(Orthogastropoda: Heterobranchia) Parasitic on Bivalves in Yamaguchi Prefecture

The malacologicalsocietymalacological society of Japan

VENUS (Jap. Jour. Malac,) fl wr Vol, 58, No,4 <1999): ]65-I74

Two New Species of the Pyramidellidae (Orthogastropoda: Heterobranchia) Parasitic on Bivalves in Yamaguchi Prefecture

Shigeo HoRl and Yasuhiro NAKAMuRA

lbk),o University ofFisheries, 4-5-Z Konan, Minato-ku, 7??k),o 108-8477 and Gondai-ni.shi, IVishikiwa-ku, Ube, }kimagt{chi 755-O15I

Abstr"ct: Two species of the Pyramidcllidac. Boonea suoana n, sp, and Boonea kinpana n. sp. are described. The former was found attachcd to the shell of living Barbatia (Savign);arca) virescens (Rccvc, 1844) and Lhe latLer was found on that of Atrina (Servatrina) pectinata (Reeve, 1858), both from the Seto Inland Sea coast of Yamaguchi Prefecture. Actuul fecding of Bocmea s"oana en Barbatia virescefts was eonfirmed.

Keywords: Pyramidellidae, new species. taxonomy, parasitism, Seto Inland Sea, Yamaguchi Prefecture.

Introduction

Species of the Pyramidellidae are known to be ectoparasitic on mollusks, pelychaetes, sipun- c}ids, etc., with bivalve species especially numerous among their hosts (Roberston & Mau-

Lastovicka, 1979 and others). Recently, on the Seto Inland Sea coast of Yamaguchi Prefeeture, two

pyramidellids wcre found en two separate bivalve species: Barhatia (Savign.yarca) viresceiis (Reeve, 1844), which common]y inhabits the intertidal zone Qf rocky sheres, and Atrina (Servatrina) pectinata (Reeve, 1858) taken on subtidal gravelly sand-rnuddy bottoms by fishermen. Detailed morphological analysis of these two pyramidel]ids revealed them to be undescribed species. In this paper we describe thern as new species and also record their parasitism.

Materials and methods

Living s'pecimens and their habitats were photographed in thc ficld with Minolta Sigma 3xi with 52 mm lens by Y. Nakamura. Shell morphology was observed and photographed with stereomicro- scopes (Nikon SM-Z; WILD M400) and a scanning electronic microscope (JSM-5200J.V) by S. Hori. Soft pEtrts were observed and dissected with a steromicroscope (Nikon SM-Z) and a cem- pound microscope (OLYMPUS CH-2) by S. Hori.

Abbreviations: AMS: AustraLian Museum, Sydncy; BMNH: BriLish Museum (Natural History), London; D: shell diameter (mm>; H: shell height (mm); MNHNi Mus6um National d"Histoire Naturelle, Paris; NMNH: NaLional Museum of Natural History, Washington D.C., USA; NNM: National Natuurhistorisch Museum, I.eiden, the Netherlands; NSMT: National Scicncc Muscum, Tokyo; SEMi scanning electronic microscope; SMNH: Swedish Museum of Natural History, Slockholrn, Sweden; YMZ: Yamaguchi Muscum (ZoolQgy), Yamaguchi, Japan.

NII-Electronic Library Service The malacologicalsocietymalacological society of Japan

166 VENUS: Vol. 58, No.4 (1999)

Ilaxonomy

Superfamily Pyramidelloidea Gray, 1840 Family Pyramidellidae Gray, 1840 Genus Boonea Robertson, 1978 7'}T]e ,!pecies: Jaminia seminuda C. B, Adams, 1839 (original designation).

Boonea suoana n. sp.

