<Echiura:Echiuridae)

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Species Diversity, 2004, 9, 109-123

Synonymy of the West-Pacific Echiuran Listriolobus sorbillans

Teruaki Nishikawa

The A]dgqya Uitiversity Museum, Chikusa-ku, IVtlgQya, 464-860I Jtipan

E-mail: nishikawa@'num.nagaya-u.ac,.tp

(Received 10 June 2oo3; Accepted 4 December 2003)

Examination of the syntypes of Listriolobus sorbillans (Lampert, 1883) from the Philippines and new specimens from Moreton Bay, eastern Aus-

tralia, and the Ryukyu Islands, Japan, together with a literature survey, re-

veals that it is a senior synonym of L. billitonensis Fischer, 1926 recorded

flrom thc Java Sea and L. riuiciuensts Sato, 1939 from southwestern Japan.

Observations on individual variation in the ratio of proboscis to trunk

length, the number of longitudina] musele bands, and the number and arrangement of gonoducts are presented. A tabular comparison of all the known species of the genus Listriotobus is given, together with some new

taxonomic information about the congeners and allies.

Key Words: Listriolobus, Echiura, taxonomy, synonymy, revision,

Introduction

The echiuran genus Listriotobus Spengel, 1912, belonging to the family Echi- uridae (for family-group nomenclature see Nishikawa 1998), is distinguished from the closely related Ochetostonea Leuckart and RUppel, 1828 by the inner-most oblique muscle layer of the trunk wall, which is continuous where it is visible between the longitudinal muscle bands in the former genus but separated into fascicles in the latter (see, e.g., Spenge] 1912; Fisher 1946, 1949; Stephen and Edmonds 1972; Edmonds 1987; Biseswar and Moodley 1989; Nishikawa 1992; fbr historic ob- jections to the separate status of these genera see Bock 1942). The eriginal deseriptions of many species referred to these two genera [including Listriolobus sorbiltans (Lampert, 1883) in the present study] lack information about the above-stated diagnostic feature of the oblique muscle layer, and, therefbre, the generic affiliation of such species needs a critical reexamination. For ex- ample, Biseswar and Moodley's (1989) reexamination of the holotype of Oche- tostoma capense Jones and Stephen, 1955 resulted in the transfer of this species to Listriolobus. During my preparation for this critical study, I had the opportunity to inspect the syntypes of Thatassema sorbtltans Lampert, 1883 from the Philippines and discovered its conspecificity with Listriolobus riukiuensis Sato, 1939, so far recorded from the Ryukyu Islands of southwestern Japan (Sato 1939; Nishikawa 1992). The first redescription of the syntypes of T, sorbillans since its establishment is given herein to confirm its affiliation to the genus Listriolobus. Furthermore, some taxo-

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11O Teruaki Nishikawa

nomic, nomenclatural, and biogeographical information is presented on the basis of newly collected specimens from Japan and Australia, as well as a literature survey, to provide a fbundation fbr a thorough taxonomic revision of the genus Listri- olobus and allies in the future,

Historical Background

Establishment of the genus Listriolobus Spengel (1912) pointed out that the anterior-most pair of nephridia (=gonoducts in the present study) is always situated anterior to the ventral setae, and the "Interbasa]muskel" (-interbasal muscle) is always absent, in such specimens of the genus Thalassema that have the longitudinal muscle layer of the trunk separated into bundles and also have three or more pairs of gonoducts. He thereupon proposed a taxonomic division of such specimens into two groups on the basis of `tThalassema his actual reexamination of the echiurans then described as erlythrogrammon", including its holotype housed at the Forschungsinstitut Senckenberg (stil1 there: D. Fiege, pers. comm.). "Septalleisten" One group was composed of the specimens with (derived from the fascicules of the oblique muscle layer between the longitudinal muscle bands) and included some of the syntypes of Thalassema caudex Lampert, 1883 (those col- lecteci from the Red Sea, while those from the Indian Ocean were then unexam- ined), The genus name Ochetostoma Leuckart and RUppell, 1828 was revived by Spengel (1912) as valid for this group, its type species being Ochetostoma erlythrogrammon Leuckart and RUppell, 1828. The other group included the specimens of `"71 e)lythrQgrammon" in the sense of Sluiter (1884) and Wilson (1900), as well as "Septalleisten". Spengel's (1912) own specimens, all lacking the For these specimens a new genus Listriolobus was erected by Spengel (1912) without type designation and any nominal species included therein (see below). Later, Fischer (1926) established Listriolobus billitonensis Fischer, 1926 for Sluiter's (1884) many specimens firom coastal sand of Billiton Island, Indonesia, and L. bahamensts Fischer, 1926 for Wilson's (1900) one specimen from off Great Abaco Island, Bahamas, and also for Spengel's (1912) single specimen from Florida, These two species are obvi- ously available, since they were published before 1931 and accompanied by bibliographic references (ICZN 4th ed., Art, 12); the whereabouts of the name-bearing types of these two species are now unknown.

