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70 VE}.i(. (J.S.E. -22-(-i.? i96L2-

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A Study on the Radu!ae of the Japanese (1)* ----The Genera PurPwra, Thais and MancineUa-

Kohman Y. ARAKAwA

Miyajima Aquarium, Hiroshima, Japan

(]S

The present study was carried out in my student life under the guidance

of the late Dr. Isao Taki, the former curator of zoology in the National

Science Museum, Tokyo. I expected to go on with the study and to publish

the results in a more complete form, but for certain reasons the pursuit of

the work in the same course has been laid aside for years, hence I intend

to publish the results, so far as gained, on the occasion of the memoria1

number for h is death.

Acknowledgements are due to the late Dr. Isao Taki for his kind guidance

and encouragements rendered to me during my stay in the Museum and to

Dr.library.Tokubei Kuroda for his generosity in offering me to refer to- his private

Thanks are also extended to Dr. Tadashige Habe who read the ma- ' nuscrlpt and gave me valuable advices and criticisms in the course of the study.

"PzvrPztra" Aarenumber of species which have been referred to the

reported to occur in the Japanese and her neighbouring waters. They

are-regarded as carnivorous, generally making a prey of other of

their own phylurn. Adapting themselves to the feeding habits, all of them

possess rather strong rachiglossate radulae which are formulated in 1-C-1.

The radulae have multicuspidate rachidians with cusps varying three to five

in number according to species and roughly crescent-shaped laterals which

show no clear-cut distinction among the members of the genus.

From a conchological point of view, the precise limits of this genus have

been somewhat ill-defined and confused on account of the extensive variation

'Contributions from the Miyajima Aquarium Laboratory, No. 10. t'.i [Z S; ,'j LLI'i.I71 Er l;G zi<1tc re tiJFYti jte{ f}"t ."ta'Y ] O

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･Japanese ARAKAvvA: Radulae of Muricidae (1) 71

in the shell forms. But the members of this genus are subdivided into three

distinct groups based chiefly on the characterisitics of the rachidian teeth of

the radulae as follows:

Group 1 ---Rachidian Radula. tooth 5-cuspid and ornamented with strong comb-

toothed outer denticles on the outside of the lateral cusps;

marginal cusps prominent and sharply pointed at its tip: base broad. ---Persica Species. Linn6, Panama R6ding

Group 2

Radula.- Rachidian tooth 5-cuspid and furnished the outside of the

lateral cusps with small saw-toothed outer denticles: marginal

cusps not prominent and rather obtuse: base broad. ---armigera 'clavigera Species. Link, bromti Dunker, bzffu Lamarck,

Lischke, distingztenda Dunker et ZelebGr, echinata Blain-

ville, hiPPocastanum Linn6, luteo.stoma }Iolten, Pseztdodia-

dema Yokoyama

Group 3

Radula. Rachidian tricuspidate and devoid of marginal cusps; outer

denticles absent; base narrow but rather massive. ･

Species.-echinulata Lamarck, intermedia Kiener, mancineUa

Linn6, lata Kuroda, siro Kuroda, tz･eberosa R6ding

Besides, the following five spec{es that have been referred to this genus

are known to occur in our territory. But nothing has been reported with

regard to their radular characters up to the present so far asIam aware.

rngosa Born, mzaltilineata KUster, squanzosa Pease, jovanica ? Phi- lippl, "zutabilis. Link . From the result of dissection of the radulae, it is evident that the groups

2 and 3 are not cengeneric with the genus PzarPura (group 1) be ¢ ause of

showing no agreement with those of PurPma in radular characters. I pro- pose, therefore, the group 2 should be placed to the genus Thais in having

the 5-cuspid rachidians with saw-toothed outer denticles as those of Thais-

tyPe, .not of Parpm-ra, while the subgenus Mancinella (group 3 ) should be

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given generic rank in view of the very rnarked differences between these

radulae and those of PurPztra.

The detailed descriptions and figures of the radulae in the members of

PurPura, Thais and Mancinella are here given.

Genus PurPura Brugui6re 1789

Type, BuccimtmPersiczimLinn6

"Thais " The description and the figure of the radula in Persica L. was

given briefiy by Cooke (1918) in the followings:

"Central cusp long and broad; side cusps small but conspicuous,

two-thirds way down; outside, 4-･5 strong deeply-cut denticles, one

'' of which climbs; knob large and elevated.