(Fig. 1-9, 19)

7ype materiats: 76 specimens. Holotype NSMT-Mo 71441: H 3.7. D 1.75, Muramatsu, Ube City, Yamaguchi PrelL, Oct, 16, 1997, coll. by Y. Nakamura; a single papatype NSMT-Mo 71442: Yashima Island, Kaminoseki-cho, Yamaguchi Pref., Aug. 12, 1997, coll. by S. Hori; four paratypes YMZ-Mo 6286: Kuwabara, Tokuyama City, Yamaguchi Pref., Aug. 19, 1997, coll. by S. Hori &

H. Fukuda; fuur paratypes AMS C204130: Muramatsu, Ube City, Yamaguchi Pref., Oct. I6, 1997, coll, by Y. Nakamura; fbur paratypes BMNH 19990440: ditto; four paratypes NMHN: ditto; four paratypes NMNH 880642: ditto; four paratypes NNM 59383: ditto; four paratypes NSMT-Mo 71443: ditto: four paratypes SMNH 5151-5154: ditto; eight paratypes NSMT-Mo 71444: Cape Maruo-zaki, Ube City, Yamaguchi Pref., Oct. 18, 1997, coll. by Y. Nakamura; four paratypes

NSMT-Mo 71465: Cape Kurosaki, Chosei, Ube City, Yamaguchi Pref., Oct. 28, 1997, coll. by Y,

Nakamura; 20 paratypes NSMT-Mo 71445: Capc Maruo-zaki, Ube City, Yamaguchi Pref., Nov, 28, 1997, coll. by Y, Nakamura; 10 paratypes NSMT-Mo 7l446: Hinoyama, Ube City, Yamaguchi

Pref., Jan. 27, 1998, coll. by Y. Nakamura.

Description: Shell (Figs l-7). Shell ovo-cenic, thick, lustrous, and opaque white to slightly translucent white. Protoconch (Fig. 7) of at least 1,5 whorls, diameter 250 um, translucent white, smooth; protoconch heterostrophic at angle of 130" to teleeconch axis; 30-35 % of protoconch sub- sumed in first teleoconch whorl, with earliest portion completely concealed. Teleoconch of 4.5 whorls, slightly cenvcx-sided, mildly gradate. Suture distinct, slightly tabulated just abapically. Growth lines distinct, sometimes coarse, prosocline, flexed forward (i.e. ventrally). Numerous, minute, indistinct spiral striae present overall. Base with fOur distinct, narrow spiral grooves, Interspaces of grooves wider than grooves. In some specimens, body whorl bears additional spjral grooves on subshoulder (Fig, 5), or three spiral grooves are present on pcnultimate whorl and body whorl adapical to periphery (Fig. 4). Axial scutpture absent. Body whorl 65 % of shell height;

periphery convex. Aperturc 43 % of shell height, rhombic to ovate. Columella thick, cencave. Single columellar fold on posteriormost part of columella; perpendicular to columella axis; almost obsolete and not visible in ventral view. Inner lip covered with an extremely thin, indistinct callus.

Outer lip moderately thin. Palatal sculpture absent. Umbilicus not open. Periostracum translucent

pale brown, thin, completely covering shell. Operculum (Fig, 11). Opercu]um thin. ovate, translucent yellow, paucispiral, with subcentric nucleus and moderately coarse growth lines; notch absent. External soft parts. Soft parts translucent white, with tiny dark brown specks on mentum, mantle edge, and cephalic tentacles,

Head-foot (Fig. 8). Head with cephalic tentacles situated antero-laterally, Cephalic tentacles elongate subtriangular, cortnate at base, yentro-laterally folded. Tentacular pad composed of a cluster of

long cilia, situated subterminally on inner side of tentacular apices. Eyes black, subepithelial, on

median side of tentacles, separated from each other by about 113 of head width, Mentum tongue-

like, without notch, postcro-dorsally separated from anterior end of head, Anterior edge of foot

NII-Electronic Library Service The malacologicalsocletyofmalacological society of Japan

Hori & Nakamura: Twe New Species of Parasitic Pyramidcltidac i67

Figs. 1-7. Boonea suoana n. sp. X )l- V 7 V:- IL V. 1-2: Holotype, H 3.70, D 1.75 (NSMT-Mo 71441). 1: light photograph; 2: SEM photograph. 3-6:SEM photographs of paratypes (NSMT-Mo 71443). 3: H 3.10, D 1.40; 4] H 2.70, D l.35; 5: H .90, D 1.IO; 6: 1.60, D O.95. 7: protoconch of one of paratypes (NSMT-Mo 71443).

