The malacologicalsocietymalacological society ofJapanof Japan

Nrc Jap. Jour. Malac. (VENUS) Vol. 36, No. 2 (1977):81 88

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Mtwa ngE

(ru･[･1rt*mp\sustuRe?tfag)

Notes on Genkaimurex varicosa (KURODA, 1953)

(Prosobranchia: Neogastropoda)

Akihiko MATsuKuMA

(Department of Geology, Faeulty of Science, Kyushu University)

Ten living specirnens of Genka-imurea: varicoso (KuRoDA) weTe eollected from a sand bottom in 94m of water in the Sea of Japan, off Yamaguchi Prefecture. They were found attaehed to the left valve of Pecten (Notovola> albica"s (ScHR6TER) in which they had drilled holes. G. vam"cosa sometimes impre･sses a faint attachment scar upon the scal]op shells and apparently does not damage the soft paTts of the scallops. This species may suek juiees from the scallops. The boreholes made by G. varicosa are often repaired interiorly by the hosts.

Some of the living speeimens have been kept in a tank during November, 1976 May, to 1977, to observe their feeding behavior. G. varicosa･ has a raehi- glossate radula and is a hole-boring inactive predator, namely, parasite or commensal on molluscs, preferably on P. (N.) albdeans. I advocate that G. varieosa should be plaeed in the Murieidae, although it shows some' features similar to the Coralliophilidae, in whieh the original authoT placed this speeies.

Introduetion Genhaimurex va･rioosa was originally described by KuRoDA (1953) on the basis of the specimens from the Genkai Sea, off Fukueka, west Japan. The original material was collected by the dredging nets of scallop-fishing boats from sand bottoms of about 45m depth. In general features this species closely resembles some species belonging to the Ocenebrinae of the Muricidae, but G. varz'cesQ, according to KuRoDA C1953), lacks a radula and its shell is ornamented with spiral eords which are made up uf microscopie seales. Henee KuRoDA (1953) plaeed this speeies in the Rapidae (=Coralliophilidae).

Several examples of this un ¢ ommon species were eolleeted by one dredge haul during a marine survey carried out by Tsugio SHuTo and others on board the Researeh Vessel Tanseh-MaTu of the Ocean Researeh Institute, University ef

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82 VENUS: VoL 36, No.2(1977)

Tokyo, in the southwest extremity of the Sea of Japan in November 20-27, 1976.

Some specimens were kept in a tank during November 24, 1976 to May 19, 1977,

to observe their feeding behavior. This study deals with the feeding behavior and systematic position of G. vaTicosa. Radular morphology of this species is

originally deseribed herein.

Acknotvledgements-I wish to express my gratitude to Drs. Tsugio SHuTo, Yasuhiko

KAMADA, Koichiro MAsuDA, Shozo HAyAsAKA, Kazuo OKAMoTg, Hiroshi NoDA, and

Kenshiro OGAsAwARA, for their fruitful co-operation in the field work and for helpful

criticism of the manuscript. Appreeiation is extended to Drs, Melbourne R. CARRIKER,

Emily H. VoKEs and Norman F. SoHL for their eritical reading and helpful eomments.

I am grateful to Mr. Katsuyeshi SATo fQr his many suggestions and diseussion on

the subject.

Material

Then living specimen (GK-M 10007-16) were collected fTom sand bottoms of about 94 m depth by one haul of a dredge operated around St. II-4, off Yuya Bay,

Yamaguchi Phefeeture Clat. 34e28.5'N; long. 130"50.4'E). Geetkai?n･zarex va･ricosa (GK-M 10007-9 and 10011-16) were found attached to living speeimens of Pecten (Notovola) atbicans (ScHR6TER), GK-M 10017-18. 0xyperas bernaTdi (PILsBRy), Polinices vestitus KuRoDA, and several speeimens of starfishes were also collected

by the same net. These eollections of G. va･ricosth and P. (N.) albicans are

deposited in the Department of Geology, Kyushu University.