I'ztrPetra Panama (Roding) (== rudolPhi Lam. ) (Pl. 5, fig. 1)

The rachidian tooth is 5-cuspidate on the broad base; .the central cusp is

rather thin and narrow but sharply pointed at the tip, which reaches appro-

ximately 1.7 times as long as the lateral cusps; the lateral cusps are recurved

posteriorly; a large inner denticle is set at one-third way up on the inside of

the lateral cusps; on the outside, there are four long outer denticles which

show, on the whole, an appearance of the teeth of a eomb; the marginal

cllsps are conspicuous and sharply pointed at the tip; the base is broad,

roughly rectangular in shape and waved below. The lateral teeth are cres-

centshaped in outline and show the common features with those of other

members of the genus.

Genus Thais ROding 1798 Type, 1-kais lena R6ding=Mzerex fusezas Gmelin==Nerita nodosa Linn6

``Thais The radula o ± nodosa L. (PitrPura neritoidea Lam. )'' was illus-

trated by Troschel (1869) in his Das Gebiss der Schnecleen (Bd. Ili, Taf.

XII, fig. 12.). . Thais armigera (Link) (Pl. 5, fig. 7)

The rachidian tooth has five main cusps set on the broad base. The central

cusp fianked by two small lateral cusps is rather thick and strong; the lateral

cusps ceme up approximately two-thirds of the length of the central cusp; one

small inner denticle is located at one-third way up on the inside of the lateral

cusps; on the outside, five or six small outer denticles are serrated like the

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ARAKAwA:. Radulae of MuriEidae.(1> Japa.n. -e.se 73

teeth of a saw, one of which is high up along the outer margin; the marginal cusps are small and blunt at the tip; the base is broad and singly arched below. The laterals are common to those of other species of the genus. Thais bromti (Dunker)

The central cusp is long and sharply pointed, but is not so thick as that of the above species. It attains about two times as long as the lateral cusps; the lateral cusps turn feebly outwards and are prbvided with a large inner

denticle on the inside; the area intervening between the lateraland the mar- .

ginal cusps are ornamented with six or seven small denticles, some of whlch

climb up on the outside of the lateral cusps; the marginal cusps with a blunt are recurved tip weakly outwards; the base is broad and curved slightly below. ' Thais distinguenda (Dunker et Zelebor) (Pi. 5, figs. 2--4) The rachidian tooth possesses five main cusps; the central cusp is rather strong, thickened at the center and arched posteriorly; on eithei side of the

central cusp, the similarly shaped lateral cusps flank directing upwards in

the anterior view, which reach about three-fifths of a length of the central

cusp; a large inner denticle is situated one-third way up on the in$ide of the

lateral cusps; on the outside, there are three deeply-cut outer denticles; the

marginal cusps are small and bluntly pointed at the tip; the base is roughly

rectangular in shape and fiattened below.

Thais hiPPocastanienz'gLinn6) (r=- leieneri Deshayes) The rachidian tooth has five marked cusps on the basal plate; the central cusp is the thickest and longest of all the cusps, and is flanked by two

lateral cu.q.ps which are recurved feebly outwards and reach nearly half a

length of the central cusp; the lateral cusps are provided with a large inner

denticle which is upright and climbs half way up on the inside; the spaces

between the lateral and the marginal cusps is serrate with four outer den-

ticles, one of which climbs rather low down along the outside of the lateral

cusps; the marginal cusps with an obtuse tip are very small and turn weakly

outwards; the broad base is flattened at the both ends and arched below.

Thaislzateostoma(Helten) (Pl. 5, fig. 5) The rachidian tooth has a long and sharply pointed central cusp which

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IP62- 74 VENUS: 22 .(1}.

attains abctut two time$ as long as the lateral cusps; the lateral cusps are

rather short and thick, and turn outwards; one small inner denticle climbs

about half way up on the inside; the four denticles are serrated on the out-

side, one of which climbs low down; the marginal cusps are small and

obtuse; the base is broad and slightly arched below. .

The laterals are nearly crescent in outline with a broad base.

. Thais Pseadodiadema Yokoyama (Pl. 5, fig. 6)

. The present species shows a close similarity in its radular characters to

that of the above species.

The rachidi,an tooth is roughly triangular in outline and 5-cuspid on the

broad base; the central cusp is long and sharp, and is fianked by two short

$imilarly shaped lateral cusps; the lateral cusps which attain half a length

of the central cusp are slightly inclined outwardly; one small denticle climbs

half way up on the inside of the lateral cusps; the marginal cusps are very

small, not conspicuous and obtusely pointed at the tip; four small denticles

intervene between the lateral and the marginal cusps, one or two of which

are slightly high up along the outside of the lateral cusps; the base is broad

and singly curved below. The laterals are sickle-shaped in outline.