slightly indented medially, Pedal gland opening roughly at middle of postcrior 1/3-1/4 of foot sole, fo11owed by a distinct longitudinai groove continuing to posterior tip of foot sole, Pallial cavity (Fig. 8) (Specimen of 2,3 × 1.3 mm shell). Pallial cavity ca. O.8 mm × O.4 mm, gradually narrowing posteriorly to cennect visceral mass. A pair of ciliated strips (i,e, dorsal and ventrul ciliatcd strips) on right lateral part of pallial cavity, running fbr anterior 3/4 of cavity, joined

NII-Electronic Library Service The malacologicalsocietymalacological society of Japan

16S VENUS: Vel. 58, No.4 (1999)

to posterior mantle roof. A gland underlies the longitudinal middle 113 Qf ventral ciliated strip; gland ovate, of yellow cells but paitly of brown cells; releases ycllow exudate when animal dis- turbed. Gill entirely absent, Pigmented mantle organ of O.2 × O,15 rnm, on middle of antcrior 113 of pallial roof; short ellipsoid, of yellow cells on right to middle and brown cells on left. Pallial kidney of ca. O.3 × O.3 mm, cxtending from posterior end of cuvity te immediately posterior to pigmented tnantle organ; evate to subtriangular narrowing anteriorly, opaque white, Pericardium at left-posteriormost part of cavity, circular, pale pinkish yellow. Pallial vein extending from pericardium to postcrior left side of pigmen{ed mantle organ, Alimentary system (Fig, 9) (Specimen of 2.3 × 1.3 mm shell). tn retracted condition, introvert- proboscis opens on dorsal surface of mentum base and extends posteriorly to pass through circum- ocsophageal nerve ring and enters cephalic haemocoel; proboscis 1.5 mm in length and O.1 mm in width, with granulese surface; outer surface features several string-Iike, thin retractor muscles. Proboscis retractor muscle branches from posteriermost part of outermost layer of introvert-proboscis, attaching to columellar muscle at another end; muscle ca. O.25 mm in maximum width;

attachcd by a pair of buccal ganglia at middle. Introvert-proboscis followed by buccal sac of ca. O,3 × O.1 mm, containing mouth. oral tubc, oral stylet, and stylet bulb, Mouth on anteriormost part ef buccal sac surrounded by an oral sucker censisting ef a thick wal] of radially-oriented muscles.

Oral stylet ]jes in ventral poition ofbuccal sac; stylet of O.25 mm in length and O.03 rnm in width, cuticular anteriorly tapering flagclliform. Orul tube in dorsal portiun ol' buccaL suc, running parallel with oral stylet for whole length of buecal sac, Stylet bulb on postero-ventral part of buccal sac, globular in shape. A small, ovate musculur pouch is attached to posterior end of stylet bulb, pro- truding posteriorly, A thin, muscular string arises from posterior tip of muscular pouch, running to anterior end ot' oesuphagus. Buccal sac connecting buccal pump situated postero-dorsally, which is dividcd into anterior (Le. buccal pump I: bp I) and posterior parts (i,e. buccal pump II: bp JI). Bp I of ca. O.25 × O,1 mm, elongate fusiform in outline and round in cross-section; bp II ofca. O.35 X

O.1 mm, elongate ovatc in outline and flat in cross-section. Oesophagus arising on ventral surfacc of bp I-II junction; at least 2.5 mm in tQtal Iength and O.3 mm in width, with minutely granulose surface, extending into visceral mass. A pair of sa]ivary glands long, vermiculatc, ca. O.75 mm in length and O, 1 mm in width, of many variable sized salivary cells which situated along central lon-

gitudinal lumen; posterior end with a small, flat, circular rerminal appendage. Salivary duet origi- nating from anterior end of each salivary gland, pcnetrating ventral surface of a bp I-II junctien, running through waJl of bp T, and reaching stylet bulb. A pair ui' thin. muscular strings originate from anterior end of each salivary gland and cxtend tQ base of buccal gangliu on middle of proboscis retractor muscle.