Confused definition of genus Listriolobus As shown above, it is clear that Spengel (1912) recognized the genus Listri- otobus as lacking the interbasal muscle, as rightly pointed out by Bock (1942). How- ever, Fisher (1946: 234) reversed the definition of this genus in terms of the inter- "interbasal basal muscle, stating muscle of setae [is] present", probably based on the occurrence ef the muscle in L. pelodes Fisher, 1946, This misunderstanding on the part of Fisher has been fbllowed by most subsequent authors (e.g., Stephen and Edmonds 1972; Edmonds 1987; Biseswar and Moodley 1989). Fisher (1946) trans- ferred 71halassenza sorbillans Lampert, 1883 to the genus Listriotobus. Thus, L. sor- bittans has been in¢ orrectly believed to have the interbasal muscle, while L. riuki-

uensis lacks it, as is clearly shown by its original description, This represents the

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Synonymy ofaWest-Pacific echiuran 111

"L. reason why claimed, not Fisher (1946:234) riukiuensis .,, isprobably a Listri- olobus.'i Soon afterwards, Fisher (1949) rightly revised his previous definition of the genus Listrioiobus, explicitly stating that the interbasal muscle is present or absent in species of the genus; this definition is revived in the present study, So far as the prevailing echiuran classification is concerned, it seems unnecessary to divide this genus into two according to the presence or absence ef the muscle. For exam- ple, the genera Thalassema (s. str.) and Ochetostoma both include species with and without the interbasal muscle (see Stephen and Edmonds 1972; Biseswar 1988).

Taxonomy

Genus Listriolobus Spengel, 1912

Listriolobus Spengel, 1912: 316

Diagnosis Eemended by Fisher (1949) and in the present study]. Longitudinal muscles of body wall grouped into bands (at least in adults); inner-most oblique muscles continuous, never separated into fascicles between longitudinal muscle bands; one to three pairs (often with some anomalies) of gonoducts with their gonostomes located proximally; gonostomal lips elongated and often coiled spirally; interbasal muscle present or absent. Remarks. Fisher (1946, 1949) and Stephen and Edmonds (1972) regarded the original description of the genus Listriolobus as a nomen nudum, and Fisher attrib- uted its authorship and date te Fischer, 1926. However, this seems incorrect according to the ICZN 4th ed. (International Commission on Zoological Nomencla- ture 2000). Spengel (1912) gave a definition of the genus; though he failed to make a type designation and did not assign any nominal species to the new genus, this does not make the genus a nomen nudum, since it was proposed before 1931 (ICZN 4th ed., Art. 13.3), Thus, this genus takes the authorship and date of Spengel, 1912, as was rightly designated by Stephen and Edmonds (1972) and fo11owed by subsequent authors. Since Fischer (1926) is the first to include expressly the nominal species (Listri- olobus biltitonensis Fischer, 1926 and L. bahamensis Fischer, 1926) in the genus "originally Listriotobus Spengel, 1912, these two species are deemed to be the in-

cluded nominal species" eligible fbr type fixation (ICZN 4th ed., Art. 67.2,2). The type species is L. bahamensis Fischer, 1926 by Fisher's (1946) subsequent designation (ICZN 4th ed,, Art. 69,1),

Listriolobus sorbillans (Lampert, 1883) [Japanese name: Tatejima-yumushi] (Figs 1-2, Tables 1-2)

Thatassenza sorbillans Lampert, 1883: 340-341; Shipley 1899: 352 (no new record); Augener 1903: 349; Wharton 1913: 243-247, text-fig, 1.