Genus Mancin.e･lla Link 1807 Type, Mztrex mancinella of authors, not of Linn6 or Gmelin (=- PztrPiepta gemmzalata Lamarck)

"1"ribztlzss Troschel <1869) gave an illustrat:,on of the radula in man,f:ine.lla Larn." in his monograph (Bd. IA, Taf. XII, Fig. 16.) and Cooke (Ibid.) also

"1'hais figured and described that of gemmulata Lam. (-= manciezella , Linn6, pars)" as follows:

"Central cusp long, thick and broad, rather deeply set in the upper

margln; side cusps small in comparlson, not denticled, but there is a slight broadening of the lower part of the inner edge, as drawn by Tro- schel; no outside denticles, knob just a raised hump. A Cambridge to the specimen shows throughout a tiny sharp dentic!e, closely adherent inside of the side cusps at the base. In a specimen from Durban the broadening of the inner edge almost amounts to a blunt denticle; in one from Rotuma the knob is prominent." ,

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ARAKAwA: Radulae of Japanese Muricidae (1) 75

Mancii ella alozaina [R6ding] (Pl. 5, fig. 8) The rachidian tooth is tricuspid on the narrow massive base; the cent.cal

cusp is extremely thick and long in contrast with the lateral cusps and

strongly arched posteriorly and.excavated by a deep longitudinal groove

along the mid-dorsal line; the small lateral cusps turn slightly outwards and

bend strongly to the posterior. They attain approximately one-fifth of a

length of the centrai; there is no denticle on eith･er side of the lateral cusps

but a slight broadening or protuberance on the inside; the base is massive

and merely curved below.

Mancinella lata (Kuroda) (Pl.6, fig.3)

The rachidian tooth has three main cusps set on the massive base; the

central cusp is very.thick, long and triangular in shape, which is arched

posteriorly and excavated by a longitudinal groove. The small lateral cus'ps

which come up only one-fifth of a length of the central cusp are set with a

inner denticle at one-third way up on the inside; the base is thick, narrow

and singly arched below.

Mrancinella tzeberosa (R6ding) (Pl. 6, fig. 5)

The rachidian teoth is tricuspid on the base; the central cusp reaches

approximately 2.5 times as long as the lateral cusps; the lateral cusp is short

and arched outwards; there is one inner denticle at the bottom of the hollow

intervening between the central and lateral cusps, which is not attached to

either; outerdenticle i3not pre$ent on the outside; the base with rounded

ends is almost straight below.

Mavzcinella siro (Kuroda) (Pl. 6, fig. 8)

The central cur)p is rather short and triangular in shape, which reaches

2.3 times of a length of the lateral cusps; the lateral cusps are singularly

denticled at one-third way up on the insrde; there are no denticles on the

outside but a bare open space; the base is rather broad and singly curved below.

Mancinella echimelata (Lamarck)

The rachidian tooth tricuspidate and almost triangular in outline; the

central cusp i$ remarkably thick and large, and is arched posteriorly; the

small lateral cusps are recurVed outwards turniag strongly to the posterior;

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Table1. Showing the sizes and localities of the '$peclmens examined in the study. - tttt t- -tt t t t tt ttt- --t- t tt i Shell SizeNo. of[Wid . of Rach. Genus Name species Namel Locaiity cm) Rows -'1"lsexl(in 1 'Sl.n.-.rr.!xp.-).-...

I - L/-[17.10 PurPura Panama (Japna) 1 0.35 Thais armtgera Yaku lsland IM × 5 .70F 228 O-22 1L v ･-- --'I4 j (Japan) O.16 iKominato, bronni Chiba M . 32 >/..2.58i,.,31 O.24 !,4.00>t " u :Hatuse,MiuraPen. F O.24 1i3.20 ! -- - distinguenda Yaku lsland >c2 .63I O.14 ' - ,v Torishima Island / M 3.46 >c2 .77i O.17 -' " i' (Japan) I-'i3.53 O.13 hippo- ･ Yoron lsland M × 2 73 272 O.16 castanum :I - " " l,3.62 >･c3 .oo,i.4ol･ O.15 i, ] - - v e ,2 . 00 >･f. O.08 i E luteostoma Shibasaki F 2.72 × 1 .60I 211 O.18 L i " " iF 07 >f. 2 .611 237 O.25 1 l4. 112.75 I " Manazuru × 1 .72i･ O.10 ,M / 1 ii2.73 It - V Hachijo Island M × 1 .90･ O.12 - 111rr1i1..1!1.26 U nt O.l2 ! l Pseado- Hachijo lsland i O.05 diadema '-

u v >cO 1 O.05 l11

,v u ,-- . 1O )x:ol3:i II O.06 i1.00 l r- v V X.O t67 O.05 1' :

v iF - Mancinella , intermedia I3.23× 2 .05i O.17 : 1l2.62 -- " i u IM ><2 -4o[ O.19 1 i ･F li lata i Yaku lsland O.24

" u IF O.29 ! -- mancinella v O.I 8'

siro Morito, LM "" 227 O.27 i 13.67 'r I - v l Niijima Island × 2 .91I O.19 l2.45! lt '- -- 1 u ; Hachijo lsland i3 . 50 ), ,c O.22 ' iM -- tuberosa 1 Yoron lsland l4. 00 >,: 3 .12 O.22 1

,: u IM i4.20 × 3 .30' - O.24 :-- (Ja pan) ! O.08 tt - I

F.,ef female, M.: male, No.rachidof Rows: Number of rowsof teeth ofL radula, Wid.