Cenita] system (Figs 8, 1 1) (Specimen of 2.3 × 1.3 mm shell), A single lobe of ovotestis present on adapica] poT"tion of convcx side of visceral coil. Hermaphrodite duct arising on anterior end of

ovotcstis. extendin.e abapically alung concave side of viscerar coil, reaching anterior end of viscer-

al coil via elongate seminal vesicle with pinkish, shining wa]i. Seminal receptac]c situated on right

of visccral coil; tiny, covers abapical proximal part .elebular, paleyellow. AIbumen gland large portion of convex side of visceral coil; slightly translucent, grayish white. Large section of antcrior to middle albumen gland overlain by mucous gland, which is divided into antcrior left part (i.e. ante- riur mucous gland) and anterior right to posterior part (i,e. postcrior mucgus gland). Anterior mucous gland ovate, slightly translucent whitc; posterior mucous gland elongate, slightly translucent grayish white, media]ly overlain with brown pigmentatien. Pallial gonoduct extends anteriorly beneath right pait of pallial fioor; not surrounded by gland cctls. Penial complex absent in cephalic haemocoel, btit beneath mentum as an ovate muscular body covered with a thin muscular sheath of O.2 × O.16 mm (Fig. 11). 71vpe locality: Muramatsu, Ube City. Yamaguchi Prefecture (around 33'S8'N. 131"20'E)

NII-Electronic Library Service The malacologicalsocietymalacological society ofJapanof Japan

Hori & Nakatnura: Two New Spccies of Parasitic Pyramidellidae 169

msh prm

･Z.･71-.--

/･xl bpI

xEy

tas .c.bp 1 sg 9

Figs 8-11. Boonea suoana n. sp. XtV e 'f'} V. 8: animal extracted frem shell. 9: alimentary system. 10: penial complex. 11: opcrculum. Scaiei SOOum for 8; 25eptm for 9, 11; 150ptm for 10. Abbreyiations. ag: albumen gland; amg: anterior mucous gland; bg: buccal ganglion; bp: buc- ca] pump; bs: buccal sac; ct: cephalic tentacle; dcs: dorsal ciliatcd strip; dg: digestive gland; e: eye; gvc: gland underlying ventral ciliated strip; ip; introvert-proboscis; k: pallial kidney; m: mentum; mb: muscular body; mm: muscular membrane; mp: muscular pouch; ms: muscular string; msh; muscular sheath; oe: oesophagus; op: operculum; ot: oral tube; ovt: evotestis; pc: pericardium; pmg: pesterior mucous gland; pmo: pigmented mantle organ; prm: proboscis retractor muscle; rm; retractor muscle; s: oral stylet; sb: stylet bulb:. sd: salivary duct; sg: salivary gland; sr: seminal receptacle; su: orul sucker; sv: seminal vesicle; tas: terminal appendage of salivary gland; ycs: ventral ciliated strip.

NII-Electronic Library Service The malacologicalsocietymalacological society of Japan

170 vENUS: Vol. 58, No.4 (1999)

Etymology: The name refers to Suo, a middle-age province covering the southeastern part, of the present Yamaguchi Prefecture: Suo includes the type locality and all the other recognized localities of the present spccies. Ecoiogicat note: In total 76 specimens of the present species were found on about 30 living specimens of Barbatia (Savignyarca) virescens (Reevc. I844) attached to ur cmbcdded in shaded

portions of sides or under-sides of stones between the middle and the lower intertidal zene of rocky shores. All specimens were fbund alone or in aggregatiens of two te four individuals (1.6-3.7 mm in shell height) on the middle to posterior part of thc ventral margin of the shell of B, virescens (ca. 10-50 mm shell length) (Fig. 19). When some specimens of Boonea suoana were put into a small container with seawater together with a Barbatia (S, ). virescens, they were seen to extend the proboscis and suck the bivalve's body fluid from the mantle edge by contracting the buccal pump inside the proboscis. Remarks: The shell of Boonea suoana somewhat resembles Menestho shataii Nomura (1936: pp. 36-37, pl. 3, figs 20a-b, 21a-b, as Menetsho (Menestho)) from Shiogama Bay, nertheastem Honshu. However, Boonea suoana differs from the latter in being of smaller adult size (H: 3.7 with 4.5 whorls vs. 4.5 with six whorls) and in having a relatively shorter shell (HID: 2,1 1 in specimen with 4.5 whorls vs. 2.5 in specimen with six whorls). Furthermore, the spiral grooves of Boonea suoana are present especially Qn the base of the body whQrl but occasionally also on between the