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112 TeruakiNishikawa

Listriolobus sorbillans: Fisher 1946: 234; Stephen and Edmonds 1973: 425-426 (no new record). Listriolobus billitonensis Fischer, 1926: 110 (by bibliographical reference to Tha- lassema erlythrogrammon of Sluiter, 1884: 58-79, pl. 3) . Syn. nov. Listriolobus riukiuensis Sato, 1939: 359-362, text-figs 10-13; Stephen and Edmonds 1973: 425 (no new record), Syn. nov. ?Listriolobus bulbocaudatus: Davie 1998: 68 (with an unnumbered photograph of an extended proboscis in the field). [IVec Edmonds, 1963]

Specimens examined. Syntypes of L. sorbilZans: deposited in Museum fUr "Zoologisches Naturkunde der Humboldt-Universitat zu Berlin as Museum Berlin Katalog-Nr. 1219, Thalasserna sorbillans, 2 syntypes, Philippines, leg. Semper", one with 25,5mm long proboscis and 66.5mm leng trunk, while other with proboscis missing and 106.5 mm long trunk; intact trunks dissected by me with permission of

the museum. Holotype of L. riukiuensis: deposited in the Zoological Laberatory, Graduate "Okinawa School of Science, Tohoku University, Sendai, labeled as No. 7, Listri- otobus riukiuensis n. sp., Kabira, Ishigaki-jima [-Kabira Bay of Ishigaki Island in Okinawa Prefecture], 26/II/1937, [collected by] Ohshima [=Prof, Hiroshi Oshima, see below], Masaki and Miyake", with ea. 140mm long proboscis and 75mm long incomplete trunk (its posterior part missing as mentioned in the original description). 0ther specimens, often incomplete due to iniuries at collection, from intertidal

sandy tlats in the Ryukyu Islands, southwestern Japan, deposited in the Nagoya University Museum (NUM), registered as NUM-Az: 0351, bottom of Kabira Bay, Ishigaki Is., 1 Apr. 1975, T. Nishikawa coll., 2 inds; 0352, Haneji Sound, Okinawa Is., 5 Nov, 1988, H. Uchida coll,, 5 inds; 0353, Haneji Sound, Okinawa Is., 16 July 1992, T. Nishikawa coll., 8 inds; 0354, Yanyu, Kasari Bay, Amami-Ohshima Is,, 4 Nov, 1995, H. Yamashita coll,, 2 inds; 0355, Nagura Bay, Ishigaki Is., 10 Nov. 1993, I. Soyama coll., 1 ind,; 0356, Tekebu, Kasari Bay, Amami-Ohshima Is., 19 Nov. 1993, I. Soyama coll., 10 inds; 0357, Funaura, Iriomote Is., 24 June 1994, T, Nishikawa coll., 5 inds;

0358, Kabira Bay, Ishigaki Is., 25 June 1994, T. Nishikawa coll., 3 inds; 0359, Haneji

Sound, Okinawa Is,, 26 June 1994, T. Nishikawa coll., 17 inds; 0360, Shirahama, Iri- omote Is,, 4 May 1996, T. Nishikawa coll., 10 inds; 0361, Haneji Sound, Okinawa Is.,

30 July 1996, T, Nishikawa coll., 10 inds; 0362, Haneti Sound, Okinawa Is., 31 Mar,

1998, T. Nishikawa coll., 18 inds. Specimens from Moreton Bay, eastern Australia: NUM-Az0349, sandy fiat in firont of Moreton Bay Research Station, University of Queensland, North Strad- broke Is., intertidal, 8 Apr, 2003, T. Nishikawa coll,, 4 inds; NUM-Az0350, ibid., 7

Fig, 1. A syntype ofListriolobus sorbilgans (Lampert, l883). A, body, ventral view; B, ventra!

setae; C, internal merphology of anterior end of trunk, dorsal view. right gonoducts omitted fbr clarity; D. proxjmal part of 2nd right gonoduct, showing coiled gonostomal lips; E, internal morphology of posterior end of trunk, dorsal view. Trunk musculature and mesenteries

omitted in C and E. Abbreviations: al, alimentary canal; an, anus; av, anal vesicle; dv, dorsal

vessel; gd, gonoduct; gl, gonostomal lip; lm, longitudinal muscle band; nv, neurointestinal vessel; p, proboscis; rc, rectal coecum; rv, ring vessel; t, trunk wall; vn, ventral nerv cord; vs, ventral seta: vv, ventra] vessel. Scales: A, 1 cm; B, O.5mm; C and E, 5mm; D, 1 mm.

