nephridiopores anterior to anus. Spindle muscle originates on body wall anterior to anus. Discussion. The species is similar to S. robustus which differs by having unattached (free) nephridia. This species is considered cosmopolitan in temperate to tropical waters. In the West Pacific it is found from New Zealand (Kermadek Islands) to Japan and is common in South China Sea, from South Vietnam to Hainan Island. Usually collected from the intertidal it has also been reported from depths of up to 2000 m. This species prefers muddy sand, mangroves and silty sediments., 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 42, DOI: 10.5281/zenodo.279772

Aspidosiphon gracilis (Baird, 1868) (Fig. 5 D���H) Material. Nha Trang Bay: Tre Island, Dombay Harbor, 10 m depth, tube of Cerianthus filiformis, 1 specimen. Description. Trunk long and thin, 20 mm long, about 2 mm wide, yellow-grey or light brown, with minute papillae; introvert 1.5 X trunk length. Anal shield weakly developed, composed of noncontiguous brown papillae and dark platelets arranged in weakly defined longitudinal rows. Caudal shield light brown, conical, with distinct radial grooves. Unidentate hooks arranged in rings in the distal introvert; proximal part of the introvert with conical hooks. Base of unidentate hooks with bifurcated posterior edge. Retractor muscles originate close to the posterior trunk end, at 5���8 % of trunk length from the caudal shield. Gut with 8���10 loops; spindle muscle attached posteriorly. Nephridia are free, 60 % of trunk length. Discussion. This species varies from other representatives of the subgenus Aspidosiphon (Aspidosiphon) in the structure of both the anal and caudal shields. Aspidosiphon gracilis is a tropical species known from the Indian and Pacific Oceans. It has been found from Australia to the Philippines in the West Pacific. It inhabits coral rocks and mollusk shells in intertidal and shallow water., 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 51, DOI: 10.5281/zenodo.279772

Phascolosoma arcuatum (Gray, 1828) (Fig. 3 A���B) Material. South Vietnam: Mekong River mouth, intertidal, mangrove, 30 specimens. Description. Trunk 60���90 mm long and about 10 mm wide; light yellow-brown or brown-greyish skin with large domelike dark-brown papillae distributed over the entire trunk and more closely set at the anterior and posterior end of the trunk. Introvert 2 X trunk length; hooks up to 70 ��m in height, without secondary teeth, warts or toes; with streak (apical canal) widely expanded basally; arranged in numerous (up to 100) complete and incomplete rings. Dorsal retractor muscles originate 10 %, ventral retractors 15 % of trunk length from the posterior end. Retractor muscles appear to coalesce to a single muscle with four roots in preserved specimens. Gut with 30���50 loops; spindle muscle attached posteriorly. Nephridia about 1 / 3 of trunk length. Discussion. Eight other species of the subgenus Phascolosoma are known from the South China Sea. These are well distinguishable from the P. arcuatum by their hook structure. In contrast to P. nigrescens, P. pacificum and P. stephensoni, P. arcuatum lacks basal warts. P. pacificum has, in addition, nephridia equal to the trunk length. P. nigrescens differs from P. arcuatum by presence of hook streak with an enlarged median swelling, and hooks of P. stephensoni are characterized by the presence of smooth narrow streak, clear crescent, and and a distinctive triangle. P. g l a b r u m has hooks with a large rounded bump on the concave side and basal toes. The remaining four species in the subgenus, P. agassizii, P. albolineatum, P. perlucens and P. scolops, vary from P. arcuatum by a lower number (P. albolineatum the tip of each hook is bent at an obtuse angle that is a unique character for this species, while hooks of P. agassizii lack a basal expansion of the streak. Hooks of P. perlucens are characterized by the presence of a large rounded hump on the concave side, and those of P. scolops have a distinct triangle, well separated from the narrow streak. Phascolosoma arcuatum is a common species in the Indo-West Pacific (from India and northern Australia to south China and Taiwan) found in brackish water environments such as intertidal muddy bottoms and mangrove estuaries., 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 pages 46-48, DOI: 10.5281/zenodo.279772

Nephasoma pellucidum (Keferstein, 1865) (Fig. 2 A���B) Material. Nha Trang Bay: Hon Rock, 10���15 m depth, coral rubble, 10 specimens; Mung Island, 7���15 m depth, sand, 1 specimen. Description. Trunk spindle-shaped, 20���25 mm long and 3���4 mm wide; introvert shorter than trunk, with scattered hooks of two types ��� small, about 50 ��m, and large, up to 300 ��m in height. Tentacular crown with 20���30 whitish transparent tentacles. Trunk is translucent, pale tan, with large uniformly distributed digitiform papillae. Body wall with continuous muscle layers; two retractor muscles originate in the mid trunk. Gut with 25���30 loops; spindle muscle not attached posteriorly; contractile vessel with vesicular swellings. Nephridia free, about 35���40 % of trunk length, nephridiopores adjacent to anus. Discussion. This is the only species of Nephasoma that is common in shallow waters of the Indo-West Pacific. In the West Pacific, it has been found inhabiting sandy bottoms and dead corals from Australia and Indonesia to southern Japan., 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 44, DOI: 10.5281/zenodo.279772