sutures, while those of M. shataii a]ways occur over the whole teleoconch. It is almost impossible to judge the generic position of the present species based on shell characters, because there are three nominal gcnera which partly or l'ully share shell characters with the present species: Odostomia, Menestho, and Fargoa, The prescnt species cannot be included in these genera, and must clearly be assigned to the genus Boonea by virtue of having the penial complex situated beneath the mentum, as demonstrated in a few nominal species of Boonea (Robertson, t978: p. 361; Hori & Okutani, 1995, 1996; Wise, 1996). The feeding observcd in the present study clearly indicates that Boonea s"oana is parasitie on Barhatia (Savignyarca) virescrens,

Boonea kiupana n. sp.

(Figs 12-18, 20)

71ype materials: 13 specimens. Holotype NSMT-Mo 71447: gravelly sand-muddy bottoms, ca. 3 km ot'l'shore between Cape Ube-misaki and Cape Kurosaki, Ube City, Yamaguchi Pref. (on Atrina (Servatrina) pectinata (Reeve, 1858) landed at Port Tokonami, Ube City), Dec. 20, 1997, coll. by Y. Nakamura; a single paratype NNM 59384; four paratypes NSMT-Mo 71448: ditto; a single paratype SMNH 515S: ditto; a single paratype YMZ-Mo 6287: ditto; a single paratype AMS C204131: ditto, Man 22, 1998, coll. by Y. Nakamura; a single paratype BMNH 19990441 : ditto; a single paratype MNHN: ditto; a singlc paratype NMNH 880643: ditto; a single paratype MSMT- Mo 71449: locality as above, Mar. 22, 1998, coll. by Y, Nakamura. Description: Shell (Figs 12-15), Shell ovate, thick, lustrous, and opaque white. Protoconch (Fig. 16) of at least 1.5 whorls, diameter 350 um, translucent grayish white, smooth; protoconch heterostrophic at angle of 1400 to teleoconch axis; 50-55 % of protocench subsumcd in first teleoconch with earlie$t portion completely concealed, Teleoconch of five whorls, moderately convex- sided. Suture distinct, constricted; in some specimens, suture stepped and tabulatedjust abapically (Fig. 13). Growth lines distinct, prosecline, slightly flexed fOrward (i..e, vcntrally). Numerous, minute, slightly wavy spiral striae present overall. Axial sculpturc absent. Body whorl 64 % of shell height; peripher convex. Aperture 51 % of shell height, ovate. Columella thick, strongly concave. Single columellar fold on posteriormost part of columella; well-developed, eblique to columella

NII-Electronic Library Service The malacologicalsocietymalacological society of Japan

Hori & Nakamura: Two New Spccies of Parasitic Pyramidellidae Vl

axis. Inner lip with no callus. Outer lip moderately thick. Palatal sculpture absent. Umbilicus not open. Periostracum translucent pale yellow, thin, completely covering shell, Operculum (Fig. 18). Operculum auriform, paucispiral, with subcentric nucleus, Middle of columellar margin bears a shallow netch which interlocks with columellar fbld of shell. Area anterior

of columellar side of attached surface thickened in shape of a broad spiral band; this area opaque cream-celoured, bearing coarse growth lines and in middle part an obscure, translucent yellow, narrow spiral band. Marginal part of operculum thin, translucent yellow, with minute growth lines. Head-foot. Head with cephalic tentacles situated antero-laterally. Cephalic tentacles elongate sub-

trittngular, connate at base, ventro-laterally folded. Eyes black. subepithelial, on median side of ten-

tacles, separated frQm each other by ubout 113 of head width. Mentum tQngue-like, without notch,