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Apr, 2003, S, Litherland coll., 3 inds. Description of the syntypes of L. sorbitlans. Complete specimen cemposed of proboscis 25,5 mm long and up to 7.2mm wide, and trunk 66.5 mm long and up to 20mm wide. Proboscis simple and thick. Trunk wal1 thickened and papillose at both extremities, due probably to contraction when collected or fixed. Trunk musculature consisting of outer continuous circular layer, middle longitudina] layer divided into 14 bands (including mid-ventral two bands adjacent to each other, likely miscounted as one if observed externally), and inner-most, thin and continuous oblique layer. One pair of ventral setae, without interbasal muscle. Three pairs of gonoducts, anterior-most situated anterior to setae, with no gametes in- side; gonostomes proximal, with gonostomal lips elongated and spirally coiled, Trunk vascular system of usual type (Fig. IC), composed of short dorsal vessel along and for mostly unattached to mid-dorsal line of alimentary canal, long ventral vessel associated with almost whole length of ventral nerve cord, and neurointestinal vessel connecting dorsal and ventral vessels. Neurointestinal vessel issu- ing from ventral vessel between posterior two pairs of gonoducts, soon bifurcated inte large loop, and dorsatly terminating on each side of ring vessel around alimentary canal. Posterior extremity of dorsal vessel connected to dorsomedian part of ring vessel. Ventral vessel terminating at rectal ceacum. Pair of anal vesicles (Fig. IE) ca. 35 mm long in complete specimen, ca. 45mm long in other. Additional description of other specimens. Trunk dark red in life, due partly to dark reddish erythrocytes in coelom and partly to reddish trunk wall (reddish coloration fading away after fixation with formalin), with longitudinal white lines representing muscle bands; proboscis pale yellow. Two-fifths to half of body length of living individuals comprising proboscis according to my observations on Japanese specimens relaxed with menthol; this proportion changeable

Table 1, Ranges of trunk Iength for specimens with complete tminks, and ranges of number

of longitudinal muscle bands in all available specimens, from materials collected at Kasari (Amami-Ohshima Is,), Haneji Sound (Okinawa Is.), Kabira Bay (Ishigaki Is.), Funaura and Shirahama (Iriomote Is.), and Moreton Bay (eastern Australia), as well as in syntypes from the Philippines.

No. of )onigitudinal Trunk Length in mm I.ocality (Date of collection) muscle bands (No, of individuals) (No. of individuals)

Kasari (Nov. 1993) 17.0-39.0 (10) 12-14 <10) Kasari (Nov. 1995) 2B.O-36,5 (2) 13 (2)13 Haneji Sound (Nov. 1988) 19.0-29.5 (7) (7)12-15 Haneji Sound (July 1992)' 34,O-49,O (3) (7) Haneji Sound (June 1994)" 15.5-69.0 (13) 12-14 (16) Haneji Sound (July 1996)' 36.1-95.4 (6) 13-15 (10) Haneji Sound (Mar. 1998) 60.7-1oo.O (10) 13-15 (13) Kabira Bay (June 1994)' 65.0 134,O (3) 14-16 (3) Funaura (June 1994)" no data 12-14 (5) Shirahama (May 1996) 126.0-202.0 (4) 13-16 (4) Philippines (unknown) 66.5- 106.5 (2) 14 (2)11 Moreton Bay (Apr. 2003)' 93.0-220.0 (7) 15 (7)

* Material includes specimen(s) with gametes in the gonoducts.

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Synonymy of a West −Pacific echiuran 115

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116 Teruaki Nishikawa

(sometimes extremely so) when fixed. In preserved specimens, for trunk length see Table 1 and fbr relative length of proboscis to trunk see Fig, 2, Longitudinal muscle bands very rarely bifurcate or anastomosing, their number in middle of trunk ranging from 11 to 16 with modes of 13 or 14 in different samples (see Table 1); 13 in holotype of L. riukiuensis. Very thin layer ef longitudinal muscle fibers detectable between longitudinal muscle bands in thin sections (not shown>, No interbasal muscle. Gonoducts usually in three pairs as in syntypes, but with some anomalies in number (four to eight gonoducts in total) and arrangement (Table 2): only second and third (postsetal) pairs present with first pair missing [indicated as "Rl(O)Ll(O)"]; only first (presetal) and second (postsetal) pairs present with third "R3(O)L3(O)"]; pair missing [as three usual pairs present plus one additional gonod- "L4(1)"]; uct posterier to third pair on left [as or three usual pairs present plus two "L3(3)"]. gonoducts added to left one of third pair [as Gonostomal lips long and straight (never coiled) in specimens collected and relaxed by me, while markedly coiled in holotype of L. riukiuensis and some other specimens. Trunk vascular sys-