Observations

The specimens of G. varicoso in hand are rather young and characterized by ovately pyriform, sma.11, and yellowish brown shell with a moderately long canal, large body whorl and rather small spire. The pretoconch is smooth, paucigyrate

consisting of about one and three-quarter volutions. The teleoeonch eonsists of about four and a quarter rapid]y inereasing whorls, of which the earliest one is

coarsely caneellated. The suture is deep. The whorls are ornamented with massive, crowded axial folds and variously sized spiral eords which are made up of dense microscopic scales. The axial folds number about ten or eleven on the body whorl. The aperture is evate and white with a tint of purple within. The inner lip is enamel-white. The outer lip is weakly and finely denticulate inside. The anterior eanal is not closed in young specimens and curves slightly to the right and away

from the aperture. The smallest speeimen, GK-M 10013, has a thin yellowish

brown periostracum with sparse hair. The epereulum, with a nucleus on the lateral margin, is chitinous and yellowish brown in color. Measurements.-

specimen height(mm) width(mm) GK-M

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MATsuKuMA : Notes on Genkaiwturex varicosa 83

1000710008100091001010011100121001310014100151001624.6 14.6

7.117.820.4 3.910.913.0

6.6 3.3

8.7 4.8

3.2 2.0

5.7 3.0

9.4 4.9

8.3 4.7

Radula

The radula of G. vaTicosa is rachiglossate in form with three teeth in each

row. The radula of a specimen (GK-M 10009) is about 3.5mm in length and

the number of tooth-rows is about 220. Width of the rachidian tooth is 24"m in

cc

LT c A RT A - I B- c cc

tc B H mc Text-fig. 1

Text-fig. 2

Text-fig. 1. Some morphological features of Genkaimurex varicosa (KuRoDA), GK-M leo7. A : Operculum with a nucleus on the lateral margin. B : Protoconch and cancellated earlier whorls. C : Spiral cords with dense microscopic scales. Unite bars indicate respectively 2mm for A, 1mm for B and O, 85 rnm for C.

Text-fig. 2. Radular teeth of Genfeaimurex varicosa (KuRoDA), GK-M 10009. A :Dorsal view of rachidian (RT) and lateral tooth (LT). B : Left lateral view of rachidian teeth, cc, central cusp; lc, lateral cusp; mc, marginal cusp. Unite bar indicates 20 Am for A and B.

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84 VENUS: Vol. 36, No.2<1977)

GK-M 10008 and 54"m in GK-M 10009. The rachidian has 5 cusps of which the

central one is long, curved posteriorly, sharply pointed and situated at the midd]e.

Eaeh lateral cusp is moderately long and sharply pointed. A small denticle protrudes from the base of the lateral cusp between the central cusp and the

lateral one. Each marginal eusp is rather short, Two weak denticles/ protrude

from the basal plate between the marginal cusp and the lateral one. The sickle-

shaped laterals with the broad base are long, narrow, eurved inwards and sharply

pointed, and are devoid of any cusp and denticle.

Behayior

The speeimens of G. var"icosa in hand were found attached to the left valve of

P. (N.) albicthn6. Drilled holes and faint attachment scars made by these snails

were observed. G. varicosa also drilled holes while maintained in the laboratory.

The borehole is a nearly circular with a steep cylindrical wall and a completely

bevelled outer edge. The outer diameter of boreholes varies from O.25 to 1.19 mm.

Bottoms of ineomplete boreholes are eoneave, In general features boreholes made

by G. varicosa closely resemble those drilled by small-sized murieids, e.g. Bedevina

biriteX7i (LIscHKE), The boreholes are often repaired interiorly by host scal]ops

and G. varicosa apparently does not damage the mant]e and other soft parts of the host. An interiorly repaired borehole attributed to muricid predation has been reported from the Gosport FormatiQn (Middle Eocene) of North America (SILER,

1965). The faint and nearly eircular attachment scar is made of calcareous

material which is secreted by G. varic'osa. Some attachment scars･ of G. varicosa

are shallowly hollowed. Some capu]id speeies, sueh as Caputus dilata･tus ADAMs,

Copueus spendiyeieola HABE, and Capullus da･nieli (CRossE), have been known to

impress somewhat faint or definite scars upon their host bivalve shells. These

eapulid impressions are a hollowed-out sear without･ any ealcareous deposits.