,IE'tX' ee

zma-wwe

-.vl:IS/i# iggE,,,

Figs 12-18. Boonea kimpana n, sp, } >7sc 7 iF' k lf. 12: light photograph of holotype, H 6.85, D 3.00 (NSMT-Mo 71447). 13-15: light photogTaphs ofparatypes (NSMT-Mo 71448). 13: H 6.30, D 2.80; 14: H 6.20, D 2.80; 15: H 6.10, D 2.60. 16: protoconch of one of paratypes (NSMT-Mo 71448). 17: she]I surface of holotype. 18: operculum, Scale: 500 ptm.

NII-Electronic Library Service The malacologicalsocietymalacological society of Japan

172 VENUS: Vo]. 58, No.4 (l999)

postero-dersally separated from anterior end of head,

Genital system. Penial complex absent in cephalic haernocoel.

7:ype tocatity: About 3 km offshore betwecn Cape Ube-misaki to Cape Kurosaki, Ube City, Yamaguchi Prefecture (around 33055'N, 131O18'E); gravelly sand-muddy bottoms of ca. g m deep. Et.vmotogy: The namc refcrs to Kinpa, the middle-age name tbr Tokonami district, Ube City, where the present species with itb host wcre found. Ecotogical note: In total 13 specimens of thc present species were found on fbur living speci- rnens ofAtrina (Servatrina) pectinata (Reeve, 1858) tHibhed from gravelly sand-muddy bottoms in the subtidal zonc by fishermen. All specimens were found alone to in triple (5.10-6.85 mm in shell height) among the scales on the surfacc closc to the posterior margin of the shell of A. (Se.) pectinata (ca. 200 mm in shell length) (Fig. 20). It was observed that all the paired or tripled individuals were ca. 1O mm apart from each other.

Remarks: The shell of Boonea kiupana is similar to that of Odostomia (Sin"atodostomia) inbana Nomura (1938: pp. 70-71, pi. 12, fig. 95a-b) from northeast Honshu, but Boonea. kiiu)ana

is distinguished from the latter in having a more solid and slender shell, Iess convex-sided wherls, and a closed umbilicus. The growth lincs of Boonea kiupana are prosocline, while opisthocline in O. (Si.) inbana; furthertnere, the outer lip ot' Boonea kifipana is simple, while that of O, (Si.) inbana has a sinus at its adapical end. tn shell characters, the present spccics can be considered to be related to the genera Odostomia and Boonea from its ovo-cenic shell with strong columellar fold and smooth surface (surface is not always smooth but variously sculptured in Boonea (Robertson, l978)). But, anatomically, Odob'tomia has a penial complex in thc cephalic haemocoel (Fretter & Graham, 1949; Wise, l996). while Boonea has one beneath the mcntum (Robertson, 1978; Hori & Okutani, ]995, 1996; Wige, 1996). In the present species, a penial complex is definitely absent from the cephalic haemocoer.

19 20

Figs 19. Three individuals of Boonea suoana

NII-Electronic Library Service The malaoologioalmalacological societysooiety of Japan

Hori ＆ Nakamura ： Two Ncw Species of Parasitic Pyramidellidae 173

− Although its presencc or absence beneath the mentum have still not been confirmed ， we provision ally allocatc the present species to the genus B θ θ nea ・ Experinlents fbr confirming feeding on A peetinata have no ヒ been conducted yet． In thc field， however ， Boonea たinpana was fbund only on the shell of A ． pec ’in‘lta and not in any surrounding materials or sediments ． Further ， Boonea たinpana was found at匸ached to the sheli of A ． pectinata 一 solely on the surface a （ljacent to the posterior margin ， a position which would allow Boonea kin out body fluid．These observations ρ侃 α easily to reach the mantle edgc of A ． pectinata for sucking suggests that Boonea Aゴ’zpana is lnost likely parasitic on A ・pectinata ・ − Acknowtedgements ： We express our gratitude to Messrs． Tsugio Azuma and Se重ii Hamada （bo血 Ube City ， Yamaguchi Prefecture）for 三lllowing thc junior author to co1 正ect Boo ノ卍θ α kinpana from Atrina （Se 厂りatrina ）pectinata （Reeve ，1858）among thじir ca しches ． We are also gratcful to Mr ． Paul Ca11〔｝mon （Elle to Dr Hiroshi Scientific PublicaLi〔）ns ）for his valuable comlnents Qn manuscript ． Special thanks are due ． − Saito（NSMT ）who kindly assisted our examinatiQn with k 〕w vac 巳 um SEM ． This work was partly suppor 卜 ed by the Fujiwara Natural History Foundation tQ thc senior authQr ．