tem as in syntypes; ventral origin of neurointestina} vessel located at various lev- els between ventral setae and second pair of gonoducts. Eggs in gonoduct disk- shaped, ca, 130um in diameter and 65"m thick; sperm with ca. 5ptm long heads. Conspicuous rectal coecum and pair of anal vesicles; in well-preserved specimens, many funnels, 80-100 sim in diameter, visible on surface of anal vesicles. Remarks. Listriolobus riuki"ensis was proposed by Sato (1939) for a single incomplete specimen, lacking the posterior part of its trunk, from Kabira Bay, Ishi- gaki Is., southwestern Japan. Morphological comparison of its holotype and newly

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Fig. 2. Relationship between trunk length in Listriotobus sorbitlans, among fixed specimens from the Philippines (the type locality), Ryukyu [s]ands (southwestern Japan), and Moreton Bay (eastern Australia).

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Synonymy of a West-Pacific echiuran 117

collected complete specimens from the type locality and others in southwestern

Japan with the syntypes of L. sorbiltans has revealed no significant diffk]rences between these two species, except in the relative length of proboscis to trunk. As

shown in Fig. 2, this ratio is slightly lower in the syntypes from the Philippines

and specimens from Australia than in Japanese specirnens. This difference may be attributable to geographical variation, although further evaluation should wait until more specimens have been collected from outside Japan. The specimens with only two pairs of postsetal gonoducts in the present material are reminiscent of L. pelodes, L. cqpensis Jones and Stephen, 1955, and L, brevirostris Chen and Yeh, 1958, but the former specimens are clearly distinguishable from these three species, all of which have only 7-8 longitudinal muscle bands (see Table 3). All the examined specimens in the present study are thus considered censpecific; L, riukiuensis, therefore, should be regarded as a junior synonym of L. sorbillans. "the Fisher (1946: 234) pointed out that diagram of the blood vessels [in the original description of L. riuhiuensis] is not the Listriotobus pattern''. My reexamination of the holotype of L. riukiuensis has, however, revealed that the vascular system is wrongly illustrated in text-fig. 12 of Sato's (1939) description, and is quite the same as that in the syntypes of L. sorbillans (Fig, 1) and the other well-preserved specimens examined in the present study, L`Historical In the Background" above, I noted that L. biilitonensis was erected "[Tlhalassema by bibliographic reference to Sluiter's (1884: 58-79) eilythrcigrammon" "im collected by Sluiter himself Sande der KUste der Insel Billiton" in the Java Sea

"pressing (p. 58); he got many individuals there at ebb tide by the foraging proboscis on the sand with the fingers and digging up the trunk with the other hand" [Chuang's (1962: 80) translation from Sluiter's German original], My efforts to find the name-bearing type of L. billitonensis have been unsuccessfu1. According to Sluiter's (1884) description, the living body was, when moderately stretched, up to 22-24 cm long, including the 6-8 cm long proboscis, with the proboscis's potentially stretching three to four times as long as usual, although much shrunken when fixed; there were 13-14 longitudinal muscle bands, and three pairs (one presetal and two postsetal) of gonoducts. Although no information was provided concerning the interbasal muscle, it seems clear that this species lacks the muscle (see "Historical Background"), like L, bahamensis (see below). These ecological and morphological features are well consistent with those of L. sorbillans; therefore, L. billitonensis is here treated as a junior synonym of L. sorbillans, Wharton's (1913) description of many specimens frem Mindoro Island, the Philippines, referred to Thatassema sorbillans, includes trunk musculature char- acteristic of Listriolobus but lacks any reference te the interbasal muscle. To verifY this point, I have tried to obtain Wharton's specimens or newly collected ones from the same locality for examination, but so far in vain. Until proved otherwise, his identification may better be regarded as valid. Moreton Bay is the type locality of L. bulbocaudattts Edmonds, 1963, regarded as a junior synonym of L. brevirostris Chen and Yeh, 1958 by Edmonds (1987). In an illustrated guide to the biota of Moreton Bay (Davie 1998), a photograph of an extended proboscis in the intertidal zone of a sandy flat is ascribed to L. bulbocaudatus. The present study has, however, revealed that the species was probably really L. sorbtllans. The specimens of true L. bulbocaudatus or L. brevirostris firom More-