Rach.: Width of ian tooth.

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ARAKAwA: of Muricidee 77 Radulae Japanese (1)

there is ene small inner denticle at one-third way up on the inside of the

lateral cusps; the base is narrow, massive and slightly arched below. The

laterals are nearly lunate in outline with a broad base.

``Thais Remarks: Cooke (1918) described the radula of echinzalata (Lam. )"

coliected from Karachi, and according te his description the radula has

5-cuspid rachidian with outer denticles on the outside of the lateral cusps.

But the results obtained from my re-examination based upon the specimens

collected from variQus localities in Japan proves that the radula of this species

has a tricuspid rachidian lacking outer denticles as that of Mancinella, not of

Thais. Hence the discrepancl,es may be due to his misidentification for the

specimen. (for more detailed notes, see The Venus, 20 (1): pp. 69-75. )

Ma7zcinella intermedia (Kiener) (Pl. 6, fig. 4) ' The central cusp comes up to about 1.7 times as long as the lateral cusps;

the lateral cusps are very strong and are provided with a inner denticle at

one-third way up on the inside; the outer denticle i$ absent; the base is

rather broad, almost rectanguar in shape and straightened at the basal

margln. ,

References

1) Cooke, A.H. 1919. The radula in Thais, DruPa, Morula, ConcholePas, CreL

nia, IoPas and the allied genera. Proc.Malac.Soc.,XIII,(4)pp.90-110.

2) Troschel, F.H. et Thiele, J. 1856--1893. Das Gebiss der Schneeken fUr Be-

grttndung eiper NatUrlichen Classifieation untersucht von Dr. F,H. Troschel.

Bd. II, Taf. XII.

3) PeiL A.J. 1938. Radula Notes--5. Proc.Mulac.Soc. XXIII, (2) pp. 97-100.

4) J?i{ Ix',r,iE-H3 ･ ?fi,'-"IS 1931. g'Eue0)'ei'!iiltc 2: L.v(r cD･P?.H)'f.(i (i"'R) Jap. Jour. Malac.,

Venus. II, pp. 190 l98.

5) C!ench, W.J. 1947. The genera PurPura and Thais in the Western Atlantic.

Jehnsonia, II, (23) pp. 61 91.

6) Tanaka, Yataro.' 1950. Injuring Mechanisms of Oyster Drill (P"rPura clavi- gera) to Young Oyster (Ostrea gigas). Jap. Jour.Sci.Fisheries, XV, (9) pp.

447 457.

7) Arakawa, Kohman. Y. 1957. The mounting methods of radulae of the gastro-

pods. Collecting and Breeding. XX, (2) pp. 52--58. ,

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8) -----".m.1957 (a). On the Remarkable Sexual Dimorphism of the Radula of

DruPella, Jap.Jour.Malac.Venus. XIX, (3--4) pp. 206--214.

9) 1958. Some Notes on the Radula of PurPura echinulata Lamarck.

Ibid. XX. (1) pp. 69-75.

Explanation of Plates 5-- 6. '

Pl. 5. Radula in PurPura, Thais and Mancinella.

Fig. 1. Rachidian tooth of PurPura Panama (Linne) Canterior view).

2, Rachidian tooth of Thais distinguenda (Dunker et Zelebor>

(anterior view).

3. The same (antero-dorsal view).

4. The same (dorsal view).

5. Rachidian tooth of T. Iuteostoma (Holten) (anterior view)

6. Rachidian tooth of T. Pseudodiadema (Yokoyama) (anterior view).

7. Rachidian tooth Qf T. armigera (Link) (anterior view),

8. Raehidian tooth of Mancinella alouina [ROding] (left side view).

PL 6. Radula in Mancinella.

Fig. 1. Rachidian tooth of Mancinella alouina [R6ding] (anterior view).

2. Lateral tooth of M. alouina.

3.Rachidian tooth of ML lata (Kuroda) (anterior view).

4. Rachidian tooth of M. intermedia (Kiener) (anterior view).

5. Rachidian tooth of M. tuberosa (R6ding) (anterior view).

6. The same (dorsal view).

7. Lateral tooth of M. tuberosa.

8. Rachidian touth of M. siro (Kuroda) (anterior view).

9. The same (antero-dorsal view).

.

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