二枚貝に寄生する山口県産トウガタガイ科貝類の 2 新種

堀成夫・中村康博．山冂県瀬戸内海沿岸から二枚貝類の殻表に f・1着する 2 種のトウガタガイ科．貝類の未記載種が発見さ

れたので，新種として記載する。

・ Boonea suoana n ． sp ．スオウクチキレ噺種新称）

：でが透色〜わかに半透明白色。胎殻は約 2 層，径は記載殻は卵円錐形厚質，光沢あり，不明白ず ° の〜埋 250 μ m ，半透明白色で平滑；胎殻軸は後成殻軸に対して 130 傾く；胎殻 30 35 ％が後成殻にはとる没する；胎殻頂部は完全に隠れる。後成殻は 4 ．5 層からなり，側面は丸く，肩部段状な。縫合

坦がされる，成は明瞭時に粗い；前傾し，前方（腹方）は明瞭で，縫合下にわずかに平部形成長線，

のいらに湾曲する。殻表全面に多数の微細で不明瞭な螺条がある。殻底には 4 本明瞭で細螺溝を巡

す；螺溝間は螺溝より広い。個体によっては体層の肩部下にさらに螺溝を 1 本巡らす，または第 2 層

〜つの体層の周縁より後方に 3 本．の螺溝をも。縦彫刻はない u 体層は殻高の 65 ％を占め，そ周縁は〜 1 丸い。殻口は殻高の 43 ％の高さをもち，菱形卵形。軸唇は厚く，凹む。軸唇後端に軸襞が個あ

めてからは見えない内唇は極めて薄く不明る；軸襞は軸唇に対して垂直で，極弱く，小さく，腹面。

いパルいはかいは透色瞭な滑層で覆われる。外唇はやや薄。ラタ彫刻はな．臍孔開な。殻皮半明淡褐 − でに n NSMT Mo 71441 ：殻高 3．70 mm ，殻径 1．75 mn1 。薄く，殻を完全覆う完模式標本

模式産地：山口県宇部市村松海岸。

生態：岩礁地帯の中潮線から低潮線付近の転石に付着した Barvatia （Savign．varca ） virescens （Reeve，

エいエの〜 1844 ）カリガネガイに付着してる状態で発見された。カリガネガイの殻の腹縁中部後部に，

〜ガエガのば単独または 2 4 個体が集まって付着していた。実験室内で，カリネイ外套縁に口吻を伸

して体液を吸引するのが確認された。

備考：本種の殻形態は Menestho shataii Nomura ．1936 のそれに幾分似るが，成貝のサイズが小さい

いこのこと，殻がやや太短こと，螺溝が弱く主に殻底にあるとにより区別される。本種属位を殻形態

でのにつによって判断することは不可能であるが，本種は陰茎複合休を頭部血洞はなく口吻基板下も

ーンレことにより，Boone α ブクチキ属（新称）におかれる。

一 NII-ElectronicN 工工 Eleotronio Library Service The malaoologioalmalacological societysooiety of Japan

174 VENUS ： Vol ．58， No ．4 〔1999 ）

・ Boonea kinpana n ． sp ．キンパクチキレ（新種新称）

記載：殻は卵形で厚質光沢があり透色。はと 1、5 ，，不明白胎殻少なくも層からなり，径は 350 μ ln ， ° 半透明灰白色で平滑；胎殻軸は後成殻軸に対して 140 傾く；胎殻の 50 〜 55 ％が後成殻初層に埋入す