"dredged "dredged ton Bay were from 8-10 fathoms" (Edmonds 1963: 243) or from

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118 Teruaki Nishikawa

mud" (Edmonds 1987: 132). Thus, it seems that Moreton Bay is inhabited by two speeies of Listriotobus, L. sorbitlans living intertidally and L. brevirostris (-L. bulbocaudatus) subtidally. Moreover, the present find of L. sorbillans from Moreton Bay sheds new light on Augener's (1903) old record of this species based on a single specimen from Sydney, Australia, whose possible identity with Ochetostoma aus- traliense Edmonds, 1960 was once suggested by Edmonds (1987), I have failed to learn the whereabouts of Augener's specimen, and therefore, his record is included rather tentatively in the present study, Shore collections in Sydney and vicinity, far south of Moreton Bay, are necessary to solve this problem. Geographical distribution. Ryukyu Islands, southwestern Japan, intertidal (Sato 1939; Nishikawa 1992; present study); Philippines, exact locality unknown (Lampert 1883); Buquete Is., Port Galera, Mindoro Is., Philippines, intertidal (Wharton 1913); Billiton (- Belitung) Is., Java Sea, intertidal (Sluiter 1884); Sydney (Augener 1903) and Mereton Bay, intertidal (present study), easter'n Australia. Biological notes. In Port Galera of Mindoro Island, Listriolobus sorbillans "found was in the top layer of sand, more than 100 specimens being collected in a space 1 meter square" (Wharton 1913: 244). In Okinawa, Ishigaki, and Iriomote Is- lands of southwestern Japan, my field observations revealed that the animal lives rather commonly and abundantly in more or less protected intertidal sandy or silty fiats, sometimes in peripheral areas of mangrove swamps. The maximum den- sity of proboscides was 10m-2 at Funaura, Iriomote Island, on 24 June 1994. The proboscis was found extending over the bottom surface in shallow tidepools, always with its ventral, convex surface upwards, as long as 10-40cm in Japan, and

up to 20cm in Australia; the trunk was found vertically in the superficial layer of the bettem, dewn to 30-40 cm. When disturbed, the proboscis always withdrew into the substratum very quickly. The burrow entrance was always furnished with ra- diating trails made during the proboscis's feeding activity. In Japan, the echiurans are sometimes discovered in the bottom without any signs of a protruding proboscis; therefore, population densities estimated only by ceunting the number of stretching proboscides are likely to be underceunts. Oshima's (1933, 1935) records of echiuran proboscides on some shores of Iri- omote Island may represent those of L. sorbitlans, although he failed to cellect the

specimens for identification; a similar life mode has been recorded also for Ochetostoma erlythrogrammon in Singapore by Chuang (1962), but my field work at Iriomote Island has so far produced specimens on]y of L. sorbillans with extended proboscides. A bivalve, Pseudopythina ochetostomae Moreton and Scott, 1989, oc- curs in the burrow of L. sorbillans in southwestern Japan (Kosuge et al, 2003). The breeding season of L. sorbillans may be summer in Japan (Table 1). More attention should be paid to the ecological role of this large echiuran, with emphasis on its role in bioturbation (see e.g., Hughes et al. 1996), oxygen sup- ply to the deeper layers of the bottom, and biodiversity of burrow-dwelling organ- isms (Kosuge et al. 2003). Additional finds of this species are very probable on protected sandy flats from a wide area of the West Pacific, although such habitats are likely to have been damaged or destroyed by human impact.