A non-sculptured eapulid species, Hyalorisia tosae7tsis OTuKA, leaves an attach-

ment scar which is made of caleareous deposits, but this species is always a

eommensal on Lute(zmzessium sibogai (DAUTZENBERG & BAvAy) and notches the

edge of the shell just below the anterior auriele of the host. Preferred orientation

of boreholes is characteristic of some boring snails (natieid: ANsELL, 1960;

MATsuKuMA, 1976; muricid: KINosHITA & NAKAGAwA, 1934; MATsuKuMA, in

preparation; capulid: ORR, 1962; KOsuGE & HAyASHI, 1967; MATSuKuMA, in

preparation). The position of boreholes made by G. varicosa in shells of P. (N.)

albictzns is not limited to any preferred region of the shell surface,

During November, 1976, to May, 1977, G. v'aricosa in a tank drilled holes in the shells of Ruditapes phizapmnarum (ADAMs & REEvE), Caeceelca chinensis DEsHAyEs, Siphonalia sp., and G. varicosua. The bored bivalves died a few days

after the dril]ing, but bered Siphonalia and Genkai･murex continued to live more

than six months. During this period the borer was observed once to leave the host

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MATsuKuMA : Notes on Genhaimttrex varicosa 85

and sit en a shell fragment on the bottom or wall of the tank. After several days

of resting the borer again climbed on the host shell to the borehole which it had

drilled. These observations and the partially or eornpletely repaired boreholes

with attachment sears in the shells of P. (N.) albicans verify that G. van'cosa

lives for a considerable period of time on the host shell. G. van'cosa may suck juiees from the seallops. G. va7'icosa is not an active predator but a hole-boring

inactive predator, namely, parasite or commensal on molluscs, preferably on P. (N.) aLbiccvns. Small boreheles in the shell of Amusium jap/oni(wwz (Gmelin) (MATsu- KvMA, 1976) may be attributed to parasitism or commensalism of this species.

Systematics

Shell features, such as the smooth paucigyrate protoconch, coarsely cancellated

earlier whorls, and the ehitinous operculum with a nucleus on the lateral rnargin,

are charaeteristie of muricids and eoralliophilids. Although its finely sealed spiral

cords reminiseent of the Coralliophilidae, shells of some muricid snails, e.g.

Ergalatax contractus (REEvE) and many oeenebrid species, are ornamented

with similar finely sealed spiral cords, G. varieosa is an inactive predator or

eommensal with the raehiglossate radula and drills holes in its host she]1. Its

feeding behavioT and radu]ar morphology are closely allied to those of the

Muricidae, but this species does not devour fiesh of the host and impresses the

faint attaehment･ scars upon the host shell. Several species belonging to the

Coralliophilidae, e/.g, Corcalliophila steaf"nsii PiLsBRy, Coralliophila swrifor'mis

KIRA, and Coraltiophila violaeea (KIENER), are parasitie on sea-fans and corals (HABE & KosuGE, 1967; HIGo, ed., 1973) while G. varicosa is usually collected

from the nets of scallop-fishing boats (KuRoDA, 1953; TAKAHASHI & OKAMOTO,

1969). G. vaTicosa may be parasitic or commensal on scallops. I advocate that

G. varicosa should be placed in the family Muricidae, although it shows some

features similar to those of the the Coral]iophilidae, in which the original author

placed it.

Family Muricidae DA CesTA, 1776

Genus Genhaimurex KuRoDA, 1953

Type species: Genhaimm'ex varicosa･ (KuRoDA, 1953) (original designation).

Genkaimurex varicosa (KuRoDA, 1953) 1953 CoraLCiophila (Genkaimurex) varicosa: KuRoDA, Venus, vol. 17(3),

pp. 120-121, text-figs. 7-8. 1959 CoraZ"ophila (Genka･imuresc) varicosa KuRoDA: KIRA, Col. Il]us. Shells

Japan, p. 64, pl. 25, fig, 17.

1967Genhaimurex va-ricosa KuRoDA; HABE & KosuGE, Com. Shells Japan Col.,

p. 73, pl. 29, fig. 5-

1969 Coralliophila (Genhai7nurex) varic/osa KuRoDA: TAKAHASHI & OKA-

MoTo, Cat. Moll. Shells Fukuoka Pref,, p. 44, pl. 7, fig. 10.

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86 ： 36 2 1977 VENUS VoL ， No ． （ ）

1973 α imurex 勿 α 幅 oos α ： ed ． Gonk KuRoDA HIGo ， ． Cat．Mol1 ．Fauna Japan

Is1．Adj ．Area ， p ．126．

要 約

ウ ネサ ン ゴ ヤ ド 1丿 ガ イ は 黒 田 （1953） に よ り ，形 態的 に は ア ク キ ガ イ 科 の 腹足 類 に 似 る が ，歯 舌 を 欠 き ，殻 表 は 覆 瓦 状 の 鱗状 片 を 密 に 具 え る 螺 状 刻 脈 で 覆 わ れ る と い う 点 で 後 者 と は 区 別 さ れ る と し