る；胎は全にれるはい殻頂部完隠。後成殻 5 層からなり，側面はやや丸。縫合は明瞭で括れる；個体

によってはとって段状な縫合直下に平坦部を形成する。成長線は明瞭で前傾し，わずかに前方（腹方）

に湾曲する。殻表全体にわずかに波打った微細な螺条を多数もつ。縦彫刻はない。体層は殻高の

％を占め，周縁は丸い。殻口は殻の 51 ％の 64 高高さをもち，卵形。軸唇は厚く，強く凹む。軸唇後

にがるはパ端軸襞 1 個あ；軸襞発達し，軸唇に対して斜め。内唇に滑層はない。外唇はやや厚い，，ラ

タル彫刻はない。臍孔は開かない。殻皮は半透明淡黄色で薄く，殻を完全に覆う。完模式標本

NSMT − ： Mo 71447 殻高 6 ．85 mm ，殻径 3 ．50 mmQ

：〜模式産地山口県宇部市宇部岬黒崎の約 3km 沖合。

：生態潮下帯の砂利混じりの砂泥底に生息する Atrina （Sen ・atrina ）pectinata （Reeve ．1858 ）タイラ

のいいのギ殻表に付着してる状態で発見された。タイラギの後縁に近殻表鱗片状突起の間に単独で，

〜いいいまたは 2 3 個体が互に約 10mm 離れて付着していた。実験室内での摂餌実験は行ってな。

備考：本種の殻形態は Odostomia （Sinuatodestomia ） inbana Nomura ，1938 のそれに似るが，殻が厚

いことのいこい，螺層側而丸みが弱と，臍孔が開かなこと，成長線が前傾すること，および，外唇後

にいこと端湾入がなにより区別される。本種の陰茎複合体は頭部血洞に確認されなかった。おそらく

本は口基のに茎っていこー種吻板下陰複合体をもるとが予測されるため，暫定的に Boonea ブンクチ

キレ属におく。

References

Fretter， V ．＆ Graham ， A ，．1949 ． The structure and mode Qf life of the PyramideUidae ， parasitic opistho − branchs． J．ルfan Biol． Ass ．｛ノ．κ ．，28 ：493−532． Hori ＆ − ，S ． Okutani，T ．，1995．A new pyramidellid gastropod ectoparasi 【icon ση め o η 加 η （Suchittm）monil rum − ife （Lamarck ）from Tomioka ， Arnakusa ， Western Kyushu ． Venus ，54 （4）：247 258． Hori ． ectoparasitic − ， S ＆ Okutani，T ．，1996．A new pyramide］lidgastropod on Con ” s．Venus，55 （1）： 7 14．

Nomura ， S ．1936 ． Pyramidelhdae from Siogama Bay Northeast Honsy − ，，白， Japan，SaitoHo on Kai Mu ．y ．Res． Butl．，10 ： 1−108 ， pls 1−12 ． Nomura ， S ．．1938 ． The third report on Pyramidellidae based upon the specimens preserved in the c 〔川 ection − of thc Sait6 H6 on Kai Museum ． −on ． Res ， BuU ．： 1−88 1−15， SaitoHo Kai Mus ，16 ， pls Robe 貫 son ． R ．，1978． Spermatophore of six eastern north American pyramidellid gastropods and their sys − − tematic significance （with the new gcnus Boonea ）． Biol． Bu 〃．，155 ： 360 382． Robortson R ．＆ Mau −Lastovicka T ．1979 ．The ectoparasitism ，，， of Boonea and Fa rgoa （Gastropoda： − Pyramidellidae）． Biot． BuU ．，157： 320 333， Wise J，1996 ． Mo hology and relationships of certain ，，叩 phylogenetic pyramide且lidtaxa （Heterobrancllia）． Ma 〜acologia ，37 （2）： 443 −511．

匚Received ： August 25 ，1999 ； Accepted： October 30，1999］

一 NII-ElectronicN 工工 Eleotronio Library Service