Comparisons among Congeners towards a Generic Revision Table 3 compares the six species currently assigned to the genus Listriolobus. Some taxonomic changes in the genus since the monograph of Stephen and Ed-

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monds (1972) are: the transfer of Ochetostoma copense Jones and Stephen, 1955 to this genus by Biseswar and Moodley (1989); recognition of L, butbocaudatus Ed- monds, 1963 as ajunior synonym of L. brevirostris Chen and Yeh, 1958 by Edmonds (1987) (see above); and recognition of L. billitonensis Fischer, 1926 and L. rtukiuen- sis Sato, 1939 as junior synonyms of L. sorbillans (present study), As stated earlier, the original descriptions of many echiuran species that were referred to the genera Ochetostoma, 77ialassema, and so on, lack information about the fasciculation of the oblique muscle layer. Because of this, Stephen and Ed- monds (1972) included some species in the genus Ochetostoma only tentatively, with the possibility of moving them to the genus Listriolobus. Two such species are Thalassema arkati Prashad, 1935 and 71 bornbayense Prashad and Awati, 1929.

Their type-series are kept in the Zoelogical Survey of India, and Dr. B. P. Haldar kindly sent me the paratypes for examination. The paratype of T bombayense from Bombay beach (No. w 1526/1) is 55.5 mm long with the proboscis missing; it is provided with distinct fascicules of oblique muscle between the lengitudinal muscle bands, and, therefbre, is safely assignable to the genus Ochetostoma. On the other hand, my examination of a paratype of T. arkati (No. 3176/1), with a 7.5mm long proboscis and 30mm long trunk, collected from Sandheads, mouth of the river Hooghly, by Captain C. Park on 11 January 1934, showed the oblique muscle to be

"short, continuous; the variously branched gill-like processes" en the proboscis margin noted in the original description (Prashad 1935: 42) were not detected at all. Although a decisive conclusion should await examination of the holotype, T. arkati probably belongs to the genus Listriolobus, and if so, it might be comparable with L, cqpensis and L. brevirostris, because these three species all have seven to eight longitudinal muscle bands and two post-setal pairs of gonoducts. Then, Ochetostoma arkati (Prashad, 1935) sensu Wesenberg-Lund (1959; see Biseswar 1988: 66) can be regarded as an additional species of the genus Ochetostoma. With his correct understanding the concept of the genus Listriotobus, Fischer (1926) synonymized 17ialassema caudex (see above), T, kokotoniense Fischer, 1892, T. stuhlrnanni Fischer, 1892, and T. Ieptodermon Fischer, 1892 with Ochetostoma erythrQgranzmon. In spite of the suggestion by Stephen and Edmends (1972) that T. kokotoniense might be]ong to the genus Listriolobus, Fischer's (1926) synonymiza- tion should be accepted. Fischer's above-stated nomenclatural acts are supported by my examination of the holotype of T kokotoniense (registered as V. 1994), the syntypes of T. stuhlmanni (V. 1995 and V. 1996), and the syntype of T. Ieptodermon (V, 1993), all housed in the Zoo]ogisches Museum, Universitat Hamburg. "Historical As was already mentioned in the Background", Listrioiobus bahamensis was established by Fischer's (1926i 110) bibliographical reference to the "Tiere, die von den Bahamas resp. Florida stammten". He was referring to Wil-

"7Vialassema son's (1900: 176-177) specimen of erythrQgrammon" from off Great Abaco Island, Bahamas, and another from Florida, briefiy referred to by Spengel (1912i 312) as prebably identical with the former. According to Wilson's description, the body is 16cm long, including a 3cm long proboscis, and there are 16 longitudinal muscle bands and three pairs (one presetal and two postsetal) of gonoducts accompanied by spirally-coiled gonostomal lips. My efforts to examine these two specimens remain unsuccessfu1. Although there is no information concerning the interbasal muscle in this species, it doubtlessly lacks the muscle (see above), Later, Fisher <1949: 483) correctly referred an incomplete smal1 specimen from Cuba,

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120 Teruaki Nishikawa

唱 σ q （一5 （ベ朝 … 燭一卜 OO 目菅 0 つ σ5 DQ パ蒡ゆ一自 H 一 α 邸一 o 噂寸冖一． α O 一づ唱剃（（［ O つ H ◎Ω 邸路の唱（［ Og 』ロく自の Φ （も卜＝（ α 囗』劃倒 QD 寸嘔 gワり Φ Φ H 【自而あ口唱』寸一 O 二 q 口コ OOO 邸一』ロo 』 O ω の邸づ H のり一 ≧ 一イ嘱甸口一 ℃ ）例） O に邸口 O あ． uD の一』一 Φ ≧ 弱、リロ口 ω 国邸一 ⊆ 囗 d d 口一而 O ））［【二 q ◎ 跫 σ5d ℃ 」 Od 自眉口肩コ」 ‘ 』 q Φ 糧而〔［ OO 日口』 h 製 Q の【‘ の。ゴ Q も ρ 箪一一刺謂 ℃ 〇 O 呂 ω 一頭 O ← ロ帽＝コ鬥邸国【の【国 QV 国二 5 【））国一） Σ 囗而）リ国 Φ σ50 冂〇ヨ幽僑あ O QO Q 固匡