て カ ブ ラ ガ イ サ ソ ゴ ヤ ガ の ， 科 （ ド リ イ 科 ） 新 種 と し て 記 載 さ れ た 。

筆 者 は ，1976年 秋 ，山 口 県 油 谷湾 沖 水 深 94m 付近 の 砂 底 よ り本種10個 体 を ，イ タ ヤ ガ イ 生 貝 の 左 殻

に し た の で ゴ 付 着 状 態 ま ま 採 集す る 機 会 を 得 た 。 イ タ ヤ ガ イ 左 殻 L に は ， ほ と ん ど の ウ ネ サ ン ヤ ド リ

ガ の い イ 付 着 し て た 位 置 に ，不 明 瞭 な付着痕跡 と ， 穿 孔 が み ら れ た 。付 着 痕 は 卵 円形 で ，石 灰 質 の 沈

澱 物 か ら な り カ ツ ラ ガ イ の に み る よ み い ， 付着 痕 られ う な 明 瞭 な く ぼ は 見 だ さ れ な か っ た 。 穿 孔 は

ほ ぼ 円筒 状 で ，未 完 成 の 穿孔 の 底 は 丸 くえ ぐ られ ，タ マ ガ イ 類 の 穿孔 に み られ る よ うな 中央 部 の 高 ま

は い り 見 られ な e 穿孔 は し ば し ば 内部 か ら 修復 さ れ て お り，イ タ ヤ ガ イ の 外 套 膜 ，そ の 他 の 軟 体部 に

い も明 瞭 な 損 傷 は 見 だ さ れ な か っ た 。

ウ ネ サ ン ゴ ヤ ド リ ガ イ は 約 半 年 間 の 水 槽 で の 飼 育期間 中 ，ア サ リ ， ク チ バ ガ イ ，SiPhonalia sp ．，及

の サ ン ゴ ヤ ゴ び 他 ウ ネ ド リ ガ イ に 穿孔 を 行 な っ た が ，小型 の 二 枚 ．貝を除 き，SiPhonatiasp ．，ウ ネ サ ン

ヤ ド リ ガ イ は に せ つ 背 中 穿 孔 者 を乗 た ま ま 半 年 以 上 も生 き づ け た 。 穿孔者 は 時折 り巻 貝 の 背 中 か ら降

の に の の り ，水 槽 壁 や 貝 殻 片 移 動 L．た が ，数 口 後 に は ま た も と 穿孔 付近 に 戻 っ た 。 こ れ ら の 観 察結 果

か ら は 不 な い い こ ，木種 活発 穿 孔性 捕食者 （寄 生 者 ） あ る は 穿 孔 性 共 生 者 で あ る と う と が で き よ う。

3 つ い 2 か の い 個 体 に て 歯 舌 を検討 し た 結 果 ， うち 個 体 ら尖 舌 型 歯 舌 が 見 だ され た 。中 歯は 左 右対 称 で ， 5 歯尖 を 有 し ，中歯尖 と側 歯 尖 の 間 に 1 小 歯 ，側 歯尖 と 縁 歯尖 の 間 に 2 小 歯 を 有 す る 。従 来 か 1 ら本 種 は 粛舌 を 欠 く と さ れ ， 今回 検討 し た 個 体 か ら も歯 舌が 見 い だ され な か っ た 。 こ れ は 恐 ら く， 本 種 が 穿 孔 性 腹足 類 で あ る こ と か ら ，摂 餌中 の 個休 で は proboscis （吻 ） を餌 の 殻内 に 挿 入 し て お

り 採 の に proboscis が ち て し っ た た め で い ， 集 際 ぎれ ま は な か と 想像 さ れ る 。

ウ ネ サ ン ゴ ヤ ド リ ガ イ は 尖 舌 型 の 歯舌 を有す る 穿孔性 腹足 類 で あ り ，殻 の 特 徴 ，イ タ ヤ ガ イ と密 接

に 伴 な っ て 採 集 さ れ る と い う こ と と も あ わ せ 考 え る と ，サ ン ゴ ヤ ド リ ガ イ 科 で は な く，ア ク キ ガ イ 科 ・ の 員 と し て 扱わ れ る べ き で あ ろ う。

References cited

ANsELL A ． D ．1960 ． ？7 ？Ls α ， ． Observations on predation of Ve ． stTi tttla （DA CosTA ） by