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qo 【一〇〇一も口售だ琶售甚届〇 O Φ で u 。゜。為のの。D O O Φ ρ ρ ρ 鈴 oa 』口巴邸応邸 O 山 O 鼠脇（菅の．触（の一り O qD HO 嵩一の一 Q g 。の。，の・。心』〇 O コ自眺 O 泊』目円コ昌和日〜 ρ bO ONkN 巴唱 O 日鑑巴巴角 O 9 区口自 H 邸唱邸 5 O 国 N 』 °っ゜っウ） O 蛉 σ D 二鴇 ρ 亀D 一圃一の）≧ 口編（ 9 紬日 b ρ 口 O 目【〉 σっ O O Oeq O O ‘ 【潤剃 σ＝ O σっ咽ロコ一一』ロ Ou ロニ』ウ × り邸鯛一 O 〇芝（ qo り（ ‘ 日』 Φ 口口〉軸 u Ω 冖〉 ≧ 口ご昌 bp 口口而 O u 自一）口一，日【O 5 【〇』 Oo O 図 qD 一呂螂のあ H う ω ロヨコ邑 O ・ H 剛口［ ← ゴ邸一 ρ O O 目』 h 駒図 b ‘ ω ．』 Ω O 輒一一 q 【印つ的＼口芝鯛 H 【． ρ ← Ou O 因り σ5 刷臼一Φ 』邸吻鴇的穏 Φ q 謡の穐 kN 0ワの貸の O 蹇 0ワのヨりの魁 O Φ 腐 OkN 遣旧鬥冖「肩の N 旨ミ丶祀輻り惷建 “一唱 ◎ 国． 8 む O 裔 QkO Φ Φ 的択、陶ミやも鋤旬 kQ む謝 § 」』【弋 q Q Q り O O 』，．，，．．缶函邸 → q 刈 q q 園苦 ← 膏砦

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Synonymy of a West-Pacific echiuran 121

which lacked the interbasal muscle, to this species, As Table 3 shows, L. bahamensis is proven quite similar to L. sorbillans and may be distingriishab]e only by a slight difference in the number of longitudinal muscle bands (16 in the former, ver- sus 11-16 with modes of 13-14 in L. sorbitlans). More material is needed from the Bahamas and vicinity for meaningful consideratien of the possible separate taxonomic status of these two species,

Acknowledgements

I would like to express my sincere gratitude to E. B. Cutler of the Museum of Comparative Zoolegy, Harvard University, for critical reading of the manuscript,

and to B, P. Haldar of the Zoological Survey of India, B. Neuhaus of the Museum fUr Naturkunde der Humboldt-Universitat zu Berlin, and H. Ruhberg and P. Stjewe

of the Zoologisches Institute und Zoologisches Museum, Universitat Hamburg, for providing me opportunities to examine type and other specimens. Thanks are also due to the late S. J, Edmonds of the South Australian Museum, E. B, Cutler, R. Bis-

eswar of the University of Duran-Westville, G. TrOster of the Zoologisches Institut

und Museum der Universitat GOttingen, J. Scholz and D. Fiege of the

Forschungsinstitut Senckenberg, and J. Bleeker of the Zoological Museum, Uni-

versity of Amsterdam, for useiul information and!or suggestions as to the location

of type materials, to S. Litherland and other members of the Moreton Bay Research Station of the University of Queensland fbr material and help in field work, to H. Uchida of the Sabiura Marine Park Research Laboratory, I. Soyama in Fujisawa, and the late H. Yamashita in Isahaya fbr materials, and to M, Nishihira of Tohoku University for habitat infbrmation. Financial support was provided in part by Grants-in-Aids from MEXT (Nos. 09041155 and 13440253) and JSPS (No. 12575008), and by the Fujiwara Natural History Foundation in 1995.

References

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