Ncaticα α 1〔1θ 西 ． ． α 伽 oo 〜． ． 34 157 −164 ． （FoRBES ） Proc M Soc London ， ，

IIABE T ，＆ KosuGE ． ． ” con shells o 」α α n color ． ， ， S 1967 Com ノ p in Hoikusha ， 223 pp ．，

64pls ．， Osaka ， Tokyo ．

HIGo S ． ed ． 1973 ． A cat α ・logue o mollusean α u ↑za o α α nese α ， （ ） ブ ノ プ the J P Isl ↑tds and 醜 θ α （tゴα cent area ． Nagasakiken −Seibutsu−Gakkai ，397 pp ．， Nagasaki ． ’ KINosHITA T ．＆ NAKAGAwA K 1934 ． Observation ． α α α ， ， of borings by TritOnali ゴ pom c

（DUNKER ），Yoshokuk α ishi，10 ，187−190．

KIRA ， T ・1964 ・ Colored illustra・tions o the 8 ん ells o 」α α π ， 240 ．71 ． ／ ア P Hoikusha ， PP ， pls ，

Tokyo Osaka ， ．

KosuGE S ．＆ HAYAsH1 S ．1967 ． Notes on （ α ． ， ， the feeding habits of ブapulus dil tatus

A ．ADAMs 1860 ． 砿 ． α α ． no − − ， （Gastropoda ） S Rep Yokoszak 吻 Mus ， ．13 ，45 54 ，pls 。1 2 ． KuRoDA ， T ． 1953． New genera and species of Japanese Rapidae ． Venus ，17 イ3 、 ． 117 − 130 ．

naticid MATsuKuMA ， A ，1976 ． Predation by Recent snails of two species of α レ 曙 慨 副 8

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MATsuKuMA : Notes on Genkaimurex varicosa 87

(Bivalvia). Rep. Ii'ish. Res. Lab,, Kyushu Univ., no. 3, 15-31. ORR, V. 1962. The drilling habit of Capultts danieli (Crosse) (Mollusca:Gastropoda). Veliger, 5, 63-67. SILER, W, L. 1965. Feeding habit of some Eocene carnivorous gastropods, Texas Jour. Sci., 17(2), 213-218,

TAKAHAsHI, G. & OKAMoTo, M. 1969. A catalogue of molluscan shells of Fukuoka PrefectuTe. 154 pp., 22 pls., Fukuoka.

Explanation of Plate I

Figs. 1-5. Genhaimurex varicosa (KuRoDA). ij i:-v-v="-itr SV h'd.

Ia, b: GK-M 10007, height 24.6 mm, width 14.6 mm. 2: GK-M 10008, height 7.lmm, witdh 3.9mm.

3: GK-M 10014, height 5.7mm, width 3.0mm. 4: GK-M 10016, height 8.3mm, width 4.7mm. 5: GK-M 10009, height 17.8mm, width 10.9mm. -V Figs. 6, 7. Boreholes in Pecten (Notovota) albicans (ScHR6TEiR). ( pt ifl Vc#eJ'52x 7tF<.

6: GK-M 10018, height 65.8mm, width 73.9mm. 7: GK-M 10017, height 67.5mm, width 78.2mm.

Fig. 8. Borehole in Ruditapes phillpp･inoru?n (ADAMs & R5515> made by Genzkaimurem

varicosa, GK-M 10010. 0uteT diameter of the borehole is 1.0/mm, VJi:v-ytf-V FY 'C -V- )VRc X D 7 P te9et 6iLk7it. ptloA-ff 1. 0 mm. Figs. 9, 10. Attachment scars and boreholes in Pecten (Notovola) a-lbicans made varinosa. -V- rf 'V 'Cd by Genkaimurex 9-* 7 F Y rb"d }c k o S V h"d ec#}t 5iLt:Jit8dkt tsfi. 9: Attaehment scars and boreholes in the seallop, GK-M 10018. The left borehole is drilled by G. varicoga GK-M 10010, and outer diameter of the borehole is

1.1 mm.

10: Attachment scars and boreholes in the seallop, GK-M 10017. The left borehole

is drilled by G. varicosa GK-M 10007, and outer diameter of the borehole is 1.2mm. The right borehole is made by G. varicesca GK-M 10oo8, and outer diameter is O.6mm,

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88 VENUS : Vol. 36, No.2 <1977)

Plate I ist .catAdet/2

-ifIW'

'

9

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